R-value (insulation) as ASHRAE 90.1 and the IECC prescribe U-values. However, R-value is widely used in practice to describe the thermal resistance of insulation products, layers, and most other parts of the building enclosure (walls, floors, roofs). Other areas of the world more commonly use U-value/U-factor for elements of the entire building enclosure including windows, doors, walls, roof, and ground slabs. The SI (metric) unit of R-value is whereas the I-P (inch-pound) unit is For R-values there is no difference between US customary units and imperial units, so the same I-P unit is used in both. Some sources use ″RSI″ when referring
National Office of Building Technology and Administration National Office of Building Technology and Administration The National Office of Building Technology and Administration* () was a Norwegian government agency responsible for managing laws and rules related to building and construction, authorises rules related to documentation of construction materials and their properties, as well as approving companies related to the "Plan- and Building Act". The agency gives however jurisdiction to local municipalities, along with the County Governor, in appealing individual building permits. Since 1 January 2012, the office has taken on the title of Directorate of Building Quality (Norwegian: "Direktoratet for Byggkvalitet)." The Directorate of Building Quality is organized