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Originally published in Perspectives, Spring 2009
THE ENVIRONMENTAL CRISIS, and hence green building design, revolves around a wide range of issues: habitat destruction, storm water runoff, air pollution, erratic climate change, and excessive resource use. However, the on-going consumption of energy to operate, condition, and light a building, as well as the energy embodied in maintenance, is the largest single source of environmental damage and resource consumption attributable to buildings. Concerns regarding energy security and carbon emissions have sharpened the focus on energy in green buildings, as the growth rate of energy consumption continues to increase, particularly in countries such as China, Russia, India and Brazil. Reducing operational energy use and increasing durability should be the prime concerns of architects who wish to design and build “green” buildings. I have reached this conclusion after spending years looking at actual building energy consumption, reviewing countless computer simulations and being involved in numerous green building charrettes. It has even been suggested (Lstiburek, 2008) that 80 per cent of a “green” architect’s concern should be directed towards reducing energy consumption during operation. Scientific life-cycle energy analyses have repeatedly found that the energy used in the operation and maintenance of buildings dwarfs the so-called “embodied” energy of the materials. For example, studies have found that a building’s operating energy was between 83 and 94 per cent of its total energy use, over a 50-year life-cycle (Cole and Kernan, 1996 and Reepe and Blanchard, 1998).
Despite the massive amount of evidence pointing to the importance of energy consumption in green design, designers and rating programs still seem fixated on material choices, not energy reduction. Architects’ efforts tend to concentrate on the arrangement of spaces, massing, cultural influences, and the selection of finishes. Designing buildings that consume little operational energy is not a normally exercised skill: it requires much greater technical understanding of heat transfer And radiation physics, weather and sun, and mechanical equipment operational details than architects usually possess. Nevertheless, it is the architect who is responsible for making most of the significant choices that affect energy consumption. The trend in recent decades has not been encouraging. According to Natural Resources Canada data from actual bills for the year 2000, the energy consumption of buildings built between 1980 and 1999 is barely less than buildings built before 1920. The real savings from improved window technology, more efficient equipment, and better design tools have disguised the fact that we are wasting more energy because of over-ventilated, over-glazed, and under-insulated buildings.
If a building’s orientation, massing, window area/shading, insulation arrangement, and air-tightness are not properly optimized, no amount of mechanical engineering, heat pumps, chilled slabs, natural ventilation or green materials can make the building a “low-energy” building. And if it is not a low energy building, it is not a green building. Complex under-floor air systems, double facades, green roofs, and heat pumps are all examples of technology with potential, but will not save energy if the architect’s design (let alone the mechanical engineer’s) is not appropriate. In many cases these technologies are added to a poorly conceived building, and the result is average energy consumption despite the use of good, or even exceptional, mechanical design and equipment. Efficient and high-tech equipment and controls can moderate, but not make up for, energy-inefficient building design.
[...] The full article is available back issues Perspectives Magazine.