The built environment must undergo dramatic changes to meet climate change targets. The World Business Council for Sustainable Development (WBCSD 2009) calls for a worldwide building sector energy reduction of 77 percent below projected 2050 levels. In Britain, the residential sector is the largest consumer of energy and the main emitter of CO2. Although energy policy in the UK has emphasized energy efficiency in housing (eg, DTI 2003; DEFRA 2007), the country now recognizes that more radical and transformative changes are needed, particularly for existing homes (DECC 2009). Killip (2008) estimates that transforming the entire UK housing stock by 2050 will require 500,000 refurbishments of older, inefficient properties every year. The sheer scale of these transformations requires radical changes in both technology and work practices. The large technical potential for improvement in the housing sector has been demonstrated, requiring an integrated combination of ambitious demand reduction strategies (eg, insulation, improved airtightness, more efficient appliances, behavior modifications) and low and zero carbon (LZC) technologies such as solar technologies and heat pumps (eg, Boardman et al. 2005; Marchand et al. 2008). Research shows that to reach higher levels of carbon savings in refurbishment (eg, 50 percent or more) it is not just one technology that needs to be implemented, but a suite of coordinated strategies that treats the dwelling, services it provides, and its occupants as an integrated system (Hermelink 2006; Roudil 2007). We call this the “house as a system” approach. The carbon savings from performing holistic retrofits, even without occupant participation, should not be underestimated. Ürge-Vorsatz, Petrichenko, and Butcher (2011) argue that there is a 79 percent difference between implementing a “state of the art” performance approach in new buildings and renovations