HYGRO-BAT

There is a gain of interest for Coupled Heat-Air-Moisture (HAM) transfers processes in buildings. Researchers from building energy field foresee here an opportunity to reduce energy needs for buildings. Indeed, some recent works had shown the impact of mass transfers on energy behaviour of buildings, under varying external and internal loads. However, even if a lot of work had been done, we are still not able to explain some observations. For example, differences between simulated and measured values have been remarked in a few national and international projects (Annex 24 and 41 of International Energy Agency, French ANR PREBAT OPTI-MOB). The reason of these differences is not really known: measuring system, properties of materials, HAM models themselves? Past and current projects showed the complexity of the problem, but, up to now, were not able to explain clearly reasons of divergence and elaborate adapted tools. However, this is a fundamental question, because energy savings are expected precisely in dynamic thermo-hygric behaviour. Indeed, few publications, where the impact of dynamic moisture conditions is analysed, show energy savings up to 30%. Our project gathers the experience of leading French institutions in this field around experimental and numerical benchmarks. Our ambition is to understand and master main physical phenomena and to elaborate experimental (characterisation methods) and numerical (coupled HAM-BES simulation) tools . Our main objective is to elaborate a methodology for hygro-thermal design of buildings, based on reliable tools and methods. The aimed methodology should be able to qualify and to quantify the novel solutions, representing energy impact of mass transfers. Proposed project uses wood-based construction, and more generally construction materials based on vegetal fibres, as application example. These materials have interesting hygroscopic properties and complex hygro-thermal behaviour. Moreover, the perspective of the further economic development of the corresponding industrial sector in France seems promising. We propose a progressive working plan starting at precise measurements of material properties, as reliable inputs for numerical models. Then measurements and numerical simulations of dynamic behaviour of materials and wall assemblies will be performed, first under well known laboratory conditions. Then a more complex scale of building behaviour under real climate will be assessed, first in an idealised way (using well known PASSYS cells) then using real buildings. The possibilities of integration of project results in official standards will also be assessed. HYGRO-BAT project is proposed by 13 institutions: 7 research laboratories form Universities (CETHIL, LEPTIAB, TREFLE, LERFOB, LERMAB, LOCIE, LMDC), 3 semi-public technical centres (CEA-INES, CRITT-Bois, CSTB) and 3 enterprises (EDF, LIGNATEC, NR GAÏA).