Influence of Boundary Conditions on the Estimation of Thermal Properties in Insulated Building Walls

The objective of this study is to evaluate the ability of inverse techniques to estimate the resistance and the capacity of a highly insulated multilayer wall under real weather conditions. The wall is equipped with temperature sensors inside and on its inner and outer surfaces, and the boundary conditions have been measured over a 14-day period. Uncertainties on various parameters of the model are evaluated, including internal and external convective heat transfer coefficients (+/- 20% and +/- 7 W.m-(2).K-1 respectively), external long-wave heat transfer coefficient (+/- 0.15 W.m-2.K-1) and solar absorption coefficient (+/- 0.06). A sensitivity analysis demonstrated the high correlation with some parameters defining the thermal performance of the walls (thermal resistance or capacity). A solution is proposed to limit the number of identified parameters, while allowing the identification of the thermal resistance and the thermal capacity of the walls. There are two cases: either the weather conditions are accurately measured (temperature, short- and long-wave radiation) and the thermal characteristics can be assessed, or intrusive sensors are installed, and the thermal characteristics can be evaluated more accurately.