The influence of the airtightness of the insulation layer in a partially filled cavity construction is discussed. In theory it is assumed that the insulation forms a continuous layer that is perfectly fixed against the inner wall of the cavity, leaving an air space between the outer wall and the insulation. However, in practice we frequently notice the presence of air gaps in the insulation layer, and of a second small cavity between the insulation and the inner wall. The influence of these inaccuracies on the heat transfer is studied by means of experimental research and computer simulations.

This paper presents the results of extensive measurements on a partially filled cavity wall (temperature profiles, heat loss), using a calibrated Hot Box-Cold Box. These results are compared with calculations of the temperature profiles and the overall heat transfer. A second series of measurements deals with the influence of the slope of the cavity.