Life cycle inventory of buildings: A calculation method

Traditionally, life cycle assessment (LCA) is mostly concerned with product design and hardly considers large systems, such as buildings, as a whole. Though, by limiting LCA to building materials or building components, boundary conditions, such as thermal comfort and indoor air quality, cannot be taken into account. The life cycle inventory (LCI) model presented in this paper forms part of a global methodology that combines advanced optimisation techniques, LCI and cost-benefit assessment to optimise low energy buildings simultaneously for energy, environmental impact and costs without neglecting the boundary conditions for thermal comfort, indoor air quality and legal requirements for energy performance. This paper first outlines the goal and scope of the LCI. Then, the partial inventory models as well as the overall building inventory model are presented. Finally, the LCI results are shown and discussed for one reference dwelling for the context of Belgium.     

Life cycle energy analysis of buildings: An overview

Buildings demand energy in their life cycle right from its construction to demolition. Studies on the total energy use during the life cycle are desirable to identify phases of largest energy use and to develop strategies for its reduction. In the present paper, a critical review of the life cycle energy analyses of buildings resulting from 73 cases across 13 countries is presented. The study includes both residential and office buildings. Results show that operating (80-90%) and embodied (10-20%) phases of energy use are significant contributors to building's life cycle energy demand. Life cycle energy (primary) requirement of conventional residential buildings falls in the range of 150-400 kWh/m² per year and that of office buildings in the range of 250-550 kWh/m² per year. Building's life cycle energy demand can be reduced by reducing its operating energy significantly through use of passive and active technologies even if it leads to a slight increase in embodied energy. However, an excessive use of passive and active features in a building may be counterproductive. It is observed that low energy buildings perform better than self-sufficient (zero operating energy) buildings in the life cycle context. Since, most of the case studies available in open literature pertain to developed and/or cold countries; hence, energy indicative figures for developing and/or non-cold countries need to be evaluated and compared with the results presented in this paper.     

Life cycle assessment: A case study of a dwelling home in Scotland

The article provides a life cycle assessment (LCA) of a 3-bed room semi detached house in Scotland. Detailed LCA of five main construction materials i.e. wood, aluminium, glass, concrete and ceramic tiles have been provided to determine their respective embodied energy and associated environmental impacts. Embodied energy of various construction materials involved has been estimated to be equal to 227.4 GJ. It is found that concrete, timber and ceramic tiles are the three major energy expensive materials involved. It as been calculated that concrete alone consumes 65% of the total embodied energy of the home while its share of environmental impacts is even more crucial.     

An embodied carbon and energy analysis of modern methods of construction in housing: A case study using a lifecycle assessment framework

There is a growing interest in comparing the energy and consequential carbon embodied in buildings using different methods of construction and alternative materials. This paper compares the embodied carbon in a low energy, affordable house constructed using a novel offsite panellised modular timber frame system, in Norfolk UK with two traditional alternative scenarios. A lifecycle assessment (LCA) framework is used to conduct a partial LCA, from cradle to site, of the construction. An inventory of the materials and fossil fuel energy utilised in the construction was used to calculate the primary energy consumed and the associated embodied carbon. The embodied carbon was found to be 34.6 tonnes CO₂ for a 3 bedroom semi-detached house, 405 kgCO₂ per m² of useable floor area. When compared with traditional methods of construction the modern methods of construction (MMC) house resulted in a 34% reduction in embodied carbon. Despite timber being the predominant structural and cladding material, concrete is the most significant material (by proportion) in embodied carbon terms, responsible for 36% of materials related embodied carbon.     

Indonesian residential high rise buildings: A life cycle energy assessment

This study evaluates the effect of building envelopes on the life cycle energy consumption of high rise residential buildings in Jakarta, Indonesia. For high rise residential buildings, the enclosures contribute 10-50% of the total building cost, 14-17% of the total material mass and 20-30% of the total heat gain. The direct as well as indirect influence of the envelope materials plays an important role in the life cycle energy consumption of buildings. The initial embodied energy of typical double wall and single wall envelopes for high residential buildings is 79.5 GJ and 76.3 GJ, respectively. Over an assumed life span of 40 years, double walls have better energy performance than single walls, 283 GJ versus 480 GJ, respectively. Material selection, which depends not only on embodied energy but also thermal properties, should, therefore, play a crucial role during the design of buildings.     

Life cycle energy assessment of a typical office building in Thailand

A typical office building in Thailand was analyzed using the life cycle energy analysis (LCEA) method to illustrate the argument. Results indicate that although life cycle energy (LCE) distribution is concentrated at the operating phase, the embodied energy of buildings is a non-negligible fraction of the LCE balance. Energy (electricity) used for lighting and HVAC systems in the operation phase and; the manufacture of concrete and steel were the most significant elements in the buildings life cycle. Application of a combination of energy saving measures, showed that 40-50% of energy (electricity) used in a typical office building in Thailand can be saved. Preliminary analysis indicated that recycling building materials can also contribute additional energy savings (about 8.9%) to a buildings LCE profile. Therefore reducing energy consumption should be a priority for not only the operation but also other life cycle phases. It is suggested that both embodied and operating energy should be accounted for within the context of energy efficiency through the incorporation of LCEA into the existing Thai building energy code.     

Life cycle primary energy analysis of residential buildings

The space heating demand of residential buildings can be decreased by improved insulation, reduced air leakage and by heat recovery from ventilation air. However, these measures result in an increased use of materials. As the energy for building operation decreases, the relative importance of the energy used in the production phase increases and influences optimization aimed at minimizing the life cycle energy use. The life cycle primary energy use of buildings also depends on the energy supply systems. In this work we analyse primary energy use and CO₂ emission for the production and operation of conventional and low-energy residential buildings. Different types of energy supply systems are included in the analysis. We show that for a conventional and a low-energy building the primary energy use for production can be up to 45% and 60%, respectively, of the total, depending on the energy supply system, and with larger variations for conventional buildings. The primary energy used and the CO₂ emission resulting from production are lower for wood-framed constructions than for concrete-framed constructions. The primary energy use and the CO₂ emission depend strongly on the energy supply, for both conventional and low-energy buildings. For example, a single-family house from the 1970s heated with biomass-based district heating with cogeneration has 70% lower operational primary energy use than if heated with fuel-based electricity. The specific primary energy use with district heating was 40% lower than that of an electrically heated passive row house.     

Energy use in the life cycle of conventional and low-energy buildings: A review article

A literature survey on buildings’ life cycle energy use was performed, resulting in a total of 60 cases from nine countries. The cases included both residential and non-residential units. Despite climate and other background differences, the study revealed a linear relation between operating and total energy valid through all the cases. Case studies on buildings built according to different design criteria, and at parity of all other conditions, showed that design of low-energy buildings induces both a net benefit in total life cycle energy demand and an increase in the embodied energy. A solar house proved to be more energy efficient than an equivalent house built with commitment to use “green” materials. Also, the same solar house decreased life cycle energy demand by a factor of two with respect to an equivalent conventional version, when operating energy was expressed as end-use energy and the lifetime assumed to be 50 years. A passive house proved to be more energy efficient than an equivalent self-sufficient solar house. Also, the same passive house decreased life cycle energy demand by a factor of three – expected to rise to four in a new version – with respect to an equivalent conventional version, when operating energy was expressed as primary energy and the lifetime assumed to be 80 years.     

Life-cycle energy analysis of buildings: a case study

Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as life-cycle energy analysis. With Kyoto target obligations necessitating the quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. If conducted in primary energy terms, such analyses directly reflect greenhouse gas emissions, except for a few processes which involve significant non-energy related emissions such as cement manufacture. A Life-Cycle Assessment would include these issues, as well as other environmental parameters, though probably with a corresponding decrease in system boundary completeness. This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Australian based case study to demonstrate its use in evaluating alternative design strategies for an energy efficient residential building. For example, it was found that the addition of higher levels of insulation in Australia paid back its initial embodied energy in life-cycle energy terms in around 12 years. However, the saving represented less than 6% of the total embodied energy and operational energy of the building over a 100-year life cycle. This indicates that there may be other strategies worth pursuing before additional insulation. Energy efficiency and other environmental strategies should be prioritized on a life-cycle basis.

La consommation d'énergie est un paramètre très utilisé lorsque l'on veut mesurer l'impact des bâtiments sur l'environnement. Des études conduites récemment ont mis en lumière l'importance de l'énergie opérationnelle et celle de l'énergie intrinsèque dégagées par les bâtiments pendant leur durée de vie. L'analyse énergétique des bâtiments pendant leur cycle de vie est une méthode d'évaluation de l'énergie d'un bâtiment pendant sa durée de vie. Pour respecter les objectifs de la Conférence de Kyoto, il faut quantifier les émissions de gaz de serre au niveau national; il semble donc de plus en plus probable que la pratique de ces analyses va aller en augmentant. Si elles portent sur l'énergie primaire, ces analyses rendront parfaitement compte des émissions de gaz à effets de serre, sauf pour quelques procédés industriels, comme la fabrication du ciment, où les émissions de ces gaz ne sont pas liées à l'énergie. Toute évaluation du cycle de vie doit tenir compte de ces questions mais aussi d'autres paramètres environnementaux, mais avec, sans doute, une moindre netteté des limites des systèmes. Le présente communication expose brièvement quelques uns des problèmes théoriques liés aux analyses ènergétiques sur le cycle de vie et s'appuie sur une étude de cas australienne pour démontrer son utilitè à évaluer d'autres stratégies de conception de bâtiments à usage d'habitation à faible consommation d'énergie. On a constaté, par exemple, qu'en Australie le fait d'ajouter des niveaux d'isolation remboursait en 12 ans environ l'énergie intrinsèque initiale en terme d'énergie sur le cycle de vie. Toutefois, les economies répresentaient moins de 6% de l'énergie intrinsèque totale et de l'energie opérationnelle du bâtiment sur un cycle de vie de 100 ans. Cela veut dire qu'il serait peut etre intéressant d'envisager d'autres stratégies avant d'augmenter l'isolation. On devrait donner priorité à l'efficacité énergétique et à d'autres stratégies environnementales sur la base du cycle de vie.     

Life-cycle energy analysis of buildings: a case study

Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as life-cycle energy analysis. With Kyoto target obligations necessitating the quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. If conducted in primary energy terms, such analyses directly reflect greenhouse gas emissions, except for a few processes which involve significant non-energy related emissions such as cement manufacture. A Life-Cycle Assessment would include these issues, as well as other environmental parameters, though probably with a corresponding decrease in system boundary completeness. This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Australian based case study to demonstrate its use in evaluating alternative design strategies for an energy efficient residential building. For example, it was found that the addition of higher levels of insulation in Australia paid back its initial embodied energy in life-cycle energy terms in around 12 years. However, the saving represented less than 6% of the total embodied energy and operational energy of the building over a 100-year life cycle. This indicates that there may be other strategies worth pursuing before additional insulation. Energy efficiency and other environmental strategies should be prioritized on a life-cycle basis. La consommation d'energie est un parametre tres utilise lorsque l'on veut mesurer l'impact des batiments sur l'environnement. Des etudes conduites recemment ont mis en lumiere l'importance de l'energie operationnelle et celle de l'energie intrinseque degagees par les batiments pendant leur duree de vie. L'analyse energetique des batiments pendant leur cycle de vie est une methode d'evaluation de l'energie d'un batiment pendant sa duree de vie. Pour respecter les objectifs de la Conference de Kyoto, il faut quantifier les emissions de gaz de serre au niveau national; il semble donc de plus en plus probable que la pratique de ces analyses va aller en augmentant. Si elles portent sur l'energie primaire, ces analyses rendront parfaitement compte des emissions de gaz a effets de serre, sauf pour quelques procedes industriels, comme la fabrication du ciment, ou les emissions de ces gaz ne sont pas liees a l'energie. Toute evaluation du cycle de vie doit tenir compte de ces questions mais aussi d'autres parametres environnementaux, mais avec, sans doute, une moindre nettete des limites des systemes. Le presente communication expose brievement quelques uns des problemes theoriques lies aux analyses energetiques sur le cycle de vie et s'appuie sur une etude de cas australienne pour demontrer son utilite a evaluer d'autres strategies de conception de batiments a usage d'habitation a faible consommation d'energie. On a constate, par exemple, qu'en Australie le fait d'ajouter des niveaux d'isolation remboursait en 12 ans environ l'energie intrinseque initiale en terme d'energie sur le cycle de vie. Toutefois, les economies representaient moins de 6% de l'energie intrinseque totale et de l'energie operationnelle du batiment sur un cycle de vie de 100 ans. Cela veut dire qu'il serait peut etre interessant d'envisager d'autres strategies avant d'augmenter l'isolation. On devrait donner priorite a l'efficacite energetique et a d'autres strategies environnementales sur la base du cycle de vie.     

From net energy to zero energy buildings: Defining life cycle zero energy buildings (LC-ZEB)

There are various definitions of ‘zero energy’ and ‘net-zero’ energy building. In most cases, the definitions refer only to the energy that is used in the operation of the building, ignoring the aspects of energy use related to the construction and delivery of the building and its components. On the other hand the concept of ‘net energy’ as used in the field of ecological economics, which does take into account the energy used during the production process of a commodity, is widely applied in fields such as renewable energy assessment. In this paper the concept of ‘net energy’ is introduced and applied within the built environment, based on a methodology accounting for the embodied energy of building components together with energy use in operation. A definition of life cycle zero energy buildings (LC-ZEB) is proposed, as well as the use of the net energy ratio (NER) as a factor to aid in building design with a life cycle perspective.     

Life cycle energy of single landed houses in Indonesia

Building enclosures contribute 10–50% of the total building cost and 14–17% of the total material mass. The direct as well as indirect influence of the enclosure materials plays an important role in the building life cycle energy. Single landed houses, the typical houses in Indonesia, have been chosen for this study. The life cycle energy of the house enclosures and energy consumed during their life spans shows intriguing results. The initial embodied energy of typical brick and clay roof enclosures is 45 GJ compared to the other typical walls and roof material (cement based) which is 46 GJ. However, over the 40 years life span of the houses, the clay based ones have a better energy performance than the cement based ones, 692 GJ versus 733 GJ, respectively. The material selection during the design phase is thus crucial since the buildings have at least 40–50 years’ life span.     

Using national input/output data for embodied energy analysis of individual residential buildings

Embodied energy (EE) analysis has become an important area of energy research, in attempting to trace the direct and indirect energy requirements of products and services throughout their supply chain. Typically, input-output (I-O) models have been used to calculate EE because they are considered to be comprehensive in their analysis. However, a major deficiency of using I-O models is that they have inherent errors and therefore cannot be reliably applied to individual cases. Thus, there is a need for the ability to disaggregate an I-O model into its most important ‘energy paths’, for the purpose of integrating case-specific data. This paper presents a new hybrid method for conducting EE analyses for individual buildings, which retains the completeness of the I-O model. This new method is demonstrated by application to an Australian residential building. Only 52% of the energy paths derived from the I-O model were substituted using case-specific data. This indicates that previous system boundaries for EE studies of individual residential buildings are less than optimal. It is envisaged that the proposed method will provide construction professionals with more accurate and reliable data for conducting life cycle energy analysis of buildings. Furthermore, by analysing the unmodified energy paths, further data collection can be prioritized effectively.     

A matrix in life cycle perspective for selecting sustainable materials for buildings in Sri Lanka

This paper presents a matrix to select sustainable materials for buildings in Sri Lanka, taking into consideration environmental, economic and social assessments of materials in a life cycle perspective. Five building elements, viz., foundations, roofs, ceilings, doors and windows, and floors are analyzed based on materials used for these elements. Environmental burdens associated with these elements are analyzed in terms of embodied energy and environmental impacts such as global warming, acidification and nutrient enrichment. Economic analysis is based on market prices and affordability of materials. Social factors that are taken into account are thermal comfort, interior (aesthetics), ability to construct quickly, strength and durability. By compiling the results of analyses, two building types with minimum and maximum impacts are identified. These two cases along with existing buildings are compared in a matrix of environmental, economic and social scores. Analysis of the results also indicates need for higher consideration of environmental parameters in decision-making over social and economic factors, as social and economic scores do not vary much between cases. Hence, this matrix helps decision-makers to select sustainable materials for buildings, meaningfully, and thus helps to move towards a more sustainable buildings and construction sector.     

Life cycle assessment in buildings: State-of-the-art and simplified LCA methodology as a complement for building certification

The paper presents the state-of-the-art regarding the application of life cycle assessment (LCA) in the building sector, providing a list of existing tools, drivers and barriers, potential users and purposes of LCA studies in this sector. It also proposes a simplified LCA methodology and applies this to a case study focused on Spain. The thermal simulation tools considered in the Spanish building energy certification standards are analysed and complemented with a simplified LCA methodology for evaluating the impact of certain improvements to the building design. The simplified approach proposed allows global comparisons between the embodied energy and emissions of the building materials and the energy consumption and associated emissions at the use stage.The results reveal that embodied energy can represent more than 30% of the primary energy requirement during the life span of a single house of 222 m² with a garage for one car. The contribution of the building materials decreases if the house does not include a parking area, since this increases the heated surface percentage. Usually the top cause of energy consumption in residential building is heating, but the second is the building materials, which can represent more than 60% of the heating consumption.     

Cradle-to-gate life cycle inventory of vancomycin hydrochloride

A life cycle analysis on the cradle-to-gate production of vancomycin hydrochloride, which begins at natural resource extraction and spans through factory (gate) production, not only shows all inputs, outputs, and energy usage to manufacture the product and all related supply chain chemicals, but can highlight where process changes would have the greatest impact on raw material and energy consumption and emissions. Vancomycin hydrochloride is produced by a low-yield fermentation process that accounts for 47% of the total cradle-to-gate energy. The fermentation step consumes the most raw materials and energy cradle-to-gate. Over 75% of the total cradle-to-gate energy consumption is due to steam use; sterilization within fermentation is the largest user of steam. Aeration and agitation in the fermentation vessels use 65% of the cradle-to-gate electrical energy. To reduce raw materials, energy consumption, and the associated environmental footprint of producing vancomycin hydrochloride, other sterilization methods, fermentation media, nutrient sources, or synthetic manufacture should be investigated. The reported vancomycin hydrochloride life cycle inventory is a part of a larger life cycle study of the environmental consequences of the introduction of biocide-coated medical textiles for the prevention of MRSA (methicillin-resistant Staphylococcus aureus) nosocomial infections.     

Life-cycle assessment applied to buildings: gaps in knowledge

ABSTRACT

Life-Cycle Assessment (LCA) is a comprehensive method for environmental product evaluation. This study aims to analyse the development of the research on the use of the LCA methodology in buildings and to identify the knowledge gaps in this field. For this, articles were selected through a systematic review of the literature. The results show that LCA is only a simplification of reality. The application of the methodology in buildings is recent and requires more research to face the remaining challenges, such as standardising of methodology and inventories; optimising data acquisition and comparing studies; new methodologies aimed at reducing the limitations of traditional LCA, including other parameters such as the dynamic characteristics, so as to establish benchmarks for different buildings.     

Options to reduce the environmental impacts of residential buildings in the European Union—Potential and costs

A typology of buildings representative of the building stock for the EU-25 was developed characterizing 72 building types in terms of their representativity, geographical distribution, size, material composition, and thermal insulation. The life cycle impacts of the building types were calculated for different environmental impact categories both at building and EU-25 level. The use phase of buildings, dominated by the energy demand for heating is by far the most important life cycle phase for existing and new buildings. The environmental impacts were allocated to single building elements. Ventilation, heat losses through roofs and external walls are important for a majority of single- and multi-family houses. Three improvement options were identified: additional roof insulation, additional façade insulation and new sealings to reduce ventilation. The measures yield a significant environmental improvement potential, which, for a majority of the buildings types analyse represent at least 20% compared to the base case. The major improvement potentials at EU-level lie with single-family houses, followed by multi-family houses. Smaller reductions are expected for high-rise buildings due to the smaller share in the overall building stock. For both roof insulation and reduced ventilation, the measures were shown to be economically profitable in a majority of buildings.     

Life cycle energy analysis of a zero-energy house

Most zero-energy concepts focus on a reduction of the non-renewable operational energy use in buildings rather than taking the reduction of their life cycle energy use as a starting point. Nevertheless, the life cycle embodied and end-of-life energy will become more important, especially in buildings with low operational energy. Therefore, the life cycle energy use of a Belgian zero-energy reference house is examined by means of life cycle energy assessment. The influence of design decisions and regulations on the building construction type, the building services, and the performance of the building envelope are investigated. In terms of thermal performance of the building, the results show that the life cycle embodied energy in zero-energy houses with passive or standard thermal performance was not substantially different. From a life cycle energy perspective, passive house requirements are not essential criteria for zero-energy houses in Belgium. On the other hand, large life cycle energy savings were obtained through a proficient selection of all building construction materials and services. For the life cycle embodied energy in building constructions, the best timber frame and masonry houses were equally efficient. Wood pellets and photovoltaic panels were decisive factors in the life cycle embodied energy of building services.

Les concepts <<zéro-énergie>> sont axés pour la plupart sur une réduction de l'utilisation de l'énergie d'exploitation non renouvelable dans les bâtiments plutôt que de prendre la réduction de leur consommation d'énergie sur le cycle de vie comme point de départ. Néanmoins, l'énergie grise sur le cycle de vie et l'énergie de fin de vie vont gagner en importance, en particulier dans les bâtiments nécessitant une faible énergie d'exploitation. La consommation d'énergie sur le cycle de vie d'une maison belge «zéro énergie» de référence est donc étudiée au moyen d'un bilan énergétique du cycle de vie. Sont étudiés l'influence des décisions de conception et de la réglementation sur le type de construction du bâtiment, les services au bâtiment, et les performances de l'enveloppe du bâtiment. En termes de performance thermique du bâtiment, les résultats montrent que l'énergie grise sur le cycle de vie n'était pas fondamentalement différente dans les maisons «zéro énergie» offrant des performances thermiques passives ou standard. Du point de vue de l'énergie du cycle de vie, les exigences d'une maison passive ne sont pas des critères essentiels pour des maisons «zéro énergie» en Belgique. En revanche, d'importantes économies d'énergie sur le cycle de vie ont été obtenues par un choix opéré avec compétence de tous les matériaux de construction et services au bâtiment. S'agissant de l'énergie grise sur le cycle de vie dans la construction de bâtiments, les meilleures maisons, qu'elles aient été à ossature bois ou en maçonnerie, ont été tout aussi performantes. Les granulés de bois et les panneaux photovoltaïques ont été des facteurs décisifs concernant l'énergie grise sur le cycle de vie des services aux bâtiments.

Mots clés: services aux bâtiments, énergie grise, analyse énergétique du cycle de vie, [construction] passive, bâtiments résidentiels, <<zéro-énergie>>     

Life cycle cost implications of energy efficiency measures in new residential buildings

The importance of the built environment from an environmental impact and energy use perspective is well established. High thermal efficiency of the constructed building envelope is a key strategy in the design and construction of buildings which limit use of active space conditioning systems. Australia's current housing stock is thermally poor and national energy performance standards are relatively weak when benchmarked against international best practice. A lack of data has impeded the policy debate and a significant gap in analysis remains a lack of empirical research into the life-cycle cost implications of increased building thermal efficiency, particularly for residential buildings. This paper applies an integrated thermal modeling, life cycle costing approach to an extensive sample of dominant house designs to investigate life cycle costs in a cool temperate climate, Melbourne Victoria. Empirical analysis provides new insights into lifetime costs and environmental savings for volume housing design options and identifies sensitive factors. Results suggest that the most cost-effective building design is always more energy efficient than the current energy code requirements, for the full time-horizon considered. Findings have significant policy implications, particularly in view of present debates which frequently present higher energy efficiency standards as prohibitive from a costs perspective.