The hygrothermal behaviour of rooms : combining thermal building simulation and hygrothermal envelope calculation

The hygrothermal behavior of a building component exposed to weather is an important aspect of the overall performance of a building. Today the hygric transport phenomena through a building envelope are well understood and a realistic assessment of all relevant effects can be carried out by one of the numerous models and computer programs, that have been developed in different countries over the last years. The calculation of the hygrothermal performance of a part of the envelope is state-of-the-art, but until now, the total behaviour of the actual whole building is not accounted for. Its importance is increasing as modern dwellings become more airtight and show elevated indoor humidity levels. This requires the detailed consideration of all hygrothermal interactions between the indoor air and the envelope. In this paper a new holistic model, that takes into account the main hygrothermal effects, like moisture sources and sinks inside a room, moisture input from the envelope due to capillary action, diffusion and vapor ab- and desorption as a response to the exterior and interior climate conditions, heat source and sinks inside the room, heat input from the envelope, the solar energy input through walls and windows and hygrothermal
sources and sinks due to natural or mechanical ventilation will be presented.