Abstract
The thermal resistance of a wall can be readily measured in steady-state. However, such a state is seldomly achieved in a building because of the variation of outdoor conditions as well as the high thermal inertia of building materials. This paper introduces a novel active (dynamic) method to measure the thermal resistance of a building wall. Not only are active approaches less sensitive to external temperature variations, they also enable to perform measurements within only a few hours. In the proposed methodology, an artificial thermal load is applied to a wall (heating of the indoor air) and its thermal response is monitored. Inverse techniques are used with a reduced model to estimate the value of the thermal resistance of a wall from the measured temperatures and heat fluxes. The methodology was validated on a known load-bearing wall built inside a climate chamber. The results were in good agreement with reference values derived from a steady-state characterization of the wall. The method also demonstrated a good reproducibility.
Highlights
From the perspective of limiting greenhouse effect, two approaches have to be considered: the development of the use of renewable energies and the limitation of global energy consumption
A non-negligible difference is usually observed between theoretical estimations and in situ measurements of the thermal performance of buildings: this often referred to as the “performance gap” [1]
Thermal insulation of buildings has a key role to play in the reduction of greenhouse gases emissions
Summary
From the perspective of limiting greenhouse effect, two approaches have to be considered: the development of the use of renewable energies and the limitation of global energy consumption. For the sake of completeness, let us add the QUB/e method [3] to this review. For the thermal insulation of building walls, there are only two existing standardized techniques, namely ISO 9869-1 [4] and 9869-2 [5] They do not accurately evaluate a thermal resistance in many situations, especially if heat transfers are far from being in steady-state regime and if the indoor-outdoor temperature gradient is too small. This is mainly because these approaches are passive methods, strongly influenced by climate conditions
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