Abstract

A society based on fossil fuels is not sustainable for two reasons. The most obvious reason is that fossil fuels are not in infinite supply. Although fossil fuels will never run out from a technical standpoint, at some stage the remaining fossil fuels will become so expensive and so difficult to extract that in practical terms they will have been exhausted. The second reason that a society built on fossil fuels is not sustainable is that as anthropogenic greenhouse gas (GHG) concentrations continue to increase in the atmosphere, the climate will continue to warm and, with it, the pressure to change course. At some point, long before fossil fuel resource have been exhausted, this pressure is likely to become overwhelming - although not before substantial damage has already occurred. GHGs are emitted to the atmosphere during the combustion of fossil fuels and from land use changes primarily due to deforestation and intensive agriculture. Over the long term, GHG emissions from combustion of fossil fuels will be the single largest factor in future human-induced warming of the climate, since long-term land use emissions are constrained by land availability. At present, buildings rely on fossil fuel energy, either directly through on-site use of fossils fuels for space heating and for hot water, or indirectly through the use of electricity that is generated from fossil fuels. It has been demonstrated that buildings currently account for more than one third of all global energy use and of the associated GHG emissions. To phase out fossil fuels requires limiting the growth in total energy demand to levels that can be satisfied with renewable forms of energy. In order to have any possibility of supplying future energy needs entirely through carbon-free energy, the energy efficiency of the global economy must improve dramatically. Significant reductions in building energy use will lead to a correspondingly significant reduction in the use of fossil fuels, thereby reducing the emissions of GHGs. The broad principles that should be adhered to when responding to the threat from global warming have been laid out by the United Nations Framework Convention on Climate Change (UNFCC); a document which has been signed and ratified by 186 countries. The UNFCC declares that its ultimate objective is the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner”. Although the UNFCC does not specify what constitutes “dangerous anthropogenic interference”, it does include three explicit criteria required for its achievement. The requirement that GHG concentration caps should be set so as to enable economic development might appear to place a lower limit on the allowable caps. This might seem to conflict with the requirements concerning protection of ecosystems and of food production were it not for the additional proviso that economic development must be sustainable. A nearly universal perception persists that low-energy buildings consistent with GHG stabilization and overall environmental sustainability must await the development of new technologies that entail major capital costs. However, it has been clearly demonstrated that there is no need to wait for this technological progress since (i) major energy-saving technologies already exist, (ii) existing technology transfers would produce major energy reductions, and (iii) delaying energy intensity reduction programs will irreversibly close significant windows of opportunity. Consequently, the primary barriers to achieving deep reductions in GHG emissions are neither technological nor economic, but, instead, involve the nature of the design process, an overwhelming lack of awareness, and an over-reliance on established procedures. Namely, the major impediments to reducing building energy use are behavioural. Consequently, buildings can act both as loci for improvements in energy efficiency and as collectors for renewable energy in forms that permit sustainability.