* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download components, materials and technologies in practical pursuit of
Survey
Document related concepts
Architectural design values wikipedia , lookup
Building regulations in the United Kingdom wikipedia , lookup
Zero-energy building wikipedia , lookup
Autonomous building wikipedia , lookup
Building material wikipedia , lookup
Sustainable development wikipedia , lookup
Sustainable landscaping wikipedia , lookup
Sustainable urbanism wikipedia , lookup
Green building on college campuses wikipedia , lookup
Sustainable city wikipedia , lookup
Transcript
CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 1 of 7 COMPONENTS, MATERIALS AND TECHNOLOGIES IN PRACTICAL PURSUIT OF SUSTAINABLE BUILDINGS HENRY SKATES+, BRIAN NORTON*, AND JOHN STOREY+ + Centre for Building Performance Research, Victoria University of Wellington, Wellington, New Zealand. *Centre for Sustainable Technologies, University of Ulster, Newtownabbey, BT37 0QB, N Ireland ABSTRACT The strategic issues underlying the selection of appropriate technologies that contribute to the environmental sustainability of buildings are discussed. Specific examples of building technologies that facilitate the goal of achieving sustainability are described. Design objectives are identified as having a significant influence on the selection of sustainable technologies, while value judgements often allow for the inclusion of technologies that have adverse environmental impacts. Six houses, three from New Zealand and three from the UK are discussed with regard to the choice of sustainable technologies. KEYWORDS: Sustainable buildings; renewable energy; material use; environmental impact; life cycle analysis. INTRODUCTION Buildings worldwide have individual and collective, direct and indirect, impacts on the environment both present and future as illustrated in Fig. 1. Each building, by occupying land, alters the ground and vegetation, changes water courses and wildlife habitats and, in both construction and use, consumes resources, labour, materials and fuel for power, heating and maintenance. Within the European Union it has been estimated that buildings consume about 40% of energy, produce 30% of carbon dioxide emissions and generate 40% of waste materials. Sustainability, in this instance, means “meeting the needs of the present without compromising the ability of future generations to meet their own needs” (WCED, 1987). Sustainable construction is thus the “creation and responsible tenure of a healthy built environment based on resource efficient and ecological principles” (Kibert, 1994). This is accomplished through the adoption of a holistic view of the world and human interactions with it, under which every function is cognisant of and within the limits of both the local and global ecosystems. This perspective has been summed-up by the phrase “think global, act local”. Sustainable buildings are characterised over their period of use by: • Consuming minimal resources (materials, energy and water). • Efficiently using environmentally benign materials and energy. • Minimising both direct and indirect waste and pollution including good indoor and outdoor air quality. • Integrating harmoniously with the natural environment. • Contributing by location and services to a sustainable urban form and transport system. • Being safety constructed and healthy to use. • Facilitating social development. • Being capable of adapting to special needs. CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 2 of 7 These characteristics relate to diverse aspects, differently measured, of a building’s commissioning, design, construction, occupation and demolition. An optimised strategy thus has to be underpinned by subjective value judgements as to the importance of each objective. Fig. 1. Global-Local Links and Impacts of Buildings Broad strategies to achieving sustainable buildings are summarised in Table 1. Table 1. Strategies Leading to Sustainable Buildings Objective Strategy Use less: energy, materials, water, and land. Conserve: natural environment, bio-diversity. Maintain: healthy indoor environment, accessible outdoor environment. Reuse, recycling, use of renewables, loose fit, long life, efficient use, life-cycle design, renovation, low maintenance. Optimise land use, prevent pollution, avoid regrading, and encourage ecological harmony. Healthy materials, adequate ventilation, breathing skins, provision of public transport, amenities, services, noise abatement, socially inclusive access. IMPERATIVE CRITERIA Sustainable buildings should use technologies, materials and energy to meet the following criteria: • Low energy use in the occupation of the building. • Low embodied energy materials, processes and products should be used where possible. • Selection should be based on the source and origin being managed sustainably and where extraction, processing and manufacture conform to best practice environmental management. CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 • • • • • • • Page 3 of 7 Anticipate the needs of building users – facilitate changing requirements. Wherever possible recycled or reused materials, products and components should be used in construction, refurbishment and repair and all surplus materials on site should be separately sorted and recycled or incorporated in the building or reused to minimise waste. The building should be designed to optimise opportunities on its proposed site, taking into consideration aesthetic and climatic factors as well as energy and material resources. Materials, which do not incorporate toxic; solvents, chemicals, preservatives and synthetic resins, should be used to safeguard the health of construction workers and building occupants. Renewable technologies should be utilised where appropriate for electricity generation, heating and cooling. The construction of a building should use local materials, requiring as little transportation of resources as possible. Be designed to be as self sufficient as possible. The implementation of sustainable buildings requires a wide-range of broad measures that may be grouped as shown in Table 2. Table 2. Actions in Support of Sustainable Housing Design Considerations Consider environment impacts of materials. Optimise design with respect to construction logistics. Design for durability, reuse, re-cycling and repairability. Design for low resource use. Adaptable design. Life-cycle approach to design. Set sustainability criteria in design brief. Construction Process Reduce the environmental input of site operations, supply logistics and materials use. Minimise, manage and recycle site waste. Retain soil, vegetation and watercourses where possible. Avoid damage and pollution. Broker demolition materials. Technology Selection Government Intervention Base product development on life cycle cost rather than initial cost. Improved energy standards. Minimise pollution and energy use in manufacturing, use and demolition. Exclusively best practice in regulations. Reliable, accurate product ecolabelling. Durable low maintenance and repairable products. Reuse/recycle of materials. Shorten environmentally benign product development time to market. Planning to promote public transport use. Promote the use of healthy materials. Retention of natural ecology required by building codes. Promote eco-labelling of buildings, their sub-systems and components. Universal labelling of all products with full disclosure of all by- products, waste etc.. Promote use of brown-field sites. Promote common life-cycle analysis methods and databases and provide incentives for move to life cycle procurement. Promote ethical investment and development strategy. Funding sustainable initiatives. Educate and inform public of issues. CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 4 of 7 As may be seen, governmental actions, and as a prerequisite, public demand, to promote economic and social sustainability are explicit. There are also crucial obligations on designers and constructors. This paper, however, focuses on building technologies that can facilitate the sustainability of buildings. TECHNOLOGY SELECTION The selection by designers of building materials, products and component technologies can be conservative, which hinders the introduction of new technologies. Though often arising from unproven long-term performance of innovative systems, this conservatism is driven both by familiarity - by using what was used before, and by the designer’s actual or perceived expectations of clients’ needs. Major clients are thus, by explicit communication of their wish for sustainable buildings, able to encourage the development and implementation of underlying technologies. Central and provincial government can be particularly successful in this activity, as they are often the largest clients. For example, in the 1970's and 1980's the UK central government’s use of co-ordinated procurement based on performance specifications has been shown (Cheetham, 1997) to reduce innovation market risks for the manufacturers of building components. A particular technology will be a useful contributor to the overall sustainability of a building only for a specific set of contexts. The latter will vary depending on building use, location, climate, competing technologies, economic and social acceptability and regulatory imperatives. Selection must therefore commence with consideration of the broadest range of generic technologies on the basis of life-cycle environmental and economic analyses. In reality, seeking to produce buildings that are benign environmentally and viable economically is often a pragmatic qualitative process. For small projects the additional cost of further design work to attain more unequivocal sustainability is difficult to justify. The outcomes of pragmatic sustainable building design are often useful exemplars despite their inherent compromises (Skates et al, 1998). For those in developed countries, generic and technology-specific time-limited life-cycle analyses are available (see, for example, for solar water heaters, Smyth et al (2000)). For developing countries, not only are they not available, but also the appropriate underlying public policy consensus is only now being developed. In particular in developing countries it is important, as noted by Muttagi (1998) that the pursuit of sustainability in buildings, and also in a wider context, does not reinforce economic disparities or instigate unwanted patterns of social change. The widest open participation in making underlying value judgements is thus essential. Vernacular or traditional building design solutions are frequently either inherently sustainable or the most sustainable within pertinent economic parameters. Where this is the case, in broad terms, the only additional technologies required are those that meet needs unsatisfied by traditional means. TECHNOLOGICAL EXAMPLES Consider the following specific examples of sustainable domestic buildings in the New Zealand and United Kingdom climates respectively. They each subscribe to technologies that support sustainability set in the context of a passive solar design underpinned by good practice in energy conservation but in each case value judgements have been made with regard to the inclusion of additional technologies. New Zealand Examples The objective of the Southpark Solar Vision home designed for a specific client by architect Roger Buck is a passive solar house with a range of other energy-saving features included. The primary passive solar strategy is direct gain windows with high thermal mass to store collected energy and higher than normal insulation levels. The house is primarily of concrete construction including floors, walls and roof. This is combined with a fairly open plan to expose as much of the structural mass surface area as possible to sunlight. Innovative sustainable technologies include shower trays that recover heat from waste hot water and a gas fired sterling engine producing electricity and hot CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 5 of 7 water for under floor heating and provision has been made for solar hot water heating. Rainwater is collected and taken to an existing irrigation system. Whilst achieving the design objective of an energy efficient house, the building also uses a number of less than environmentally benign materials to achieve this objective. Take for example the high-embodied energy of concrete (Alcorn 1996) or the hazardous waste by-products in the production of PVCu as used in the window frames. Clearly there are environmental impacts other than renewable energy, which need to be considered in achieving a sustainable building. The eco-friendly home in Waitakere City was designed as a speculative development to look like a ‘normal’ New Zealand home. The objective here was maximum desirability and while energy efficiency was not top of the agenda, it has been given reasonable consideration. Low mass walls are used on a concrete floor slab. Sustainable technologies included in the design are reusable rainwater, low water use and energy efficient appliances. Low environmental impact sustainable materials are used throughout the house and the health and wellbeing of the occupants has been addressed with attention being given to indoor / outdoor flow, indoor air quality and reduced electromagnetic flux. A heat pump air conditioner is used to provide heating in winter and cooling in summer (cooling is required in the Auckland climate in the summer). An additional heat pump is used to provide hot water heating. In the effort to make this home look normal, some basic passive solar design principles have been overlooked. Typical New Zealand houses have up to 40% of the wall area as glazing on all elevations. This house is no exception. However, due to inappropriate levels of glazing, solar control glass has had to be used on the north elevation. This will reduce the benefits of winter sun. The house was on public display for six months before being offered for sale. The house sold easily, reinforcing the fact that the design objectives were clearly met however compromises have been made in the passive solar design strategies employed, resulting in potentially increased energy use. The objective of the Wellington eco house was to address contextual and cultural sensitivity and cost as well as environmentally conscious design in a local authority house for rent. Due to the unknown lifestyle and social needs of future tenants, it could not be assumed that occupiers would be committed to, or even be aware of environmental ideas (Storey 1994). Complicated environmental control regimes or mechanisms that require significant maintenance were therefore rejected in favour of automatic or simple operating systems. Robust materials such as concrete masonry walls and floors were chosen for their long life expectancy and resistance to wear and tear. Sustainable technologies include a Trombe wall on the north façade and direct gain windows and skylights. Natural ventilation along with ample thermal mass in the floors and walls is used to control summer overheating. Like the eco friendly house in Waitakere, heat pumps are used for domestic hot water and air conditioning. A night storage heater supplements the heating from the air heating system. A separate granny flat also incorporates a roof mounted solar water heater. Water conservation is addressed, as are health issues. Again like the Waitakere house, the Wellington house was on public display for six months and many visitors were disappointed to learn that the house was not for sale. Clearly again, the house met the design objectives of being a desirable home to rent, being contextually, culturally and environmentally sensitive, but certain aspects of the design are questionable in a sustainable context. The extensive use of poorly insulated concrete masonry not only has high embodied energy but subjected to an intermittent heating regime common to many households today, may actually increase overall energy use. This is an inherent problem when designing for an unknown user. United Kingdom Examples The Vale house at Southwell in Nottinghamshire, England sets out to be autonomous. The only connections to mains services are for telephone and a two-way electricity connection. The house design was predicted to rely only upon the resources of the land, which it occupies. Among the many technologies employed are super-insulation, on-site rainwater collection and filtering for domestic use and a sewage composter for waste. A heat-recovery mechanical ventilation system is used to preheat incoming ventilation air and thirty-six photovoltaic 60-Watt panels largely meet electricity demand. CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 6 of 7 These additional technologies combine to make the house autonomous thus achieving the design objectives. The house is an excellent example of what can be achieved but this comes at a price. The space required for the sustainable technologies accounts for approximately 30% of the floor area and represents a substantial initial cost overhead; in addition the photovoltaic array occupies a portion of otherwise useable garden space. This necessity of autonomy demanding so much space is a paradox in terms of sustainability (Hawkes, 1995). There are limits to the density at which houses like this can be built with sufficient resources to meet their needs. The Solar House in Magherafelt in Northern Ireland was designed to have net zero carbon dioxide production from the site, hence the acquired name “Zero C02 House” (Anon, 1996). The house is built on reclaimed land, and like the Vale house, uses low heat-loss glazing, has high levels of thermal insulation, uses heavyweight construction to provide high thermal mass and has a ventilation system with heat recovery. It also has wood burning facilities for heating using site-grown timber (In the case of the Vale house the trees felled to make room for the house were not replanted and were thus a finite resource). This house too has grey-water recycling through a reed bed and pond system, but the water is only used for the garden and car washing. The inclusion of a single-phase mains parallel wind turbine is designed to meet demands for electricity consumption. In addition, the house makes use of evacuated heat pipe solar collectors for heating domestic hot water. All in all the cost of the additional sustainable technologies represents approximately 25% of the total building cost. Again this house meets the design objectives, but also like the Vale house, there are clear-cut restrictions to replicating the Zero C02 House in the mass housing market. The Skates’ house in Antrim, Northern Ireland was designed with a pragmatic approach balancing affordability, buildability and sustainability with the main design aim being year round low cost thermal comfort (Skates and Norton, 2000). It too was built on reclaimed land and makes use of passive solar design principles. Like the previous examples it incorporates low heat-loss glazing, high levels of thermal insulation and mechanical ventilation with heat recovery, but instead of having high thermal mass, relies on a highly efficient fast response heating system to provide even annual and diurnal internal temperatures. Some spaces have been allocated to easily accessible service ducts to allow for the inclusion of additional sustainable technologies such as solar water heating and grey water recycling as they become attractive economically. The cost of building this house was on a par with traditional construction even though a number of innovative construction methods and materials were incorporated. The adoption of a pragmatic stance, which balances affordability, buildability and sustainability, requires that the design make use of both sustainable materials and less than benign materials such as concrete and PVCu, but only in limited amounts, and only because it was prudent either financially or technically to do so. CONCLUSION Sustainable buildings are a contribution to the achievement of holistic environmental sustainability. This paper discusses the strategic issues underlying the selection of appropriate technologies that contribute to the environmental sustainability of buildings. Specific examples of building technologies and the goal of achieving sustainability are described. The characteristics of the lifetime use of sustainable buildings are identified. These characteristics relate to diverse aspects, differently measured, of a building’s commissioning, design, construction, occupation and demolition. Six houses, three from New Zealand and three from the UK are discussed with regard to the choice of sustainable technologies. Each house seeks to contribute in its own way to the achievement of holistic environmental sustainability. In reality, an optimised strategy is often compromised by subjective value judgements as to the importance of each objective. There has, on occasion, been a tendency to pursue the goal of sustainable buildings through self-sufficient or autarkic solutions. While such exercises are interesting, and often have considerable educational value showing what is possible rather than what is currently viable, they do not, by their individual nature, often address some of the mainstream issues such as replicability. It is only after practical sustainable technological choices have been made including adopting appropriate measures to minimise building energy, that CIB World Building Congress, April 2001, Wellington, New Zealand Paper: NOV 46 Page 7 of 7 decisions need to be made for example as to whether energy will be produced at the building (by solar heating, photovoltaic, wind generation, etc) or purchased from utilities. Site factors, economic viability, and environmental life-cycle analysis rarely combine to lead to a self-sufficient approach, rather an optimal mix emerges. Design objectives are identified as having a significant influence on the selection of sustainable technologies, while value judgements often allow for the inclusion of technologies, components or materials that have some adverse environmental impacts. The house designs discussed strive to be sustainable environmentally. Those designs that achieved a comparable initial cost to prevailing costs for similarly-sized dwellings, did so via pragmatic compromises in materials and technology selection. Those designs (such as the "Vale" and "Zero CO2 House") which tend to be self-sufficient or autarkic solutions have a much higher initial cost. Whilst the energy use of the latter designs is certainly environmentally benign, they are not readily replicable. Widespread use of the large plot size required would lead to low urban densities leading to unsustainable transport use. Thus the adoption by house-builders of a pragmatic but leading-edge approach to sustainable design can be concomitant with commercially-viable site densities and more broadly sustainable urban forms. REFERENCES Alcorn, A. (1996). Embodied Energy Co-efficients of Building Materials, Centre for Building Performance Research, Victoria University of Wellington. Anon., (1996). Zero C02 House, EDS 70, Department of Economic Development, Belfast, Northern Ireland. Cheetham, D. W. (1997). The use of performance specification in the procurement of building components. Proc International CIB Symposium W92 on Procurement, Montreal, Canada, pp. 61-70. Hawkes, D. (1995). Realising the autonomous house, The Architects Journal, Vol. 201, pp. 37-39. Kibert, C. (1994). Proceedings of the First International Conference on Sustainable Construction, Tampa, Florida, November, pp Muttagi, P. K. (1998). Sustainable Development - A third world perspective. Sustainable Development and the Future of Cities (B Humm and P K Muttagi, Eds.) Intermediate Technology Publications, London, pp. 1-18. Skates, H. and Norton, B. (2000). Sustainable by Degrees: An Irish Example, Proceedings of the CAA/NZIA Vision Re Vision Conference, Wellington, New Zealand Skates, H., Norton, B. and Mannis, M. (1998). An Affordable Sustainable Housing Design for the Irish Context, Proc 5th World Renewable Energy Congress, Florence, pp 1439-1442. Smyth, M., Eames, P. C. and Norton, B. (2000). Life cycle assessment of a heat retaining integrated collector/storage solar water heater (ICSSWH). Proceedings of the 5th World Renewable Energy Congress, Brighton, UK. Storey J. B., (1994). Eco House: An Environment, User, Context Friendly Home, Proceedings First International Conference on Sustainable Construction (CIB Task Group 16) pp 27-36, Tampa Florida. World Commission on Environment and Development (WCED) (1987), Our Common Future - the Brundtland Report, Oxford University Press, Oxford.