Abstract
Building envelopes are constantly subjected to temperature and moisture gradients. This loading induces a complex response, particularly for highly hygroscopic insulating materials. Latent effects can no longer be neglected for these materials in which heat and moisture transfers are strongly coupled. The purpose of this article is to analyze the behavior of a wood fiber insulation subjected to non-isothermal loading under a vapor concentration gradient. An experimental setup and a mathematical model of hygrothermal transfer were developed to analyze the behavior of the wall. The mathematical model describes the main physical phenomena involved, notably water vapor adsorption and the dependence of thermophysical properties in state variables. The experimental setup developed allows studying a wall under controlled conditions. The temperature and relative humidity profiles within the wall were measured. The evolution of the profiles with time suggests that the adsorption of the water vapor occurs together with the redistribution of liquid water within the envelope. The comparison of the experimental results with the numerical model shows good agreement although the prediction can be improved during the transient phase. The comparisons of these results with a purely diffusive thermal transfer model show the limits of the latter and permit quantifying the latent effects on the total heat transfer.
Highlights
The construction sector represents a considerable source of energy saving and greenhouse gas reduction [1]
In addition to study the evolution of the water content in a strongly hygroscopic material and proposing data to validate transfer models, we propose a detailed analysis of latent effects in a wood fiber insulation material subjected to non-isothermal conditions under a vapor concentration gradient through experiments and numerical modeling
The analysis of the hygrothermal behavior of the wood fiber insulation for the different stresses presented was first done on the basis of the experimental results
Summary
The construction sector represents a considerable source of energy saving and greenhouse gas reduction [1]. A type of building is emerging characterized by strong thermal insulation intended to limit losses through the envelope Under these conditions, large heat fluxes by conduction are considerably reduced but it is no longer possible, to neglect latent effects, especially for strongly hygroscopic materials. We are witnessing renewed interest in low-energy impact materials and especially for plant-based materials such as wood and its derivatives whose strongly hygroscopic nature is known. This interest can be explained by the moisture buffer effect of this type of material on the hygrothermal behavior of buildings [3,4,5]
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