The material-related processes involved in sustainability can be simplified by focusing on grey energy (the amount of energy required for the manufacture, transport, storage, sale and disposal of a product), which is expended in the three phases: construction, operation and demolition of a building. An initial line of approach can be found in a “reduction” of the building measures, whereby in our part of the world, the requirements in terms of operating energy partly correspond to those for grey energy.
Under the heading of grey energy, different optimization ap-proaches are conceivable for four segments of a building:
• Structure. In a new development, the primary structure is the most energy-intensive element in terms of grey energy. The primary energy invested in the structure corresponds more or less to the weight. Lightweight forms of construction are, therefore, preferable, where other constraints – such as sound insulation – permit.
• Facade. In the facade of a building, the grey-energy content is generally high in respect of the manufacturing process. Transparent components are the most energy-intensive ones in relation to their area (ill. 3). Their design should, therefore, always be coupled with further functions, such as improved daylighting or solar-energy gains. The great demands imposed on the facade in terms of weather resistance result in high material strains. These can be overcome through an appropriate form of construction. Simple roof and facade forms reduce the costs for junctions and connection details, which as a rule require a much greater input of grey energy than planar elements. Similarly, by optimizing material thicknesses and ensuring a lower weight, the outlay for the metal supporting construction for curtain-wall facades can be reduced.
• Functional surfaces. As a result of heavy wear and tear, repeated cleaning and frequent replacement, the functional surfaces within a building will have a similar significance in terms of grey energy to that of the facade (ill. 3). Initially, grey energy can be saved by reducing the constructional outlay. Soffits that are directly mounted or applied in a planar form have a markedly lower content of primary energy than suspended soffits. In the case of floor finishes, great durability reduces the primary-energy content over the life cycle, as can be seen in high-grade surfaces such as stone pavings, which also entail comparatively low cleaning costs (ill. 4).
• Services and technology. Technical installations are the most underestimated element in terms of grey energy. As a rule, the primary energy in new construction is below 10 per cent; but technical components often have a relatively short life, and rapid advances in technology suggest a greater frequency of replacement in the future (ill. 5). The planner can at least safeguard other elements by creating a reversible design for the technical components.
The second line of approach, namely energy optimization, is based on the relationship between grey energy and operating energy. This will depend largely on the desired functional life and the degree of comfort required in a space, as well as on the technical content of energy services (ill. 6). As far as energy consumption is concerned, great importance is assumed by the operating energy invested in materials. The reduction of care and maintenance work plays a major role, therefore. Surfaces like parquet or stone floors diminish the input for cleaning in comparison with carpets or textured, elastic floor finishes. In addition, the long-term conservation of the building fabric can be served by ensuring good accessibility to technical systems and simplifying their replacement (ill. 7).
In buildings with a very long-term use (e.g. housing structures and offices in special locations), the significance of the energy tied up in a component increases with time. Ill. 6 shows the dominance of housing, which is likely to increase further with current trends towards energy efficiency. As a rule, durable materials are ecologically more valuable than those with a low energy input at the production stage, but which require more frequent renewal (ill. 8).
In general, the life and durability of building components play an important role in terms of the primary-energy content in the life cycle. Studies of the sustainability of a building have mainly been based on the durability of such components. But a high general level of durability is not always necessary. It may even have a negative effect on the flexibility of use of a structure or space. The replacement of components may result from technical, safety or aesthetic factors or changes in regulations.
With short-term building assignments, a trend-setting, modern design can often be an eye-catcher. Materials with less durability would seem suitable for such situations (ill. 9). On the other hand, a design that is too trendy can easily lead to a premature exchange of elements before their technical life is over – as the result of “visual wear” – whereas a clear, qualitative architectural statement can enjoy great esteem over a long period. The evaluation of materials from the point of view of sustainability is a new working area.
Relevant aspects (ills. 10, 11) include primary-energy content (renewable/non-renewable); global warming potential (GWP 100); other emissions if relevant, such as ozone-degradability potential (ODP) or acidification potential (AP); the reduction of emissions in built space; and material performance and durability.
To evaluate the primary-energy content of measures, the global-warming potential and environmental effects worldwide, the planner has at his disposal data for compiling an ecological balance (based on ISO 14040). The most comprehensive freely accessible databank without links to a specific product is that of the Federal German Ministry for Transport, Building and Urban Planning (BMVBS) at ökobau.dat Some 800 records in combination with state servicing allow a detailed study of materials. Known under the abbreviation EPD (environmental product declaration) and based on ISO 14025, a series of manufacturer-related data are at present being drawn up in the context of an ecological balance. Also known as “Type III environmental declarations”, these allow a comparison to be made between the data of different manufacturers throughout the EU. An examination is carried out by an independent third party, thereby ensuring great reliability in the quality of the data.
Type I environmental product declarations (ISO 14024) allow labels like Euro Blume to provide evidence of specific product quality on an international basis, especially in the field of building biology. Both kinds of product declaration can be found in evaluations of sustainability and certification systems thereof. The US LEED system, for example, cites among its goals recycling quotas and a definition of the maximum content of harmful substances in building components, as well as the use of timber with a Forest Stewardship Council (FSC) seal. As a “first generation” certification system, it singles out evaluable aspects of sustainable building on a relatively haphazard basis. More consistent is the method of the Swiss SIA 112/1 “recommendation for sustainable building” included in the “Diagnosesystem Nachhaltige Gebäudequalität” (see “DETAIL Energie Atlas”). The greatest number of factors relating to the appropriate use of materials for sustainable building is contained in the German seal of quality for sustainable building (DGNB).
The assessment of materials is still in its infancy, and major pro-gress can be expected in the future. In a market that is slowly changing from being landlord-oriented to tenant-oriented, however, only those buildings will survive in the long term that distinguish themselves through the sustainable quality of their architecture, including the application of the appropriate materials.
