Thermal Resistance Measurements of a Well-Insulated Wall Using a Calibrated Hot Box

Abstract

Thermal resistance measurements of a well-insulated residential wall are con ducted using a calibrated hot box operated under a range of winter and summer cli matic conditions. The wall consists of two insulated wood-frame sections with stag gered framing, having a nominal thermal resistance of R-27 F·ft ²·h/Btu (4.8 K·m²/ W). The measured thermal resistance is examined as a function of mean wall temper ature and compared with predictions using the ASHRAE parallel-path method, the ASHRAE isothermal-plane method, and a temperature-dependent thermal conduc tivity finite-difference model Good agreement between measured and predicted values is obtained using both ASHRAE methods and the finite-difference model. At mean wall temperatures above 40°F (4.4°C), the ASHRAE parallel-path method tended to overpredict, while the ASHRAE isothermal-plane method tended to underpredict the overall thermal resistance. The effects of the compression of glass- fiber blanket insulation and nail penetrations on the overall thermal resistance are m- vestigated.