Simulations as the way of bridging the gaps between desired and actual hygrothermal performance of buildings

This paper deals with a common moisture problem in Swedish houses – the occurrence of high moisture levels in attics, and with a remedy proposed by building authorities – the ventilation of attic by outdoor air. The aim of the work is to identify  operating scenarios for an attic that lead to a moisture accumulation on internal side of the roof and to investigate whether ventilation (governed by wind) may help in removing the moisture excess. The role of the attic ventilation is analyzed by comparing attics with different air infiltration rates from a dwelling. The investigation aims to exemplify that, by using advanced simulations, a number of sound conclusions can be made by these virtual experiments in a rather easy and inexpensive way.