by RCI Publications
Cool single-ply membranes with highly reflective surfaces have come to represent over 50% of the commercial roofing market. Each year, well over 1.5 billion square feet of these white membranes are installed. However, as with many changes, there have been concerns about unintended consequences associated with this large shift. For example, in northern regions, condensation buildup has been a frequent concern. A review by this author showed that such instances were relatively rare, and that good roofing practices would largely avoid the issue.1 However, that review was focused on systems using polyisocyanurate (polyiso) insulation installed above steel deck construction.
In the coastal regions of California, Oregon, and Washington (i.e., the West Coast), low-slope roofing is frequently installed over plywood or oriented strand board (OSB) decks above wooden rafters. Fiberglass insulation is installed between the rafters as shown schematically in Figure 1. Fiberglass insulation facers are vapor retarders, but it is very difficult to install the product in such a way that air doesn’t readily pass up through the system and into the space below the deck. Let’s look closely at the features of this system that can contribute to condensation issues. Read more.