To read the full-text of this research, you can request a copy directly from the author.
Abstract
The implementation of innovative materials for energy saving is a main focus in the building sector. In this context, aerogels-enhanced systems are often indicated as promising materials for enhancing building envelope thermal resistance. In particular, aerogel blankets have already shown potential in retrofitting projects, while the development of aerogel glazing systems and aerogel-embedded renders is still object of research. This paper describes some aerogel-enhanced systems that were developed over the last few years at Ryerson University, namely aerogel glazing systems, aerogel plasters, aerogel concrete tiles and panels and aerogel fiber blankets. The results of thermal characterization tests of these new materials are reported. These new systems are then assessed for the retrofitting project of an educational building. An extensive energy audit was conducted through measurements of the envelope hygrothermal parameters, the building air-tightness, and several indoor environmental parameters. The audit helped to create an accurate energy model that was used for assessing several energy saving measures.
To read the full-text of this research, you can request a copy directly from the author.
... The research [14][15][16] reported the results of thermal conductivity behavior of aerogelenhanced blankets. The research [14][15][16] presented comparative thermal characterization results of aerogel blankets and established the thermal conductivity as 0.013 W/(m K). ...
... The research [14][15][16] reported the results of thermal conductivity behavior of aerogelenhanced blankets. The research [14][15][16] presented comparative thermal characterization results of aerogel blankets and established the thermal conductivity as 0.013 W/(m K). The research [14][15][16] developed and presented some new aerogel-enhanced blankets. ...
... The research [14][15][16] presented comparative thermal characterization results of aerogel blankets and established the thermal conductivity as 0.013 W/(m K). The research [14][15][16] developed and presented some new aerogel-enhanced blankets. ...
The main development direction of energy efficiency technologies in construction is the creation of various materials with complex structures and unique strength, thermal properties, and other properties. The aerogel is a material with high porosity and excellent thermal insulation properties. This paper provides state-of-the-art aerogel applications for the additive manufacturing of energy-efficient buildings. This work provides the experimental and numerical assessment results of the thermal conductivity of aerogel-enhanced blanket, the experimental assessment results of thermal performance of aerogel-enhanced building structure, the experimental assessment results of the aerogel application as a mixture powder component of the concrete mixture to printing buildings, and the experimental assessment results of the aerogel application as a parget powder component. Experimental results show the effect of aerogel powder component application: thermal conductivity decreased by 25%.
... Opaque aerogel-based insulation products include boards, blankets, wallpapers, and plasters in which fibers reinforce aerogel. Since silica aerogel has low mechanical strength and stability, nonwoven fibers (carbon, mineral, or glass fibers) are used as a reinforcement [38] (Table 1). When the fibers, or the fibrous matrix, are added to the pre-gel mixture, which contains the gel precursors, the resulting dried composite is an aerogel-based panel. ...
... Aerogel-based plasterboard is made of gypsum or concrete, increasing thermal resistance but with less flexibility than low-density fiber panels [18,38]. Lucchi 2015 [39] cited a rigid panel (Aerowool by Rockwool ® ), made of a rock wool matrix combined with silica aerogel, which is coated on one side with a gypsum fiber layer and with the interposition of a vapor barrier (conductivity 0.019 W/mK; equivalent air thickness about 3 cm), high breathability, and low aesthetic and material invasiveness. ...
... The marketing of these products is now well underway. Spaceloft by Aspen has a thermal conductivity of 0.015 W/mK at 0 °C [38,39]. The peculiarity of this product is that a rather thin flexible blanket (th. 10 mm) is suitable for narrow curves and limited interior spaces (floors, walls) and thermal conductivity is 2-2.5 times lower than traditional thermal insulation materials [17]. ...
This paper presents a literature review about aerogel-based products for building, focusing on the plasters used within the architectural restoration sector. Aerogel has entered the construction field in the last two decades as a component of many insulation products, due to its high thermal performance. Aerogel-based plasters allow the matching of high thermal performance and limited thickness. This makes them suitable when retrofitting an existing building and also when restoring a heritage building. We analyze the results of recent research, focusing on the most commonly used methods for assessing the thermal performances and durability of aerogel-based plasters. As a result of this review, we propose a guideline for manufacturing samples destined for laboratory tests.
... Commercial glazing products based on granular aerogel are available, including Lumira ® produced by Cabot [10]. Aerogel granules are used to fill the interspace between panes, resulting in highly insulating, but not transparent, fenestration units [11][12][13][14][15][16][17][18][19][20]. These products are suitable for use in applications where diffuse light is desired, including skylights and some daylighting applications. ...
... Fabricating monolithic silica aerogels that have the size and the optical properties suitable for incorporation into vision glass glazing units would open this technology to a broader market but is significantly more challenging [6,20]. Research in this area has been ongoing for decades. ...
Transport of heat through windows accounts for more than 25% of heating and cooling losses in residential buildings. Silica-based aerogels are translucent with extremely low thermal conductivity, which make them attractive for incorporation into the interspaces of glazing units. Widespread incorporation of monolithic-silica-aerogel-based windows could result in significant energy savings associated with the heating and cooling of buildings. However, monolithic silica aerogels do not have the optical clarity of vision glass, due to light scattering by the solid matrix, and often have surface imperfections, both of which render these materials less appealing for glazing applications. Here, we demonstrate a variety of approaches to preparing aesthetically pleasing monolithic silica aerogel by a rapid supercritical extraction method for incorporation into glazing units, including: (1) process improvements that result in monoliths with higher visible light transmission; (2) innovative mold design for the preparation of uniform aerogel monoliths; (3) glazing designs that use thinner monoliths; and (4) the incorporation of artistic effects using dyes and laser etching to prepare glazing units with mosaic- or stained-glass-like patterns in which surface imperfections are perceived as features of the design rather than flaws.
... Aerogel enhanced system for building insulation -Aerogel-enhanced insulation technology is a high thermal resistance material and the installation of this technology in the building envelope generates energy potential savings about 34% with limited impact on the building performance (Berardi, 2017). -The high costs of aerogel-enhanced products pose a barrier to building the system whilst the payback period is over 17 y (Berardi, 2017). ...
... Aerogel enhanced system for building insulation -Aerogel-enhanced insulation technology is a high thermal resistance material and the installation of this technology in the building envelope generates energy potential savings about 34% with limited impact on the building performance (Berardi, 2017). -The high costs of aerogel-enhanced products pose a barrier to building the system whilst the payback period is over 17 y (Berardi, 2017). ...
Green building technologies (GBTs) have gained significant momentum as a result of the environmental, energy management and societal problems within the building sector. The insulated block/eco-block is a GBT, which consists of an insulation material that prevents hot/cold air to enter inside buildings, conserve energy and improve indoor comfort in comparison to conventional block. However, conventional building techniques are still dominant in developing countries due to a lack of people's knowledge about GBT, poor interaction with building experts and low support from policymakers. Public acceptance of the eco-block technology is essential for its successful introduction into society. This paper is the first one to systematically review 45 peer-reviewed articles in this field of study with a focus on eco-block. Recent publications have extended theoretical models like (TPB, TAM, DOI, VBN and UTAUT) to study green building consumption. Lack of subjective knowledge about eco-block, lack of trust in the suppliers of eco-block, high price sensitivity, poor education and low-income households are recognised as the major barriers to the technology adoption. The contribution of the paper lies in establishing an original adoption decision framework that groups together a set of (contextual factors, psychological factors and demographic factors) to fill the research gap. The adoption framework could eventually assist the construction experts to analyse the different stages involved in the residents' decision to adopt the eco-block building technology. The paper culminates with a discussion on the application of the conceptual framework as a reference in future GBT usage.
... More than 90% of the aerogel consists of air. It is the lightest solid substance that is ever known [9]. The study's main aim is to show future building façade based on the aerogel's capability on the window's performance. ...
... There are different types of aerogel in buildings like blocked aerogel, loose granular aerogel, fib-panel aerogel, mat and rolls, blanket, aerogel plasters, and concrete aerogel. They are used for opaque parts of the buildings [9]. Nevertheless, aerogel plastic panes or double-glazed windows filled by aerogel are used for the transparent portions of buildings [6]. ...
Aerogel is a sort of engineered porous substance. It has unique chemical and physical properties with different types of opaque and translucent. It is considered one of the most encouraging materials in various applications such as spacecraft and buildings. In building, translucent aerogel uses for window construction. It plays a vital role in enhancing building thermally and acoustically. Despite its high cost, aerogel is a brittle material. It is hard to produce large-sized free crack windows and prevents the window from being operable. It is not optically transparent, which isolates occupants from the outside view. These limitations restrict architects from using aerogel as windows on façades freely. Improved aerogel windows can get better efficient glasses, larger sizes, and transparency that experiences the natural quality of the light and outside view. It may give the building more functional façades that can fulfill people’s needs in the future. So, the study will evaluate the efficiency of façade in the future. The study aims to predict the capability of improved aerogel in creating a façade that achieves human needs while increasing the efficiency of the building from different perspectives. It examines improved aerogel windows and their role in enhancing current residential buildings in northern Iraq. Ecotect and Dialux software are used as research tools. The paper concluded that the capability of improved aerogel will give the building a new façade that is more environmentally friendly and provides human comfort while still transparent compared to the current facade.
... However, new and innovative thermal insulation can perform with relatively less insulation depth (Filate, 2014). Berardi, 2017, determined that aerogel blankets are already showing their effectiveness in retrofitting projects, while the development and adoption of aerogel enhanced rendering and aerogel incorporating glazing systems is progressively being used (Berardi, 2017). Berardi (2018) carried out a successive study to investigate the benefits of using aerogel-enhanced systems for the retrofitting project of an educational building as a case study. ...
... However, new and innovative thermal insulation can perform with relatively less insulation depth (Filate, 2014). Berardi, 2017, determined that aerogel blankets are already showing their effectiveness in retrofitting projects, while the development and adoption of aerogel enhanced rendering and aerogel incorporating glazing systems is progressively being used (Berardi, 2017). Berardi (2018) carried out a successive study to investigate the benefits of using aerogel-enhanced systems for the retrofitting project of an educational building as a case study. ...
Reducing the energy needs of existing buildings has a significant place in reducing global energy demands. High energy savings can be achieved with passive renovation suggestions in existing buildings. In this study, the effect of the proposed renovations for an educational structure in Safranbolu on the heating and cooling demands of the building was determined with a simulation program. Energy improvements of up to 70 percent have been achieved through passive improvement designs in orientation and insulation material. The highest energy saving (69.31 %) was realized through a scenario of rearranging spaces from the north side to the south side where the number of users is relatively high and selecting a 20 cm aerogel thermal insulation material. While the heating and cooling load, in accordance with the definition of a zero-energy building, could not be reached in this scenario, the study showed the importance of holistic decisions taken in the design phase of the building with respect to energy-efficient building design.
... Practically, ca. 97% of silica-aerogel is air, efficient as thermoinsulator, given that the high volume of the air suppresses the heat transfer in the form of conduction and convection and also, the silicon dioxide has a reduced thermal conductivity and a high reflectance [14][15][16][17][18]. ...
... Powders are materials that influence the spectral properties of a polymer coating. In this study, the silica was introduced in the powder material to form silica-based aerogels in order to reduce considerably the material surface emissivity due to its over 90% reflectance versus the surrounding environment [9][10][11][12][13][14][15][16][17][18]. Moreover, glass microspheres were employed due to their similarity with silica-aerogels, as they embed in their structure a relatively big volume of air, and also due to their low expansion thermal coefficient that prevents the formation of cracks and a greater wettability potential [19][20][21][22][23][24][25]. ...
A series of methods were employed to assess the performances of advanced coating materials based on components that can modify the spectral parameters of the surfaces on which these materials are applied in order to obtain passive military camouflage. Powder materials with high infrared (IR) reflectance were used to obtain this type of coatings, which also ingrain in their structure a significant volume of air that allow limitation of the radiative heat transfer of the coated source. The components were embedded in a polyurethane matrix, which facilitated the coating process on different surfaces. The bicomponent polyurethane-based binder used within the different composition tested is transparent to incident IR radiation, has no organic solvents, is highly flexible and possesses remarkable physical, chemical and mechanical properties: high surface adhesion, high flexibility and resistance against a number of chemical agents and external factors with destructive effect. The efficiency of these composite materials was further demonstrated by analyzing the thermal images of different objects.
... The thermal conductivity of aerogel is much lower than conventionally used thermal insulation materials like foam glass, cotton wools, polystyrene foam, mineral wools, polyurethane foam [31]. The addition of hydrophobic silica aerogel in cementitious composite could lower strength [32], flowability [14] due to its lower adhesive properties and fragile nature. The lightweight density and brittleness of aerogel make it challenging to create a homogeneous mix between aerogel and cementitious composites. ...
... Generally, aerogel is used as a volumetric replacement of fine aggregates and replaced with sand, silica fume, nano-silica, and fly ash. Aerogel has been used in several studies as fine aggregates from a few nanometers to 4 mm in size [32,65]. Few investigations have been carried out on aerogel incorporated lightweight concrete/mortar, where aerogel is replaced with lightweight aggregates like expanded glass aggregates ranging from 1 to 3 mm size, expanded perlite ranging from 1.18 to 4.75 mm size, and fly ash aggregates ranging from 4 to 8 mm size [14,16,66,67]. ...
With the increase in global warming, the demand for more sustainable and thermal insulating cement-based lightweight composite increases. From the past few decades, researchers worldwide have carried out extensive research on lightweight concrete using various lightweight aggregates. The use of aerogel as an aggregate in lightweight concrete is the most promising building application these days. With the exceptional characteristics of thermal insulation, ultra-low density, high adsorption, high surface area, aerogel shows a remarkable behavior. Although, the poor mechanical characteristics and high cost of aerogel have negative effects on the aerogel-incorporated concrete. This article is aimed to present a complete in-depth review of aerogel incorporated cementitious materials in terms of production/synthetisation, fresh rheology and proportioning, mechanical, microstructural, and durability properties, including water absorption, capillary water absorption, fire resistance, and exposure to elevated temperature, thermal insulation properties, and economic perspectives of aerogel. Particular emphasis has been given to study the hygrothermal behavior of aerogel-based cement composites. In addition, the present investigation gives a summary of case studies that have been performed for aerogel-based cementitious products used in buildings. The study suggests the promising future of aerogel as lightweight thermal insulating composites with sufficient mechanical properties.
... There are several options and evidence for their varying effectiveness, including recently advanced options. For example, Berardi [14] investigated the properties of aerogel systems with plasters, concrete tiles/panels and fibre blankets, emphasizing that these materials have great thermal performance, but they are too expensive to be used for a sustainable economic return. Also, Zhou et al. [15] investigated the performance of internally insulated walls with aerogel-based high insulating plaster and renders such as lime mortar and mineral plaster, indicating that internal retrofitting using such materials can alter the hygrothermal performance of walls and, for this reason, recommended caution in their use. ...
... The interviewees suggested insulating floors, ceilings, roofs and walls, and to reduce the loss of heat through windows by adding secondary glazing and using curtains, shutters and blinds. Examples of insulation systems used in literature are shown in Section 2 of the current paper e.g., [14][15][16]. ...
Climate change mitigation targets have put pressure to reduce the carbon footprint of cultural heritage buildings. Commonly adopted measures to decrease the greenhouse gas (GHG) emissions of historical buildings are targeted at improving their energy efficiency through insulating the building envelope, and upgrading their heating, cooling and lighting systems. However, there are complex issues that arise when mitigating climate change in the cultural built heritage sector. For instance, preserving the authenticity of heritage buildings, maintaining their traditional passive behaviours, and choosing adaptive solutions compatible with the characteristics of heritage materials to avoid an acceleration of decay processes. It is thus important to understand what the enablers, or the barriers, are to reduce the carbon footprint of cultural heritage buildings to meet climate change mitigation targets. This paper investigates how climate change mitigation is considered in the management and preservation of the built heritage through semi-structured interviews with cultural heritage experts from the UK, Italy and Norway. Best-practice approaches for the refurbishment of historical buildings with the aim of decreasing their energy consumption are presented, as perceived by the interviewees, as well as the identification of the enablers and barriers in mitigating climate change in the cultural built heritage sector. The findings emphasise that adapting the cultural built heritage to reduce GHG emissions is challenging, but possible if strong and concerted action involving research and government can be undertaken to overcome the barriers identified in this paper.
... Getting wet of the insulation in rooms with high humidity (basements, technical subfloors) negatively affects the thermal insulation qualities of the material and leads to its sagging under its own weight. Figure 1 shows the most common thermal insulation materials, in particular, used in heat supply, which are sorted in decreasing order of their thermal conductivity [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In addition to traditional insulators, liquid nano-ceramic thermal insulation materials have gained widespread use recently, incorporating hollow gas-filled or vacuum-sealed microspheres with various synthetic binders [7][8][9][10][11][12][13][14][15]. ...
In the pursuit of conserving non-renewable fuel and energy resources and mitigating harmful emissions into the atmosphere, thermal insulation is commonly employed in practice for heated elements, including but not limited to building exteriors, boilers and furnaces, thermal power equipment, pipelines, and the like. The primary characteristic of any insulation material lies in its thermal conductivity, particularly under operational conditions. The research object is liquid nano-ceramic thermal insulation located on the surface of a round-section pipeline with a circulating heat carrier. The research subject is the thermal conductivity properties of the insulation material under operational conditions. The research aim is to determine the thermal conductivity coefficient of liquid nano-ceramic thermal insulation coating on the surface of the pipeline. The research method involves the laws of steady-state heat conduction and heat transfer for a two-layer cylindrical wall. Research findings indicate that for a steel pipeline measuring 76×3 mm with insulation thickness of 3.5 mm, the thermal conductivity coefficient of the liquid nano-ceramic thermal insulation material amounted to 0.0145 W/(m⋅K). Disregarding the radiative component, the thermal conductivity coefficient equals 0.0135 W/(m⋅K). Conclusions drawn suggest that the obtained value of the operational thermal conductivity coefficient of the liquid nano-ceramic thermal insulation material aligns with the manufacturer's claimed material thermal conductivity of 0.014 W/(m⋅K) and with the findings of other researchers. Minor discrepancies in magnitudes may be attributed to the extended period of insulation usage on the pipeline surface, which at the time of the conducted scientific investigations was approximately 1.5 years.
... aerogel and 0.1488 W·m −1 ·K −1 , respectively, for plaster with 36% vol. aerogel [35], it can be said that our own economic compositions of aerogel-incorporated plasters are promising and can be considered suitable for the façade application of buildings. Regarding the economic cost and considering the values of the thermal conductivities of the obtained silica aerogel-incorporated cement and lime plasters, the optimum aerogel content is 40% vol. in contrast to the results obtained by other researchers. ...
Silica aerogel has remarkable properties, particularly its translucence/transparency, extremely low thermal conductivity and density. Due to these properties, it can be used for the thermal insulation of buildings for energy saving, cost saving, and enhanced comfort. In this context, aerogel products such as aerogel blankets have already started to demonstrate their effectiveness in retrofitting projects and the development and adoption of aerogel glazing systems and aerogel-enhanced renders is promising. Other products, for example, through the incorporation of silica aerogel granules in cement and lime renders were obtained, with high thermal insulation properties, to achieve energy efficiency on buildings facades. This research aims to come up with new aerogel particle composition insulation plasters at cost-effective rates for application in building insulation. Their physical apparent mass density, mechanical–flexural and compressive strengths, thermal conductivity, and properties were investigated. As an experimental study, the thermal conductivities of six sets of cement and lime plasters with aerogel particles (0.1–4.0 mm) were investigated and it was concluded that the thermal conductivity of cement and lime plasters with 80% aerogel was 0.2287 W·m−1·K−1, about 3.4 times smaller than the respective value of traditional lightweight plasters of 0.76 W·m−1·K−1, while the cement and lime plasters with less than 40% aerogel showed a thermal conductivity value as low as 0.3172 W·m−1·K−1. It was confirmed that the end product plasters’ mechanical qualities included low apparent mass densities, no apparent shrinkage, and mechanical strength values that matched those of the prepared compositions. This suggests that the obtained plasters are suitable for use in both new constructions and renovation projects.
... In addition to glazing systems, it is mainly used as thermal insulation. In general, it is used wherever there is a need to effectively reduce the building's energy losses (Berardi, 2017). The basic features and benefits are provided in Table 1. ...
To maintain indoor comfort, buildings and the construction sector in general consume 30-40% of the World’s total energy. This is mainly due to air conditioning, ventilation, and heating. The least effective and weakest elements of the building envelope are windows and glazed surfaces. So far, several technological solutions have been designed to reduce heat losses and eliminate excessive heat gains through transparent surfaces. In recent decades, aerogel has attracted attention, mainly known for its excellent thermotechnical properties and trans�parent structure. As a result, it is considered one of the most promising thermal insulation materials for building applications. This paper provides a comprehensive review of aerogel glazing systems, their properties and future potential in the construction industry (especially in the energy efficiency of buildings).
... The authors presented comparative thermal characterization results of aerogel blankets and established the thermal conductivity as 0.013 W/ (m K). The authors developed and presented some new aerogel-enhanced blankets [13]- [15]. ...
The main development direction of energy efficiency technologies in construction is the creation of various materials with a complex structure and unique strength, thermal and other properties. The aerogel is a material with high porosity and excellent thermal insulation properties. This paper provides the state-of-the-art of aerogel applications for the additive manufacturing of energy efficient buildings. This work provides the experimental and numerical assessment results of thermal conductivity of aerogel-enhanced blanket, the experimental assessment results of thermal performance of aerogel-enhanced building structure, the experimental assessment results of the aerogel application as mixture powder component of the concrete mixture to printing building and the experimental assessment results of the aerogel application as parget powder component. Experimental results show the effect of aerogel powder component application: thermal conductivity decreased by 25%.
... Aerogels have much lower heat conductivity than traditional thermal insulation materials such as foam glass, co on wools, polystyrene foam, mineral wools, and polyurethane foam [34]. However, the incorporation of hydrophobic silica aerogels in cementitious composites may lead to reduced strength [35] and flowability [16] due to t lower adhesive properties and fragile nature. The lightweight density and bri leness of aerogels present challenges in achieving a homogeneous mix between aerogel and cementitious composites. ...
This study investigates the applicability of Principal Component Analysis (PCA) for distinguishing construction materials. The approach enhances data presentation, revealing distinct clusters and variable impacts on materials. This perspective provides valuable insights into concrete materials, guiding materials science and engineering practices. Our findings show the capacity of PCA to show a clear distinction between concrete and non-concrete composites. Compressive strength significantly affects certain composites, being influenced by aerogel loading. The peculiar role of aerogel density among the other factors is a ributed to their possession of the smallest thermal conductivity. To address moderate total variance of PCA, segregation into concrete (C) and non-concrete (NC) categories is explored, offering a more robust distinction and higher clustering. Concrete materials show higher variance, emphasizing the effectiveness of the segregation approach. PCA highlights aerogel density's influence on thermal conductivity on concrete materials. For non-concrete materials, a moderately higher variance is noted, emphasizing the critical role of aerogel-related properties (size and density). These findings underscore the importance of aerogel characteristics in shaping material behaviour.
... Huang et al. [25] verified that aerogel blankets provided the minimum optimum insulation thickness for use in a typical Chinese building compared to XPS, EPS, PU, and glass fibre (GF); furthermore, aerogel offered the fastest reduction in greenhouse gas emissions with increasing thicknesses [25]. Moreover, regarding retrofitting, the use of aerogel-containing thermal renders instead of recurrently used thermal insulator materials (like EPS and XPS) practically benefits from its application method over the substrate surface, which may be rough and uneven, and, even so, can be applied with a continuous thermal insulation layer with gaps and joints reasonably filled [26]. ...
The current climate change context raises the demand for reducing energy and environmental impacts while keeping an economic balance and building users’ comfort. Thermal insulation solutions are potential allies in ensuring the adequacy of existing buildings for challenging sustainability requirements. In this scenario, silica-aerogel-fibre-based thermal renders are innovative solutions for which integrated approaches still lack information, and they should be compared with benchmark multilayer solutions, such as those based on expanded polystyrene (EPS), extruded polystyrene (XPS), mineral wool (MW), and insulated corkboard (ICB), to evidence their prospective economic, environmental, and energy benefits. This paper quantifies the optimum insulation thicknesses, life cycle savings, payback periods, and environmental impacts of innovative thermal renders compared to conventional thermal insulation materials when applied as a retrofit in existing facade walls. The results show that cost-optimised thermal renders with sisal fibres led to the best overall performance. Higher heating needs led to higher optimum render thicknesses and life cycle savings. With a 0.02 m thickness, aerogel-fibre-based thermal renders outperformed other materials in terms of heating-degree days (HDD) from 1000 °C·day onwards; they can save approximately EUR 60∙m−2, 1000 MJ∙m−2, and 100 kg CO2 eq∙m−2 while presenting a U-value 13% lower throughout their 30-year lifetime when compared with the second-best multilayer solution with XPS.
... This material has more than twice the thermal insulation performance of traditional gypsum plaster. Buratti et al. [23] developed an aerogel plaster using aerogel and insulating gypsum for the renovation and restoration of old buildings. They compared its thermal performance with the commonly used traditional plaster system in buildings, as shown in Fig. 6. ...
In recent years, the problem of energy saving and consumption reduction in the construction industry has attracted more and more attention. The state has also put forward higher requirements on the energy saving, environmental protection and fire safety of building exterior wall insulation in terms of policies. Aerogel materials are considered to be the most promising thermal insulation materials in the future due to their excellent thermal insulation properties and fire resistance. In this paper, the preparation process and application of aerogel inorganic cementitious composites were investigated, mainly aerogel cement composites and aerogel gypsum composites. We analyzed the recent research results, and focused on the preparation optimization and application prospects of aerogel inorganic cementitious composites. In the preparation of aerogel inorganic cementitious composites, many researchers have proposed different preparation methods to optimize the interface between aerogel and inorganic cementitious materials in order to avoid the strength degradation caused by doping aerogel. At present, preparing aerogel into aerogel slurry for compounding is considered to be a relatively optimal incorporation method. It is found that aerogel inorganic cementitious composites have great prospects for thermal insulation applications in the construction field. However, due to the high cost of aerogel preparation and the poor interfacial bonding between aerogel and inorganic cementitious materials, the application of aerogel in building thermal insulation is limited. This paper has reference significance for studying the application of aerogel in the construction industry.
... In 2015, 51% of the total energy consumed by households in the United States was used to power heating, ventilation, and air conditioning systems. 1 As global temperatures continue to reach new extremes, it is imperative that the insulation performance of building materials be maximized to reduce energy loss through the building envelope, and thus reduce overall building energy consumption. One place where building materials are in need of improvement is windows, which account for ∼30% of heat loss from homes. 2 Silica aerogels are a leading candidate as a thermal insulation coating for window applications due to their ability to reach porosities in excess of 90% and thermal conductivities as low as 13 mW/m K. 3,4 However, typical aerogel syntheses involve supercritical drying that results in hazy monoliths due to light scattering by pores exceeding 40 nm in size. In addition, their high porosity and low density reduce their mechanical robustness, limiting their widespread application to windows. 5 Silica gels are typically synthesized from molecular precursors, often tetraalkoxysilanes or trialkoxyalkylsilanes, which polymerize in solution in three stages. ...
Silica-based aerogels are a promising low-cost solution for improving the insulation efficiency of single-pane windows and reducing the energy consumption required for space heating and cooling. Two key material properties required are high porosity and small pore sizes, which lead to low thermal conductivity and high optical transparency, respectively. However, porosity and pore size are generally directly linked, where high-porosity materials also have large pore sizes. This is unfavorable as large pores scatter light, resulting in reduced transmittance in the visible regime. In this work, we utilized preformed silica colloids to explore methods for reducing pore size while maintaining high porosity. The use of preformed colloids allows us to isolate the effect of solution conditions on porous gel network formation by eliminating simultaneous nanoparticle growth and aggregation found when using typical sol-gel molecular-based silica precursors. Specifically, we used in-situ synchrotron-based small-angle X-ray scattering during gel formation to better understand how pH, concentration, and colloid size affect particle aggregation and pore structure. Ex-situ characterization of dried gels demonstrates that peak pore widths can be reduced from 15 to 13 nm, accompanied by a narrowing of the overall pore-size distribution, while maintaining porosities of 70-80%. Optical transparency is found to increase with decreasing pore sizes while low thermal conductivities ranging from 95+/-13 mW/m*K are maintained. Mechanical performance was found to depend primarily on effective density and did not show significant dependence on solution conditions. Overall, our results provide insights into methods to preserve high porosity in nanoparticle-based aerogels while improving optical transparency.
... Heat transfer within these materials has two major routes, (through the gas phase in the pores and through the solid phase). Despite the fact that aerogels already have many industrial applications [3,[5][6][7], their breakthrough in the building insulation market [8][9][10] is still expected. This specific application requires the mass production of a low-cost product with good mechanical properties and excellent thermal properties. ...
Composite aerogels can include fibers, opacifiers and binders but are rarely designed and optimized to achieve the best thermal/mechanical efficiency. This paper proposes a three-dimensional X-ray tomography-based method for designing composites. Two types of models are considered: classical and inexpensive homogenization models and more refined finite element models. XrFE is based on the material’s real three-dimensional microstructure and/or its twin numerical microstructure, and calculates the effective conductivity of the material. First, the three-dimensional sample is meshed and labeled. Then, a finite element method is used to calculate the heat flow in the samples. The entire three-dimensional microstructure of a real or fictitious sample is thus associated with a heat flow and an effective conductivity. Parametric studies were performed to understand the relationship between microstructure and thermal efficiency. They highlighted how quickly a low volume fraction addition can improve or ruin thermal conductivity. A reduced set of three formulations was developed and fully characterized. The mechanical behavior was higher than 50 KPa, with thermal efficiencies ranging from 14 to 15 mW·m·K−1.
... Aerogels have also been used as additives to finishing plasters in lower volume percentages (ca. 2%) achieving improved thermal performance compared to normal plasters (Berardi, 2017;Kim et al., 2013). ...
To achieve the ambitious target of climate neutrality of the EU set out within the EU Green Deal, a reduction of energy use in the highly energy consuming building sector is critical. To achieve this, the renovation of existing buildings has been given a key role, starting with the Renovation Wave initiative. In fact, a large proportion of existing buildings in the EU are characterised by a high energy consumption for heating and cooling, often caused by poor or non-existent thermal insulation, as well as outdated heating and cooling systems. It is hence critical to improve their energy-efficiency through renovation to reduce the significant impact of the built environment on the total EU energy household and associated greenhouse gas emissions. Additionally, in Europe’s seismic regions, earthquakes can cause significant human and economic losses, with a large impact on society. Recent seismic events have highlighted the vulnerability of older buildings with structural deficiencies that are in dire need for seismic retrofitting. A large proportion of the EU building stock requires renovation from both structural and energy perspectives. Recent scientific developments highlight better cost-effectiveness, safety and efficiency can be achieved when taking an integrated approach. This report presents materials and technologies developed and presented in the scientific literature.
... infill walls or structural masonry), particular attention is paid to intervening on external walls, strengthening the existing elements while additionally providing thermal insulation. Typical thermal retrofits nowadays use mineral wool, polyurethane (PUR) or polystyrene (EPS or XPS) as insulation materials, which have thermal conductivity values (λ) around 35 mW/m⋅K [25], while very low values of 3.5-8 mW/m⋅K can be obtained for Vacuum insulation panels (VIPs), or advanced materials like aerogel-incorporated plasters with λ-values between 10 and 15 mW/m⋅K [50,51]. Different avenues can be identified in the literature such as the application of composite materials or prefabricated panels, either cement-based or timber-based. ...
Ageing of the building stock is an issue affecting many regions in the world. This means a large proportion of existing buildings being considered energy inefficient, with associated high energy use for heating and cooling. Through renovation, it is possible to improve their energy-efficiency, hence reducing their significant impact on the total energy household and associated greenhouse gas emissions. In seismic regions, additionally, recent earthquakes have caused significant economic losses, largely due to the vulnerability of older buildings not designed to modern standards. Addressing seismic and energy performance by separate interventions is the common approach currently taken, however to achieve better cost-effectiveness, safety and efficiency, a novel holistic approach to building renovation is an emerging topic in the scientific literature. Proposed solutions range from integrated exoskeleton solutions, over strengthening and insulation solutions for the existing building envelope or their replacement with better materials, to integrated interventions on horizontal elements like roof and floor slabs. To identify pathways to combined seismic and energy retrofitting of buildings, a state-of-the-art review of all materials and solutions investigated to date is presented. This is followed by a critical analysis of their effectiveness, invasiveness, building use disruption as well as their impact on the environment. The assessment of current combined retrofitting research highlights a great potential for their application, with a potential to provide cost-effective renovation solutions for regions with moderate to high seismic risk. Still, to-date there is a lack of experimental research in this field, a need for further work on truly integrated technologies and their validation through applications on existing large-scale buildings. Moreover, there is a need for adequate design methods, regulations and incentives that further the implementation of integrated retrofitting approaches.
... In buildings, aerogels can be applied in many forms and in different construction materials: as wall insulators, in fenestration, and incorporated in cements and plasters [5]. Furthermore, they can be applied in older buildings, improving their energy efficiency without compromising the aesthetics of façades [64,65]. However, their high cost and difficult handling (silica aerogels are known for being fragile and shedding particles) are still inhibiting their ubiquitousness. ...
Nowadays, our society is facing problems related to energy availability. Owing to the energy savings that insulators provide, the search for effective insulating materials is a focus of interest. Since the current insulators do not meet the increasingly strict requirements, developing materials with a greater insulating capacity is needed. Until now, several nanoporous materials have been considered as superinsulators achieving thermal conductivities below that of the air 26 mW/(m K), like nanocellular PMMS/TPU, silica aerogels, and polyurethane aerogels reaching 24.8, 10, and 12 mW/(m K), respectively. In the search for the minimum thermal conductivity, still undiscovered, the first step is understanding heat transfer in nanoporous materials. The main features leading to superinsulation are low density, nanopores, and solid interruptions hindering the phonon transfer. The second crucial condition is obtaining reliable thermal conductivity measurement techniques. This review summarizes these techniques, and data in the literature regarding the structure and thermal conductivity of two nanoporous materials, nanocellular polymers and aerogels. The key conclusion of this analysis specifies that only steady-state methods provide a reliable value for thermal conductivity of superinsulators. Finally, a theoretical discussion is performed providing a detailed background to further explore the lower limit of superinsulation to develop more efficient materials.
... However, besides insulation, additional factors are involved in the retrofit technology to improve the energy performance of buildings [16]. Berardi et al. [17] quantified improvements in the thermal performance of a building by retrofitting it via the use of aerogel in the window system. Park et al. [18] observed a marginal improvement in the thermal performance of buildings by using PCM. ...
This study focuses on the energy performance of low-rise residential buildings and on the technological improvements required to improve their performance. As most low-rise residential buildings in Korea are old, they are being renovated to improve their energy efficiency. However, as renovations are expensive, the government intends to apply low-cost energy-efficient technologies that are currently in use as well as quantify their performances. To this end, low-rise residential buildings in villages were selected for the survey; among these, five buildings were evaluated for the application of energy-efficient technologies. Based on the survey, which included information on the actual energy consumption, the reliability of the simulation analysis was verified, and the effects of the technologies were evaluated. The survey focused, in particular, on the airtight performance of the implemented technologies, the efficiency of the heating equipment, and the insulation performance. Moreover, the performances were validated quantitatively by actual measurements. As a result, the energy saving for each technology were evaluated, and the corresponding annual savings were calculated. Finally, the payback period of the investment was evaluated using economic analysis.
... Thermal breaks are the insulating components incorporated within the envelope to interrupt the heat flow path and reduce the undesired effects of thermal bridges [111,42,46]. Silica aerogels' lightweight and ultrahigh insulation properties make them the most promising high-performance materials for the next-generation building insulations [103,100,39,39,40,11,20,10,59,65,54,91]. Silica aerogels consist of a mesoporous internal structure of silicon dioxide bounded chains with high porosity (around 90%) and specific surface area that results in their superinsulation performance [63,66,71,67,35,8]. ...
This work develops a multiphase thermomechanical model of porous silica aerogel and implements an uncertainty analysis framework consisting of the Sobol methods for global sensitivity analyses and Bayesian inference using a set of experimental data of silica aerogel. A notable feature of this work is implementing a new noise model within the Bayesian inversion to account for data uncertainty and modeling error. The hyper-parameters in the likelihood balance data misfit and prior contribution to the parameter posteriors and prevent their biased estimation. The results indicate that the uncertainty in solid conductivity and elasticity are the most influential parameters affecting the model output variance. Also, the Bayesian inference shows that despite the microstructural randomness in the thermal measurements, the model captures the data with 2% error. However, the model is inadequate in simulating the stress-strain measurements resulting in significant uncertainty in the computational prediction of a building insulation component.
... Aerogel have also been used as additives to finish ing p las ters in lower volume percentages (ca. 2%) achieving improved thermal performance comp ared to n orm al p la ste rs (Berardi, 2017;Kim et al., 2013). Despite increasing experimental evidence, research on simplified modelling is still ne e ded to facilitate the use of TRM and other composite materials for strengthening masonryinfilled RC frames. ...
The European building stock is ageing and requires significant renovation efforts to improve its energy performance and ensure structural safety and resilience. Within the European Green Deal, the Renovation Wave initiative promotes increases in building renovation rates to ensure that ambitious EU energy saving targets for 2030 and beyond can be achieved. To incentivise renovation further, integrating energy retrofitting with seismic strengthening is explored in the Exploratory Research project iRESIST+ by investigating a novel seismic-plus-energy retrofit. The research conducted in iRESIST+ is of high timeliness and has relevance for the policy areas related to the energy efficiency of buildings, circular-economy principles, as well as resilience. In iRESIST+, the combination of inorganic textile reinforced mortar (TRM) composites with thermal insulation materials is explored. A review of the experimental studies on TRM highlighted their potential for seismic strengthening, but also their suitability for combined seismic and energy retrofitting. Based on the gathered scientific literature, a new macro-modelling approach for TRM-strengthened infilled reinforced concrete (RC) buildings was developed, and then used to quantify the effectiveness of the retrofit in increasing the in-plane capacity of the iRESIST+ prototype structure. By conducting a series of incremental dynamic analyses, the results were expanded, showing improvements in the dynamic behaviour of mid-rise RC buildings, with reduced damage at higher earthquake intensities. Fragility curves of existing mid-rise RC buildings, typical for the EU building stock, as well as a TRM-retrofitted building were then constructed, showing that the losses of a building with low seismic design level can be reduced to those of a modern, high-code structure. A broader study on combined energy and seismic retrofitting was then conducted across twenty European cities in five different seismic and four climatic zones, in order to assess the retrofit for all possible combinations of seismic hazard and climatic conditions. Typical masonry and RC buildings were defined in terms of their energy and structural characteristics and were associated with the building population of each city. By means of building energy modelling and seismic fragility assessments, the potential reductions in losses, after applying the iRESIST+ integrated retrofitting concept, for each building type were modelled. The results were extended to the entire building stock of the case study cities to assess different renovation scenarios. In the case of non-action, i.e. keeping the current annual renovation rate of around 1%, the ambitious targets of the EU Green Deal in terms of energy use reductions cannot be achieved. Instead, if renovation rates are tripled to 3%, the energy use for heating and cooling may be reduced by up to 32.5%. This would lead to reductions of around 30% in CO2 emissions across all cities by 2030 for the residential sector. In terms of seismic performance, the assessments of different building typologies showed high seismic loss reductions particularly for older and mid-rise structures in moderate to high seismic hazard zones. A combined monetary metric based on expected annual losses was established considering energy costs and costs related to structural damage. It was found that combined retrofitting can reduce investment payback periods substantially in moderate to high seismicity regions. Overall, this report highlights the potential of combined retrofitting with TRM and thermal insulation for the EU building stock. The proposed retrofit is cost-effective and lends itself to large-scale applications due to its easy application and reduced building down-time compared to traditional retrofitting. Finally, the validity of the proposed approach will be evaluated experimentally on the iRESIST+ prototype structure at the European Commission´s Joint Research Centre (JRC) ELSA laboratory in Ispra.
... Even though there was significant improvement in energy performance by using aerogel panel windows, the payback period was estimated to be 138 years. This high payback period was attributed to the high cost of aerogel glazing, and hence it was suggested that this option was not economically viable for the building without special subsidies (Berardi, 2017(Berardi, , 2018. However, it was concluded that, these results might vary for different buildings in different locations. ...
Nanotechnology has proved to be a promising candidate to improve the energy performance of buildings. Nano aerogel has been widely explored in the recent past, and its viability in buildings remains an ongoing research challenge. This chapter presents an overview of advanced glazing technologies, aerogel and its properties, and various aspects of aerogel windows and glazing units including: application in buildings, research progress, commercial status, case-studies and challenges ahead.
... Mineral aggregates allow good thermal properties to be obtained, but it is necessary to improve plaster with nanomaterials, such as aerogels, to achieve a better thermal insulation level. The thermal conductivity obtained using this LWA was very low (about 0.027 W/mK [17][18][19] ), this thermal plaster did not show any significant thermal performance variation when exposed to an aging process, and only a high humidity level was found to affect the λvalue, albeit only slightly [20,21] . However, the final product is not always economically viable [22] as a result of the high production cost of aerogel. ...
In the last few years, thermal insulating plasters have started to be an attractive solution for the insulation of already existing wall structures, especially old masonry ones, where refurbishment interventions can involve the replacement of damaged plasters. Intensive research efforts are being made to reduce the thermal conductivity and the environmental impact of these materials by optimizing their mixtures (combination of lightweight aggregates, binders and additives). In the present study, the hygrothermal performance and environmental impact of the different perlite-based plasters that are currently being developed have been investigated. A series of analyses has been carried out, at a material scale, by means of heat flow meter apparatus, to determine the relationship between the perlite content and the thermal properties. Moreover, the effect of the moisture content on λ has been analyzed, and the embodied energy and embodied carbon of the four mixtures have been assessed using both the cradle-to-gate and the cradle-to-site approaches. Furthermore, in-situ measurements have been conducted at a demonstration site, at a component scale, and a series of heat and moisture transfer simulations has been carried out to evaluate the actual thermal behaviour of the plaster under real operating conditions. The thermal conductivity values of the four plaster mixtures ranged from between 0.118 W/mK and 0.059 W/mK, thus demonstrating that the perlite concentration had a significant impact on the reduction of thermal conductivity and that the embodied energy of the applied material (5 cm thickness) decreased as the perlite content increased. Moreover, the results of the measurements on the demonstration building and the hygrothermal simulations have revealed that the thermal insulating plaster is able to reduce the U-value of the wall. However, an increase of 26–30% of the actual thermal conductivity should be considered when the material is exposed to real operating conditions.
... Several studies [46e48] have been conducted to examine the use of insulating materials for the thermal upgrade of existing vernacular and historic buildings to meet present-day standards. Innovative solutions, such as the use of vegetation on walls [50], aerogels [51], PCMs [52] and vacuum insulation panels [53] have also been proposed. ...
This paper presents a comparative study on the thermal performance and embodied energy of traditional and contemporary walling systems. Three types of building elements were examined: vernacular adobe load-bearing walls, and contemporary thermally insulated infill walls composed of either fired clay bricks or drywall panels. Their behaviour under thermal loads was investigated by means of heat flux analysis using 3D Finite Element (FE) models. The embodied energy was estimated using data from the literature. In addition, alternative refurbishment solutions for improving the thermal performance of each system were examined. According to the outcomes obtained, contemporary masonry systems have lower thermal transmittance compared to traditional constructions. However, adobe walls are capable of providing thermal comfort by efficiently controlling temperature fluctuations, mainly due to their higher thermal mass. The results also highlight the low embodied energy of traditional earthen structures; this is attributed to the simple production and construction processes adopted, as well as to the exclusive use of local raw materials. Most of the refurbishment solutions hereby considered result to a significant upgrade of the systems’ original thermal performance.
Modern technologies are more than ever adopting intelligent designs that respond to environmental variants to produce more desirable outcomes. In the building and housing industries, intelligent designs aim to conserve energy through temperature controls and energy storage and distribution systems. In this context, an intelligent Aerogel insulation system is modelled and studied for the exterior building walls. Aerogel with a thermal conductivity of about 0.012 W/m-K has a superior insulating property, and an intelligent design built around it would introduce additional energy storage and delivery enhancements to the system. In this study, a test room and a control room in an open urban environment were built, and the intended intelligence, first considered by choosing Aerogel that has the potential to be engineered with smart properties according to researchers in composite material science, and second was considered by automation which was applied manually to the test room. The calculated thermal conductivity of an external wall with intelligent Aerogel insulation is -(1.83 ± 0.06) × 10 ⁻¹ W/m. The negative sign is an attribute of a system function rather than of a material. The external wall with intelligent Aerogel insulation, in comparison to an identical non-insulated wall, exhibited 2.7 times better energy conservation.
In nature, many fibers with warmth‐retention properties, such as the hair of polar bears and rabbits, both have a hollow cross‐section structure. The static air in fiber cavities can effectively inhibit heat conduction and serve as an effective thermal insulator. In this work, the high‐performance heterocyclic para‐aramid polymer was selected as the spinning solution, and aerogel hollow fiber was prepared by coaxial wet spinning and freeze‐drying techniques. The effects of spinning solution concentration and lyophilized solvent on the micromorphology, mechanical properties, and specific surface area of heterocyclic para‐aramid aerogel hollow fiber (HPAAHF) were systematically studied. The produced HPAAHF possessed excellent mechanical properties (tensible strength ~3.85 MPa), high specific surface area (~ 260.90 m² g⁻¹), and lightweight advantages. The thermal conductivity of HPAAHF was only 0.0278 W m⁻¹ K⁻¹, indicating its excellent thermal insulation properties. The aerogel fabric exhibited outstanding flame retardancy properties, with a total heat release of only 0.7 MJ m⁻² in the cone calorimetric experiment, making it a self‐extinguishing fabric. In addition, phase change material was injected into the hollow structure to obtain aerogel‐phase change material composite fibers, which exhibited great energy storage prospects. As a result, the high‐performance heterocyclic para‐aramid polymer‐based aerogel hollow fiber was successfully prepared and had multifunctional applications in thermal insulation, flame retardancy, and heat energy storage fields.
In this work, the results of investigations of polyurethane materials were presented. Innovative materials based on polyurethane-polyisocyanurate (PUR/PIR) foam were obtained. Different types of additives (flame retardants, aerogels – additives that decrease thermal conductivity) are used in the composition of PUR/PIR foam. Foams are a type of composite composed of two phases: continuous (polyurethane polymers) and dispersed (composed of gases). All samples have been tested for thermal parameters: thermal conductivity, specific heat, and thermal diffusivity. Then they have been compared with each other and with a reference sample (RS) without additives. Based on the research, it was shown that innovative insulation materials were characterized by thermal conductivity λ in the range of 0.0254–0.0294 W/(m · K). The thermal properties of foams depending on the type and chemical composition of the material. Depending on the used substrates, their molar ratio, type, synthesis conditions, modifying agents and catalysts, a different polyurethane material is obtained.
Aerogels are three-dimensional nanostructures of non-fluid colloids connected to porous networks made of loosely packed bonded particles. They are often manufactured utilizing the sol-gel technique following a drying procedure like supercritical, freeze, or ambient pressure drying. It is the lightest solid material and has several unique qualities, including excellent insulation. Intrinsic brittleness and porous nature make their processing and handling complex, which restrict applicability in several real-world dynamic situations. An effective strategy to strengthen the silica aerogel structure is manufacturing composites with an incorporated fibrous material, which expands their uses considerably. This study covers the scientific synthesis, characterization, and applications of silica aerogel. It encourages silica aerogel composites/blankets that are strengthened by additives and fibrous material made from a wide variety of fibers and fabrics, as well as their manufacturing processes and properties. The effect of fibrous material (fiber and fabric) embedment on the final properties of composites has been extensively discussed, considering the amount of loading in the matrix and their unique characteristics, such as density, shrinkage, mechanical, thermal, and acoustic properties. Fiber-reinforced silica aerogel composites’/blankets applications are briefly discussed, indicating advancements in aerogel functions such as thermal sensors, acoustic insulators, and technical textiles such as protective clothing, medical textiles, and insulation blankets.
Silica aerogels are thermal superinsulation materials that have found increasing application in the building sector in the last ten to fifteen years. While the most common material types are opaque insulating blankets and renders, in its monolithic form silica aerogel can be almost transparent, allowing for composite translucent insulating building system.
Here, we developed and characterized a novel modular, translucent and thermally insulating building component based on silica aerogel granules, the aerogel glass brick. Both thermal and mechanical properties were tested and the former were compared to a 3D simulation of the heat transfer through the brick. A cost analysis was given and suitable applications were described.
The glass brick had a measured thermal conductivity of 53 mW/(m·K), corresponding well to the simulation results of 51 mW/(m·K), and a compressive strength of almost 45 MPa.
This makes the presented glass brick the insulating brick with the highest insulation performance reported in literature or available on the market while adding the feature of light transmission. The glass brick provides architecture with new design opportunities while increasing daylight inside buildings.
The world of today is experiencing an ever-increasing interest and focus on material scarcity and abundancy, energy efficiency and renewable and non-polluting energy harvesting. The main driving force of this increasing focus is global warming and climate changes due to emission of greenhouse gases to the atmosphere through various man-made processes. In this regard, the building sector represents one of the major sectors with a large potential for improvements, both for renovation of existing buildings and construction of new ones. Buildings which are thermally well insulated will have less energy demand for heating and cooling, i.e. energy-efficient buildings. Thus, there is a quest to invent and make thermal insulation materials with a low thermal conductivity and other suitable properties, to avoid undesirable thick building envelopes as would have been the case when applying traditional thermal insulation materials in situations where a large thermal resistance is required. This has led to an increased interest for today's state-of-the-art thermal insulation materials with low thermal conductivities, where especially commercial vacuum insulation panel (VIP) and aerogel products have experienced increased use during the last decades. However, VIPs and aerogels have several disadvantages, among them high costs for both VIPs and aerogels, and the loss of vacuum, either by perforations or long-term diffusion One of the promising candidates for becoming the high-performance or super insulation material (SIM) of tomorrow is nano insulation materials (NIM). The utilization of the Knudsen effect in order to reach very low thermal conductivities represents the governing principle of NIMs. Wanting the SIM and NIM to be functioning with air at atmospheric pressure in their pores, the size of the pores should be made very small in the nano range well below 100 nm according to calculations exploiting the Knudsen effect. NIMs may be manufactured in several ways, and herein a few possible pathways will be discussed. A special focus will be given on the experimental synthesis and investigations of hollow silica nanospheres (HSNS) by applying a sacrificial template method, where the inner nanosphere diameter and the shell thickness can be controlled through the parameters of the syntheses. Thus, the HSNS may be tailor-made with the desired low thermal conductivity.
In this chapter, the methods of synthesis of polyetherols with incorporated azacyclic rings are described. The polyetherols obtained by hydroxyalkylation of isocyanuric, uric, and barbituric acids, adenine, and melamine with oxiranes, formaldehyde, and alkylene carbonates are characterized. These hydroxyalkylated azacycles are shown as substrates to obtain rigid polyurethane foams of enhanced thermal resistance. Also, the current state of molecular modification of foam compositions in order to decrease the flammability of foams is described. The decrease of flammability can be achieved by azacycle-derived polyetherol modification with boron and silicon, as well as by addition of flame retardants. Additionally, it has been shown that natural polymers; starch and cellulose can be successfully hydroxyalkylated with glycidol and alkylene carbonates. The polyetherols obtained from cellulose and starch can be applied to obtain highly thermally resistant, biodegradable polyurethane foams, which are the milestones in green chemistry of polymers.
This work develops a systematic uncertainty quantification framework to assess the reliability of prediction delivered by physics-based material models in the presence of incomplete measurement data and modeling error. The framework consists of global sensitivity analysis, Bayesian inference, and forward propagation of uncertainty through the computational model. The implementation of this framework on a new multiphase model of novel porous silica aerogel materials is demonstrated to predict the thermomechanical performances of a building envelope insulation component. The uncertainty analyses rely on sampling methods, including Markov-chain Monte Carlo and a mixed finite element solution of the multiphase model. Notable features of this work are investigating a new noise model within the Bayesian inversion to prevent biased estimations and characterizing various sources of uncertainty, such as measurements variabilities, model inadequacy in capturing microstructural randomness, and modeling errors incurred by the theoretical model and numerical solutions.
The term aerogel is used for unique solid-state structures composed of three-dimensional (3D) interconnected networks filled with a huge amount of air. These air-filled pores enhance the physicochemical properties and the structural characteristics in macroscale as well as integrate typical characteristics of aerogels, e.g., low density, high porosity and some specific properties of their constituents. These characteristics equip aerogels for highly sensitive and highly selective sensing and energy materials, e.g., biosensors, gas sensors, pressure and strain sensors, supercapacitors, catalysts and ion batteries, etc. In recent years, considerable research efforts are devoted towards the applications of aerogels and promising results have been achieved and reported. In this thematic issue, ground-breaking and recent advances in the field of biomedical, energy and sensing are presented and discussed in detail. In addition, some other perspectives and recent challenges for the synthesis of high performance and low-cost aerogels and their applications are also summarized.
Silica aerogels hold remarkable properties, particularly their translucence/transparency and extremely low thermal conductivity and density, for buildings thermal insulation purpose. Incorporated in composites or framing systems, they reduce the overall weight of the building envelope while increasing its thermal resistance, being especially valuable for energy-efficient retrofitting solutions, spanning from covering façades to window panes. This review presents the production process of silica aerogels in brief, their relevant properties regarding building’s needs, and a full survey of last years’ scientific achievements on silica aerogel-containing materials for buildings, such as panels, blankets, cement, mortars, concrete, glazing systems, solar collector covers, among others.
The construction sector consumes large amounts of energy during the lifetime of a building. This consumption starts with manufacturing and transferring building materials to the sites and demolishing this building after a long time of occupying it. The topic of energy conservation and finding the solution inside the building spaces become an important and urgent necessity. It is known that the roof is exposed to a high amount of thermal loads compared to other elements in a building envelope, so this needs some solutions and treatments to control the flow of the heat through them. These solutions and treatments may be achieved by using nanomaterials. Recently, nanomaterials have high properties, so that this made them good elements to the strategy of energy conservation in the architectural field. Accordingly, the research problem lay in "the lack of studies that deal with strategies to use nanomaterials in the roof of the building (especially the administrative building) in order to achieve energy conservation within its spaces". Then the research aims to: "Determine the efficient of nanomaterials in the roof to improving the thermal performance and achieving energy conservation in the indoor environment of the buildings in Iraq". This research's theoretical aspect has focused on using nanomaterial and their applications in roof systems. While in the experimental aspect, an administrative application to test a mass of identical administrates building in the design. In this research, simulation of the standard roof with nanomaterial, cool roof, and standard roof systems has been done using the Ecotect program. The results obtained in this research showed that the nanomaterial affected the thermal performance and achieved the indoor environment's quality by reducing to energy-consuming in the administrative building in the hot-dry climate of Iraq.
Aerogel are synthetic light weight material obtained in a gel form with gas without any shrinkage. The first form of aerogel is produced by using Silica gels. There are several other types of aerogels such as carbon-Based aerogel, clay-Based aerogel and silica-Based aerogel. Aerogel are mostly in solid form with extremely low conductivity and possess very low density and high porosity (<100nm). Aerogel are water repellent material. In recent years, Aerogel have attracted towards various sectors, including building construction based on their promising properties and surprising applications in wide range of technical spaces. Aerogel based materials are prepared for its high-performance thermal insulation applications in building sectors. Despite, it also used in manufacture of chemical products, Electronics, thermal and acoustic insulations, energy absorbers, space suits and in building systems. This paper reviews the properties, formation and applications of aerogel in various sectors and its abundant utilization in building construction.
Current massive wall-building materials can be characterized by having either low thermal conductivities and thus low bulk densities and low compression strength or high compressions strength, high bulk densities and high thermal conductivities. In this paper, the first results of a research project are presented, in which a new aerogel-based construction material is developed that exhibits extra ordinary heat-insulating and load-carrying properties. By embedding silica aerogel granules in a high strength cement matrix “High Performance Aerogel Concrete” is developed, which combines the benefits of conventional concrete (compressive strength, unlimited moldability) with the properties of a heat insulating material. So far, various mixtures were examined in terms of their compressive strength and thermal conductivity. The first results are very promising with compressive strength between 3.0 MPa and 23.6 MPa and thermal conductivities between 0.16 W/(mK) and 0.37 W/(mK).
In recent years, silica aerogels have attracted increasingly more attention due to their extraordinary properties and their existing and potential applications in wide variety technological areas. Silica aerogel is a nanostructured material with high specific surface area, high porosity, low density, low dielectric constant and excellent heat insulation properties. Many research works have been carried out concerning aerogel production and characterization. In this review paper, research work and developments in synthesis, properties and characterization of silica aerogels will be addressed. Particular attention is paid to drying which is a critical step in aerogel synthesis and makes the production of this material more economical and commercial.
Since aerogel-enhanced materials provide significantly higher thermal resistance than conventional materials, they have received increasing attention over the past few years. In this study, a variety of aerogel-enhanced materials including aerogel-enhanced plasters, blankets, and boards, with different percentages of aerogel were prepared and investigated. The consistency of the thermal properties under a wide range of temperatures and humidity conditions was studied. In particular, the temperature and moisture-driven changes of the thermal conductivity of the samples were quantified. In addition, to characterize the permeability and hydrophobicity behaviour of the samples, water sorption curves, moisture storage capacity, and the vapour permeability were studied. The test conditions swung temperature ranges from −20 • C to +60 • C and moisture content ranges from 0% to 95% in Relative Humidity (RH). The results show that the aerogel-enhanced insulating materials have remarkably low thermal conductivity under different hygric conditions. This study shows that compared to the standard testing condition, the maximum increase in the thermal conductivity was 100% under 95% RH, while the greatest temperature-driven increase in the thermal conductivity was 12% at the maximum tested temperature. Both these effects were recorded in the aerogel gypsum board samples. The humidity-driven changes in the thermal conductivity of aerogel-based products are significantly greater than temperature-driven changes. The thermal resistance of the investigated materials decreased under extreme humidity condition, therefore, drying mechanism or providing a protection layer must be considered to prevent moisture accumulation and performance attenuation.
Aerogel-enhanced insulations provide significantly higher thermal resistance than typical building insulating materials; thereby their application in the building sector seems very promising. However, their performance under various environmental conditions should be properly addressed and significant amount of R&D activities are still required to investigate the long-term performance of aerogel-enhanced insulation products. This study focuses on the accelerated aging of several aerogel-enhanced materials using several laboratory-controlled conditions. The long-term impact of several environmental factors (such as elevated temperature, freezing and thawing cycles and high humidity levels) on thermal performance of aerogel-enhanced insulation materials is analysed.
Aerogel was one of the most promising nano-materials for use in buildings and its thermal performance was widely discussed in the literature while an accurate study of acoustic properties was never provided. The aim of the paper is to investigate experimentally the influence of granules size on both thermal and acoustic properties of granular aerogels and aerogel-based solutions (a plaster and a translucent polycarbonate panel) for energy saving in buildings. Several kinds of aerogels were investigated, ranging from small granules (0.01–1.2 mm) to large granules (1–4 mm). For each kind of aerogel, the absorption coefficient (α) and Transmission Loss (TL) were measured at normal incidence in a traditional impedance tube, taking into account 5 thicknesses (15, 20, 25, 30 e 40 mm) and thermal conductivity (λ) was evaluated by the Heat Flux Meter, setting up an appropriate methodology because of the sample nature. The aerogel granules outperformed the conventional insulating materials: depending on the particle sizes, λ varies in 19–23 × 10^(-3) W/(mK) range at 10 °C. The smallest granules (highest density) had the best performance, both in terms of thermal and acoustic insulation: α-values and TL better than the ones of rock wool were achieved (α = 0.95 and TL = 15 dB at about 1700 Hz). The good acoustic behavior was confirmed also considering the two aerogel-based solutions for buildings: the peak of the absorption coefficient of the aerogel-based plaster was 0.29 at about 1050 Hz, compared to a value of about 0.1 of conventional plasters; simultaneously, λ diminished from 0.7 W/mK to 0.05 W/mK.
Retrofitting of buildings defined as cultural heritage with respect to energy consumption and thermal comfort of the occupants is a demanding endeavor due to the additional requirements of the conservation aspect. Within a pilot project an inhabited mill in Sissach/Switzerland whose first mention dates back to the 14th century has been retrofitted by using a highly insulating external rendering containing SiO2 aerogel and mainly mineral admixtures namely hydraulic lime, calcium hydroxide, white cement, aerogel granules, light mineral aggregate, water retaining agent, air-entraining agent, except the organic hydrophobic agent. By a rendering thickness of 5–6 cm, the thermal transmittance through the walls was reduced to one third of its original value and the thermal comfort in the 6 apartments improved substantially including a reduction in mold growth risk. The characteristics of the aerogel based rendering have been discussed especially with respect to preservation aspects. By installing temperature and moisture sensors on the original wall and beneath the insulating rendering it was shown that its application on the original walls fulfils the requirement for avoiding moisture accumulation. Further, hygro-thermic simulations were performed extrapolating temperature evolution and water content for a period of 5 years. The object represents a new paradigm in the energy efficient restoration of the built heritage and simultaneously respecting the conservation aspects. The project has been carefully monitored by the state office (Basel-Landschaft) for preservation of monuments.
In the UK, 20% of houses were built before 1919 and are protected from energy efficiency requirements that would unacceptably alter their character. To meet carbon emission reduction targets, however, it is necessary to keep the number of buildings exempt from energy efficiency improvements to a minimum. The need to preserve the aesthetic and structural qualities of historic buildings makes energy retrofit complicated and costly but these arguments should not be used to resist change. The research presented in this paper investigates how conservation professionals in the UK approach and sanction energy retrofit measures in historic buildings. It provides an overview of the current UK legislation and guidance relating to energy efficiency in heritage buildings and presents findings from a study focused on the approach of conservation professionals to retrofit slim profile double glazing (SPDG). It finds that there is regional variation to energy retrofit in historic buildings between Scotland and the rest of the UK, and that individual conservation professionals hold different views on the use of SPDG, which leads to inconsistencies in its application. Recommendations are made for a more consistent approach to window upgrade as a means of improving the energy efficiency and comfort of historic buildings and for greater interdisciplinary cooperation to align conservation of energy with conservation of heritage.
One of the major challenge facing the achievement of nZE standards in existing buildings is the economic issue: the evidence of monetary gains of energy savings facing high investment costs seems still rather limited to the investors’ eyes. In this context, LCC methods have gained much importance in recent years. However, they present a limitation due to the notable simplifications and hypothesis usually made for input parameters that may affect the results.
In order to overcome this limit, this work suggests a probabilistic LCC based on uncertainty and sensitivity analysis via Monte Carlo methods and illustrates it through a building case study under several retrofit scenarios sighting the target nZE. The methodology allows investigating the economic effectiveness of alternative measures, giving insight into possible ranges of the economic indicator related to a specific design option. The analysis is focused on a micro-economic dimension and based on the availability and reliability of inputs data and on their proper characterization with Probability Density Functions. Variance-based methods for sensitivity analysis are employed to establish the most influential parameters on output uncertainty. The paper demonstrates the potentials of a probabilistic LCC in providing a more realistic decision support about investments for energy efficient projects.
Nowadays to reduce the energy loss as well as to minimize the emission of the green house gases of buildings can be solved by thermal insulating. Silica aerogels have a promising potential in the building and construction sector as thermal insulation due to their excellent thermal conductivity. At the present time the applications of silica aerogel blankets are truly widespread. This study focuses on the moisture induced degradation of the thermal conductivity of the above mentioned insulation slabs. Experimental studies show that the thermal conductivity of the aerogel blankets can be increased significantly (approximately 20–40%) after wetting them. For this case different types of investigations were carried out to investigate the changes in the thermal conductivity derived by the moisture content. Firstly, in order to see the temperature sensitivity of the moisture up-taking, sorption isotherm curves were registered at 283, 293 and 303 K after 24 h after drying and wetting at 5 different relative humidities. Secondly, the decrease of the thermal conductivity was followed with a Holometrix type heat flow meter of individual aerogel slabs after wetting the dried samples for 0, 4, 8, 12, 16, 20 h at 293 K and 90% relative humidity in a Climacell type climatic chamber. Finally, the change in the thermal resistance of a brick based wall covered with 0.013 cm thick aerogel insulation was registered by calibrated chamber method in function of the quantity of sprayed water. From the measurement results calculations were executed to see the changes of the thermo-physical properties of the aerogel samples due to the water absorption. The novelties of the article can be found in the comparison of the measurements of the same values and properties carried out by different methods Moreover, the measurement results formed the basis of Building Energetic Simulations in order to show roughly the effect of the moisture.
The ability of a rapid supercritical extraction (RSCE) process implemented in an industrial hot press to produce silica aerogel monoliths (AMs) with properties suitable for use in fenestration products was investigated. The effects of hot-press processing parameters such as press force and heat-up and cool-down rates on the size (area) and quality (presence of cracks and optical flaws) of the AMs produced, and on the manufacturing cycle times required to produce them, were studied. AMs of 14 × 14 × 1.27 cm were produced in a 6.5 h RSCE process using a laboratory scale (267 kN) hot press. Evacuated window prototypes were prepared by packaging aerogels in the interspaces of a double-glazing system under vacuum. The aerogels were found to have high translucency (>80% transmittance) in the red portion of the visible spectrum. The double-glazing evacuated aerogel windows were found to have thermal resistivity of 1.21-1.55 K·m2/W.
Nowadays in many countries, the building sector is the largest energy consumer and one of the best ways to reduce energy demand of buildings is the reduction in heat losses through the envelope. In this scenario, insulating materials with aerogels have growing interest and new applications such as insulating aerogel-based renderings are in development. This chapter deals with the analysis of superinsulating applications for building envelope such as aerogel-incorporated concrete- and aerogel-based renders. After an overall analysis of the market trend for these innovative systems, the rendering compositions, the physics, thermal, acoustic, and hygrothermal properties of aerogel-based renders are discussed. In situ applications of the new developed render are analyzed and the potential of the investigated materials is highlighted, by considering experimental measurements in Sect. 2.4. Finally, a comparison with traditional solutions and the future trends are considered.
Energy Efficiency (EE) has become a common target for all buildings: the European Directive 2010/31 specifies that every new building must consume very little fossil energy (Nearly Zero Energy Building) by 2020; this deadline for public buildings is fixed by the end of 2018. However, modify the existing heritage is not easy. This is particularly true for historical public buildings belonging to the cultural heritage, because many energy solutions in the field of renovation are not compatible with historic constructions, which need to preserve authenticity and integrity. The paper discusses this critical issue by using a particular building in Italy: analysis, diagnosis and energy audits have been developed for the case study of the School of Engineering in Bologna, a representative building in the history of modern construction. Results of the microclimate monitoring campaign in different classrooms show how the lack of thermal control, together with poorly insulated envelopes' components, determine high energy consumption. Selected modifications with a minimum impact have been considered for the energy retrofit. Results show a potential energy saving up to 32%, demonstrating how energy saving in historical buildings may be achieved by means of limited and non-invasive interventions on physical and material processes.
A South-East oriented façade of a protected building of Politecnico di Milano has been retrofitted on its inner surface with respect to energy consumption and thermal comfort. Four prototype solutions including special perlite boards and aerogel composite materials have been used. The analysis envisaged both monitoring by means of temperature, moisture and heat flux sensors at demo scale, and Heat and Moisture Transfer modelling. The study has been carried out before and after retrofit. The present investigation is concerned with the comparison between simulation and measurements. A parametric analysis permitted both the validation of assumptions made for numerical simulations and the identification of the most affecting variables.
Although it is often stated that the energy consumption in buildings accounts for more than 30% of total global final energy use, only a few studies analyze updated data about the current building energy consumptions or focus on comparing different countries. Similarly, models that predict future trends in building energy demand often use contrasting algorithms which result in diverse forecasts. Scope of this paper is to present and discuss data taken from several studies about the building energy consumptions in US, EU, and BRIC (Brazil, Russia, India, and China) countries and to provide an updated inventory of useful figures. Comparisons among countries are used to show historical, actual, and future energy consumption trends. Data presented by the World Bank, the United Nations Environment Program, the Intergovernmental Panel on Climate Change, and the International Energy Agency are compared with national reports as well as with research studies. The variety of the approaches used in each of the previous sources was considered fundamental to allow a complete review. The paper shows that the total building energy consumptions in BRIC countries have already overcome those in developed countries, and the continuous increase in the building stock of the BRIC countries creates an urgency for promoting building energy efficiency policies in these countries. At the same time, the policies actually adopted in developed countries are insufficient to guarantee a significant reduction in their building energy consumption in the years to come. In the current scenario, at least a doubling of the global energy demand in buildings compared to today’s levels will occur by 2050. To avoid this forecast, cost-effective best practices and technologies as well as behavioral and lifestyle changes need to be diffused and accepted globally.
Thermal insulation of building envelope plays a key-role in energy saving: a growing interest is focused on new materials, such as the recycled and sustainable ones. Innovative mineral fiber insulating panels were developed and investigated as a strategy for building refurbishment. The thermal and acoustic properties were investigated in order to compare them to conventional solutions. The thermal conductivity was evaluated by means of a Heat Flow meter apparatus: it is in the 0.031−0.034 W/(m K) range, depending on the density. The acoustic absorption coefficient and the Transmission Loss values measured by means of Kundt’s Tube showed a very good acoustic behavior, when compared to conventional solutions with similar chemical composition, but worse mechanical resistance, such as rock wool panels. The low value of thermal conductivity (0.0312 W/(m K) for a density of 165 kg/m3), together with other characteristics such as acoustic insulation improvement, sustainability (very low presence of additives, such as resin), mechanical resistance, high resistance to fire, and finally easy application in buildings with very low thicknesses (9−27 mm) suggest this solution as a very useful one for building refurbishment, especially for historical buildings.
The built environment is a significant contributor to global greenhouse gas emissions. In many industrialised nations more than 40% of carbon emissions are the result of energy consumption by buildings. There is therefore significant potential through refurbishment of the existing building stock to significantly reduce energy consumption and the associated carbon dioxide emissions. This chapter evaluates the problem and provides best practice advice on refurbishment measures aimed at reducing a building's overall energy consumption. The chapter also includes case study examples and provides details on how refurbishment measures can be assessed through post-occupancy evaluation.
Many large institutions do not have a means to gauge electricity consumption for their campus building portfolios. The installation of utility meters is typically outside of the institution's budget. A multiple linear regression approach to estimating consumption for academic buildings is an ideal tool that balances performance and utility. Using 80 buildings from Ryerson University (Toronto) and the University of Toronto, significant building characteristics were identified that showed a strong linear relationship with electricity consumption. Four equations were created to represent the diversity in size of academic buildings on both campuses. Tested using cross-validation, the coefficient of variation of the RMSE for all models was 33%, with a range of error between 20% and 43%. The models were highly successful at predicting high-level electricity consumption at Ryerson University with an average error of 14.8% for five building clusters. Using metered data from each cluster, raw estimates for individual buildings were adjusted to improve accuracy.
Modeling and simulation of energy consumption in 86% of the Ryerson University (RU) campus buildings is presented. Energy simulation models were developed for 16 major Ryerson University buildings. Commercially available software was used for the prediction of energy use. All of the possible sources and uses of energy in the buildings were accounted for in the modeling and simulation. Simulation result showed that 26% of total energy was used by lighting, 19% of total energy used by plug load, and 4% of total energy was used by miscellaneous equipment. The remaining 51% of energy use was for heating, ventilation and air-conditioning (HVAC) systems. In addition, the Princeton scorekeeping method (PRISM), a widely used method in energy conservation studies, has been used to analyze the same RU buildings for comparison and verification.
The base case simulation result and the Princeton scorekeeping method result were compared with the Campus Planning actual use bills for electricity, steam and deep lake water cooling (DLWC) demand for the Ryerson campus. The simulation result underpredicted electricity use by 5.7% and steam consumption by 6.3%, while the Princeton scorekeeping method underpredicted electricity use by 2.7%, and overpredicted steam consumption by 6%.The average energy intensity was determined as 1.04 GJ/m2 (91,576 Btu/ft2) for the 86% of the total area of Ryerson campus. Sensitivity analysis was conducted by (1) adding a heat recovery system and (2) reducing
lighting schedule.As a result, the former analysis predicted an annual energy saving of 5.6% for cooling load and 76% for the heating load, while the latter analysis predicted an annual energy savings of 10% for cooling load and 21% for electricity demand, while the heating load increased by 14%.
Aerogels, due to their superior thermal insulating properties, are slowly and steadily finding application in the building industry. In this paper, first a review on the synthesis of aerogels is presented. Aerogel preparation involves expensive precursors, chemicals, and the need for supercritical drying, making the production relatively more expensive compared to the current conventional building insulations. Several approaches that may lead to potential reductions in aerogel prices are also discussed. Next, the theory behind the thermal transport in aerogels is described. The reduction in the thermal conductivity of the aerogel is attributed mainly to the presence of nanoscale pores and the low solid volume fraction. Finally, the potential cost-effectiveness of aerogels as thermal insulation for internal wall retrofit applications is evaluated. Costs for several scenarios are estimated where aerogel blankets with different target R-values were installed from the interior of the building on top of the gypsum board. Further, these estimates are compared with retrofit costs associated with the application of conventional building insulations on the interior surface of the wall to achieve similar thermal performances. For a target value of 0.7 m2·K/W(R-4 ·ft2-°F/Btu), the cost analysis shows that significant savings of∼35% can be achieved by installing aerogel compared to interior conventional insulation methods. For a target value of 1.41 m2 ·KJW (R-8 h ft2 ·°F/Btu), the aerogel method is determined to be cost-effective compared to the current price range of conventional insulation methods, except for the fiberglass method. In addition, for a target value 2.11 m 2·K/W (R-12 h·ff2·°F/Btu), it is found that the aerogel method is ∼18%-23% less expensive compared to the cases where the conventional insulation is applied on the exterior surface of the wall.
The building sector is one of the key consumers of energy in Europe; consequently, European Union has enacted several directives dealing, directly and indirectly, with energy efficiency in building aiming to reduce the buildings energy use. Those directives, while dealing with existing buildings, do not take care of the Architectural Heritage in a specific uniform way adopting the derogation regime: exceptions are available at the national level to exclude from their application buildings listed in the Architectural Heritage as historic buildings. Thus any country can adopt its own rules to include or exclude buildings from respecting the energy efficiency requirements for existing buildings. Consequently, up to now no general rules, codes and standards are available for energy retrofit of historical and architectural valuable buildings. On the other side, no international act, in the field Architectural Heritage conservation, deals with energy and energy retrofit. Furthermore, the European Union Treaty does not comprise the Cultural Heritage as matter of European legislation. Thus to cover this gap between historic/historical building and energy retrofit a lobbying action is needed, managed by the national Cultural Heritage authorities, which can steers EU policy in a more effective way towards energy retrofit of historic/historical buildings.
Latest European Union programs related to energy efficiency underline the need for retrofitting existing buildings, which are responsible for 40% of EU final energy consumption. Although new buildings can be constructed with high performance levels, the majority of the building stock, characterized by a low energy performance, still needs renovation. Thanks to its potential to deliver high energy and CO2 savings, green retrofitting of existing buildings can thus play a pivotal role in creating a sustainable future. In this context, interventions on buildings constructed before 1945 (commonly defined as “historic buildings”) mean a higher benefit/cost ratio, because, in many cases, green retrofitting can be linked to unavoidable refurbishment works and renovated buildings can take on an interesting market value. However, an important part of these historic buildings in Italy is composed of cultural heritage buildings; these buildings require a specific design approach, and green retrofitting is often not attractive from an economic point of view. The remarks reported in this work aim to stimulate a discussion on operational procedures, barriers and challenges that investors, professional figures and supervisory authorities can encounter when they are engaged in the green retrofitting of historic buildings belonging to Italian cultural heritage.
The paper proposes a method for reliable energy diagnoses, aimed at integrated design of energy refurbishment of existing buildings, with reference to historical architectures. The approach is structured according to three main phases: (a) the building performance assessment, by combining in situ monitoring and documental information; (b) the numerical studies by hourly energy simulations with a deepening about the calibration methodology; (c) the investigation of potential energy savings, environmental benefits and economical profitability of selected energy efficiency measures.
Interior insulation is often the only possible post-insulation technique to improve the thermal performance of single leaf masonry walls. As a result of potential damage patterns such as frost damage, interstitial condensation and mould growth however, there is often some reluctance to adopt this technique. To fully exploit the capacity for energy savings offered by interior insulation while avoiding hygrothermal failure, a reliable risk assessment is extremely important. This requires a probabilistic approach, since the uncertainty of all influencing parameters might result in widely varying results.
Among currently available window systems, aerogel granulate glazing systems are considered promising for achieving good thermal and visual comfort in buildings. In aerogel granulate glazing systems, it is important to evaluate how convection in the granular-filled cavity affects their thermal performance because double glazing systems, which have a similar structure, show variable thermal properties related to the convection effect. In this study, it is shown that the granular-filled cavity hardly influences the air permeance, and therefore, convection can occur in such cavities. Nevertheless, a mock-up of commercially available aerogel granulate window shows practically identical window U-values in hot box measurement with various tilt angles. In other words, convection in the granular cavity does not affect the thermal performance of aerogel granulate glazing systems. The center-of-glass U-values are 0.28 and 0.69 W/(m2 K) for aerogel thickness of 60 and 30 mm, respectively. The total window U-values (using a wood frame) are 0.69 and 0.84 W/(m2 K) for aerogel thickness of 60 and 30 mm, respectively. Furthermore, the granular aerogel in the cavity subsided by ∼3% of its total volume after the hot box measurement. The risks posed by this subsidence under actual conditions should be assessed in later research.
This study aimed to evaluate reaction conditions for deposition of SiO 2 nanoparticles on the surface of cellulose fibers and their influence on moisture adsorption of the hybrid organic–inorganic material formed. SiO 2 nanoparticle deposition was carried out with the sol–gel process testing four reaction times (2, 12, 18, and 24 h) and three contents of the tetraethyl-orthosilicate (TEOS) precursor (1.9, 4.2 and 8.4 g g −1 of cellulose fiber). Modification time and TEOS content directly influence the amount of Si deposited on the fiber surface, nanoparticle diameter distribution, thermal stability, and resistance to moisture adsorption. There is a tendency of slight increase of nanoparticle size and the amount of Si deposited with increasing reaction time. SiO 2 nanoparticles were bonded on the surface of the cellulose fibers and are able to improve thermal stability of the material, increasing onset degradation temperature. The moisture adsorption capacity of the modified cellulose fiber was reduced up to 50%.
This study aims at examining the energy behaviour of the buildings' multi-layer exterior wall structures. Most of the studies dealing with this issue have considered a continuous operation of the cooling/heating systems. Our objective here is to find the best wall structure and the number and position of insulation layers within exterior walls for continuous heating, intermittent heating, and no heating operation modes for some commonly used construction materials. Furthermore, among the different materials used, a recently patented insulating coating based on the (super)-insulating materials “Silica Aerogels” is being assessed. Results from a one-dimensional heat transfer numerical model in a multi-layer wall structure are compared to on-site measurements of an experimental set-up, having the new aerogel-based coating, under real weather conditions. The numerical model is then used to carry out all the simulations. Several assessment parameters are used: time lag, decrement factor, energy consumption, and thermal comfort index. Results show that for continuous and no heating cases, the best wall from maximum time lag and minimum decrement factor perspective is dividing the insulation layer into two and placing one at the middle of the wall and one at the exterior surface. For intermittently heated spaces, placing the insulation material as one layer at the interior wall surface is the most efficient from an energy consumption perspective. Also, when using the thermal comfort index for the no heating operation mode, the best performance is achieved when placing the insulation at the interior wall surface. For most of the cases studied, the aerogel-based insulating coating shows better performance than other insulating materials.
Monolithic silica aerogels are well known for their low thermal conductivity (approximately 15 mW/(m K)) (Aegerter et al. (Eds.), 2011. Aerogels Handbook, first ed., Springer-Verlag New York, LLC, New York, NY). Their low relative density (typically less than 5%) reduces conduction through the solid and their small pore size, typically less than one hundred nanometers, on the order of the mean free path of air, reduces conduction through air, as well as convection and radiation. As they are fragile and brittle, they are often used in a granular form in thermal insulation, with some increase in their thermal conductivity from the air between the granules. Here, we describe a technique for compacting a bed of granular silica aerogel that reduces the thermal conductivity from 24 mW/(m K) (when uncompacted) to 13 mW/(m K) (after compaction). We find that there is an optimum level of compaction to minimize the thermal conductivity: at higher levels of compaction, the contact area between the granules increases and the granules densify, increasing conduction through the solid.
Aerogel is a kind of synthetic porous material, in which the liquid component of the gel is replaced with a gas. Aerogel has specific acoustic properties and remarkably lower thermal conductivity (≈0.013 W/m K) than the other commercial insulating materials. It also has superior physical and chemical characteristics like the translucent structure. Therefore, it is considered as one of the most promising thermal insulating materials for building applications. Besides its applications in residential and industrial buildings, aerogel has a great deal of application areas such as spacecrafts, skyscrapers, automobiles, electronic devices, clothing etc. Although current cost of aerogel still remains higher compared to the conventional insulation materials, intensive efforts are made to reduce its manufacturing cost and hence enable it to become widespread all over the world. In this study, a comprehensive review on aerogel and its utilization in buildings are presented. Thermal insulation materials based on aerogel are illustrated with various applications. Economic analysis and future potential of aerogel are also considered in the study.
Monolithic silica aerogels provide exceptional thermal insulation but have low mechanical properties. For instance, their flexural strength is typically 0.03–0.08 MPa. Here, we report on the development of a truss-core sandwich panel filled with compacted aerogel granules, designed to provide both mechanical support and thermal insulation. Mechanical and thermal properties of the sandwich panel prototype were measured and compared with theoretical models available in the literature. The models give a good description of the properties of aerogel-filled truss-core sandwich panels.
This review is focused on describing the intimate link which exists between aerogels and thermal superinsulation. For long, this applied field has been considered as the most promising potential market for these nanomaterials. Today, there are several indicators suggesting that this old vision is likely to become reality in the near future. Based on recent developments in the field, we are confident that aerogels still offer the greatest potential for non-evacuated superinsulation systems and consequently must be considered as an amazing opportunity for sustainable development. The practical realization of such products however is time-consuming and a significant amount of R&D activities are still necessary to yield improved aerogel-based insulation products for mass markets.
This research identified the possibility of application as an insulation building material by mixing aerogels with the cement paste as well as their thermal performance. The aerogel is a very stable material against water because of their skeleton’s characteristics, so that re-treatment of aerogel had to be preceded before mixing with cement pastes. Chemical and physical stability caused by the re-treatment of aerogel in the cured cement were confirmed by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). Moreover, thermal conductivity of aerogel cement was 0.135 W/m K which is 75% of aerogel-free cement’s thermal conductivity, 0.533 W/m K.
Fenestration of today is continuously being developed into the fenestration of tomorrow, hence offering a steadily increase of daylight and solar energy utilization and control, and at the same time providing a necessary climate screen with a satisfactory thermal comfort. Within this work a state-of-the-art market review of the best performing fenestration products has been carried out, along with an overview of possible future research opportunities for the fenestration industry. The focus of the market review was low thermal transmittance (U-value). The lowest centre-of-glass Ug-values found was 0.28 and 0.30 W/m2 K, which was from a suspended coating glazing product and an aerogel glazing product, respectively. However, the majority of high performance products found were triple glazed. The lowest frame U-value was 0.61 W/m2 K. Vacuum glazing, smart windows, solar cell glazing, window frames, self-cleaning glazing, low-emissivity coatings and spacers were also reviewed, thus also representing possibilities for controlling and harvesting the solar radiation energy. Currently, vacuum glazing, new spacer materials and solutions, electrochromic windows and aerogel glazing seem to have the largest potential for improving the thermal performance and daylight and solar properties in fenestration products. Aerogel glazing has the lowest potential U-values, ∼0.1 W/m2 K, but requires further work to improve the visible transmittance. Electrochromic vaccum glazing and evacuated aerogel glazing are two vacuum-related solutions, which have a large potential. There may also be opportunities for completely new material innovations, which could revolutionize the fenestration industry.
A comparative assessment of internal versus external thermal insulation systems for energy efficient retrofitting of residential buildings is performed by means of detailed numerical simulations. A 99.6 m2 one-storey apartment located at a mid-level of a multi-storey building is utilized as a “benchmark” case; the external walls of the building are considered to be non-insulated, a typical condition for the majority of the existing Greek building stock, which has been constructed before 1980. The annual thermal and cooling energy requirements are estimated by performing simulations using the TRNSYS software; the effect of insulation layer location (external, internal), meteorological conditions (warm Mediterranean and temperate Oceanic climate regions) and “energy conscious” occupant behaviour (passive, active) is examined by means of a parametric study. Both external and internal thermal insulation configurations are found to significantly reduce the total energy requirements; on average, external insulation outperforms the internal insulation configuration by 8%. Meso-scale hygro-thermal simulations are also performed using the in-house developed HETRAN code. A significant risk for water vapour condensation emerges only in the case of internal insulation installed in the temperate Oceanic climate region. Internal insulation requires approximately 50% less investment cost than the external insulation, thus resulting in a lower payback period.
Retrofitting of existing buildings offers significant opportunities for reducing global energy consumption and greenhouse gas emissions. This is being considered as one of main approaches to achieving sustainability in the built environment at relatively low cost and high uptake rates. Although there are a wide range of retrofit technologies readily available, methods to identify the most cost-effective retrofit measures for particular projects is still a major technical challenge. This paper provides a systematic approach to proper selection and identification of the best retrofit options for existing buildings. The generic building retrofit problem and key issues that are involved in building retrofit investment decisions are presented. Major retrofit activities are also briefly discussed, such as energy auditing, building performance assessment, quantification of energy benefits, economic analysis, risk assessment, and measurement and verification (M&V) of energy savings, all of which are essential to the success of a building retrofit project. An overview of the research and development as well as application of the retrofit technologies in existing buildings is also provided. The aim of this work is to provide building researchers and practitioners with a better understanding of how to effectively conduct a building retrofit to promote energy conservation and sustainability.
A new kind of rendering based on silica aerogel granulates was developed showing a high performance namely a low thermal conductivity and a low vapour transmission resistance, a combination of characteristics unachieved by existing renderings. This insulation rendering has a clear advantage over insulation boards which need a plane subsurface, adjustment, gluing and even fastening by means of dowels. A thermal conductivity of around 25mW/(mK) and a water vapour transmission resistance of 4 has been achieved. Its applicability to walls both manually and by a plastering machine was proven and measures were taken to keep the thermal conductivity low for both methods. Its first market will be in retrofitting of old and historically sensitive buildings.
Innovative glazing systems with silica aerogel in interspace were investigated for energy saving in buildings.
Aerogel is a promising transparent insulating material, due to its low thermal conductivity (down to
0.010Wm�1 K�1), high solar factor, high daylight transmittance and remarkable lightweight. Four samples
were constructed with float and low-e glasses and granular or monolithic aerogel in interspace
(14 mm thickness). The main optical characteristics of the samples were measured, in order to estimate
the light transmittance sv, the solar factor g and the colour rendering index Ra, in compliance with EN
410/2011. Finally, the thermal transmittance was calculated. The monolithic aerogel glazings showed
the best performance with respect to granular systems, both for light transmittance (0.62 between
two 4 mm float glasses) and thermal insulation (0.6Wm�2 K�1). The solar factor was 0.74. Results
showed a very promising behaviour of aerogel windows when compared to the windows normally used
in Italy and in EU countries: monolithic aerogel between two 4 mm float glasses gave a 62% reduction in
heat losses, with a 17% reduction in light transmittance when compared to a double glazing with a low-e
layer; a high solar factor and colour rendering were also assured.