The effect of air movement on the heat and moisture characteristics of building constructions

The reduction of energy consumption related to buildings is of great importance. In order to calculate the energy consumption of a building, the heat transfer modeling of constructions is important. Moreover, some software tools also simulate moisture transport simultaneously to improve the design of building constructions. If we look more closely to these combined heat and moisture models, the effect of air movement inside the construction is not taking into account by almost all models. The main reasons are twofold: First, in practice it seems to have only a minor effect on the energy consumption. Second, the modeling and simulation of the air movement was quite complicated so far. The recent development of multiphysics modeling tools give cause to revisit the following problem: How important is the effect of air movement on the heat- and especially the moisture characteristics of building constructions? The method of research was as follows: First, selection of a common building construction type. Second, modeling and simulation of six cases: 1D, 2D and 3D heat and moisture transport models each with and without air movement based on the selected construction. The used internal and external boundary conditions (i.e. temperature, humidity and wind induced pressures) were based on a local (Dutch) climate. Third, evaluation of the results. The paper presents the details of the mentioned method and a discussion of the results. It is concluded that (as expected) the heat characteristic of the studied building construction is only minor affected by air movement. However, our results indicate that air movement seems to have much more impact on the moisture characteristic as presumed so far. Moreover, the use of multiphysics models enables and simplifies the research of possible important effects that are not included in other standard heat and moisture simulation tools.