Roof Ventilation With Spray Foam

One of the biggest benefits of using spray foam is to get greater airtightness.

Roof ventilation with spray foam.

Build the rafters and secure the 5 8 inch cdx sheathing material. That is now a conditioned part of your house just like any room in your house. Now we use attic ventilation when we use products like fiberglass because we have to manage the moisture. This type of spray foam offers the specific benefits of continuous insulation interior wall cavity fill and unvented attic applications.

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. Wood has an r value of about one per inch of thickness. If spray foam is used a vent space may still be needed directly under the roof deck. Spray the foam.

How to vent a foam insulated roof step 1. This is not an issue specific to spray foam as much as it is a characteristic of peel and stick membranes. The point i m making here is that a sealed attic should be well all sealed up. 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.

These forms are only 1. Leave a gap on both sides. Mark bomber s book spray polyurethane foam in external envelopes of buildings reports on research that demonstrates ccspf under typical building conditions i e. 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. But with spray foam ventilation is not an issue.