2. The need
Global energy consumption for commercial buildings has been increasing over recent decades, mainly due to increasing populations and economic development worldwide [2, 24]. For example, the percentage of energy used for transportation, domestic and service sectors from 1991 to 2011 in the UK has exceeded by ~5% the energy used by industry [2, 24]. Likewise, in the USA, which accounts for 19% of the world energy consumption, the amount of energy used by domestic and commercial building has increased to over 40% of the total in 2009; 70% of which is derived from fossil fuels [2].