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The Embodied Impact of Existing Building Stock
Abstract
This chapter provides the reader with a better understanding of the life cycle environmental impacts, with a focus on the embodied impact of existing building stock. A systematic literature review is conducted to paint a clear picture of the current research activities and findings. The major components of embodied impact and parameters influencing the embodied impact are outlined and explained. Lastly, this chapter discusses the major barriers for the embodied impact assessment, and a potential analysis framework is proposed at the end.
... Regardless, the commonly accepted guidelines and methods of assessment and measurement for embodied energy have not been established. Previous studies demonstrate considerable variation in reported embodied energy values due to the high number of variables [3,4], including building materials [5] and building construction types [2]: there is inadequate published information on whole building life-cycle embodied energy reports [6]. Aside from a lack of consensus on measurement and procedures, embodied energy emissions and related carbon emissions are being largely ignored [7] as the focus is solely on operating energy. ...
Knowledge and research tying the environmental impact and embodied energy together is a largely unexplored area in the building industry. The aim of this study is to investigate the practicality of using the ratio between embodied energy and embodied carbon to measure the building’s impact. This study is based on life-cycle assessment and proposes a new measure: life-cycle embodied performance (LCEP), in order to evaluate building performance. In this project, eight buildings located in the same climate zone with similar construction types are studied to test the proposed method. For each case, the embodied energy intensities and embodied carbon coefficients are calculated, and four environmental impact categories are quantified. The following observations can be drawn from the findings: (a) the ozone depletion potential could be used as an indicator to predict the value of LCEP; (b) the use of embodied energy and embodied carbon independently from each other could lead to incomplete assessments; and (c) the exterior wall system is a common significant factor influencing embodied energy and embodied carbon. The results lead to several conclusions: firstly, the proposed LCEP ratio, between embodied energy and embodied carbon, can serve as a genuine indicator of embodied performance. Secondly, environmental impact categories are not dependent on embodied energy, nor embodied carbon. Rather, they are proportional to LCEP. Lastly, among the different building materials studied, metal and concrete express the highest contribution towards embodied energy and embodied carbon.
The construction of new buildings requires the use of a substantial amount of materials, which have an associated embodied energy for manufacturing, transport, construction and end-of-life disposal. A number of inventories have been developed to collate the typical embodied energy or carbon emissions associated with different building materials and activities, and these can be used to quantify the environmental impacts of different construction methods. However, uncertainty exists in the estimation of embodied CO2-e emissions and other environmental impact results, due to i) inconsistencies in typical embodied carbon emissions values in inventories; ii) errors in estimations of material quantities; iii) assumptions regarding building lifetimes, and iv) errors in estimations of transport distances.
This current study quantified the uncertainties associated with the calculation of lifetime CO2-e emissions in a case study net-zero, in terms of operational energy, educational building. This study examined the lifetime impacts of building materials for the building based on a detailed Life Cycle Assessment (LCA) that had been previously undertaken for this site. The study considered the 19 building materials which most heavily influenced the total, transport and recurring embodied carbon footprint of the building and a probability distribution was generated to represent the variability for each of the following uncertain parameters: Lifetime, Embodied CO2-e and transport distance over the building’s life. Random sampling was used to generate input variables (1000 samples) based on a probability distribution of each uncertain parameter relative to the building materials. Through the use of a Monte Carlo simulation, the environmental impact for each construction material for a 50-year building lifetime was predicted. Unlike the conventional LCA approach, which provides a single deterministic value, cumulative Monte Carlo distribution curves were used to provide a range of embodied CO2-e emissions for each construction material, and the whole building, through the lifetime of the building. The obtained results revealed a distribution of the total embodied CO2-e of a building which ranged from 2,951 tCO2-e to 5,254 tCO2-e. This variation in the life cycle carbon emissions highlights the importance of considering an uncertainty analysis in the LCA analysis.
The construction sector is facing increasingly strict energy efficiency regulations. Existing buildings have specific technical, functional and economic constraints, which, in fulfilling regulations, could lead to costly and complex renovation procedures and also lead to missed opportunities for improving their energy performance. In this article, the methodology for comparing cost-optimality in building renovations, developed in the International Energy Agency (IEA)-Energy in Buildings and Communities (EBC) Annex 56 project, is extended with a life cycle assessment by including embodied primary energy and carbon emissions in the calculations. The objective is to understand the relevance of embodied energy and carbon emissions in the evaluation of the cost effectiveness of building renovation solutions towards nearly zero energy buildings, as well as the effect of the embodied values in the achievable carbon emissions and primary energy reductions expected in an energy renovation. Results from six case studies, representative of different regions in Europe, suggest that embodied values of energy and carbon emissions have a decreasing effect-ranging from 2 to 32%-on the potential reductions of energy and emissions that can be achieved with renovation measures in buildings. In addition, the consideration of the embodied energy and carbon emissions does not affect the ranking of the renovation packages.
Building materials have different consumption patterns of energy and emissions of carbon dioxide during their production. These differences result from the treatment of the raw materials and the techniques applied to production. Subsequently on an environmental classification one wonders what kind of constructive solution becomes more benevolent to the environment. Masonry building technique has made a comeback as an alternative to conventional reinforced concrete structures with ceramic blocks for closing the spans. The present study refers to the environmental comparison of these two systems. As the definition of functional unit has been introduced to facilitate the comparison of different existing alternatives, the walls are chosen as the functional units, for different building plans and conditions. The comparison considers the most important environmental parameters, i.e. the embodied energy and the carbon footprint. Results obtained indicate that masonry-building walls have a lower embodied energy and carbon footprint compared to those of conventional building. The differences vary with the length of the walls, but are over 22% and reach some 55%. It is hoped that the different wall types considered will enable the comparison of the two options for real application.
Greenhouse gas (GHG) emissions from construction processes are a serious concern globally. Of the several approaches taken to assess emissions, Life Cycle Assessment (LCA) based methods do not just take into account the construction phase, but consider all phases of the life cycle of the construction. However, many current LCA approaches make general assumptions regarding location and effects, which do not do justice to the inherent dynamics of normal construction projects. This study presents a model to assess the embodied energy and associated GHG emissions, which is specifically adapted to address the dynamics of infrastructure construction projects. The use of the model is demonstrated on the superstructure of a prefabricated bridge. The findings indicate that Building Information Models/Modeling (BIM) and Discrete Event Simulation (DES) can be used to efficiently generate project-specific data, which is needed for estimating the embodied energy and associated GHG emissions in construction settings. This study has implications for the advancement of LCA-based methods (as well as project management) as a way of assessing embodied energy and associated GHG emissions related to construction.
The assessment of implementation of green chemistry principles in the synthesis of nanomaterials is a complex decision-making problem that necessitates integration of several evaluation criteria. Multiple Criteria Decision Aiding (MCDA) provides support for such a challenge. One of its methods - Dominance-based Rough Set Approach (DRSA) - was used in this research to develop a model for the green chemistry-based classification of silver nanoparticles synthesis protocols into preference-ordered performance classes. DRSA allowed integration of knowledge from both peer-reviewed literature and experts (decision makers, DMs) in the field, resulting in a model composed of decision rules, being logical statements in the form: “if conditions, then decision”. The approach poses the basis for the design of rules for the greener synthesis of silver nanoparticles. Decision rules are supported by synthesis protocols that enforce the principles of green chemistry at various extents, resulting in robust recommendations for the development and assessment of silver nanoparticles synthesis that perform at a one of five pre-determined levels. The DRSA-based approach is transparent, structured and can be easily updated. New perspectives and criteria could be added in the model if relevant data would be available and domain-specific experts would collaborate through the MCDA procedure.
The progress of business is moving fast and the key to maintain advantage and competitiveness is research and continuous improvement. Besides economic, environment is always more object of evaluation analysis. There are numerous ways to assess individually both economic and environmental aspects, but in order to guarantee a high quality of improvement, an integration of different methods and theories is required. Thus, this research provides an integration of two different approaches: The Life Cycle Assessment (LCA) and Multi Criteria Decision Analysis (MCDA). The first allows the analyst to understand the environmental issue. The second is useful in order to select the best solution for improvement. The main purpose of this study is to develop a systematic method, easy to use and giving useful results. In the present work existing methods are reviewed and integrated in a new approach proposed to support continuous improvement. A real case in an Italian bearing plant is presented.
Construction material consumption is greater than any time in history. Australia produces approximately 30 million tonnes of finished building products each year, with over 56% of this quantity, by mass, being attributed to concrete and a further 6%, steel. Globally, 23 trillion kilograms of concrete alone is consumed annually, with growing population driving increasing demands. This study assesses the environmental performance of various concrete slab systems. Historically, the focus of environmental performance in buildings has been Operation Energy (OE) requirements, however Zero Energy Buildings (ZEB) are changing this. Specifically the study investigates the environmental performance of concrete structures varying design parameters and construction techniques to optimise its embodied energy (EE). These structures are designed in accordance with all relevant Australian codes and standards. The various slab systems investigated include: beam & slab, flat slab and flat plates while concurrently considering the use of conventionally reinforced and post-tensioned construction methods. Designs were compared in terms of EE outcomes given fixed design criteria, with results indicating reductions between 23.7% and 49.1% when utilising post-tensioned construction methods.
Building materials damage to the environment during each stage of their life cycle. An important part of these damages is due to the energy consumption during the process. Many building materials sector like cement, iron, steel, glass etc use high rates of fuel and electrical energy. Greenhouse gases resulting from the use of energy lead to global warming that cause climate change. And acid rain damages living and non- living beings on the earth. In addition, volatile organic compounds and granular particles as a result of combustion of fossil sources enter the human body through the respiratory or digestive systems which lead to serious illnesses. Therefore, responsible use of energy is important for both resource efficiency and reducing environmental impacts. An important part of life cycle energy of building materials is consumed during the production and transportation processes. In this study, it is aimed to investigate initial embodied energy of cement, marble, glass and aluminum sectors in Turkey. The current situation was stated by the method of literature review and inventory analysis of the energy flow to calculate the amount of the total energy consumption of the building materials during these processes was recommended. Thus, it will be possible to compare the amount of total energy consumption in different production plants.
Identification of parameter variation allows us to conduct more detailed life cycle assessment (LCA) of energy and carbon emission material over their lifecycle. Previous research studies have demonstrated that hybrid LCA (HLCA) can generally overcome the problems of incompleteness and accuracy of embodied energy (EE) and carbon (EC) emission assessment. Unfortunately, the current interpretation and quantification procedure has not been extensively and empirically studied in a qualitative manner, especially in hybridising between the process LCA and I-O LCA. To determine this weakness, this study empirically demonstrates the changes in EE and EC intensities caused by variations to key parameters in material production. Using Australia and Malaysia as a case study, the results are compared with previous hybrid models to identify key parameters and issues. The parameters considered in this study are technological changes, energy tariffs, primary energy factors, disaggregation constant, emission factors, and material price fluctuation. It was found that changes in technological efficiency, energy tariffs and material prices caused significant variations in the model. Finally, the comparison of hybrid models revealed that non-energy intensive materials greatly influence the variations due to high indirect energy and carbon emission in upstream boundary of material production, and as such, any decision related to these materials should be considered carefully.
As operational impacts from buildings are reduced, embodied impacts are increasing. However, the latterare seldom calculated in the UK; when they are, they tend to be calculated after the building has beenconstructed, or are underestimated by considering only the initial materials stage. In 2010, the UK Gov-ernment recommended that a standard methodology for calculating embodied impacts of buildings bedeveloped for early stage design decisions. This was followed in 2011–12 by the publication of the Euro-pean TC350 standards defining the ‘cradle to grave’ impact of buildings and products through a processLife Cycle Analysis.This paper describes a new whole life embodied carbon and energy of buildings (ECEB) tool, designedas a usable empirical-based approach for early stage design decisions for UK buildings. The tool complieswhere possible with the TC350 standards. Initial results for a simple masonry construction dwelling aregiven in terms of the percentage contribution of each life cycle stage. The main difficulty in obtaining theseresults is found to be the lack of data, and the paper suggests that the construction and manufacturingindustries now have a responsibility to develop new data in order to support this task.
When deciding what alternative is more sustainable than others (i.e., selecting materials while considering environmental-, social-, and economic outputs) in the AEC industry, stakeholders need to select a method for their decision-making process. From the literature it appears to be assumed that all multiple criteria decision analysis (MCDA) methods are equal or that the differences between them does not matter, and it is left to the user to select any one. In this study we argue that methods matter. This paper explores what characteristics make a method viable and, correspondingly, what characteristics disqualify methods. We compare and contrast value-based methods versus Choosing By Advantages (CBA). In addition, we explore what characteristics would make a method be aligned with lean thinking. We have found that methods that rank factors or values, such as value-based methods, require a high level abstraction, inducing unanchored conflicting questions. In contrast, CBA methods base judgments on anchoring questions, which are based on valuing the importance of advantages between alternatives. CBA produces fewer conflicting questions and allows stakeholders to discuss what they value in a richer context. We discuss why we think that CBA methods are superior to other methods for making sustainability decisions. In addition, we discuss why CBA is in line with lean thinking.
Certifications such as the Passive House Standard aim to reduce the final space heating energy demand of residential buildings. Space conditioning, notably heating, is responsible for nearly 70% of final residential energy consumption in Europe. There is therefore significant scope for the reduction of energy consumption through improvements to the energy efficiency of residential buildings. However, these certifications totally overlook the energy embodied in the building materials used to achieve this greater operational energy efficiency. The large amount of insulation and the triple-glazed high efficiency windows require a significant amount of energy to manufacture. While some previous studies have assessed the life cycle energy demand of passive houses, including their embodied energy, these rely on incomplete assessment techniques which greatly underestimate embodied energy and can lead to misleading conclusions. This paper analyses the embodied and operational energy demands of a case study passive house using a comprehensive hybrid analysis technique to quantify embodied energy. Results show that the embodied energy is much more significant than previously thought. Also, compared to a standard house with the same geometry, structure, finishes and number of people, a passive house can use more energy over 80 years, mainly due to the additional materials required. Current building energy efficiency certifications should widen their system boundaries to include embodied energy in order to reduce the life cycle energy demand of residential buildings.
Global warming, depletion of natural resources, acid rains, air and water pollutions, and ozone depletions are some of the environmental consequences that are deemed attributable to human activities on planet earth. Sustainable practices have been therefore evolved as main remedies to tackles these issues. Green roof strategy is one of these practices that not only provides heat island amelioration and thermal comfort for occupants but also reduces energy consumption of buildings as well as add aesthetic values to the environment. This paper targets to run a review on the application of green roof strategy. The review scans a time frame from 2002 through early 2012 with a focus on energy related topics on energy related topics of green roofs. The review discussed various types of green roofs, components of a green roof, economic revenues, and technical attributes. Many general advantages and few general disadvantages of green roofs in one hand and pros and cons of green roofs with respect to energy utilization on the other hand are also synthesized. Some recommendations for future study are also proposed.
There is a growing incentive within the construction industry to design low energy buildings which incorporate increased levels of insulation whilst also encouraging the use of ‘green’ materials which have a low environmental impact and can contribute positively to sustainable building strategies. Silica aerogels have received an increasing amount of attention in recent years as a contemporary insulation material, but their wide-spread use is currently hindered by high costs and their high embodied energy. This research project explores the development of a composite insulation material proposed as an alternative to silica aerogel, which consists of natural components including clay and a biopolymer obtained from seaweed known as alginate. Prototype specimens have been developed and characterized in terms of their mechanical properties and microstructure allowing comparisons to be made between five alginate types, each obtained from a different seaweed source. Whilst all of the composites tested offered an improvement over the control sample, the results also demonstrated that the type of alginate used has a significant influence on the compressive strength and modulus values of the resulting composite materials. An analysis of the production process additionally demonstrated that the freeze-drying element can have a significant impact on both the environment and financial costs of producing such a material.
Since the appearance of the first edition of ‘Energy Simulation in Building Design’, the use of computer-based appraisal tools to solve energy design problems within buildings has grown rapidly. A leading figure in this field, Professor Joseph Clarke has updated his book throughout to reflect these latest developments. The book now includes material on combined thermal/lighting and CFD simulation, advanced glazings, indoor air quality and photovoltaic components. This thorough revision means that the book remains the key text on simulation for architects, building engineering consultants and students of building engineering and environmental design of buildings. The book’s purpose is to help architects, mechanical & environmental engineers and energy & facility managers to understand and apply the emerging computer methods for options appraisal at the individual building, estate, city, region and national levels. This is achieved by interspersing theoretical derivations relating to simulation within an evolving description of the built environment as a complex system. The premise is that the effective application of any simulation tool requires a thorough understanding of the domain it addresses. © 2008, Faber Maunsell. Published by Elsevier Ltd. All rights reserved.
With the world's uncertain energy outlook, buildings should be designed and constructed to use lesser fossil fuel-based energy and have lower environmental impacts. In the past decades, the research and practice have successfully focused on reducing the operational energy use. As a result, the share of embodied energy, the other energy component, has increased in the life cycle energy use of buildings.
The present article provides an overview of literature on embodied energy use in buildings in several directions. It reports on key estimation methodologies and tools for embodied energy and presents the embodied energy values for different types of buildings, as studied by the extant literature. It also examines embodied energy in relation to operational energy and highlights the recent shifts in share and significance of embodied energy in the building life cycle energy use. The article also presents a review of the embodied energy of tall buildings and explores the relation between embodied energy and building height. Finally, major strategies to reduce embodied energy, and research gaps and trends in the field are covered.
The current regulations to reduce energy consumption and greenhouse gas emissions (GHG) from buildings have focused on operational energy consumption. Thus legislation excludes measurement and reduction of the embodied energy and embodied GHG emissions over the building life cycle. Embodied impacts are a significant and growing proportion and it is increasingly recognised that the focus on reducing operational energy consumption needs to be accompanied by a parallel focus on reducing embodied impacts. Over the last six years the Annex 57 has addressed this issue, with researchers from 15 countries working together to develop a detailed understanding of the multiple calculation methods and the interpretation of their results. Based on an analysis of 80 case studies, Annex 57 showed various inconsistencies in current methodological approaches, which inhibit comparisons of results and difficult development of robust reduction strategies. Reinterpreting the studies through an understanding of the methodological differences enabled the cases to be used to demonstrate a number of important strategies for the reduction of embodied impacts. Annex 57 has also produced clear recommendations for uniform definitions and templates which improve the description of system boundaries, completeness of inventory and quality of data, and consequently the transparency of embodied impact assessments.
The built environment is recognized as a major hotspot of resource use and environmental impacts. Life Cycle Assessment (LCA) has been increasingly used to assess the environmental impacts of construction products and buildings and a new trend is characterized by the application of LCA to larger systems such as neighborhoods during early design phases. Assessing urban development projects at the master-planning stage raises the issue of inventory data collection, especially for building materials which are reported to account for about 20% of primary energy consumption in buildings, and up to 45% of associated greenhouse gas emissions. Urban planners focus on the urban morphology and little information is known about the buildings characteristics apart from their general shape. This paper proposes a simplified model for the assessment of buildings embodied energy and embodied carbon in relation with urban planners’ design levers. The model relies on the decomposition of buildings into functional elements in order to be sensitive to the shape of the buildings. A detailed sensitivity analysis and contribution analysis of the model is conducted on two types of generic building forms, in order to investigate the influence of parameters relating to shape on the embodied energy and embodied carbon of a building. The sensitivity analysis shows that
the parameters relating to shape (such as the dimension of the buildings) are more influential on the embodied energy and embodied carbon per square meter of building than the ones relating to the elements themselves (such as the wall thickness). The contribution analysis also brings evidence of the relation between the compactness factor and the embodied energy and embodied carbon of a building.
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A comprehensive case study life-cycle analysis(LCA) was conducted on a four-story National Register historic building with a projected 75-year life span located in Medina, New York. Three adaptive reuse options were compared: historic preservation, renovation, and new construction; six different energy performance targets were constructed and compared as well. The study comprises two parts: a life-cycle energy analysis and a life-cycle environmental impact analysis. In this life-cycle analysis, the building assembly group that consumes the most embodied energy was identified, related suitable renovation options were analyzed, and conclusions were drawn based on the results. The aim of the research was to address the balance between energy and environmental benefits and drawbacks for different adaptive reuse options. Four impact categories (global warming potential, ozone depletion potential, human health particulate potential, and smog potential) were measured and their correlation with primary energy demand was analyzed.
This literature review addresses the Life Cycle Energy Analysis (LCEA) of residential buildings. As the fluctuation in the choice of functional units, boundaries of the system, life cycle inventory (LCI) methods, metrics and impact indicators complicated the potential comparability, the guidelines of Product Category Rule (PCR) 2014:02 for buildings were applied for the normalization procedure. Even though PCR provided a clear statement of the boundaries and a complete presentation of the results, uncertainty deriving from the LCI methods and the omissions in the system boundaries indicates that further standardization is needed. The sample consisted of 90 LCEA case studies of conventional, passive, low energy and nearly zero energy residential buildings (nZEB). Additional analysis identified an underestimation between case studies that use process instead of hybrid analysis, as the average value of embodied energy in hybrid analysis appears to be 3.92 times higher than in process analysis case studies. The highest value of embodied energy for an nZEB case study quantified with process analysis appears to be lower than all the input-output hybrid case studies. A revised definition, according to current trends and requirements in energy efficiency regulations, was also provided as an update of their consistency in time. Operating energy appeared to dominate in life cycle energy of residential buildings in the past. The results of this review show an increasing share of embodied energy in the transaction from conventional to passive, low energy and nZEB, despite the reduction in the total life cycle energy that could reach up to 50%. The share of embodied energy dominates, mainly in low energy and nearly zero energy buildings, with a share of 26%–57% and 74%–100% respectively. In passive buildings, the share of embodied energy varies within a range between 11% and 33% that reaches the embodied energy limits of both a conventional and a low energy building. The use of renewable energy sources (RES) in a passive house, for the production of electricity, classifies it in the range of embodied energy of an nZEB. A significant gap of 17% in the share of embodied energy, between the nearly zero and the most energy efficient building examined in the current review, is identified. This difference appears to be more important for the conventional and passive buildings, indicating the relative significance of embodied energy through time and towards the nZEB. Furthermore, if uncertainty and the underestimation of embodied energy deriving by process analysis were considered this gap could be different. The increase of embodied energy in buildings, indicates that a whole life cycle energy analysis may be needed in the methodological framework of current energy efficiency regulations.
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In the study of sustainable building materials, the comparison of the life cycle environmental performance of steel and reinforced concrete has been a popular and important topic. Based in Singapore, this is one of the first studies in the literature that applies both attributional and consequential life cycle approaches to compare the global warming potential and embodied energies of these two materials, which are widely used for the structural parts of buildings. It was found that 1 kilogram (kg) of steel can be replaced by 1 or 4.25 kg of reinforced concrete. Two consequential scenarios for each of three combinations of primary and secondary steel were assessed. It was found that reinforced concrete produces less carbon dioxide emissions and incurs less embodied energy in most of these cases, but when different sustainable primary steel-making technologies were incorporated, these results may be reversed. We applied consequential life cycle assessment and scenario analysis to describe how changes in the demand for structural steel and reinforced concrete in Singapore's building industry give rise to different environmental impacts. Specifically, the consequential life cycle approach revealed that, over the short term, the impact of substituting steel with reinforced concrete depends on the difference in impacts resulting from the transportation of these two materials within Singapore. Based on these lessons, integrated technology policies to improve the overall sustainability of using steel for construction were proposed.
Reliable values for the embodied energy of materials are increasingly required for life cycle analyses of buildings. Different methods for estimating embodied energy coefficients can result in variations in these values. This may cause uncertainty with designers attempting to select materials on the basis of environmental impact and could jeopardise the specification of lower energy materials such as timber. This paper reviews the methods by which embodied energy analyses are carried out and highlights reasons for variations in embodied energy values. It reports on some recent research in Australia in which the production processes for particular timber building products have been studied to give estimates of embodied energy in terms of non-renewable primary energy. The results of these analyses are presented and compared with embodied energy data from other researchers.
There is considerable information available concerning the energy used in buildings, but until recently little attention was paid to the energy used to produce and transport building products. This energy, often called "embodied energy", is of growing importance in the context of assessment of environmental impacts and the fight to reduce greenhouse gas emissions. This article discusses techniques for calculating embodied energy and considers its strengths and weaknesses as a measure of environmental impact. Significant savings in energy use and carbon dioxide emissions are clearly possible through environmentally aware choice of building products.
The structure of a typical office building contributes roughly one-quarter to one-third of the total embodied energy. Although the occupation phase of a building's life cycle currently dominates energy use, as operational energy use is minimized through high-performance design, construction and equipment, embodied energy will play a larger role in the overall energy consumption of a building. Consequently, the structural system should be a primary target for reducing the embodied energy of a building. Parking garages offer an ideal case study for comparing the embodied energy of a variety of structural systems. As above grade parking garages have little operational energy use outside of lighting and have few materials or systems beside the structure, the embodied energy of the structure comprises a majority of the environmental impacts during its life-cycle. By selecting existing parking garages built over the last 10 years of similar height and in the same seismic zone, the design loads, column lengths and structural layouts are similar. This consistency makes more accurate comparisons between structural systems possible. Using material take-offs of three existing parking structures with one-way spans, one pre-cast concrete, one post-tensioned concrete and one cellular steel, this study shows that there is little difference in the normalized embodied energy of structural systems used for parking garages if steel with high-recycled content is used. The most important step architects and engineers can take to reduce the embodied energy of a parking garage structure is to specify steel products with a high recycled content, specifically reinforcing bars and structural sections.
The construction and operation of buildings are vastly responsible for significant environmental impacts, predominantly through resource consumption, waste production and greenhouse gas emission. Environmental issues continue to become increasingly significant and hence the building operational energy efficiency and the energy required for construction and consequently, for the material production, are getting greater importance. The commercial buildings in general consumes significant amount of materials in construction and consumes significant amount of energy during operation. Therefore it is essential to determine both embodied energy and operational energy. This paper quantifies and compares the embodied energy and operational energy of concrete and steel framed structures, which are commonly used in commercial buildings. A typical high rise office building in Melbourne has been chosen for this exercise. The studied building is a fifty storey with a flat roof and the total net-lettable area of 75 570 square meters. The embodied energy contribution of the substructure, the super structure with the structural elements namely foundation, beams, columns roof, facades and stairs are investigated. The results shown that the structural building materials, concrete (with steel reinforcement) represents the largest component of embodied energy for concrete frame structure while the steel framed structure examined showed the beams represent the largest component of embodied energy. It was fond that there is no significant difference in operational energy.
In this study a Building Information Model (BIM) tool is developed to simultaneously estimate embodied and operational carbon over a 60 year life span for a typical four bedroom detached house. Using the tool, four different construction scenarios are evaluated, representing a range of current construction methods used in present day UK house building. The results show that cradle-to-gate embodied carbon represents 20-26% of the total 60 year carbon emissions, with operational carbon representing 74-80% of total emissions. Construction scenarios that reduce operational carbon by improving the thermal envelope led to a 1-13% increase in embodied carbon but a 4-5% decrease in operational carbon compared to the basecase construction method. Approaches to reduce embodied carbon in new-build housing are also studied and a 24% reduction is demonstrated through building fabric changes. The study recommends that a universally robust methodology for measuring embodied carbon will enable design decisions to be taken to reduce whole life carbon emissions through improved choice of materials. Due to material changes impacting on the thermal characteristics of a dwelling, and to an extent the structural characteristics, an integrated BIM tool will be essential in quickly establishing whole life carbon impacts during the design stage.
This paper deals with the environmental resources consumed to construct tall building structures; the consumption is measured by the energy required to obtain tall building structures and is expressed in terms of cradle-to-gate embodied energy. A reference structure composed of central core (made of reinforced concrete) and rigid frames (made of either reinforced concrete or steel) is considered. The reference structure is dimensioned and detailed for buildings from 20 to 70 stories; the embodied energy of each building is then estimated (total, of the components, per net rentable area). The results show that, if some design decisions are dictated by the embodied energy, the premium for height of the embodied energy is not substantial, which proves that tall building structures can be sustainable. However, a structure with the lowest weight does not imply the lowest embodied energy. The results also prove that the embodied energy depends mainly on the flooring system, and that steel consumes more embodied energy than Reinforced Concrete. Ultimately, the embodied energy is confirmed to be a viable tool to design sustainable tall buildings, and the results presented herein may address design toward minimizing the embodied energy, which means to save environmental resources.
Buildings alone consume approximately 40% of the annual global energy and contribute indirectly to the increasing concentration of atmospheric carbon. The total life cycle energy use of a building is composed of embodied and operating energy. Embodied energy includes all energy required to manufacture and transport building materials, and construct, maintain, and demolish a building. For a systemic energy and carbon assessment of buildings, it is critical to use a whole life cycle approach, which takes into account the embodied as well as operating energy. While the calculation of a building's operating energy is straightforward, there is a lack of a complete embodied energy calculation method. Although an input-output-based (IO-based) hybrid method could provide a complete and consistent embodied energy calculation, there are unresolved issues, such as an overdependence on price data and exclusion of the energy of human labor and capital inputs. This paper proposes a method for calculating and integrating the energy of labor and capital input into an IO-based hybrid method. The results demonstrate that the IO-based hybrid method can provide relatively complete results. Also, to avoid errors, the total amount of human and capital energy should not be excluded from the calculation.
We analyse the wood and concrete designs of the Wälludden building described by Börjesson et al. (Energy Policy 28 (2000) 575) in terms of their embodied energy, employing an environmentally extended input–output framework in a tiered hybrid life-cycle assessment, and in a structural path analysis. We illustrate the complexity of the inter-industry supply chains underlying the upstream energy requirements for the building options, and demonstrate that higher-order inputs are difficult to capture in a conventional process analysis. Our calculations show that Börjesson and Gustavsson's estimates of energy requirements and greenhouse gas emissions are underestimated by a factor of about 2, and that corresponding greenhouse gas balances are positive at about 30 t C-eq. Nevertheless, Börjesson and Gustavsson's general result—the concrete-framed building causing higher emissions—still holds.
Mitigating climate change through operational energy reduction in existing buildings is of highest priority for policy-makers in Europe and elsewhere. At the same time there is increasing understanding of the significance of impacts arising from material production for buildings. The aim of this work has therefore been to evaluate the importance of embodied GWP for refurbishment for operational energy reduction on a stockwide basis. It is further intended to judge the relative significance of embodied GWP for specific refurbishment measures implemented for operational energy reduction. We study the case of operational energy reduction in the Swedish residential building stock by 50 % compared to 1995.
The total embodied GWP to achieve the noted operational energy reduction is 0.35 Mt CO2-e/year. 83 % of this total is due to ventilation and window measures alone. Compared with previous studies assessing GWP mitigation from operational energy reduction, the “GWP payback time” is just over 3 years.
Many types of measure that contribute significantly to achieving the above operational energy goal had average embodied GWP between 10 and 20 g CO2-e/kWh operational energy reduction, notably window and ventilation measures. Indoor temperature reduction (to 20 °C), was also significant for stockwide operational energy reduction but had a very low GWP of 0.4 g CO2-e/kWh operational energy reduction. If this measure proves unfeasible to implement on a stockwide basis then more expensive measures with higher embodied GWP will be needed to achieve the stated energy reduction goal.
The paper starts from the results of one of the six case-studies of the SubTask B in the International Energy Agency joint Solar Heating and Cooling Task40 and Energy Conservation in Buildings and Community Systems Annex 52, whose purpose is to document state of the art and needs for current thermo-physical simulation tools in application to Net Zero Energy Buildings.The authors extend the Net Zero Energy Buildings (Net ZEB) methodological framework, introducing the life-cycle perspective in the energy balance and thus including the embodied energy of building and its components. The case study is an Italian building, tailored to be a Net ZEB, in which the magnitude of the deficit from the net zero energy target is assessed according to a life-cycle approach. The annual final energy balance, assessed with regard to electricity, shows a deficit which makes the case study a nearly Net ZEB, when the encountered energy flows are measured at the final level. Shifting from final to primary energy balance the case-study moves to a non-Net ZEB condition, because of the large difference between the conversion factors of photovoltaics generated electricity and imported electricity. The adoption of a life cycle perspective and the addition of embodied energy to the balance causes an even largest shift from the nearly ZEB target: the primary energy demand is nearly doubled in comparison to the primary energy case.
Global awareness of environmental impacts such as climate change and depletion of ozone layer has increased significantly in the last few years and the implication for emissions reductions in buildings are widely acknowledged. The goal, therefore, is to design and construct buildings with minimum environmental impacts. Lifecycle emissions resulting from buildings consist of two components: operational and embodied emissions. A great deal of effort has been put into reducing the former as it is assumed that it is higher than the latter. However, studies have revealed the growing significance of embodied emissions in buildings but its importance is often underestimated in lifecycle emissions analysis. This paper takes a retrospective approach to critically review the relationship between embodied and operational emissions over the lifecycle of buildings. This is done to highlight and demonstrate the increasing proportion of embodied emissions that is one consequence of efforts to decrease operational emissions. The paper draws on a wide array of issues, including complications concerning embodied emissions computation and also discusses the benefits that come with its consideration. The implication of neglecting embodied emissions and the need for an urgent policy framework within the current climate of energy and climate change policies are also discussed.
Recent efforts in the private and public sectors to move toward enhanced sustainability in the built environment have prompted the need to quantify and assess trade-offs among relevant sustainability metrics. Within the US military, for instance, many technological improvements are available to facilitate the achievement of net-zero goals for installations. These technologies must be assessed based on numerous performance criteria, and these technology selection decisions are difficult to make unaided. This paper seeks to demonstrate the use of decision-analytical techniques in which sustainable roofing technology alternatives (reflective, vegetated, or solar roofs) can be properly framed and assessed while evaluating the trade-offs between multiple performance criteria. Multi-criteria decision analysis methods are used to assess the impact of technology alternatives on sustainability framed within the popular concept of the triple bottom line (economic, societal, and environmental concerns). The framework developed in this paper can be applied to other sustainability technologies (energy, water, waste) or portfolios of numerous technologies.
This study compares three configurations of wind turbines to produce a nameplate power of 100 kW applying LCA methodology over a lifetime of 25 years. Alternatives under study are: installing twenty Endurance (EN) 5 kW, or five Jacobs (JA) 20 kW, or one Northern Power (NP) 100 kW turbines in the Halkirk region of Alberta, Canada. The comparison has been done taking life cycle energy, environment and economic aspects into consideration. Each parameter has been quantified corresponding to a functional unit (FU) of 1 kWh. Life cycle energy requirement for NP is found to be 133.3 kJ/kWh, which is about 69% and 41% less than EN and JA respectively. Global warming impact from NP is found to be 17.8 gCO2eq/kWh, which is around 58% and 29% less respective to EN and JA. The acidification (SO2eq/kWh) and ground level ozone [(VOC + NOx)/kWh] impacts from NP are also found significantly less compared to EN and JA configuration. The difference in relative environmental impacts from configurations is found to be less while performing uncertainty analysis, but does not alter the ranking of configurations. At 10% internal rate of return (IRR), electricity price for NP is 0.21$/kWh, whereas EN and JA prices are 65% and 16% higher respectively.
Due to the lack of energy intensity data for building materials and the high integration of the construction sector in national input–output tables, applications of conventional process-based life cycle inventory (LCI) and input–output (I–O) LCI models are hindered in China. This study developed a process-based hybrid LCI model to calculate the embodied energy and emissions of a typical high-rise building in China, which has a frame-shear wall and reinforced concrete frame structure. The I–O model used for building materials manufacturing is based on the 2007 Chinese economic benchmark statistics. The process-based model uses the specific data of transportation and construction activities. Results show that the embodied energy of the case building was 309,965 GJ and, the energy intensity is 6.3 GJ m−2. The embodied energy is dominated by coal and the shares of diesel fuel and electricity in total energy were significant. The embodied emissions mainly derive from the electricity sector and gas and water production due to its intensive coal consumption. Results of the process-based hybrid model were moderately higher (5–13%) than the I–O model values.
Given a general lack of research on Irish construction greenhouse gas emissions, a subsectoral embodied carbon dioxide equivalent (CO2-eq) analysis of this sector has been undertaken with the aim of overcoming some methodological challenges such as system boundary constraints, input-output aggregation, double counting of energy inputs and a general lack of data. Using this extended methodology, it is estimated that total embodied CO2-eq intensity of Irish construction in 2005 was 1,364gCO2-eq/€ with direct sub-sectoral embodied CO2-eq intensity averaging 56 gCO2-eq/€. Some 215gCO2-eq/€ is estimated to arise from domestic sources including 160gCO2-eq/€ from domestic indirect emissions. International arising emissions constituted 84% of the total. The focus of policymakers on regulating energy use in, and emissions from buildings has been on operational energy use ignoring other life cycle components such as embodied energy which can account for a significant portion of life cycle emissions. Data relating to embodied energy and emissions in buildings is limited. However, stochastic techniques can be used to estimate the distribution of emissions intensities in the building sector and sub-sectors. This thesis demonstrates this approach using apartment buildings in Ireland and how it can be used to form the basis for evidencebased policy formulation. A Monte-Carlo simulation suggests that the average probability distribution of embodied CO2-eq intensity in the sample displays the characteristics of a Wakeby distribution. The average embodied CO2-eq intensity of the sample of apartment buildings analysed was estimated to be 1,636gCO2-eq/€ with an uncertainty of 73 gCO2-eq/€. The distribution also had a long tail which can be targeted for improvement through the implementation of appropriate policies. Two policies are proposed and assessed, one regulatory and one informational. Implementing Policy Option 1 (Regulatory) for example results in an average saving of 450gCO2-eq/€.
This paper demonstrates that by understanding how energy is consumed in the manufacturing of reinforced concrete, designers can significantly reduce the overall embodied energy of structures. Embodied energy of products can vary from country to country. Therefore, to accurately estimate the embodied energy of reinforced concrete structures, data specific to the country where they are being constructed must be used. This paper presents the assessment of embodied energy in typical RC building structures in Ireland.The most common methods used to calculate EE are evaluated in this paper and the most suitable method was applied to reinforced concrete. The EE of a typical 30MPa concrete mix in Ireland is calculated to be 1.08MJ/kg. Notably cement is credited with 68% of the total EE. The major contributors of energy consumption are identified, which should aid to minimise energy consumption and optimise efficiency.A case study is presented which compares the EE of a typical reinforced concrete structure in Ireland using two concrete mix designs. The first uses Ordinary Portland Cement, while the second uses GGBS replacing half of the cement content. As expected, the EE of the GGBS mix is significantly lower (30%) than that of its counterpart.
A comparative assessment was conducted to evaluate the significant difference in the environmental burdens of using steel or concrete for the structural frame of office buildings. The study also assessed the environmental performance over the operational life of the buildings. Environmental life cycle assessment (LCA) approach revealed that there is no significant difference between the environmental performance of steelframed office buildings in comparison with concrete framed office buildings. Energy consumption and CO 2 emissions were used as relevant environmental parameters for life cycle assessments.
The construction industry including its support industries is one of the highest consumers of natural resources. In the act of consumption of natural resources during construction processes, embodied energy and greenhouse gases are emitted which have adverse effects on the natural environment. Thus, recent studies have revealed a significant interest in the quantification of embodied energy and greenhouse gases in construction processes. Unfortunately, current interpretations and quantification procedures of embodied energy and greenhouse gases are quite unclear. More also, while greenhouse gas and embodied energy quantification models are so disaggregated, studies reveal their existence in isolation without any links to other important environmental/construction management variables such as waste, time and cost. The objectives of this study are to identify the gaps in the current computation models, to reveal the relationships between the identified models and to propose a framework towards developing an integrated model for measuring embodied energy, greenhouse gases, construction waste, time and cost. The contributions of this study are three-fold. Firstly, the identification of the different models and variables, such that they can be used in computations, that can lead to consistent and comparable results. Secondly, investigate the relationships amongst embodied energy, greenhouse gases, construction waste, cost and time variables, that can facilitate the quantification process and hence potentially facilitate the engagement into low carbon building design by construction professionals. Lastly, lay the foundation for further research especially with regards to the integration of the different models and variables so that they can be measured simultaneously.
Although embodied CO2-eq analysis has seen recent developments as evident in the establishment of the ISO 14040 and 14044 LCA standards, it is recognized that due to weaknesses in gathering data on product-related emissions, embodied CO2-eq values are probabilistic. This paper presents a stochastic analysis of hybrid embodied CO2-eq in buildings to account for this weakness in traditional methods and, by way of example, applies it to an Irish construction-sector case study. Using seven apartment buildings, 70,000 results are simulated with Monte Carlo analysis and used to derive probabilistic and cumulative embodied CO2-eq intensity distributions for apartment buildings in Ireland. A Wakeby distribution with known statistical parameters and uncertainty was derived for the average embodied CO2-eq intensity of apartment building in Ireland. The mean hybrid embodied CO2-eq (ECO2-eq) intensity was estimated to be 1636gCO2-eq/€ with an uncertainty of 73gCO2-eq/€. The stochastic analysis helps to account for variability in input variables into embodied CO2-eq analysis. The application of the stochastic embodied CO2-eq analysis as demonstrated in this study can be extended to other building sectors and countries and can form the basis for the development of evidence-based policy formulation since it provides greater information on embodied CO2-eq intensities of buildings than deterministic approaches.
Sustainable material selection represents an important strategy in building design. Current building materials selection methods fail to provide adequate solutions for two major issues: assessment based on sustainability principles, and the process of prioritizing and assigning weights to relevant assessment criteria. This paper proposes a building material selection model based on the fuzzy extended analytical hierarchy process (FEAHP) techniques, with a view to providing solutions for these two issues. Assessment criteria are identified based on sustainable triple bottom line (TBL) approach and the need of building stakeholders. A questionnaire survey of building experts is conducted to assess the relative importance of the criteria and aggregate them into six independent assessment factors. The FEAHP is used to prioritize and assign important weightings for the identified criteria. A numerical example, illustrating the implementation of the model is given. The proposed model provides guidance to building designers in selecting sustainable building materials
Green roofs have several environmental benefits, such as improving building energy efficiency. The present paper provides a comprehensive study of the impact of a green roof on building energy performance. A model of green roof thermal behavior was coupled with a building code to allow the evaluation of green roof foliage and soil surface temperatures. Simulations were conducted for a single-family house with conventional and green roofs in a temperate French climate. In the summer, the fluctuation amplitude of the roof slab temperature was found to be reduced by 30 °C due to the green roof. The heat flux through the roof was also evaluated. In the summer, the roof passive cooling effect was three times more efficient with the green roof. In the winter, the green roof reduced roof heat losses during cold days; however, it increased these losses during sunny days. The impact of the green roof on indoor air temperature and cooling and heating demand was analyzed. With a green roof, the summer indoor air temperature was decreased by 2 °C, and the annual energy demand was reduced by 6%. The present study shows that the thermal impact of green roofs is not functionally proportional to the leaf area index parameter. It also shows the high dependency of this impact on the roof insulation. Finally, the simulations suggest that green roofs are thermally beneficial for hot, temperate, and cold European climates.
Conventional process-analysis-type techniques for compiling life-cycle inventories suffer from a truncation error, which is caused by the omission of resource requirements or pollutant releases of higher-order upstream stages of the production process. The magnitude of this truncation error varies with the type of product or process considered, but can be on the order of 50%. One way to avoid such significant errors is to incorporate input-output analysis into the assessment framework, resulting in a hybrid life-cycle inventory method. Using Monte-Carlo simulations, it can be shown that uncertainties of input-output– based life-cycle assessments are often lower than truncation errors in even extensive, third-order process analyses.