Volume 5, Issue 2 (March 1977)
Economic and Performance Aspects of Increasing Insulation on the Temperature of Built-Up Roofing Membranes
The energy crisis has raised demands for a substantial increase in the insulation of roofing systems, and calculations in this paper confirm that the financially most favorable insulation has a thermal resistance much higher than that of presently used systems. Objections have been raised to the increase in the thermal resistance of roofs on the basis that this will result in a substantial increase of the temperature range to which membranes are subjected, with resultant increase of membrane cracking from temperature movement. We have made a number of calculations to check on the justification of such concerns.
The results of our work, based on a number of simplifying assumptions, show that increasing the thermal resistance of insulation, over presently prevailing standards, does not significantly enlarge the thermal range to which roofing membranes are presently subjected. This applies both to changes in the ambient temperature and to solar radiation. Insulation thickness should therefore be based on considerations of economy and energy conservation, but there are still unresolved problems of decreasing impact resistance and lateral stability.