Thermal Bridging on Roofs
Here is a photo of a TPO roof that had mechanically fastened insulation through a vapour retarder onto a steel deck.
Thermal bridging occurred through the fasteners and created wetting at the facers and into the insulation. The resulting display made our review of the fastening pattern very simple!
Contrary to what some manufacturers will accept and allow, it is highly recommended in our cold climate that a second layer of insulation be installed to prevent thermal bridging, wetting of insulation, damage to the mechanical fasteners, and internal leaks.