Estimation of Global Thermal Performances of a Facade Under Real Climate
Résumé
The article aims at estimating the thermal characteristics of a facade component (highly insulated wall with a window) installed on a test cell using an inverse method. The test cell is used as a calorimeter to estimate the global properties of the facade component (including thermal bridges). The characteristics of interest are the thermal resistances and capacities and the effective window area but the thermal properties of the test cell also need to be identified as the heat balance is performed at the cell level. The problem commonly met is the correlation of a large number of parameters to be estimated and it is therefore difficult to assess physical parameters.
The methodology consists in performing two experimental tests with different temperature scenarios using a heating system and thus allowing the interior and exterior conditions to be decoupled during identification. Then, the two experimental tests were assigned to two different Resistance-Capacitance models, depending on the quality of the data. The higher the quality of the test, the more complex the model is. The purpose is to take advantage of the differences between the two experimental tests to carry out identification by parts, i.e. to estimate the parameters one after the other using the most appropriate Resistance-Capacitance model.
All estimated parameters are close to the theoretical values. The gap is greater for the effective window area, which might come from the assumption of a constant value over the evaluated period. This parameter depends on direct solar radiation. An additional specific test could resolve this challenge. Moreover, the thermal resistance of the facade is underestimated. Thermal bridges may have been missed in the calculation of the target value.