A whole building hygrothermal model has been developed on the basis of an existing detailed model for thermal simulation of buildings. The thermal model is a well-proven transient tool for hour-by-hour simulation of the thermal conditions in multizone buildings. The model has been expanded with new capabilities for transient simulation of indoor humidity conditions, taking into account the moisture buffer capacity of building components and furnishings and the supply of humidity from indoor activities. Also integrated in the model are transient calculations of the moisture conditions in the layers of all the external building envelope components.

The advantage of the new model is that both the boundary conditions for the envelope and the capacity of building materials to buffer the indoor humidity are considered in the same calculation. The model considers the latent heat effect associated with the absorption or evaporation of moisture, and it takes into account the way in which moisture in the building materials affects their thermal conductivity.

The paper presents the principles for the model and some applications and calculation results.

The model is validated against experimental data from a full-scale test cell. In the test cell, it is possible to control the release or withdrawal of humidity from the indoor space and measure the response in humidity of the air and the moisture content of building materials in the room. A sequence of experiments has been conducted using different interior materials to provide source data for the effect of moisture absorption and release. Examples of comparisons between simulated and measured data are presented.

Units: SI