Effect of longwave radiation in cold roofs: remarks on simulations

The cooling effect caused by long wave radiation between the roof surface and the sky is studied here. The external surfaces may cool down below the dew point of the air and the condensation may form [1]. Typically, the covering of cold roofs has a low thermal resistance and the condensation may form also on its downside. These phenomena are quantified and discussed here. It is shown that the amount of condensation could be surprising high, even by temperatures of external air about 0 oC and higher. The effects of different boundary conditions and of different quality of the air tightness are studied here. These phenomena should be implemented in the standard calculation procedures in the future.