Figure 2: IPCC projections of CO2 Source: IPCC (2007)
total sectoral potential at <US$100/tCO2-eq in GtCO2 5.3-6.7
2.5-5.5 mitigation potential in 2030
Low net cost Although the building sector is the largest contributor to human-related GHG emissions, it also holds the greatest potential to reduce these emissions (IPCC 2007). Based on 80 studies spanning 36 countries, the IPCC report suggests that a 29 per cent reduction in projected baseline emissions by 2020 is achievable at zero cost (below 0 US$/tCO2
-eq), while further improvements could be made with relatively low levels of investment.
Figure 2 shows sectoral estimates of the economic mitigation potential of using technologies and practices expected to be available by 2030, at various costs in US dollars per tonne of CO2
mitigation potential is expressed in GtCO2 marginal cost in US dollars per tCO2
-eq). The -eq/yr and the -eq. For each sector,
the mitigation potential is represented as three ascending bars, according to the amount that can be achieved at less than US$ 20, less than US$ 50 and less than US$ 100 per tCO2 tCO2
-eq.1 In the building sector, assuming a cost per
-eq of no more than US$ 100, the global economic mitigation potential ranges between 5.3 and 6.7 GtCO2
eq/yr by 2030. Most importantly, about 90 per cent of this potential could be achieved at less than US$ 20 per tCO2
-eq, far more than could be achieved in any of the
other sectors depicted. This range is represented by the segment within the third bar for buildings (<100). The bulk of this mitigation potential can be attributed to non- OECD/EIT (Economies in Transition) countries, followed by OECD countries and to a lesser extent EIT countries.
left to right. 342
1. Note that potential that can be achieved for less than US$ 50 per t CO2 includes the potential that can be achieved at less than US$ 20 t CO2 and similarly for US$ 100 per t CO2
-eq. Hence the bars grow in size from -
The core concept of “thermal comfort” is more of a state of mind (reflecting different cultural, class and geographical conditions) than a technical certainty (ASHRAE 2005). Assessing the right level of thermal comfort is critical to setting performance standards for buildings (Cena and Clark 1981) but requires not just an understanding of what a human body can bear, but also to what extent people are ready to make behavioural changes in the way they experience comfort in their environment. This affects the way building occupiers interact with their environment in very precise ways – from choosing to pull down external blinds to limit sun
Adapting behaviour patterns Before addressing the technical, financial and regulatory potential of green buildings and their impacts on the green economy, it is important to recognise that profound changes in attitudes and behaviour will be required amongst policy-makers, investors, consumers and occupants in order to implement real change. People spend most of their lives in their homes, places of work and other buildings; North Americans, on average, spend 90 per cent of their time indoors (United States General Services Administration 2008) and there are deeply- rooted attitudes and practices relating to how people establish patterns of comfort and efficiency. For this reason, understanding the economic and psychological rationale of decisions made by individuals and institutions is increasingly recognised as fundamental to achieving energy-efficiency improvements in buildings. For example, a recent report on energy efficiency in the USA highlighted various behavioural biases affecting consumers’ energy consumption decisions (Swim et al. 2009; Granade et al. 2009).