A comprehensive life cycle water analysis framework for residential buildings

Most studies on the environmental performance of buildings focus on energy demand and associated greenhouse gas emissions. They often neglect to consider the range of other resource demands and environmental impacts associated with buildings, including water. Studies that assess water use in buildings typically consider only operational water, which excludes the embodied water in building materials or the water associated with the mobility of building occupants. A new framework is presented that quantifies water requirements at the building scale (i.e. the embodied and operational water of the building as well as its maintenance and refurbishment) and at the city scale (i.e. the embodied water of nearby infrastructures such as roads, gas distribution and others) and the transport-related indirect water use of building occupants. A case study house located in Melbourne, Australia, is analysed using the new framework. The results show that each of the embodied, operational and transport requirements is nearly equally important. By integrating these three water requirements, the developed framework provides architects, building designers, planners and decision-makers with a powerful means to understand and effectively reduce the overall water use and associated environmental impacts of residential buildings.     

Embodied energy and cost of building materials: correlation analysis

The US building sector consumes 48% of the nation’s annual energy as operating and embodied energy. Calculating embodied energy is difficult, complex and more resource-consuming than calculating operating energy due to a lack of complete, accurate and specific embodied energy data. One commonly used method to calculate embodied energy is input–output-based (IO) analysis, which utilizes economic data. The use of economic data indicates some relationship between embodied energy and cost. Some studies have investigated whether the embodied energy of a building can be predicted from its cost. These studies analyzed the relationship of the cost and embodied energy of a building and found a strong, positive correlation. However, when analyzed at the material level, the correlation weakened. This paper develops an improved input–output-based hybrid (IOH) model to calculate the complete, accurate and material-specific embodied energy of 21 commonly used building materials. After calculating and evaluating the embodied energy, the correlation of the embodied energy and cost of materials was analyzed. The results demonstrate a very strong and positive correlation between embodied energy and cost. In conclusion, more research may be required to predict embodied energy from cost data.     

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 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 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.     

基于全生命周期理论的住宅建筑能耗计算与分析

运用全生命周期理论,结合住宅建筑的自身特点,通过建立计算模型,对住宅建筑的能耗进行了计算与分析。找出了住宅建筑各能耗之间的内在关系,为建设节能型住宅提供相应的理论依据,以促进住宅建筑的可持续发展。     

Net-zero buildings: incorporating embodied impacts

The design and assessment of net-zero buildings commonly focus exclusively on the operational phase, ignoring the embodied environmental impacts over the building life cycle. An analysis is presented on the consequences of integrating embodied impacts into the assessment of the environmental advantageousness of net-zero concepts. Fundamental issues needing consideration in the design process – based on the evaluation of primary energy use and related greenhouse gas emissions – are examined by comparing three net-zero building design and assessment cases: (1) no embodied impacts included, net balance limited to the operation stage only; (2) embodied impacts included but evaluated separately from the operation stage; and (3) embodied impacts included with the operation stage in a life cycle approach. A review of recent developments in research, standardization activities and design practice and the presentation of a case study of a residential building in Norway highlight the critical importance of performance indicator definitions and system boundaries. A practical checklist is presented to guide the process of incorporating embodied impacts across the building life cycle phases in net-zero design. Its implications are considered on overall environmental impact assessment of buildings. Research and development challenges, as well as recommendations for designers and other stakeholders, are identified.     

Life cycle energy assessment of Australian secondary schools

The Australian Department of Commerce builds many secondary schools in New South Wales every year, and the impact of energy consumption for such a type of construction has rarely been done before in Australia. Although there is a particular responsibility to ensure that public-owned projects contribute to the future well-being of the natural environment, environmental performance and energy efficiency of public projects are not well studied. In order that more informed design and planning decisions can be made about the future construction of school projects, this research paper uses life cycle energy analysis to study the total energy consumption of 20 public secondary school projects in New South Wales. The results will serve as a model for a more comprehensive analysis of energy consumption in establishing environmental performance criteria for the design and construction of future school projects in New South Wales.

Le ministère australien du Commerce construit chaque année de nombreuses écoles secondaires dans la province de Nouvelle Galles du Sud; l'étude de l'impact de la consommation d'énergie de ce type de bâtiment a rarement été faite auparavant en Australie. Bien qu'il existe une responsabilité particulière à s'assurer que les projets contribuent au développement harmonieux de l'environnement naturel, les performances environnementales et l'efficacité énergétique des projets publics ne font pas l'objet d'études sérieuses. Pour que l'on puisse prendre des décisions mieux étayées en matière de conception et de planning de futurs projets de construction d'écoles, cette communication s'appuie sur l'analyse énergétique du cycle de vie pour étudier la consommation énergétique totale de 20 projets d'écoles secondaires publiques en Nouvelle Galles du Sud. Les résultats obtenus serviront de modèles à une analyse plus complète de la consommation d'énergie en établissant des critères de performances environnementales applicables à la conception et à la construction de futures écoles en Nouvelle Galles du Sud.

Mots clés: Performances des bâtiments, énergie intégrée, analyse énergétique du cycle de vie, énergie opérationnelle, bâtiments publics, écoles     

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.     

建筑建造与运行能耗的对比分析

从建材含能和运输能耗出发,介绍了建造能耗的简化计算方法,并对目前我国住宅、普通办公建筑、大型办公建筑三类建筑建造能耗进行了案例分析。结果表明,三者的建造能耗平均水平分别约为3 850．5 500,7 300 MJ／m2,分别相当于各自8,13,9 a运行总能耗;钢材、水泥、混凝土、墙材为主要耗能用材。     

A life-cycle energy analysis of building materials in the Negev desert

Environmental quality has become increasingly affected by the built environment—as ultimately, buildings are responsible for the bulk of energy consumption and resultant atmospheric emissions in many countries. In recognizing this trend, research into building energy-efficiency has focused mainly on the energy required for a building's ongoing use, while the energy “embodied” in its production is often overlooked. Such an approach has led in recent years to strategies which improve a building's thermal performance, but which rely on high embodied-energy (EE) materials and products. Although assessment methods and databases have developed in recent years, the actual EE intensity for a given material may be highly dependent on local technologies and transportation distances. The objective of this study is to identify building materials which may optimize a building's energy requirements over its entire life cycle, by analyzing both embodied and operational energy consumption in a climatically responsive building in the Negev desert region of southern Israel—comparing its actual material composition with a number of possible alternatives. It was found that the embodied energy of the building accounts for some 60% of the overall life-cycle energy consumption, which could be reduced significantly by using “alternative” wall infill materials. The cumulative energy saved over a 50-year life cycle by this material substitution is on the order of 20%. While the studied wall systems (mass, insulation and finish materials) represent a significant portion of the initial EE of the building, the concrete structure (columns, beams, floor and ceiling slabs) on average constitutes about 50% of the building's pre-use phase energy.     

住宅空调方案寿命周期能耗和资源消耗研究

以某高层住宅为例,按北京市和上海市两地的气候和建筑热工条件,对5种常见住宅空调设计方案的生产能耗和资源消耗进行对比分析,并依据运行能耗调查数据,对3种常见住宅空调方案的寿命周期能耗进行对比分析。结果表明,户式空调和集中空调方案的生产能耗、寿命周期能耗和资源消耗均显著高于分体空调方案。对于所研究的情况,水冷式集中空调方案的寿命周期能耗是分体空调方案的6.6倍,认为分散式空调仍然是目前最节能环保的住宅空调方式,盲目推广集中式空调会使我国住宅空调能耗大幅度增加。     

Development of HVAC system simulation tool for life cycle energy management Part 1: Concept of life cycle energy management and outline of the developed simulation tool

The importance of LCEM (life cycle energy management) has been recognized from the view of life cycle energy savings for sustainable buildings. The purposes of this research are the proposal of an LCEM framework and development of prototype HVAC system simulation tools for LCEM. In this paper, the necessity of energy simulation tools for LCEM is discussed, and the outline and solution method of the simulation tool are shown.     

基于LCCA的既有居住建筑节能改造成本效益分析

为了对既有居住建筑节能改造的成本效益问题进行分析,首先运用全寿命周期成本理论分析既有居住建筑节能改造的增量成本与增量效益构成;再运用建筑能耗基本公式推导节能改造增量经济效益测算模型,并通过数学推导证明热源热网节能改造的经济效益要远好于建筑围护结构节能改造的经济效益;最后,运用增量经济效益测算模型和项目经济评价理论对实际案例的成本效益进行分析,计算结果表明:仅进行建筑围护结构节能改造存在投资额大、收益率低的特点,而仅进行热源热网节能改造本身投资收益水平较好。由此可见,建筑围护结构节能改造本身无法吸引社会资金投资,需要政府给予更多的经济激励才能吸引社会资金;而热源热网节能改造在政府适当的经济激励下能够通过市场进行改造资金筹措。     

Sustainable construction: life cycle energy analysis of construction on sloping sites for residential buildings

In 2010, the Australian residential construction sector contributed about 28% of the value of all construction and was responsible for 8% of the total energy consumption. Residential construction will continue to increase to cope with the demand due to population growth. Owing to land scarcity, construction on sloping sites has become a common construction method for residential development in Australia. This method has economic benefits but poses environmental issues as it damages topsoil, disturbs natural drainage and groundwater pathways and imposes additional stress on soil under fill. The life cycle energy consumption of the construction process is examined in relation to residential projects on sloping sites on a range of slopes and soil types in New South Wales, Australia. Forty-one detached dwellings were selected and a service life of 60 years assumed for the study. The research findings reveal that the slope for each type of soil has a positive correlation with life cycle energy consumption. As part of the onsite construction process, the results also show that the energy consumption of construction on sloping sites plays a significant factor in the life cycle energy analysis of a building.     

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 inventory of buildings: A contribution analysis

A companion paper presented the life cycle inventory (LCI) calculation model for buildings as a whole, developed within a global methodology to optimise low energy buildings simultaneously for energy, environmental impact and costs without neglecting the boundary conditions for thermal comfort and indoor air quality. This paper presents the results of a contribution analysis of the life cycle inventory of four typical Belgian residential buildings. The analysis shows the relative small importance of the embodied energy of a building compared to the energy consumption during the usage phase. This conclusion is even more valid when comparing the embodied energy of energy saving measures with the energy savings they realise. In most studied cases, the extra embodied energy for energy saving measures is gained back by the savings in less than 2 years. Only extremely low energy buildings might have a total embodied energy higher than the energy use of the utilisation phase. However, the sum of both remains small and the energy savings realised with these dwellings are large, compared to the energy consumption of average dwellings.     

Life cycle water analysis of a residential building and its occupants

Reduced water consumption is one of the objectives of many towns and cities as part of the trend towards more sustainable settlements. Information on comprehensive water usage is required for formulating conservation and management strategies. Whilst buildings are directly responsible for only 12% of global water consumption, they can indirectly account for a much more significant proportion of total water demand due to the production of construction materials as well as the goods and services purchased by their occupants. This paper analyses both direct and indirect water consumption of a conventional Australian residential building and its occupants over a 50-year period. Input–output analysis is used to comprehensively determine total water usage. The results show that the direct water consumption to operate the house is only 6.4% of the total, with a further proportion embodied in the materials of the dwelling. The water embodied in consumable items, especially food, is the most significant, representing 46% of total household water demand. Policies for minimizing water consumption should address more than just direct water usage and the findings used to influence the design of urban living in the future.

La réduction de la consommation en eau est l'un des objectifs de nombreuses villes, grandes et moins grandes, dans le cadre de la tendance actuelle à aller vers des habitations plus durables. Il est nécessaire de pouvoir disposer d'informations sur l'ensemble des usages qui sont faits de l'eau pour pouvoir formuler des stratégies de préservation et de gestion. Alors que les bâtiments ne sont directement responsables que de 12% de la consommation mondiale en eau, ils peuvent représenter indirectement une part beaucoup plus importante de la demande totale en eau, du fait de la fabrication des matériaux de construction comme des biens et services achetés par leurs occupants. La consommation en eau directe aussi bien qu'indirecte est analysée sur une période de 50 ans, en utilisant comme étude de cas un immeuble résidentiel australien classique et ses occupants. L'analyse des entrées et des sorties est pleinement utilisée pour déterminer l'usage total de l'eau. Les résultats montrent que la consommation directe en eau pour faire fonctionner la maison ne s'élève qu'à 6,4% du total, une part supplémentaire virtuelle étant constituée par les matériaux de l'habitation. L'eau virtuelle des produits consommables, en particulier des aliments, est la plus importante, représentant 46% de la demande totale en eau de l'habitation. Les politiques visant à réduire au minimum la consommation en eau devront aller au-delà du simple usage direct de l'eau, et ces résultats devront être utilisés pour influer à l'avenir sur la conception de la vie urbaine.

Mots clés: eau virtuelle?consommation des ménages?analyse du cycle de vie de l'eau?immeubles résidentiels?consommation en eau