The resistance to heat flow of a given component of a building element. It is equal to the [air] temperature difference (ºC) needed to produce unit heat flux (W/m2) through unit area (m2) under steady conditions. The units are ºCm2/W
Ministry of Business, Innovation and Employment, Glossary of terms and acronyms, Wellington, New Zealand 2010. http://wwwsosh.govt.nz/resources/glossary-u.shtml, (Occupn Hlth and Sfty - Brit) {530}