Contact Resistance in a Steel-Framed Wall

Abstract

This paper sets out to answer, experimentally, the question "how much influence does the contact tightness between steel frame and facings have on the overall thermal resistance of a wall panel?" The contact tightness has been equated to the mean contact gap between those two items. Accurate methods for both control and measurement of this gap have been utilised for this task. The experiment was devised so that precision adjustments to the contact gap could be made externally, and the wall panel was repeatedly adjusted and its thermal resistance measured, with no disturbance to any other part of the wall. The results showed that the mean contact gap could be adjusted between a mini mum of 0.5 mm and a chosen maximum of 3 mm. Variations solely in the tightness of fit between frame and facing (equated here to the mean contact gap) were found to produce up to -30% variation (16% per face), from 1.30 to 1.51 m20C/W, in the rated R-Values of the test panels studied. The effect was moderately linear.