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Surface temperature of wooden window frames under influence of solar radiation

C.J.J. Castenmiller
TNO Building and Construction, Delft, The Netherlands

Under influence of solar radiation the surface temperature of wooden window frames can reach values above 600C. High temperature can cause considerable tensions within the window frame; as a result joints can be cracked and rain water can penetrate into these joints. This penetration of rain water is often the start of considerable degradation of the window frame. Which surface temperatures can be reached depends on the colour of  used paint and the orientation of the surface. The frame sill appears to be the surface that is most heated by solar radiation; window frames that are painted in a dark colour show the highest surface temperatures because of the relatively high absorption coefficient of dark coloured paints. Calculations with an dynamic model are made to predict which surface temperature can be reached on sunny days. It appears that surface temperatures up to more than 600C can be reached. To avoid these high surface temperatures light coloured paints are preferable.

Key words: sun radiation, surface temperature, wooden window frames