Exterior surface temperature of different wall constructions

The conditions and the exterior surface of building components with high insulation are almost independent of the indoor climate. With today's increasing insulation thicknesses, the tiny heat flow from the interior is thus generally not sufficient to prevent a temperature drop below ambient conditions by long-wave emission especially during night-time. Apart from energetic consequences this temperature drop may lead to surface condensation and subsequently to soiling or microbial growth. Another factor resulting in surface temperatures below ambient conditions is the evaporation of precipitation moisture. In order to obtain realistic surface conditions by numerical simulation the heat and moisture transfer processes at the surface have to be modelled accurately, taking into account convective and radiation, precipitation, wind speed and direction. These data serve as input for a hygrothermal simulation tool. The calculated results are compared with measured surface temperatures of walls at the IBP test site. From comparisons like these appropriate surface transfer coefficients for simulation tools may be deduced and the different surface humidity sources may be quantified. Further, the simulation tool is used to compare three different types of wall construction with respect to their night-time surface temperatures.