Critical assessment of the metrics for the evaluation of wall energy efficiency in transient regime
Résumé
Within the environmental context, designing energy efficient buildings is crucial. The reliability of the standard metrics used to design and qualify efficiency is first discussed. Then, a metric is proposed based on the evaluation of the exergy destruction rate. It enables to assess the exergy loss in dynamic and transient condition. The metric is computed with the temperature and vapor pressure obtained with a coupled heat and mass transfer model. The approach is tested with experimental data obtained from a wood fiber wall demonstrator. The proposed metrics allows a more accurate assessment, particularly in dynamic and transient conditions. Two periods are considered, one with negligible and one with mass transfer through the wall. The mass transfer can account for 30% in the exergy destruction. It is also demonstrated that during a "winter climate" a satisfying approximation of the metric can be obtained if heat transfer model is used alone as in building simulation programs.
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