Environmental assessment of rebuilding and possible performance improvements effect on a national scale

The paper deals with improvements on environmental significant activities related to the life supporting function “building and housing”, using life cycle assessment (LCA). In the calculation, back-casting technique is utilised and implies to a future scenario, based on known technology. Besides heating, waste water treatment is a significant issue, according to the definition of building and housing function practised. The main conclusions from the assessment are that rebuilding is an environmentally better choice than the construction of a new building, if the same essential environmentally related functional performance is reached. Furthermore, the case study and the national estimates performed prove that the potential environmental impact can be reduced by about 70% for the heating service and 75% for the waste water system, if the suggested measures are performed.     

Life cycle analysis of housing

This paper reports the findings of a project to assess the costs and benefits of adopting environment‐friendly construction practices for social rented housing in Scotland. Two contrasted dwelling specifications — one for a conventional building (the Control) and one for an environmentally responsible building (Eco‐Type 1) — are compared using Life Cycle Analysis and Life Cycle Costing methodologies. An assessment is made of the environmental and economic implications of adopting environmentally conscious construction practices in social rented housing. It is concluded that the provision of environmentally responsible dwellings could bring large‐scale reductions in the environmental burden of housing, and economic savings for housing providers and tenants over the life cycle of a dwelling with only a small increase in capital costs.     

LCA-based environmental assessment of the use and maintenance of heating and ventilation systems in Dutch dwellings

Buildings contribute significantly to the human-induced environmental burden. This comes not only from construction and demolition but also from activities throughout the operational phase – building maintenance and energy use for climate control. This paper describes how life cycle assessment (LCA) methodology can be applied to quantitatively assess the environmental performance of the use and maintenance of heating and ventilation systems. The studied climate systems include individual non-condensing boilers, condensing boilers and heat pumps on exhaust air for heating and hot tap water combined with either collective mechanical exhaust ventilation or individual balanced ventilation with heat recovery. This study shows that a heat pump causes the highest environmental burden of all the assessed climate systems due to the electricity needed for operation, high material content of the system and the refrigerant used. If the electricity used by the heat pump is generated fully by local photovoltaic cells, environmental performance will improve, but not for all environmental impact categories. Climate systems that reduce energy demand for heating, such as ventilation with heat recovery, will reduce the environmental impact related to energy use for space heating. However, if the electricity used to operate the system increases, along with the material content of the systems and distribution networks, other environmental impact categories than those related to space heating will also increase. Finally, maintenance frequency and related transportation of maintenance workers have a marginal effect on total environmental impact.     

Life cycle assessment of ecological sanitation system for small-scale wastewater treatment

Ecological sanitation (EcoSan) concepts, relying on an environmentally sound management of water, nutrient and energy fluxes, have been poorly characterized in literature and are widely ignored by public planning authorities, architects or engineers. A comparative life cycle assessment (LCA) of an EcoSan system at an office building and of conventional systems was carried out in order to provide practical data and information to (partially) fill this gap. Compared to conventional systems, EcoSan can reduce the contribution to ecosystem quality damage by more than 60%. EcoSan leads, however, to higher damages on resources and human health and higher impact on climate change. Key improvement possibilities and research needs related to these results are discussed throughout the paper. Ecological sanitation appears to be a promising alternative to small-scale wastewater treatment. At higher scales, low water consumption conventional systems are better performing and are not likely to be replaced by EcoSan systems in the short term. Standard conventional systems have very poor environmental performances and should be upgraded as far as possible.     

Parametric study on the performance of green residential buildings in China

The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which are compared with simulated results of various scenarios of “energy efficiency” strategy and “healthy housing” environmental control. First, the simulated results show that the adaptive thermal comfort of indoor environment control is actually balanced in terms of occupancy, comfort, and energy efficiency. Second, adaptive thermal comfort control can save more energy for heating or cooling than other current healthy housing environmental controls in China's HSCW zone. Moreover, a large proportion of energy use is based on the subjective thermal comfort demand of occupants in any building type. Third, the building shape coefficient cannot dominate energy savings. The ratio of the superficial area of a building to the actual indoor floor area has a significant positive correlation with and affects the efficiency of building thermal performance.     

装配整体式剪力墙产业化住宅环境表现测评

为了客观评价装配整体式剪力墙产业化住宅和传统钢筋混凝土现浇剪力墙住宅的环境表现,论文选择规模相似、户型一致、参建单位相同的两种不同建造模式的住宅项目作为测评对象,对其高度相同的多个标准层的构件生产、施工安装及外装修过程进行了全面细致地调研,获取了资源消耗、能源消耗和施工废弃物产生量等三个方面的统计数据,并据此进行了比较和原因分析。希望本研究可为进一步的研究提供扎实的数据基础,为有关技术和管理改进、标准和政策的制定提供客观、科学的依据。     

An environmental assessment of wood and steel reinforced concrete housing construction

Wooden type of housing is ubiquitous in Japan. It is the main structure for housing; however, due to the increase in residential developments, steel reinforced concrete houses are also on the rise. This paper assesses the environmental impacts of these two types of construction. An evaluation of the two types of construction in terms of energy usage and air emissions is done. A comparison of the damage costs due to the generated emissions is also considered. Four types of emissions generated are evaluated, namely carbon emissions (CO₂), nitrogen oxides (NO_x), sulfur oxides (SO_x) and suspended particulate matter (SPM). The life cycle of the two different housing construction types is traced and environmental impacts are determined. External costs are also calculated. Furthermore, different improvement assessment scenarios are simulated to ascertain several emission reduction possibilities. The study looks into the emitted emissions from the housing construction to its final disposal of a typical residential development in Saga, Japan. Results show that much of the environmental impacts from building a house are on the Global Warming Potential due to high carbon emissions. Moreover, the construction phase generated the highest pollutant emissions from nitrogen oxides, sulfur oxides and suspended particulate matter. Steel reinforced concrete (SRC) construction has a higher environmental impact compared to the wooden type of housing construction. A longer design life for a residential house gives a reduction of about 14% in carbon emissions. Using solar energy for the operation phase has gained a reduction of 73% in the total life cycle carbon emissions.     

Materialities shape practices and notions of comfort in everyday life

ABSTRACT

The development of residential energy technologies aims to ensure thermal comfort in an increasingly energy-efficient manner. This development influences everyday practices related to comfort in everyday life in dwellings. Therefore, an empirical analysis of interviews with residents in three types of Danish detached houses, related to the building age, is used to understand how changes in technologies influence residents’ practices and notions of comfort. Detached houses are the most widespread type of housing in Denmark, constituting 44% of the housing stock. The analysis focuses on differences in heating systems between the housing types and shows how changes in technologies and material structures shape the practices of heating and airing. A shift in technology from radiators to underfloor heating was found to make a clear difference in both how houses are heated and thermal comfort is perceived. It is found that changes in material structures of houses consequently change residents’ perceptions of comfort and the related everyday practices. A more nuanced set of notions of comfort is developed in relation to different practices, and specifically the relation between airing and heating practices, as well as the context of seasons and the outdoors.     

Measuring residential duct efficiency with the short-term coheat test methodology

Assessing the thermal efficiency of a forced-air distribution system is difficult, in large part because of interactions between energy loss mechanisms and other building characteristics. This paper describes short-term coheating, a method of measuring the thermal efficiency of residential heating and cooling distribution systems in situ, and presents the results of a series of studies that utilized the short-term coheat methodology. Short-term coheat tests were conducted in 53 residential buildings including both site-built and manufactured housing. The magnitude of the distribution efficiency, defined as the ratio of the energy required to heat the building if there were no duct losses to the actual heating energy required, ranged from less than 50% for homes with disconnected ducts to more than 90% for well sealed and insulated systems. Duct retrofits were also performed at 20 of the test sites and, following the retrofits, on average, the homes required 16–17% less heating energy. These results show that residential distribution system losses can be responsible for substantial energy loss and that duct retrofits are a viable energy conservation strategy for homes with distribution systems located outside of the conditioned space.     

Optimizing tradeoffs among housing sustainability objectives

The sustainability of housing units can be improved by integrating green building equipment and systems such as energy-efficient HVAC systems, building envelopes, water heaters, appliances, and water-efficient fixtures. The use of these green building measures often improves the environmental and social performances of housing units; however they can increase their initial cost and life cycle cost. This paper presents a multi-objective optimization model that is capable of optimizing housing design and construction decisions in order to generate optimal/near-optimal tradeoffs among the three sustainability objectives of maximizing the operational environmental performance of housing units, maximizing the social quality of life for their residents, and minimizing their life cycle cost. The model is designed as a multi-objective genetic algorithm to provide the capability of optimizing multiple housing objectives and criteria that include minimizing carbon footprint and water usage during housing operational phase, maximizing thermal comfort, enhancing indoor air and lighting quality, improving neighborhood quality, and minimizing life cycle cost. An application example is analyzed to illustrate the use of the developed model and evaluate its performance. The results of this analysis illustrate the novel capabilities of the model in generating 210 near-optimal tradeoff solutions for the analyzed housing example, where each represents an optimal/near-optimal and unique tradeoff among the aforementioned three sustainability optimization objectives of maximizing the operational environmental performance of housing units, maximizing the social quality of life for their residents, and minimizing their life cycle cost. These novel capabilities of the developed model are expected to improve the design and construction of housing units and maximize their overall sustainability.     

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.     

Environmental impact of dwellings in use: Maintenance of façade components

The use of dwellings contributes significantly to human-induced environmental burden in a number of ways, including energy consumption and the maintenance and replacement of building components. The present study deals with the maintenance and replacement of external doors and windows in a Dutch reference dwelling and describes how life cycle assessment (LCA) methodology can be applied to quantitatively assess the environmental impact of various maintenance scenarios for the façade components. First, the most effective way to reduce the negative environmental impact in this context is to replace existing single and double glazing with high efficiency double glazing, thereby reducing energy consumption for space heating. Second, the use of timber frames causes less environmental impact than PVC frames with a steel core. Third, extending the service life of building components decreases the input of material resources, production processes and the waste processing of building components during the service life of a dwelling, which is beneficial to the environment. Maintenance activities should only be performed when needed, keeping the building components in good condition while minimising the transportation movements of maintenance workers. Finally, protecting timber components with an alternative paint that contains less solvent does not lower the assessed environmental impact, but low-solvent paint may be preferred because of health aspects both for maintenance workers and occupants of the dwelling.     

草和泥与英雄传说

遥远的小山村 赵中说他从每次从兰州到茶园村的乘车路线几乎是固定的:乘下午16点40分的火车,火车先从兰州到天水,天水到宝鸡,进入陕西省,再往回走,最后于次日上午9点到达四川广元.从地图上看是几个Z字型.甘肃陇南和四川广元相距不远.赵中再从广元买上一张长途汽车票,四五个小时北上后到达终点——地名叫"渭沟河口"的地方.从这辗转1个多小时的步行路程,才进到深藏于绵亘大山中的"茶园村".她很美,但是如果每一两个月都跑这么一趟,恐怕连听那首赞美小山村的歌你都会发疯.     

谢英俊以社会性的介入质疑现代建筑的方向

谢英俊在操作建筑时,对建材环保在地化、工法轻便简易、造价便宜化,与在地物理环境(采光、通风、隔热等)都有着极高的敏锐度;也同时会触及社会弱势族群(边缘族群、贫病残障、低收入所得者等)的居住权,与建筑专业被菁英垄断化等社会议题。这样的思考里,也有着对全球化过程中,弱势族群如何应对被资金与技术倾轧、甚至因此面临被人类生态圈淘汰的思索;看似简单的协力建造家屋,其实有着对人类现在所面临共同处境(绿色、永续、商业资本掌控、甚至生命意义)的深刻思考内涵,更是对现代主义建筑发展的质疑。     

Reducing inventory data requirements for scenario representation in comparative life cycle assessment (LCA), demonstrated on the urban wastewater system

Wastewater reuse has become an attractive option for alleviating the stress from water resources. Centralized wastewater reuse is a common and continuously expanding practice worldwide, but the advantages of centralized over decentralized approaches are lately being questioned. Life cycle assessment (LCA) is a well-accepted means of assessing the overall environmental performance of service systems, however, construction of a life cycle inventory (LCI) for complex systems such as urban wastewater systems, is very time consuming. Lack of resources and unavailability of data often enforce constraints on the scope of the assessment. In such cases it may be beneficial to consider the approach presented here, which manifests the differences between the studied alternatives. By eliminating processes that remain unchanged, less data and human resources are required in building the inventory, and less parameter uncertainty is introduced into the analysis. The proposed approach is demonstrated through the conceptual modeling steps of an assessment of decentralized urban wastewater reuse alternatives.     

Life cycle assessment of a single-family residential building in Canada: A case study

The present study quantified the significant environmental impacts of a two-story residential building located in Vancouver, Canada, with a projected 60-year life span: (i) an inventory of all the construction materials was analyzed, covering the building structure and exterior and interior envelopes as well as the energy consumption; (ii) four types of functional units were defined; (iii) the five top building materials were examined, and a sensitivity analysis was conducted to investigate the impact associated with the choice of building materials. Two life cycle phases, manufacturing and operation, were more significant in all of the impact categories, and two building assemblies, the walls and the roof, bore most of the environmental loads. In terms of the sensitivity analysis, the roofing asphalt had the largest impact, dominating three of the seven selected impact categories. Despite different definitions of functional units, the function of the dwelling buildings is always the same, to provide protection and housing for their habitants. Additionally, to improve the performance of an existing building, several strategies were proposed for the building renovation and maintenance, including alternative replacement materials regarding the building components with high environmental burdens, good patterns of the occupants’ consumption behaviors as well as considerations of the financial and environmental cost. Finally, limitations and challenges are discussed to explore better design decisions in future studies.     

A comprehensive model for streamlining low-energy building design

Building designers are often limited in their ability to reduce the environmental impact of buildings, due to a lack of information on the environmental performance of building components as well as inconsistencies in the way in which this information is derived. Whilst numerous tools exist to help facilitate the low-energy building design process, these typically require large investments of time and money that are often beyond those available within any particular project. This paper describes an approach for streamlining the design process to reduce building life cycle energy consumption. Building assemblies are ranked based on an assessment of the life cycle energy requirements associated with their use within a building. This facilitates early stage assessment, negating the need for a resolved design before the relative energy requirements of alternate design solutions are known. Previous work assessed the initial and recurring embodied energy as well as the operational energy requirements for heating and cooling associated with the use of a range of building assemblies, using a simplified house model. This paper presents a sensitivity analysis of variations to the floor area, shape and orientation of this model, to test the reliability and applicability of the ranking approach across a broad range of circumstances. It was found that these variations did not influence the ranked order of the assemblies in terms of their life cycle energy requirements. Thus, the ranking of assemblies appears to provide an appropriate approach for streamlining the selection of construction elements during the building design process.     

Integrated assessment method for building life cycle environmental and economic performance

Life cycle assessment (LCA) is a powerful tool to identify a building’s environmental impact throughout its life cycle. However, LCA does have limits in practice because it does not consider the economic aspect of project implementation. In order to promote LCA application, a more comprehensive evaluation of building life cycle environmental and economic performance must be performed. To address these issues, we propose life cycle green cost assessment (LCGCA), a method that combines LCA with life cycle costing (LCC). In LCGCA the building’s environmental loads are converted to environmental costs based on the trading price of CO₂ certified emission reductions (CERs). These environmental costs are then included into the building life cycle cost. Subsequently an evaluation index of green net present value (GNPV) for LCGCA can be obtained. A governmental office building in Beijing was studied using LCGCA. Several design options were compared and the sensitivity of the CER price was analyzed. The research also shows that conclusions reached by LCGCA may be different from those of traditional LCC, which does not include environmental costs. The application of LCGCA needs the support of environmental policies. A sound environmental tax mechanism is expected to be established in China soon, which will enable LCGCA to be a useful tool to guide sustainable building design efficiently.     

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 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.