Evaluation of Moisture Buffer Effects by Performing Whole-Building Simulations

The humidity of rooms and the moisture conditions of materials in the enclosure of buildings depend much on each other because of the moisture exchange that takes place over the interior surfaces. These moisture influences also depend strongly on the thermal conditions of indoor spaces and enclosure elements of buildings.

In turn, the moisture and humidity conditions have significant impact on how buildings are operated. In hot, humid climates, it may be desirable to keep the ventilation rates low in order to avoid too high indoor humidity, while in cold climates, ventilation can be used to keep the humidity low enough to ensure only a small risk of moisture damage in the building enclosure.

In either case, the indoor humidity has a direct or indirect impact on the energy performance of the HVAC system of a building. To analyze this situation, it is today possible to benefit from some recent developments in integrated computational analysis of the hygrothermal performance of whole buildings.

Such developments have led to models for whole buildings (the indoor climate, the enclosure, and the systems), which not only predict the thermal performance, such as in contemporary building energy simulation. A growing number of building energy simulation tools have added models for transient moisture migration.

The paper gives examples of two such recent developments and will highlight some calculation results that can be obtained. Finally, the paper will mention some further developments and international collaboration for the near future, introducing a proposal recommendation for a common numerical test case.