Buildings account for approximately 40% of the whole final energy consumption within European communities (European Commission, 2010). Within this sector, energy is mainly consumed at household level: in 2009, European households were responsible for 68% of total energy used in buildings, mainly for space heating (almost 70%), domestic hot water (14%), lighting and electrical appliances (13%) and cooking (4%). With a share of more than two thirds of the average energy consumed per residential unit, inefficient heating and cooling systems can cause a long-term negative impact on the general welfare of European communities through extraneous use of nonrenewable resources, heating-related pollution and considerable financial loss.