Roof Ventilation With Spray Foam

Wood has an r value of about one per inch of thickness.

Roof ventilation with spray foam.

Leave a gap on both sides. Open cell spray polyurethane foam or closed cell spray polyurethane foam ccspf insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in all climate zones see figure 1. One of the biggest benefits of using spray foam is to get greater airtightness. This is not an issue specific to spray foam as much as it is a characteristic of peel and stick membranes.

Mark bomber s book spray polyurethane foam in external envelopes of buildings reports on research that demonstrates ccspf under typical building conditions i e. Now we use attic ventilation when we use products like fiberglass because we have to manage the moisture. How to vent a foam insulated roof step 1. When installed over wood framing that has 28 to 35 per cent moisture content took approximately 35 days to dry less than 19 per cent moisture content compared to 8 5 days to dry with no foam attached.

It also reported the air sealing qualities of the foam were retained. But with spray foam ventilation is not an issue. That is now a conditioned part of your house just like any room in your house. That means you get rid of all attic ventilation whether it s passive ridge gable soffit vents or active fans.

In comparison to high density spray foam medium density spray foam is applied as a low or high pressure two component polyurethane spray foam. Temporarily secure long plastic forms between the rafters on the inside of the ceiling. Actually you should probably get rid of power attic ventilators whether or not you re sealing the attic but that s another article. Build the rafters and secure the 5 8 inch cdx sheathing material.

Spray the foam. The point i m making here is that a sealed attic should be well all sealed up.