Recent developments in fenestration design and construction have increased the demand for assessment of the thermal characteristics, particularly the thermal resistance or R-value, of windows and doors. A number of testing laboratories in North America are capable of determining the R-value of fenestration systems using test methods developed in house or available from different sources. However, the literature lacks sufficient information on test procedures and the associated uncertainty analysis of these test methods. At the Institute for Research in Construction (IRC), National Research Council of Canada (NRCC), a test method to determine the thermal transmission and R-value of fenestration systems was developed in the early 1980s. The method is based on the use of the IRC environmental test facility (ETF). The ETF is a guarded hot box with some special features, such as a constant-temperature baffle on the room side and a wind machine connected to an oscillating matrix of tubes on the weather side.

KEYWORDS: heat flow, thermal resistance, doors, windows, testing, calculating