Roof Ventilation With Spray Foam

Temporarily secure long plastic forms between the rafters on the inside of the ceiling.

Roof ventilation with spray foam.

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. How to vent a foam insulated roof step 1. One of the biggest benefits of using spray foam is to get greater airtightness. Mark bomber s book spray polyurethane foam in external envelopes of buildings reports on research that demonstrates ccspf under typical building conditions i e.

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. But with spray foam ventilation is not an issue. This is not an issue specific to spray foam as much as it is a characteristic of peel and stick membranes. 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. That is now a conditioned part of your house just like any room in your house. The point i m making here is that a sealed attic should be well all sealed up. Leave a gap on both sides.

These forms are only 1. This type of spray foam offers the specific benefits of continuous insulation interior wall cavity fill and unvented attic applications. It also reported the air sealing qualities of the foam were retained. If spray foam is used a vent space may still be needed directly under the roof deck.

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.