How To Insulate A Metal Building Roof. In this case, simply lay the insulation between the purlins. Heat rises, and therefore the building regulations requirements for heat loss through roofs are more stringent than those for walls.
Once the first roof panel is installed the insulation can be unrolled on the roof panel and slid into place. Unroll the insulation over the purlins, keeping in mind that the vapor retarder should face the inside of the building. When it reacts with the oxygen in the air and the water dries up, the polyurethane foam will expand, harden, and cure within minutes, which results in thick, rigid foam.
This will provide r value and act as a vapor barrier.
When it reacts with the oxygen in the air and the water dries up, the polyurethane foam will expand, harden, and cure within minutes, which results in thick, rigid foam. With several available performance ratings. Avoids nails or screws, which could penetrate the metal roof and cause leaks. In this case, simply lay the insulation between the purlins.