A Surprising Source of Energy Loss

Roof fasteners are probably not the first things you’d think of with respect to energy loss. The photo above was taken on a snow-covered roof and each of the black dots you see corresponds to a fastener and washer used to secure insulation, through which enough heat was lost to melt snow.  They aren’t very big (about two inches in diameter), but there are a lot of them.
The subject roof assembly consisted of an EPDM (rubber) membrane directly adhered to a layer of mechanically attached polyisocyanurate insulation, without a cover board.  Cover boards are not usually required by manufacturers of thin single-ply membranes, such as EPDM, PVC, and TPO, although they should be.
An insulating cover board installed between the primary insulation and the membrane not only helps reduce energy loss (heat loss during the winter and gain during the summer) it reduces the chance of condensation forming on the fastener plates during cold weather.  Such condensation can cause the membrane to become debonded at the fastener heads.