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Abstract

In this report, the moisture performance of a bedroom in a wooden apartment building is studied numerically using hourly weather data from 4 different cities (Helsinki, Finland, Saint Hubert, Belgium, Holzkirchen, Germany and Trapani, Italy). The bedroom is occupied for 9 hours by two adults during the night (22:00 to 7:00), the volume is 32.4 m3 and the wall surface area is 60 m2. With the basic input parameters (moisture production of 60g/h, ventilation rate of 0.5 ach and a permeable internal coating on the ceiling and walls) the moisture transfer between indoor air and the building structure is very active. With these parameters, the moisture transfer between indoor air and structures can significantly improve the indoor climate and air quality compared to the case where the internal coating is vapour tight. Moisture storage in wood based materials can reduce the peak humidity during the night and this moisture can then be removed by ventilation air during the following day. In general (at a ventilation rate of 0.5 ach), the indoor humidity is close to the outdoor humidity when the occupants enter the room (22:00) for all structures and materials. The increase in absolute humidity during the night is quite independent of the climate, but the amount of time when the indoor climate and air quality are unsatisfactory is very dependent on the climate. Passive methods of controlling the indoor climate are naturally more successful in moderate climates than in hot and humid climates, even though they provide benefits in all climates. With the basic input parameters, there are many materials that can realise an enhanced moisture performance. For example, either a hygroscopic wallboard or hygroscopic insulation can provide good performance. However, when there is a hygroscopic wallboard, the insulation behind the wallboard has little effect on the performance. Therefore, the indoor moisture level of a room with a hygroscopic wallboard is quite insensitive to the hygroscopicity of the insulation and the vapour resistance of the elements behind the wallboard. When there is hygroscopic insulation behind a non-hygroscopic and permeable wallboard (most wallboard materials have some hygroscopicity), the performance is only slightly worse than when there is a hygroscopic wallboard. These results are for the basic input parameters and the difference between different materials and solutions becomes more important when: the moisture production increases, the ventilation rate decreases, the active area decreases, the vapour resistance of the paint increases or during long term weather changes. With the basic parameters, the risk of mould growth is low, but the risk increases as the moisture production rate increases. The simulation results in this report demonstrate that thermal mass and solar shading are important for moderating indoor temperatures in northern and central European climates, but even a structure with a high thermal mass performs poorly in southern Europe when there is no heating or cooling. A room with a massive wooden floor and ceiling (200 mm) has a similar thermal performance as a room with a concrete floor and ceiling (200 mm). Also, moisture transfer can help cool the room when the outdoor temperature increases. The sensitivity of the ventilation rate is analysed and the results show that ventilation is very important for removing moisture, especially when an impermeable coating is applied. The increase in humidity during the night becomes greater as the ventilation rate decreases for all cases. With a permeable paint and a ventilation rate of 0.1 ach, the indoor air humidity increases on average by 7.4 g/h during the night, which is equivalent to the humidity increase when the ventilation rate is 0.9 ach and the paint is impermeable. Nevertheless, the amount of time that the indoor humidity exceed 60% RH during occupation, decreases as the ventilation rate decreases because the indoor temperature increases as the ventilation rate decreases. The thermal comfort and perceived indoor air quality at the end of occupation can be similar with 0.1 ach and a permeable paint as with 0.25 ach and an impermeable paint. As the moisture production increases, the fraction of the produced moisture that is stored in the wall increases very slightly. The moisture removed by the ventilation air, the moisture removed by the hygroscopic structure and moisture that remains in the indoor air are nearly linearly dependent on the rate of moisture production.

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... Single-family log houses and summer cabins are popular in Finland, where forests cover over 75 % of the country [33]. Log buildings, known for their sustainability, thermal mass and insulation properties, contribute to indoor moisture control due to wood's hygroscopic nature, which allows the material to absorb and release moisture effectively, regulating humidity levels [48]. ...
... Conversely, warmer temperatures above 26 • C combined with higher relative humidity can lead to sweating, lack of concentration, fatigue, cognitive difficulties, and depression [46,58]. The high thermal mass of log walls has been found to enhance indoor thermal conditions compared to lightweight walls, particularly in the climates of Finland and Belgium, where temperatures in log buildings were observed significantly less time in T > 26 • C and T < 18 • C [48]. ...
... ISO 13788 [10] and Finnish water-and moisture proofing guidelines of buildings [42] set thresholds for acceptable indoor moisture levels to prevent mould growth and structural damage. Log walls with naturally high thermal and moisture storage capacities have been shown to improve indoor relative humidity levels in Northern European climates by enhancing natural moisture exchange between the structure and the indoor environment [48]. ...
... Modeste Kameni et al., shows in his works that Building energy consumption increased by 14% between the 1970s and 2000s, and this demand is still growing if we look into 2033 [1]. Since in perpetual pursuit of thermal comfort, an objective aimed at its true value because knowing that it will bring him good health and better performance in the work, the man resorted to systems able to give him satisfaction [2]. Kemajou et al (2008), shows in his works that air conditioning, ventilation and air conditioning systems (HVAC) account for 50 to 70% of the electricity consumption of buildings [3] . ...
... Equation of the moisture flow inside the room The evaluation method is based on the application of the isothermal diffusion equation, giving the expression of mass flux density, in the absence of gravitational effects, during the transfer. 2 2 2 ...
... We observe that it is in this period in the city of Douala where we often see successive days of rain over several non-stop days. Temperature is easier to sense and quantify but relative humidity is delicate and can have significantly affect: thermal comfort, perception, occupant health, energy consumption and durability of building materials [2], [25]. The measurement of the dew point temperature shows us that if we neglect the treatment of wood materials, the structure will be affected, hence the choice of the heat treatment below the fiber saturation so that subject to the different variations, there is no water recovery by the envelop. ...
... Furthermore, for each of the three different ways of modelling the room volume, one may model the moisture interactions between the building envelope and the indoor following two different approaches. Either one derives numerically the coupled heat and mass transport equations within the building envelope (Kurnitski & Vuolle, 2000, Simonson et al., 2001, or one uses lumped models, where the building envelope is only considered as a moisture source and sink (Duforestel & Dalicieux, 1994), or yet simplified models (Plathner et al., 1998). ...
... Numerical simulations based on the simulation tool LATENITE were carried out by Simonson et al. (2001) to assess the indoor climate and indoor comfort offered by a wooden structure. The moisture performances of a 12 m 2 bedroom in a wood building were studied considering four different locations in Finland, Belgium, Germany and Italy. ...
... At high ventilation rate, the moisture buffering of the building materials does not play any significant role but with decreasing the ventilation rate, the amount of surface opened to moisture diffusion becomes an important parameter. Looking at different moisture loads, the results in Simonson et al. (2001) tells us that large surfaces of wood directly exposed to an indoor climate enables to withstand higher moisture loads, especially during the summer. Furthermore, it is shown that only a slight increase of the surface water vapour resistance of the building envelope decreases the Moisture Buffering Performances drastically. ...
... However, this field study was not sufficiently described to properly interpret the conclusions. Simonson et al. (2001) simulated a two-person bedroom with vapor-open walls in different climates. Labat and Woloszyn (2015) performed a detailed HAM simulation to study the differences of both vapor tight a vapor-open wall assembly and a relative humidity sensitive (RHS) ventilation system compared to a common constant ventilation rate system. ...
... When a hygroscopic interior lining and finishing are used, the interior RH is almost unaffected by the vapor permeability of the layer behind the interior lining, namely the vapor barrier. A vapor-open wall assembly with hygroscopic insulation and non-hygroscopic, but vapor-permeable interior lining preforms similarly to wall assemblies with a hygroscopic interior lining (Simonson et al., 2001(Simonson et al., , 2004. ...
Article
This paper aligns with the rising interest in improving indoor comfort and health of occupants by moisture buffering with hygroscopic materials and the use of bio-based materials with low embodied emissions. The study focuses on literature on light timber frame walls (LTFW) with bio-based insulation and hempcrete walls, both without a vapor barrier. The aim is to highlight the consequences of omitting the vapor barriers in such wall assemblies and to ensure their durability. This review examines two main questions. Firstly, is there a risk of mold growth in LTFW with bio-based insulation and no vapor barrier? Secondly, are there possible links between these building envelopes and the indoor climate and its potential effects on occupants? The findings show that the risk of mold growth in vapor-open walls depends on the external climate, user behavior and applied materials. It is influenced by several factors such as vapor pressure difference, water vapor resistance ratio, exterior finishing, presence of a ventilated cavity, and the hygroscopic properties of insulation materials. Vapor-open walls exhibit a higher risk of mold growth between insulation and exterior lining compared to walls with vapor barriers. Additionally, there is a lack of field studies that visually examine mold growth in vapor-open buildings. While simulations suggest that vapor-open buildings with hygroscopic insulation can buffer interior relative humidity fluctuations, supporting field studies are limited. Further research and field studies are needed to improve the understanding of vapor-open or permeable building and its implications on mold growth as well as on the indoor climate and effects on occupants.
... Moisture buffering is defined as the process where porous materials exchange moisture with surroundings under varied air humidity [18]. Simonson et al. [19,20] simulated the moisture performance of a bedroom in a wooden building in different climates. The results indicated that hygroscopic materials had a significant potential for improving thermal comfort and air quality. ...
... Note that this study aims to investigate the moisture buffering effect of the interior finishing layer, focusing on the influence of the factors directly related to the moisture transfer. Previous research has revealed that ventilation rate has an important influence on indoor humidity [19,74]. However, other factors are in the dominant position in cases with the fixed ventilation rate (e.g., offices with central air conditioning). ...
... Considering the four principal climate cycles, the layered porous geopolymers are designed to withstand the important variation in humidity as their internal microstructure, allowing quick absorption and desorption with the intrinsic chemistry of geopolymer that is known to be stable in water and at high temperatures. Most of the four climatic subdivisions have temperatures and humidity in the range of those described by Shirmohammadi et al.2021 as favorable for fungi development and wood degradation [23][24][25]. This led interconnected thin layers of geopolymers appear as an appropriate solution for the hygroscopic management of the indoor environment [26][27][28][29][30][31][32][33]. ...
... During the climatic periods of high relative humidity, high precipitation and relatively low temperatures, the layered porous hygroscopic materials are able to reduce indoor humidity, which, by the way, reduce the indoor enthalpy [24]. The reduction of the indoor air enthalpy decreases the energy required to cool the building and consequently, improves the indoor air quality. ...
Article
Full-text available
Soluble silica content and the concentration of hydrogen peroxide were used to achieve porous geopolymers with nano, meso and milliporosity. The use of rice husk ash as a partial replacement for metakaolin allows to maintain the SiO2/Al2O3 ratio between 1.93 and 2.71 and achieve layered bulks with the desired moisture buffering capacity. Stereo Optical Microscopy, Environmental Ecanning Electron Microscopy, Mercury Intrusion Porosimetry, and Microtomography were used with the aim of correlating the intrinsic characteristics of the porous network to the moisture buffering capacity. A detailed analysis of the results permitted to link the moisture buffering capacity to the SiO2/Al2O3 ratio and the gel pores/large pores ratio. The saturation regime of these layered porous systems was found between 20 and 27%, while the daily moisture buffering capacity varied from 0.37 to 4.82% considering cycles of desorption and absorption. It was revealed that specimens with a high volume of gel pores (nano and meso) and optimal aeration with millipores are ideal matrices for hygroscopic applications. The porous matrices were found promising for the design of building systems with passive thermal comfort.
... Local thermal comfort has been evaluated in terms of the parameter PD, Percentage of Dissatisfied Persons, through equation 1 obtained by Toftum et al. (1988) and Simonson et al. [15][16][17][18]. ...
... This method is based on a seasonal steady state energy balance on the building as a whole or on a particular building zone. The thermal inertia is introduced in terms of the utilisation factor that shows the part of energy gains (solar irradiation and others) that can be stored in building construction to be transmitted into the zone when needed, as we can see in equation 16. ...
Article
A Coruña, located in northwestern Spain, has a mild climate with a high relativehumidity as a consequence of winds. Public buildings, like Spanish school buildings,present the highest energy consumption in air conditioning during the winter season, butduring the spring the heating system is employed only if indoor conditions are belowcertain temperature and relative humidity values. Some energy saving methods could beemployed to reduce or, in some cases, replace the heating systems and, as a consequence,reduce energy consumption. Some of these methods are centred in adequate design andapplication of an HVAC system while others are focused on the study of heat and masstransfer through building envelopes. A clear example of these methods was shown whenpermeable coverings [1, 2] were employed to reduce relative humidity peaks in officebuildings, but there are other parameters, such as thermal inertia, that could help us tocompare indoor ambience with respect to energy savings. In this sense, actual software,such as HAM tools, could be employed to simulate indoor conditions and phenomena ofmaterial and energy transfer through building envelopes and their effect on indoorconditions. This chapter describes a study of methods to reduce the energy consumptionin different kinds of schools buildings by means real sampled data and HAM toolsimulations. Results showed that parameters such as thermal inertia could be influencedprincipally by solar heat gains, changing the buildings' time constant. Other parameterslike air changes per hour or permeable coverings present a clear enhancement of indoorambiences.
... Awareness of the influence of hygroscopic materials on reducing ventilation loads in buildings-and thus saving energy-is growing. The moisture-buffering capacity of hygroscopic materials, has been analyzed in several studies [1][2][3][4]. Recently, a new material property, the so-called 'moisture buffer value' (MBV), was developed [5] and describes the ability of building materials and systems of materials to exchange moisture with the indoor environment. ...
... The contribution of moisture buffer capacity of wooden surfaces on damping the relative humidity (RH) has been reported [e.g., 3,6]. Simonson et al. [1] showed that when the interior surfaces of a wooden apartment building were permeable, the maximum indoor RH was lower as compared to the impermeable case (impermeable paint). In addition, the RH dropped below 20 % for less time as compared to the impermeable case. ...
Article
Hygroscopic materials hold the potential to reduce ventilation loads in a building by damping the peak fluctuations of the indoor relative humidity. Of particular interest is the moisture buffer capacity of wooden surfaces. This paper investigates, the response of Norwegian spruce (Picea abies) samples to changes of indoor relative humidity as well as the corresponding latent heat release during moisture buffering. A climate chamber was used to subject samples to dynamic air humidity. Thermographic techniques and thermocouples were employed to measure surface temperature on the exposed surface of the spruce sample (permeable case), while a covered control sample was used as reference (impermeable case). The moisture uptake was logged synchronously by weighting cells. The results show that the surface temperature of spruce increased by 2.1 �C during moisture uptake, while only by 0.9 �C in the control sample. This finding has implications for direct energy savings when wooden surfaces are used indoors. In addition, thermography is evaluated as an appropriate measurement method for documenting latent heat release.
... It is foreseen that the building structures themselves could have much more to bring that only thermal, structural and aesthetical aspects. It is nowadays recognised that the adsorption and desorption of moisture from the building structure might play a significant role in the behaviour of the indoor moisture dynamics (Simonson et al., 2001) (Plathner & Woloszyn, 2002) (Rode et al., 2003). A concept trying to fix this phenomenon and known under the generic name of moisture buffer capacity has emerged in a recent workshop (Nordtest Workshop, 2003), but it is stressed that no consensus on a stringent definition has been reached yet. ...
... It has however been rediscovered recently since nowadays building design are in search of alternative solutions to high ventilation rates while maintaining healthy buildings. Numerical simulations with the implementation of moisture lumped models (Plathner & Woloszyn, 2002) or more sophisticated models with coupled heat air and moisture transport within the building envelopes (Simonson et al., 2001) (Rode et al., 2003) (Künzel et al., 2003) (Hameury, 2005), and where the specified boundary conditions are the only outdoor climate data, all have shown the positive effect of applying hygroscopic materials facing an indoor environment. It has been followed in parallel by experimental investigations in laboratory (Padfield, 1998) and full-scale environmental chamber (Rode et al., 2002) or even by a few in-situ measurement campaigns (Rode et al., 2003) (Hameury, 2004). ...
... This problem not yet solve although many efforts are made by the government. In literature, trough many recent experimental studies [3][4][5][6] and simulations taking into account climatic parameter of the studied sites [7][8], many authors proved that permeable materials improve the indoor ambiance perception and consequently allow to reduce the energy consumption. [9][10]. ...
... Partial steam pressure was calculated in accordance with Simonson et al [4] and presents an uncertainty of ± 0.07kpa. ...
Article
The most important objective of a building is to provide to its inhabitants a indoor comfortable climate in the respect of energizing efficiency. In last years , African electrical consumption in buildings is experiencing a marked increase, rising to values above design conditions. Consequently, power cuts occur in different periods. In this paper, we used a passive method to assess the energy consumed in various types of building in order to propose measures to reduce high energy consumption in some buildings in the Sub Saharan area. We observed that in 15 buildings studied during the two main seasons, new buildings resisted less to the outdoor climate pressure. The energy consumption was moderated in old buildings, particularly during resting hours. Marbles used in old buildings improve the indoor climate and reduced till 5.1% and 3.9% the indoor energy consumption respectively in the dry season and the rainy season. In fact, buildings with soil with marble covering can be an efficient solution to passively control of the indoor air and can allow reducing the energy
... As well as having low carbon emissions, wooden structure buildings can also provide a satisfactory indoor hygrothermal environment due to the high porosity and excellent moisture storage capacity of wood (Simonson et al., 2001;Hameury and Lundström, 2004;Li et al., 2012). Li et al. (2012) indicated that wooden materials can effectively adjust indoor humidity by decreasing the average indoor humidity and the amplitude of relative humidity. ...
Article
Light-framed timber structure (LTS) buildings have been highly valued in recent years due to their low-carbon characteristics. However, the applicability of the building envelope is closely related to indoor and outdoor conditions. The hot summer and cold winter (HSCW) climate zone in China has high humidity and great temperature variation throughout the year, resulting in distinct outdoor environments in different seasons. The indoor environment is greatly affected by energy-consumption patterns and window-opening habits, which largely depend upon the regulation operations of occupants. All these interrelated factors lead to extremely complex boundary conditions on each side of the building envelope. Whether the structures of LTS buildings are applicable in this climate zone, therefore, needs to be carefully considered. In this study, two LTS buildings with different envelopes were established in Haining, China, situated in the HSCW climate zone, and selected as the study objects. Different operation modes were adopted to create a variety of indoor environments. Under each condition, the processes of heat and moisture transfer within the building envelopes and the indoor environment were monitored and compared. The comparison indicated that the building envelope with high moisture storage and insulation ability maintained a relatively stable indoor environment, especially when the environment changed abruptly. Conversely, if the outdoor environment was equable (e.g., relative humidity within the range of 30%–60%) or intermittent energy consumption modes were adopted, the building envelope with a low thermal inertia index and weak moisture-buffering ability performed better because it enabled a faster response of the indoor environment to air conditioning. Moreover, a high risk of moisture accumulation between the thermal insulation layer and other materials with a large water vapour transfer resistance factor was also identified, suggesting a higher requirement for the vapour insulation of the envelopes of LTS buildings.
... The model took into consideration all the energy components of the moisture transfer process for adsorption, desorption, condensation, evaporation, freezing, and thawing. The conservation equations were solved simultaneously to predict the variable indoor conditions under different experimental data obtained in the field [64][65][66][67][68][69]. ...
Article
Full-text available
The hygrothermal transfer is very important for the design of a building envelope for thermal comfort, economic and energy analysis of the building envelope. The lack of reference materials on models of moisture and temperature behavior in the building, including wooden walls, is a challenge. This paper reviewed the hygrothermal transfer models for building walls. Energy and mass conservation equations with boundary and input conditions were presented in this paper for concrete, bricks, and wooden walls. The review showed the presence of mainly physical-based models, while there is a dearth of data-based models. The influence of the type of wall, orientation, thickness, the density of the material, and climatic variations on the temperature and moisture evolutions within the building materials influenced the model mechanisms. Future research gaps should include shrinkage influence on hygroscopic materials like wood due to their behavior under ambient conditions. Data-based models should be explored too.
... The model took into consideration all the energy components of the moisture transfer process for adsorption, desorption, condensation, evaporation, freezing and thawing. The conservation equations were solved simultaneously to predict the variable indoor conditions under different experimental data obtained in the field [66][67][68][69][70][71]. ...
Preprint
Full-text available
The hygrothermal transfer is very important for the design of a building envelope for thermal comfort and economic and energy analysis of the building envelope. The applications of various materials in building envelope have been studied extensively. The study presents several models for the hygrothermal transfer for various building walls. Several energy and mass conservation equations with different boundary conditions and input considerations were presented in this paper for concrete, bricks and wooden walls. The effect of hysteresis was ignored in developing most model equations, while few considered flow pattern of fluid through the wall surfaces. Due to the flexibility of Luikov models, it formed the basis for modelling the coupled heat and mass transfer for porous material independent of hygroscopic nature with different boundary conditions defined according to the geometry and orientations. The influence of type of wall, orientation, thickness, the density of the material and climatic variations on the temperature and moisture evolutions within the building materials was more pronounced. Literature, presenting imaging models using imagery software like COMSOL multi-physics, CFD etc. were scarce considering that microscopic imagery is now deployed to measure the heat and moisture evolution in materials. Future models should include shrinkage or expansion influence on the fibrous material like wood due to their behaviour under environmental condition. 1. Introduction All over the globe, structures such as housing, storage cabin for agricultural products (barns, concrete silos, mud rhombus etc.), animal houses etc. utilizes much energy for their life span. As the global population grows, more demand is placed on energy supply. Strains are imposed on both renewable and non-renewable energy resources. Therefore, energy efficiency within the building envelope has been advocated all over the world due to the large energy demand of the building and construction sector and the overall greenhouse gas emitted through the process to the environment [1]. Some researchers have estimated that building alone consumes about 36-40 % of global energy, generating close to 50 % of global greenhouse gas emission [1, 2]. However, in some countries, the IEA report has revealed that energy utilization in building alone consume over 70 % of the total available energy in those countries releasing a large amount of greenhouse gas into the environment [3]. Energy demands in a building can be categorized into energy utilization in the constructions phase and energy utilization in the operational phase [1]. Researchers
... • Humidity Control: when timber is used as interior building material or as exposed structural element, it creates a healthy indoor climate (Simonson et al., 2001) (Anttonen, 2015). The organic properties of timber add thermal benefits and helps to balance the humidity level inside a building reducing the problems with mould and allergies (Anttonen, 2015). ...
Thesis
Full-text available
Since the early 2000s, there has been a steady and heterogeneous proliferation throughout several western countries of multi-story timber-based buildings. This thesis confirms that since the first five-storey building was realised in 2004, at least 196 others were built until 2019. With many of these case-studies having been researched for the first time, the goal of this dissertation is to categorize the different international approaches and to define what are the drivers which had an effect on the design. Because the research topic is a recent development in academia, this thesis defines what multi-storey timber-based buildings actually are, and, after the discussion of existing literature, proceeds with the selection of the case-studies according to defined height and structural criteria. With the complete list of the buildings, the thesis first analyses the design characteristics of all case-studies, in order to research how these projects were built. The analysis includes thirty-two structural categories in which each case-study is classified and described. The analysis was able to show that there are many design differences between the countries involved. Some clusters of solutions can also be identified. The purpose of the second step was to understand by who and why these buildings have been built. In order to answer these questions, the thesis proceeds with each country's contextual analysis. Regulatory framework in place at the time of the project are described, but the focus is given on the stakeholders and R&D concepts involved in the realisation of the selected case-studies. Furthermore, the declared reasons for choosing a timber structure, along with the public and private typology of the commission were also researched. The contextual analysis shows, as the literature confirms, that the legal framework often sets the necessary rules for building multi-story timber-based buildings. However, the role played by the stakeholders is not secondary, and there are clear patterns of interdependence between many case-studies and the professionals involved in their construction. While private clients are often the actual drivers behind the majority of the cases, there are several countries in which the leading role is played by public initiatives. In some cases, the intrinsic properties of timber played a decisive role in the choice of the clients. This dissertation adds further valuable information regarding the constructive and contextual characteristics of multi-story timber-based buildings built over the last fifteen years, in order to show the differences and commonalities between each country involved. Multi-storey timber-based buildings are a complex phenomenon, which really depend on the nation in which they were built. At the same time, it was possible to identify international trends in their design, and major players which considerably influenced the design solutions and realisations of these buildings.
... Wood is also hygroscopic ) and cell wall moisture adsorption or desorption occurs until an equilibrium moisture content (EMC) is reached in response to variation in surrounding relative humidity (RH) and temperature. Sorption behavior influences wood dimensional stability and mechanical properties Gezici-Koç et al. 2016;Li et al. 2017;Samir et al. 2005), while it can help maintain comfortable RH inside buildings (Simonson et al. 2001). ...
Article
The objective of this work was to provide a rapid and nondestructive imaging method for evaluating the hygroscopic behavior of thermally modified lignocellulosic materials (softwood and hardwood). The difference in the hygroscopic behavior was explained by moisture content (MC) mapping results and molecular association characteristics of absorbed water (i.e. weakly, moderately, and strongly hydrogen-bonded water molecules) with wood at various relative humidities (RH). To achieve this goal, near-infrared (NIR) spectral images in the wavelength range 1816–2130 nm (covering the combination of stretching and deformation vibrations for OH) were used to visualize MC distributions over the surface of Japanese cedar and European beech samples which had been thermally treated at different temperatures. A curve fitting method was utilized to explore changes in water-wood structure characteristics based on shifts to longer wavelength in spectral signals caused by increasing MC. The curve fitting results support the recent nuclear magnetic resonance (NMR) studies that different bound water stabilities may pool in different compartments of the wood cell wall. Furthermore, water was firmly bound to wood at low RHs and H-bonds gained mobility as the number of absorbed molecules increased. It is concluded that NIR hyperspectral imaging also has the potential to be a complementary methodology for studying the transient changes of wood-water interactions before equilibrium.
... The optimum zone for RH against different types of house hold nuisances[48]. ...
Article
UK construction industry contributes 120 Mt of waste every year. Bio-based building materials may be a solution for this problem, as they combine re-use and recycling abilities together with hygroscopic characteristics, leading to buildings energy savings. For the first time, the dynamic response to hygrothermal changes of bio-based materials is examined in terms of Moisture Buffering Value (MBV), dry/wet thermal conductivity, microstructure, density and latent heat through daily cycles. It is shown that MBV is a useful tool for characterisation but needs to be combined with the shape of the change in mass of the final hygrothermal cycle. Mastering this is required to obtain significant improved indoor environment quality in buildings. Ten samples of bio-based insulation materials and one thermoplastic recycled polymer were analysed (wool, hemp, saw mill residue, wood, straw, cork and polyethylene terephthalate). Saw and wool are the most promising, as materials exhibit dynamic response to hygrothermal changes. Only half the amount of samples revealed equivalent efficient moisture transfer to be able to desorb the adsorbed quantity of water. Latent heat of vaporisation and condensation tests led to the conclusion that samples of wool and saw mill residue can qualify as bio-based materials for ‘green’ panels.
... Accessing wood's material complexity in a meaningful way requires a re-conceptualization of architectural design that moves away from a single focus of form definition and building performance, to a more bottom up approach of design formation. In the latter, material behavior is an intrinsic component of building performance, from embodied energy (Alcorn 1996), indoor moisture mediation (Simonson et al. 2001), fire resistance, structural performance, to form generation. ...
Chapter
This paper introduces a series of prototypes investigating a new architectural language in wood that is driven by a critical approach to recent technical developments in design, fabrication and material. Although wood is slowly being recognized as an advanced material for future construction due to its high performance and sustainable nature, its differentiated and unpredictable material characteristics have not only been progressively overlooked, but even been viewed as a negative attribute. Wood’s varied dimensional range has been addressed through standardization, its heterogeneous fiber structure ground and reconstituted into homogeneous composites, and finally its complex aesthetic quality has even been caricaturized into a skin-deep plastic-wood veneer texture. This paper seeks to extend research on the implications of advanced robotic fabrication and its integration into design processes that also integrate cross-disciplinary knowledge into architectural software. As innovation in technology enables architects and engineers to engage with the complexities of the material, the potential of wood is becoming accessible, leading to a new material language. Through a series of full scale, robotically fabricated design prototypes, the material performance of wood is investigated as a driver for form; its fabrication and hygroscopic performance as a driver for assembly, and more importantly, the entire design-to-fabrication-process as a method for investigation into innovation and the structural and architectural potential of future wood.
... The impact of hygroscopic materials depends on many factors: the amount and type of materials in a given room, the outdoor climate, the outdoor ventilation rate and the moisture production rate, which also depends on the indoor temperature and RH [7]. During warm and humid outdoor conditions, hygroscopic materials (wooden paneling, porous wood fiber board and cellulose insulation) may reduce the peak humidity in a bedroom by up to 35%, 30% and 20% RH when the ventilation rate is 0.1, 0.5 and 1 ach, respectively [8,9]. ...
Article
To investigate the influence of changes in relative humidity on panel moisture and resulting dimensional changes for the panel, experiments were conducted on two samples of plywood manufactured with two adhesive formulations loaded by two types of fillers, as a adhesive formulation is characterized in that it consists of a powder based on starch (AF-REF) and other consists of a mixture between the starch-based powder and the mint waste (AF-WM). By comparing the two samples tested, the plywood manufactured using adhesive formulation (AF-WM) has a low dimensional variation and a low dispersion of moisture relative to the plywood manufactured using adhesive formulation (AF-REF), however, the plywood panel manufactured from (AF-WM) showed better resistance to variation in relative humidity. On the other hand, the optical microscope was allowed to observe the vessels, woody rays, fibers and the glue line in plywood tested, the specimen taken in the transverse direction of the plywood shows that the vessels are clear on the exposed face, therefore the vessels are responsible for adsorption and desorption the moisture from different climatic environment which allows concluding that the dimensional variation and moisture dispersion in the transverse direction are higher relative to the longitudinal direction.
... Accessing wood's material complexity in a meaningful way requires a re-conceptualization of architectural design that moves away from a single focus of form definition and building performance, to a more bottom up approach of design formation. In the latter, material behavior is an intrinsic component of building performance, from embodied energy (Alcorn 1996), indoor moisture mediation (Simonson 2001), fire resistance, structural performance, to form generation. ...
Chapter
This paper introduces a series of prototypes investigating a new architectural language in wood that is driven by a critical approach to recent technical developments in design, fabrication and material. Although wood is slowly being recognized as an advanced material for future construction due to its high performance and sustainable nature, its differentiated and unpredictable material characteristics have not only been progressively overlooked, but even been viewed as a negative attribute. Wood’s varied dimensional range has been addressed through standardization, its heterogeneous fiber structure ground and reconstituted into homogeneous composites, and finally its complex aesthetic quality has even been caricaturized into a skin-deep plastic-wood veneer texture. This paper seeks to extend research on the implications of advanced robotic fabrication and its integration into design processes that also integrate cross-disciplinary knowledge into architectural software. As innovation in technology enables architects and engineers to engage with the complexities of the material, the potential of wood is becoming accessible, leading to a new material language. Through a series of full scale, robotically fabricated design prototypes, the material performance of wood is investigated as a driver for form; its fabrication and hygroscopic performance as a driver for assembly, and more importantly, the entire design-to-fabrication-process as a method for investigation into innovation and the structural and architectural potential of future wood.
... In many studies, the RH effect is considered to affect thermal comfort [47,64,65], perception of indoor air quality [66], health of the occupants [67] and energy consumption [68]. The RH effect has a big influence on the heat balance for the human body at high metabolic rates, in hot environments (high operative temperatures) and under transient conditions [69]. ...
Article
This paper reviews the most used thermal comfort models and indicators with their variants, discussing their usage in control problems referring to energy management in indoor applications. The first part addresses the recent literature referring to the thermal comfort concepts, models of human thermal comfort, thermal comfort models and indicators, thermal comfort standards, control systems, optimisation methods, and practical assessments. Then, the ambient and personal parameters used to represent thermal comfort and thermal sensation are recalled. The following part reviews the definitions and usage of a number of thermal comfort indices, mainly related to the Predicted Mean Vote (PMV), the Actual Mean Vote (AMV), and the Predicted Percentage Dissatisfied (PPD), with their modifications and variants, indicating a number of applications to different situations in indoor environments. The last part reviews the thermal comfort models used to define control strategies in indoor applications, discussing the characteristics and parameters of models based on artificial neural networks, autoregressive variants, fuzzy control, and hybrid models combining different approaches. The characteristics of these models and their usage to predict the indoor air temperature and the PMV index are discussed with reference to the identification of the several inputs used in relevant literature contributions.
... Despite this, from these same studies, it can be concluded that it is difficult to precisely quantify the phenomenon and the effect in terms of comfort for people and their health. Only in a few studies, like those of Gaur and Bansal [11] and Simonson et al. [12], have they tried to quantify this effect. They have concluded that indoor temperature is affected by moisture, and that the increase in relative humidity depends on the rate of air exchanges, outside air and moisture transfer between structures and indoor air. ...
Article
This paper presents the results of an experimental study that was conducted in 15 office buildings in the humid and cold tropics during the working hours of the dry and rainy seasons in Cameroon. This was with the aim to study the effects that local and imported materials had on indoor air quality. To achieve this objective, the adaptive model approach has been selected. In accordance with the conditions of this model, all workers were kept in natural ventilation and, in accordance with the general procedure, a questionnaire was distributed to them, while variables, like air temperature, wind speed, and relative humidity were sampled. The results showed a clear agreement between expected behaviour, in accordance with the characteristics of building construction, and its real indoor ambience once they were statistically analysed. On the other hand, old buildings showed a higher percentage of relative humidity and a lower degree of indoor air temperature. Despite this, local thermal comfort indices and questionnaires showed adequate indoor ambience in each group of buildings, except when marble was used for external tiling. The effect of marble as an external coating helps to improve indoor ambience during the dry season. This is due to more indoor air and relative humidity being accumulated. At the same time, these ambiences are degraded when relative humidity is higher. Finally, these results should be taken cognisance of by architects and building designers in order to improve indoor environment, and overcome thermal discomfort in the Saharan area.
... Local thermal comfort has been evaluated in terms of the parameter PD, Percentage of Dissatisfied Persons, through the equation 3 by Toftum et al (1988) and Simonson et al [7][8][9][10][11] An acceptable environment would be that in which less than 15% of the occupants are dissatisfied. ...
Article
This paper shows a research about improvement of indoor conditions controlling heat and mass transfer process. To do it, the first step was to sample real data in different kind of typical Spanish buildings like a set of flats, office buildings, museums and schools located in the area of A Coruña, Spain. Once obtained this data, it was analysed to determine indoor ambience problems and possible solutions related with heat and mass transfer process. In this sense, problems related with comfort conditions, energy saving, health, materials conservation and work risk were found and possible solutions like air renovation, thermal inertia, and moisture buffering were found.
... The increase in RH is about four times greater for the nonhygroscopic case than for the hygroscopic case, and the increase in W is about three times greater in the nonhygroscopic case than in hygroscopic case. Simonson et al. (2001b) also show that the increase in absolute humidity during occupation is nearly constant in three other climates (Helsinki, Finland; Holzkirchen, Germany; and Trapani, Italy), indicating that it is possible to represent the performance of the room with the initial humidity ratio (W o ), which varies throughout the year, and the change in humidity ratio (∆W occupation ),which is quite constant throughout the year. The increase in humidity ratio during occupation depends on the ventilation rate, as seen in Figure 7. ...
Article
This paper contains a numerical study of the indoor temperature, humidity, and comfort and indoor air quality conditions in a bedroom located in Saint Hubert, Belgium. The performance of the bedroom is presented for a range of constant outdoor ventilation rates (0.1 ach to 1 ach) with and without hygroscopic materials. The results show that the conditions in the bedroom improve significantly as the ventilation rate increases and when hygroscopic materials replace nonhygroscopic materials. In general, increasing the ventilation has a stronger impact on the average indoor conditions than applying hygroscopic materials, but the impacts of ventilation and hygroscopic materials can be similar during certain operating conditions. These results suggest that the ventilation rate could be decreased slightly in a room with hygroscopic materials without degrading the indoor humidity, comfort and air quality conditions. The possible decrease typically ranges from 20% to 50% depending on the variables and criteria chosen.
... ∑ 2.7 The humidity-related effects on health and indoor air quality (Simonson et al., 2001). reviewed journals, which publish high-quality scholarly articles of direct relevance to the topics discussed in this chapter. ...
Article
This chapter starts by introducing the subject of hygrothermal behaviour and some of the key scientific concepts underpinning this. This includes the transport and storage of both heat and moisture in porous construction materials and, more specifically, the hygrothermal behaviour of these materials including all relevant functional properties. The approach to numerically modelling this behaviour is explained, along with the key commercial packages currently in use. Detailed discussion of the hygrothermal behaviour of rammed earth materials is presented along with results from several recent and current research projects. Finally, the correlation between hygrothermal behaviour, the resultant quality of indoor air and thermal comfort are summarised. Details of further sources of information are presented for those wishing to explore some of the concepts discussed in this chapter in more detail.
... Although this topic had been approached earlier, several researchers have recently produced work on this area (Padfield 1998, Plathner & Woloszyn 2002 and demonstrated that the effect of moisture buffering by materials exists and is relevant for the inside relative humidity analysis. Others are still producing, taking previous work as a starting point (Simonson 2000, Mitamura et al. 2001, Simonson et al. 2001, Ojanen & Salonvaara 2003, Peukhuri 2003, Rode et al. 2003, Ramos & Freitas 2004, and grouped with other researchers in the research project IEA Annex 41: whole building heat, air and moisture. ...
Article
The hygroscopic behavior of the walls and ceiling finishing materials, as well as furniture and textiles inside the dwellings, defines their hygroscopic inertia, which can be an essential parameter for the control of surface condensation. We believe that there should be a way of predicting the level of expected hygroscopic inertia of a room based on the description of its inside finishing materials. It should be a simple method that could encourage practitioners to include this concept as a topic for the selection of inside materials. But at the same time it should have a strong scientific base to make its results trustworthy. A strategy for the evaluation of finishing materials contribution to the hygroscopic inertia of a room has been studied. The results of that study will be presented. An experimental prototype developed as a tool for the comparison of the impact of materials on the inside relative humidity variation is also introduced.
... At the same time, the average indoor air temperature in the new buildings is 1°C higher than in the old ones. From this relationship, and in accordance with Simonson's studies [13][14][15][16], we can say that this is an isenthalpic process of the same indoor ambience. If we analyse the thermal comfort and consequences of these variations, we can say that, as a consequence of this higher relative humidity, a higher acceptability of indoor ambiences in the old buildings was obtained during the dry season, and the worst acceptability was obtained during the rainy season. ...
... Dessa forma, Simonson et al. (2001), apresenta no seu estudo um esquema gráfico onde relaciona vários parâmetros relativos à saúde e qualidade do ar interior em função da humidade relativa, figura 14. Pela observação da figura pode-se referir o intervalo de 30% a 55% de humidade como sendo os limites ideais dentro dos quais deverá variar a humidade relativa no interior dos edifícios. ...
... At the same time, the local thermal comfort can be analysed. Over the last few years several empirical equations used by some authors, like Simonson [30], have been available to do an indoor air quality study. Indices, such as the percentage of dissatisfaction with the local thermal comfort, thermal sensation and indoor air acceptability were determined in terms of some simple parameters like dry bulb temperature and relative humidity. ...
... According to the simulation results of Simonson & al. [14] a room with massive wooden floor and ceiling has a similar thermal performance as a room with same thickness (200mm) concrete floor and ceiling. ...
Article
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Even though wooden floorings have been used in Finland for centuries both in residences and in civic buildings, material characteristics of wood are nowadays often unrecognized when interior materials are selected. To better understand the reasons behind the diverse positive and negative attitudes towards wooden floorings, architects, designers as well as consumers in Finland were interviewed. The key findings from the interviews are discussed in relation to literature study of the functional properties of wooden floorings. Difficulties in maintaining wooden floorings are strongly related to the knowledge and the image of wood as a material.
Article
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Increasing concerns about global warming and its impact on the environment reinforce the need for new materials and technologies. Additive manufacturing has become more relevant due to its potential to build sustainable and more energy-efficient constructions. However, the materials employed within the technology are not yet fully sustainable. Researchers employing clay as the main binder have found that, besides protecting the environment, it benefits passive control of indoor temperature and relative humidity and contributes to comfort. The mortar design as well as the necessary technological adaptations for the 3D printing of earth mortars are addressed. From a material perspective, this paper reviewed and analyzed the recent developments in additive manufacturing of clay-based mortars, highlighting the main gaps and providing recommendations for future developments in this field.
Article
Wood is usually processed into various spaces and used in buildings, packaging and furniture. Dynamic moisture sorption and humidity response inside wooden space to sinusoidally changing external relative humidity (RH) were demonstrated by using a self-assembly device, which simultaneously recorded moisture content (MC) and RH changes. Wood has hierarchical structures, which provided the basis of moisture sorption and further influenced RH inside. Internal RH changed sinusoidally, similar to external RH and MC. During internal and external moisture exchange, water molecules experienced dynamic compound actions, including moisture gradient pressure, the attraction of sorption sites and water molecules and diffusing hindrance. Consequently, MC and internal RH exhibited dynamic phase lag of over 0.39 radian. Meanwhile, moisture sorption was higher for thinner wood, especially in a longer cyclic period since more water molecules interacted with sorption sites with less diffusing hindrance. Correspondingly, the humidity change was lower inside thicker wooden spaces in a shorter period. The average internal RH and amplitude decreased by 5% and 83.7%, respectively. Dynamic humidity change hysteresis existed and showed positive relation to the cyclic period but inversely with wood thickness. The study helped better understand dynamic moisture sorption and humidity change in wooden space and facilitated the better application of wood in human life.
Article
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Laboratory studies have shown that wood has hygroscopic properties. When used as a construction material in buildings, it can thus influence indoor relative humidity and temperature. Ventilation can affect indoor climate if the temperature differ between indoor and outdoor air. The coating of indoor wood may also affect its hygroscopic properties. Few studies of wood in real buildings have been conducted. The main aim of this experimental study was to explore the association between moisture content in indoor air and wood in two classrooms. The floor plan of the two classrooms was identical. In one classroom, all wood surfaces were untreated, whereas, in the other, they were treated with a transparent varnish. Sensors measured indoor air relative humidity, moisture content in the wood, and temperature in the air and wood in both classrooms. Linear regression analysis was performed to explore possible associations. Strong positive associations between indoor air relative humidity and the moisture content in wood in the untreated classroom were found. Weak positive associations were evident in the classroom with treated wood. Ventilation reduced these associations.
Conference Paper
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Studies on hygrothermal properties of materials to passively moderate indoor humidity levels has in cold-moderate climates conclude that it helps improve Indoor Air Quality and reduce auxiliary energy loads. This research uses a validated whole building Heat And Moisture transfer energy simulation tool (WUFI Plus) to study the effect of a selected hygroscopic clay plaster on indoor environment in hot-humid climatic condition. A reference scenario was defined with use of gypsum plaster as the common wall finishing. Results indicate that clay can help buffer indoor RH especially when high indoor RHs happen. However, the effect on indoor temperatures is negligible. Results also indicate the importance of taking moisture into account in building energy calculations.
Article
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This study aims to make a comprehensive analysis on the viscoelastic behavior of typical tropical hardwoods and its influences in making musical instruments. For that a Dynamic-Mechanical Analysis was done and the mechanical parameters dependence on test control parameters like temperature, frequency and test duration time were measured. For Dalbergia Nigra the final value of Module of Elasticity (MOE) was 17551.0MPa and 0.022020 for tangent delta (tg(δ)), but a great variation in those parameters was observed during the tests, for all species the MOE increases and tg(δ) decreases, even with constant temperatures, which may be caused by water loss. Besides that, a discussion was made relating the obtained data and historical knowledge about the usages of the studied woods for musical instruments manufacture, and density was shown as the main variable for that purpose.
Chapter
Use of massive wood has increased during the last decade. The concept of massive wood, mainly as cross laminated timber elements (CLT), has become a popular building method for new constructions, both in public and private sector. Massive wood elements take advantage of wood as building material, also as an indoor climate buffer. Moholt 50|50 is a new student-housing project in Trondheim, Norway, which consists of five mass timber towers. Each of them with eight stories built in CLT on top of a concrete storey. Apart from the student homes, the buildings host facilities, such as activity center, kindergarten, commercial areas and a library, also built in CLT. This makes Moholt 50|50 a significant wooden living lab in Trondheim. The building technique follows the development from the first Norwegian CLT student housing built in Ås in 2012, and reproduced later on in similar patterns in other Norwegian cities, as Tromsø, Haugesund, Drammen, Fredrikstad, Halden, Hønefoss, Porsgrunn and Trondheim. Research on comfort and operation cost coupled to indoor surfaces are included in project Moholt 50|50. The towers are built according to Norwegian low energy standards. All surfaces are treated with water solvent varnish, apart from two stories in one of the Moholt timber towers. Four stories are instrumented to document the difference in the behavior of untreated and treated wooden surfaces. Measurements show a different indoor climate of the stories with untreated surfaces. The measurements presented give preliminary results of a measurement period which, when finished, will include one year of inhabited studios from the date of moving in.
Chapter
Die Beurteilung von Schimmelpilzbelastungen setzt einen hohen Sachverstand voraus. Eine eindeutige gesundheitliche Gefährdungsabschätzung ist aufgrund des jetzigen Wissensstandes nicht möglich. Im Sinne der Vorsorge sollte allerdings die Belastung von Innenräumen mit Schimmelpilzen minimiert werden. Mithilfe eines neuentwickelten Vorhersagemodells können für reale instationäre Randbedingungen bauliche und nutzungsbedingte Wachstumswahrscheinlichkeiten ermittelt werden. Dies erleichtert ganz wesentlich Aussagen über die Wirksamkeit von Sanierungs- oder Verbesserungsmaßnahmen. Durch die Anpassung der Beurteilungsklassen an den aktuellen Stand des Wissens kann dieses Modell, das bei seiner Entwicklung noch von einer anderen Gefährdungsbeurteilung ausging, aktualisiert werden. Die dargestellten Isoplethensysteme für die derzeit als kritisch eingestuften Schimmelpilzspezies (Aspergillus fumigatus, Aspergillus flavus und Stachybotrys chartarum) belegen, auch wenn ausreichend Daten nur auf optimalem Substrat zur Verfügung stehen, dass diese Pilze einen erhöhten Feuchtebedarf aufweisen. Dies bedeutet immerhin, dass bei einem geringfügigen Schimmelbewuchs auf den Fassaden das Vorkommen dieser Schimmelpilze eher unwahrscheinlich ist. Im Weiteren werden methodische Vorgehensweisen und Sanierungshinweise detailliert aufgeführt.
Chapter
Erhöhte Feuchte in Bauteilen kann hygienische Mängel, Schäden und Heizenergieverluste verursachen. Deshalb hatte die Feuchteschutzbeurteilung von Bauteilen schon immer eine große Bedeutung. Der Zwang zur Energieeinsparung hat im Bauwesen zu einer weiteren Verschärfung der Feuchtesituation geführt. Die derzeit gültige Norm für die Feuchteschutzbeurteilung von Außenbauteilen ist der Teil 3 der deutschen Norm DIN 4103. Neben Hinweisen zum Schlagregenschutz wird in dieser Norm ausschließlich der Schutz von Baukonstruktionen vor winterlichem Tauwasser behandelt. Eine derartige Überhöhung der raumseitigen Randbedingungen ist wenig plausibel und deshalb für die Feuchteschutzbeurteilung in der Praxis kaum geeignet. Die Vorteile der hygrothermischen Simulation liegen demgegenüber darin, die unter natürlichen Klima- und Nutzungsbedingungen auftretenden Temperatur- und Feuchteverhältnisse in Baukonstruktionen örtlich und zeitlich detailliert abbilden zu können. Die Anwendung der instationären Simulationsverfahren ist jedoch nicht allein darauf ausgerichtet, alte Rechenmethoden zu ersetzen, sondern auch die Möglichkeiten des modernen Feuchteschutzes zu erweitern.
Chapter
Maintaining moderate indoor relative humidity levels in buildings is important for ensuring occupant comfort, as well as durability of building materials. This chapter presents methods for moderating indoor humidity levels using hygroscopic materials, in the form of: (1) hygroscopic building materials, (2) a desiccant coated air-to-air energy wheel and (3) a new concept ceiling panel with a vapour permeable surface. Simulation studies in an apartment and two office buildings, in different North American cities, are presented. The simulated indoor relative humidity and percent dissatisfied with perceived air quality (PAQ) are presented to show the benefits of using hygroscopic materials in buildings. Experimental results are presented for the novel ceiling panel, with results showing the sensible and latent effectiveness’s, as well as the heat and mass flux rates obtained from the panel. The results of the simulations and experiments show that these devices and methods have the potential to improve thermal comfort and indoor air quality (IAQ), while reducing the energy consumption of the buildings.
Book
The main benefit of the book is that it explores available methodologies for both conducting in-situ measurements and adequately exploring the results, based on a case study that illustrates the benefits and difficulties of concurrent methodologies. The case study corresponds to a set of 25 social housing dwellings where an extensive in situ measurement campaign was conducted. The dwellings are located in the same quarter of a city. Measurements included indoor temperature and relative humidity, with continuous log in different rooms of each dwelling, blower-door tests and complete outdoor conditions provided by a nearby weather station. The book includes a variety of scientific and engineering disciplines, such as building physics, probability and statistics and civil engineering. It presents a synthesis of the current state of knowledge for benefit of professional engineers and scientists.
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Nowadays, there is a great deal of interest in naturally ventilated buildings and passive climate control systems located on sites that offer a good microclimate because of they are low-energy costs and the impracticality of HVAC for many libraries and archives. ASHRAE Standard defines naturally conditioned spaces as those where thermal conditions are regulated primarily by the occupants through opening and closing of the windows. This same standard reflects the fact that occupant's thermal response in such spaces depends in part on the outdoor climate. Furthermore, this response is different than in buildings with centralized HVAC system because of the different thermal experiences, changes in clothing, availability of control, and shifts in occupant expectations. Present paper presents a practical case study about indoor condition in typical natural ventilated Spanish library with the aim of propose passive climate solutions to comfort and materials preservation problems. Results showed temperature values higher than that expected and relative humidity higher than materials conservancy indications. In consequence, lower indoor air acceptability and materials deterioration was found. Passive climate control methods were proposed to get a sustainable building.
Article
The research presented in this report demonstrates the moisture, thermal and ventilation performance of a recently built ecological house in the Tapanila district of Helsinki, Finland. The single-family house (gross floor area of 237 m2 including the basement and porch) has a well-insulated (250 mm in the walls and 425 mm in the roof) wooden frame with no plastic vapour retarder. A natural ventilation system provides outdoor ventilation and district heating and a wood-burning fireplace provide space heating. The space heating energy consumption was measured to be 76 kWh/(m2·a) of which 29% was provided by wood. For comparison, Finnish houses typically consume 120 kWh/(m2·a) or nearly 60% more energy for space heating. If the building envelope of Tapanila ecological house had been insulated according to the building code, the space heating energy consumption is expected to be 40% higher. The total energy consumption (121 kWh/(m2·a)) and electricity consumption (28 kWh/(m2·a)) were quite low. As a result, the total primary energy consumption was only 162 kWh/(m2·a), while the primary energy consumption in typical Finnish houses is over 40% higher. However, the outdoor ventilation rate provided by the natural ventilation system tended to be lacking (i.e., less than the required value of 0.5 ach) even though the measured CO2 concentrations were generally below 1000 ppm when the bedroom doors were open. Extrapolating the measured ventilation data shows that the ventilation rate is expected to be about 0.45 ach (10% below the required value) in the winter and about 0.25 ach (50% of required value) in the summer when the windows are closed. When the windows are open in the summer, the outdoor ventilation rate will be higher. The moisture performance of the building envelope was good and the risk of mould growth low. In addition, the moisture transfer between the envelope and indoor air was measured to significantly influence the indoor humidity. At a ventilation rate of 0.5 ach, the results show that a porous building envelope can decrease the maximum humidity in a bedroom during the night by up to 20% RH, which may double the number of occupants satisfied with thermal comfort and perceived air quality. Furthermore, the minimum indoor humidity in the winter can be increased by about 10% RH, which is also important in cold climates. These results show that it is possible to build a house with a porous and vapour permeable envelope that is moisture physically safe and improves the indoor climate.
Article
Nowadays, Spanish public buildings employ, during the spring season, the heating system only if indoor conditions are under certain temperature and relative humidity values. A correct HVAC system design and building construction could let us reduce this energy consumption. In the last years software tools were employed to understand and predict these thermal behaviour but they underestimated the energy consumption because its energy models ignore moisture. Actual HAM tools software could be employed to simulate indoor conditions and phenomena of material and energy transfer thought building envelopes and its effects on indoor conditions. Present paper shows an example of HAM tools application to determine modifications that reduce energy consumption or improve HVAC system in real buildings. Results showed the veracity of this simulation software and that parameters like solar gain or air leakages are so important than thermal inertia.
Article
This new book presents an overview of conclusions and future works in new research and design parameters of Spanish indoor ambiences. These conclusions are based on real data conducted at the Department of Energy at the University of A Coruña. This research involved a set of ambiences such as flats, schools, libraries and ships located in the area of A Coruña, Spain. The purpose of these investigations was to determine the correlation between indoor ambiences and comfort, energy saving, work risk, health and material conservancy.
Chapter
In this chapter, the data mining techniques described in chapter 3 are applied to the case study described in chapter 4. The overcome of the difficulties associated with the analysis process of the data using appropriate techniques is demonstrated.
Chapter
The evaluation of indoor hygrothermal conditions is described, supported by a literature review. Involved parameters and standardized methodologies are summarized. The procedures for evaluation of human comfort are also briefly described.
Chapter
This chapter presents available data mining techniques that can be of interest for application in indoor environment analysis. Descriptive statistics tools are presented with the focus on probability distribution and correlation analysis. Multivariate data techniques are also addressed, with a special focus on principal components determination and cluster analysis.
Technical Report
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Climate chamber experiments were performed to investigate thermal comfort at high humidities. Subjective reports were recorded for a total of 411 subjects at frequent intervals during the three-hour experiments with 65 selected subjects equipped with instrumentation to record skin wettedness and skin temperature. The exposures ranged from 20 C/60% RH to 26 C/90% RH with two clothing levels, 0.5 and 0.9 clo, and three levels of metabolic activity, 1.2, 1.6, and 4 met. Clear differences in humidity response were not found for sedentary subjects; however, non-sedentary activities produced differences on several subjective scales. These differences, though, are dictated via heat balance and thermoregulation and cannot be separated from humidity-related effects. For metabolic rates 1.6 met and above, these data suggest that no practical limit on humidity will lower the percent dissatisfied below 25%.
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Over the last 15 years, active desiccant systems have become a common component of HVAC systems in commercial buildings needing lower-than-usual humidity levels. Ice arenas, supermarkets and refrigerated warehouses all contain refrigeration systems which cool air more effectively when most of the building's moisture load is removed by an active (heat-reactivated) desiccant system. Cost savings, comfort improvements and `process benefits' of extended-season operation for ice rinks, lower product temperature for supermarkets and improved safety for warehouses are usually enough to make the desiccant component a useful addition to such buildings.
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An annual load index for ventilation air is proposed to help improve the ability of HVAC systems to deal efficiently with the amount of fresh air. The proposed 'ventilation load index' (VLI) is the load generated by one cubic foot per minute of fresh air brought from the weather to space-neutral conditions, over the course of one year. This index consists of two numbers, separating the load into dehumidification and cooling components: latent ton-hours per cfm per year + sensible on-hours per cfm per year.
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Contrary to widespread belief among building practitioners, fungal defacement does not need surface condensation. Water activity above a threshold value suffices. In steady state, water activity can be expressed in terms of the relative humidity near the substrate. To study mold risk and establishing performance criteria for the HVAC system and the envelope, a careful analysis of the heat, air and moisture balance at building, room and surface level is required.
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Computer simulations were performed to investigate the impacts of ASHRAE Standard 62-1989 on a 100,000-ft2 (9,290-m2) office building located in three Florida cities (Miami, Orlando, and Jacksonville). The increased outdoor air requirements prescribed by the standard increased annual heating, ventilating, and air-conditioning (HVAC) energy use and operating costs by 10% to 15% when a conventional chilled-water variable-air-volume (VAV) system was employed. The conventional system was also unable to meet the increased latent load, resulting in elevated indoor humidity levels (i.e., numerous hours with relative humidity > 60%.). Several alternative technologies were investigated to determine their ability to mitigate these impacts, and some were able to maintain proper indoor humidity levels. The design engineer should carefully consider the costs and benefits of each technology before selecting the appropriate system.
Article
The hygrothermal behaviour of timber frame wall is analysed using a steady-state calculation method and a two-dimensional heat, air, and moisture transport computer model. The conditions associated with exfiltration of warm and humid indoor air are examined. The physical quantities investigated included the amount of moisture accumulated in the wall cavity during the heating season and the heat loss across the wall. Several interesting correlations between moisture accumula tion in a cavity and parameters such as leakage rate, vapour permeance characteristics of the exterior boundary, additional thermal resistance offered by an exterior sheath ing, and indoor humidity level emerge. These correlations show the advantage of us ing the analytical methods in deriving design guidelines for building components. The results from the analysis are used to identify and quantify various parameters that govern the performance of air barrier systems.
Article
This paper proposes a 'moisture admittance' model which accounts for the moisture absorption and desorption processes for predicting humidity levels in buildings. The experimental method whereby the required coefficients were derived is described and some examples of the results are given. The approaches to real buildings, as opposed to test rooms, and possible modifications to BREDEM are briefly discussed.
Article
Eight studies reported in the literature compare absence from work or number and duration of respiratory illnesses of the occupants of two building or two rooms, one of which is maintained at a higher relative humidity than the other. In six of the eight studies, the absence from work or the occurrence of respiratory illnesses is significantly lower in the humidified space. This paper reports the latest study that was conducted in hospitals and discusses the difficulties in assessing the results of the investigations. It concludes there is a high probability that increased indoor relative humidity in winter decreases the number of respiratory illnesses and that further experiments are warranted in view of the cost of absenteeism from work.