Wind washing - Pressure induced airflow through lightweight pitched roof constructions: Test roof element – measurements and simulation model HAM3D-VIE

In the case of non ventilated compact roofs the wind tightness of the construction is usually warranted by a windproof underlay membrane and the flow resistance of the thermal insulation, as well as sealed eave and ridge details. Because of the current construction practice of wind tight layers in Austria there are numerous small leakages in the eaves, the ridge and the underlay area. Because of this and the low density and length of the thermal insulation in common Austrian constructions the wind induced pressure differences between the eaves and loft area cause an air flow which cancels the thermal insulating effect of the rock wool partially or completely. During periods of high wind speed this leads however to uncomfortable low operative temperatures caused by an increased heat loss and lower surface temperatures. Based on different in-situ measurements (thermal performance and air propagation) a test roof element was constructed and implemented in a common slope of 45° in a climate chamber (hot box – cold box) to investigate different tightening measures and to validate a simulation model. In the paper the results from air flow and heat flow measurements of the test roof element variants are presented. The results lead to the validation of the 3 dimension simulation tool HAM3D-VIE. HAM3D-VIE allows variation studies of the hydrothermal performance and comfort regarding to durability and construction practice auf lightweight constructions.