After doing some research when we first started building, we agreed on metal roofing. Metal is easily installed, completely recyclable, long lasting, and it can be used for rain water harvesting without concerns over carcinogens. We found a local company that would supply 26 gauge galvanized steel roofing for a reasonable price as well as a “drip edge” flashing that would serve our runoff, as well as our facia needs.
After placing the 1/2 ‘’ OSB over the roof framing, we installed 1-1/2’’ polyisocyanurate (Often called “polyiso” for short, or generically “foam board”.) insulation. Polyiso is commonly regarded as the most eco-friendly option amongst the foam choices. Installation is simple as the boards are the same dimensions as the sheathing and our roof dimensions (8.5×24) with no peaks or valleys made the entire roofing portion very simple.
Over the polyiso, we placed a layer of water proofing superior to felt paper. The product we used is manufacture by Grace for prevention of ice dams in metal roofs near the toe of slopes. We elected to cover the entire roof in the product due to its reputation as a water barrier. The underside of the product is an asphalt-like layer that will adhere to anything and forms a strong bond to the polyiso.
Placing the drip edge and metal roofing panels proved very easy and was finished in only a few hours. As with everything else, the panels were screwed on, with considerations for wind and highway travel. The panels went together seamlessly and we have the added insurance of the weather barrier beneath.
Our roof is designed to be impermeable. We have no vents, chimneys or etc. and we designed it this way for simplicity and peace of mind. Houses must however be given opportunity to expel moisture that builds up at the roof interface. We will achieve this with soffits (vents) installed in the underside of our south, east, and west roof overhangs (the roof is tilted to the north).