Comparison of different methods for calculating thermal bridges: Application to wood-frame buildings

Nowadays thermal bridges losses in building design (standard or dynamic simulations) are generally evaluated using heat transmission coefficients from a database of usual cases. Numerous studies exist on the thermal bridges of classic constructions (concrete, brick). The originality of this paper is to deal with the particular case of the wood-frame construction. In this case, catalogs with heat transmission coefficients have been integrated into building energy simulation software used by building engineers. First, this paper proposes a scientific hindsight and a critical overview of existing calculation methods of thermal bridges. Simulations are made in steady state conditions according to the European standard and with dynamic conditions. A series of calculations was performed in order to validate the presented method. The results for wood stud thermal bridges showed that the values that are mainly used by engineering offices often lead to important errors due to the standard method and rounding choice. Secondly different models are proposed to correctly apply the thermal behavior of thermal bridges to some examples of wood-frame structure. These are based on recent articles covering the methods for thermal bridges calculation in dynamic conditions. This section shows that the most accurate models depend on the consideration of the inertia of the wood stud that concentrates all the mass of the wall unlike more conventional configurations.