A DISCUSSION ON THE SELECTION OF SUSTAINABLE BUILDING MATERIALS

Transcription

1 A DISCUSSION ON THE SELECTION OF SUSTAINABLE BUILDING MATERIALS O. Canarslan, S. T. Elias-Ozkan Department of Architecture, Middle East Technical University, Ankara, Turkey ABSTRACT: Sustainability affects the quality of our lives. Therefore, sustainable architectural design is necessary for future generation to live in a better environment. There are many things we can do to produce sustainable architecture and one of them is to select building materials which do not jeopardize the eco-balance in sustainable design. In this study, sustainable building materials will be examined and classified according to sustainability indicators as defined in published sources. It is hoped that such a classification will be useful in selecting building materials for a healthier environment. Keywords - Sustainable Building Materials, Sustainability Indicators. 1. INTRODUCTION Sustainability has been defined in the context of sustainable development as meeting the needs and aspirations of the present without compromising the ability of future generations to meet their own needs and aspirations (WCED, 1987). It is related to the quality of life in a community whether the economic, social and environmental systems that make up the community are providing a healthy, productive, meaningful life for all community residents, present and future [12]. The agenda of sustainability is leading, not to a single universal style but to a rich and complex architectural order around the world [2]. The idea of sustainable design evolved from a variety of concerns, experiences, and needs. Buildings fundamentally impact people s lives and the health of the planet. Atmospheric emissions from the use of energy lead to acid rain, ground-level ozone, smog, and global climate change [14]. The goal of sustainable design, which is also referred to as green design, is to create high-performance buildings. Architects have a huge responsibility to design buildings that do not threaten the eco-balance of our planet and yet provide human comfort without depleting global resources. The built environment accounts for almost half of all resource consumption in the world i.e. materials, energy, water and the loss of fertile agricultural land ( see Table 1) which is why architects must accept the fact that the wastes from buildings are polluting our planet and destroying the health of its inhabitants [2]. Table 1. Global Resources (Source: Green Architecture) Resource Building Use Energy 50% Water 42% Materials(by bulk) 50% Agriculture land loss 48% Coral reef destruction 50% (indirect) Buildings not only require energy but also materials of construction, which in turn require energy for their production and transportation (Pearce, 1998). The ideal situation would be to produce buildings with natural sustainable materials collected on site; these buildings should 327

2 also be able to generate their own energy from renewable sources, such as solar or wind, and manage their own waste [11]. To sum up, there is a need to exploit renewable energy sources and to develop new technologies and new solutions to building programmes. Also, there is a need to select more appropriate technologies using the best and not the cheapest method of construction, employing life-cycle assesment, seeking out local sources of energy and materials, employing local building skills and know-how [2]. It is important to note that the life cycle of a product or assembly includes the manufacturing, construction, use and maintenance, repair and renewal as well as the demolition, recycling and disposal of these items. Hence, there is a need to consider the effects and implications of each of these stages and their resulting effects on the environment, in order to produce sustainable buildings [4]. 2. SUSTAINABLE BUILDING MATERIALS Traditional building practices often overlook the inter relationships between a building, its components, its surroundings, and its occupants. Typical buildings consume more of our resources than necessary, negatively impact the environment, and generate a large amount of waste [13]. Most of the environmental effects are a result of the energy required for production and of the emission of harmful substances during surface treatment [1]. For this very reason, sustainable architecture prescribes the use of energy and materials without damaging the natural environment [7]. In this regard the following criteria gain supreme importance; minimizing material waste, assuring long-term use, choosing materials that do not have large environmental burdens and designing buildings so that they can be easily maintained, refurbished and deconstructed [3]. A building should be thought of as a complete system with specific features and performance requirements and not as a collection of separate disciplines. Sustainable design includes reduced energy consumption, using environmental friendly materials, reduced waste and pollution. In order to design sustainable buildings, selection of appropriate building materials becomes very important. According to Pearce (1998), The act of construction results in the consumption of large quantities of energy and materials over a relatively short period of time, and can generate significant quantities of waste which must be recovered or disposed. The waste and residuals from the construction process must either be assimilated by human or natural ecosystems, or be stored in landfills for future use. This downstream link to technological and ecological systems is a significant but often overlooked feature of the construction process. Additionally, transportation required to move materials and equipment to and from the site also consumes energy and results in environmental impacts due to emissions and other conflicts with natural ecosystems [5]. The building industry is a major consumer of raw materials and the type and quantity of raw materials that are extracted and the way they are processed has direct environmental impacts on the earth. Material selection affects the building occupants also, this in turn generates an indirect impact on the earth [8]. According to the programme of California Sustainable Design Program, there are many benefits to selecting sustainable materials/ products, such as: 1. Reduced maintenance costs by specifying easy-to-maintain materials 2. Reduced operational costs by selecting products that result in energy savings 3. Reduced replacement of materials by selecting durable materials 328

3 4. Reduced environmental impact by reducing unnecessary resource extraction and by minimizing waste generation 5. Reduced impacts on air quality by selecting low-emitting materials In selecting building materials, it is recommended to use materials which are durable and locally produced and obtained from renewable sources; the reasons being that [11]: Natural materials are less energy-intensive and polluting to produce and contribute less to indoor air pollution. Local materials have a reduced level of energy cost and air pollution associated with their transportation, and can also help sustain the local economy. Durable materials can save on energy costs for maintenance as well as for the production and installation of replacement products. According to the California Sustainable Design Program, there are a few key misperceptions that may hinder the use of sustainable products, because such products are widely perceived as: 1. Lesser in quality than standard products. 2. Appear different; e.g. low VOC paints. 3. Cost more. (Although it is true that some sustainable products cost more than typical products, this additional first cost is often offset by increased durability of product, reduced maintenance costs, or other benefits to building occupants such as enhanced indoor air quality.) 4. Not readily available. (Although some sustainable products are not produced in all locations, they can be delivered without undue delays.) 5. Proprietary or do not have competitive manufacturers. 3. SUSTAINABILITY INDICATORS No single comprehensive standard exists for evaluating the sustainable characteristics of all building materials. Therefore, there is a need to establish universal indicators of sustainability in order to evaluate and choose material for eco-friendly (green) buildings. Selection parameters, which are determined in subjective and objective terms, should be evaluated according to their importance. For instance, Reilly (1997) rated building materials and products according to five categories, i.e. excellent, good, fair, poor and very poor. When a material has a quality that is desirable or distinguishes it from similar products, it is called excellent and is rated as 1. If the material is not adequate in quality, it is called very poor and is rated as 5. This evaluation system can be used easily by most architects, builders and designers; however, it is very subjective and, therefore, not always reliable. The proposed rating system is presented below in Table

4 Table 2. Comparing Materials (Source: Reilly, 1997) As mentioned above, some properties of building materials can also be evaluated in objective terms; in this case analogue indicators have to be identified. Nonetheless, since all of the sustainability indicators cannot be measured on unit scales it is not possible to evaluate the sustainability level of a material in objective terms. Consequently, both evaluation systems, subjective and objective, may have to be combined in order to determine comparatively reliable sustainability indicators for selecting the most appropriate material. Different countries have developed different evaluation systems. In order to encourage the use of sustainable materials, all partners in the construction industry who are the decision makers i.e. designers, architects, engineers etc, should employ sustainability indicators while choosing building materials. For example, the California Sustainable Design Programme has formulated a grading system, which investigates materials in terms of the level of their resource consumption; manufacturing; transportation; installation; impact on building occupants; performance and end-of-use options which include disassembly, recyclability and reusability. In this grading system, materials are given points according to these indicators and are evaluated on the basis of the total points obtained. In another system developed by Pearce (1998), performance requirements for sustainable building materials are classified under four main performance groups; namely, environmental, technological, resource use and socio-economic performances. Table 3 lists the various measurable indicators under these groups, which can be used to evaluate building materials to be used for the construction project. 330

5 Table 3. Sample Information Requirements for Sustainable Building Materials (Source: Pearce, 1998) Environmental Performance Technological Performance Resource Use Performance Socio-Economic Performance Impacts on Air Quality Carbon Dioxide Hydrocarbons Impacts on Water Quality Impacts on Soil Quality Ozone Depletion Potential Site Disturbance Assimilability Scarceness Impacts during Harvest Processing Impacts Durability Service Life Maintainability Serviceability Code Compliance R-value Strength Constructability Energy Embodied Operational Efficiency Distributional Degree of Processing Source Reduction Materials Renewable Recycled/ Recyclability Reused/ Reusability Renewability Local/Transport Distance Packaging Requirements Occupant Health/ Indoor Env l Quality VOC Outgassing Toxicity Susceptibility to biocontamination Appropriateness for: Scale Climate Culture Site Economics: Contribution to Economic Development. Cost Labor Skill Requirements Labor Amount Requirements Additionally, an evaluating system, called PromisE, which comprises of an even more comprehensive list of indicator, has been prepared in cooperation with researchers of VTT Technical Research Centre of Finland, practitioners, and representatives of standardisation and building authorities. This system is based on four main concern areas of sustainability, which are: Health of users, consumption of natural resources, environmental loadings and environmental risks. Health of users includes management of indoor climate, indoor air quality, management of moist damages and illumination. Consumption of natural resources includes energy consumption, water consumption, land use, materials consumption and service life. Environmental loadings include emissions into air, wastes, sewage, bio-diversity and environmental loadings from traffic. Environmental risks include environmental risks of building site and environmental risks of building. Selection of building materials deals with surface materials emissions, management of moist damages, materials consumption, service life, emissions into air, wastes, sewage and building materials risks. The PromisE system has been developed for residential buildings, office buildings and retail buildings with different weighted values of the indicators. Table 4 lists only those indicators which are related to building materials. 331

6 Table 4. PromisE system for new buildings (Source: VTT website) [9] Weighted value of the indicator Office buildings Residential buildings Retail buildings Health of users Management of indoor climate Indoor air quality Surface materials emissions Management of moist damages Illumination Consumption of natural resources Energy consumption Water consumption Land use Materials consumption Total use of raw materials (excluding byproducts) Recycling rate of building materials Savings in space areas with help of common spaces Service life Environmental loadings Emissions into air Environmental impact of building products Environmental impact from energy use Wastes Quality of waste management of building Quality of waste management on building site Sewage Bio-diversity Environmental loadings from traffic Environmental risks Environmental risks of building site Environmental risks of building Building materials' risks TOTAL SELECTION OF SUSTAINABLE MATERIALS Materials are usually selected during the design stage of the building project. In this study, sustainability indicators for building materials have been compiled after examining the available evaluation systems. Whole building assessment schemes such as LEEDS and BREAM etc. have not been included in this compilation. Consequently, five main stages have been determined for the evaluation of building materials, which are: manufacturing, transportation, construction, usage and end of building-life. Performance indicators determined so far have been grouped under these stages, which in turn will include the related sustainability indicators. For example, environmental performance will be examined according to the percentage of all gas emissions at every stage; or economic performance will be examined in terms of material and labor costs, as well as contribution to economic development. Table 5 below shows only the stages and performance evaluation criteria, which can be expanded to include the individual indicators as listed in Table

7 Table 5. Sustainability Indicators for Building Materials to Be Used In Evaluating and Comparing Different Materials. Material X Material Y Manufacturing Stage Environmental performance Economic performance Transportation Environmental performance Economic performance Construction Stage Environmental performance Tech. performance Economic performance Usage Stage Environmental performance Tech. performance Socio-Economic performance End of Building Life Disassemble Renewable Recyclability Reusability TOTAL 5. CONCLUSION It is not easy to evaluate sustainability indicators while choosing building material because there is no clear cut and dried system for evaluating these indicators. Given that each project, its location requirements and users are unique, the evaluation criteria can also not be identical. Consequently, it is also important to determine which of the performance evaluation criteria are more important, and which stage has more impact from the point of view of the project in hand. 6. REFERENCES 1. Anink, D. et al (2001), Handbook of Sustainable Design, James & James Printed, UK 2. Edwards, B. (2001), Green Architecture, Architectural Design, Vol71, No4, Wiley Academy, Italy 3.Kohler, N. and Chini, A. R. (2005), Resource-productive Material Use, The 2005 World Sustainable Building Conference, Japan 4. Lacasse, M. (1999), Materials and Technology for Sustainable Construction, Building Research and Information, Vol27, No6, UK 5. Pearce, R. A. (1998), Sustainable Building Materials: A Primer, US 6. Reilly, J. M., (1997), Selection of Green Building Materials, US 7. Sev, A. and Özgen, A. (2003), Yüksek Binalarda Sürdürülebilirlik ve Doğal Havalandırma, Yapı, Vol262, P92-99, Turkey 333

8 8. Spiegel, R. & D. Meadows (1999), Green Building Materials, John Wiley & Sons Printed, Canada 9. vtt.fi/environ/ympluok_e.html (accessed, January 2007) (accessed, December 2005) (accessed, January 2005) (accessed, October 2006) (accessed, January 2005) (accessed, December 2004) 334