Hygrothermisches Verhalten teilgedämmter und teilbeschatteter Flachdachkonstruktionen aus Holz

Hygrothermal behaviour of partly insulated and partly shaded wooden flat roofs.

Roof constructions of commercial and industrial buildings are often formed by wooden flat roofs with large beam spans. Thus, rafters with heights over 50 cm are common. Because of economic considerations such high cavities are usually not fully insulated. Moreover, these partly insulated roofs are mostly partly shaded by parapets, technical installations or adjacent buildings. Such partly insulated and partly shaded flat roofs are critically evaluated by building physicists. The present study reveals the hygrothermal behaviour of such partly insulated and partly shaded wooden flat roofs, based on long term field and laboratory experiments carried out at the Holzforschung Austria (HFA). In addition to the level of insulation (partly insulated/fully insulated) the orientation of the elements (lengthwise to eave/at the right angle to eave) is varied. The measurements show significantly lower temperatures and higher moisture content in the cavity in the shaded area of fully insulated roof elements compared to partly insulated elements. The climate conditions in the cavity in the fully insulated roof elements are much more inhomogeneous compared to the partly insulated ones. The potential air circulation in the air layer above the insulation generates this balancing effect. Already an air layer with 5 cm height leads to more favourable conditions in the partly shaded area.