Efforts to reduce greenhouse gas (GHG) emissions and thereby mitigate global climate change are receiving increasing attention in many countries today. There is growing recognition that the current trends in energy supply and demand are not consistent with the goals of sustainable development. Of the global primary energy supply of 549 EJ in 2011, fossil fuels constituted 82%, and biofuels, nuclear, and hydro accounted for about 10, 5, and 2%, respectively (IEA 2013a). Fossil-fuel combustion is the major anthropogenic source of GHG emissions (IPCC 2013). A less significant share of anthropogenic CO2 emission is also connected to non-energy related activities including land-use practices and industrial process reactions. Fossil-fuel combustion and industrial process reactions accounted for 78% of the global total GHG emission increase between 1970 and 2010 (IPCC 2014). Figure 7.1 shows a breakdown of the global total primary energy supply (TPES) and associated CO2 emission by fuel type in 2011 (IEA 2013b). Major studies suggest that fossil fuels are very likely to account for a significant share of future primary energy use, even if effective measures are implemented to promote resource efficiency and sustainable energy systems in the global community (IPCC 2000a,b; IEA 2011). There is growing interest in strategies to reduce fossil-fuel use, thereby creating a resource-efficient built environment with low-carbon footprint.