Hot Roof Closed Cell Spray Foam

The main drawback is high cost.

Hot roof closed cell spray foam.

Closed cell spray foam. Both low density open cell and medium density closed cell spray foam can be used in an unvented attic to provide the needed thermal resistance and airtightness. If you wish to believe a certain manufacturers claims just one of many bogus ones and install an open cell product make sure it has a vapor barrier sprayed to the foam. More common of the two types of spray foam closed cell is mostly used for commercial roofing.

And again to reiterate hot roof or hot attic assemblies where the foam is beneath the roof deck are okay. If you want to use spray foam here s my advice. The amount of closed cell spray foam or rigid insulation is somewhere between 20 to 50 of the r value of the overall cavity insulation depending on your climate zone. Since it s air impermeable spray polyurethane foam can be installed alone on the underside of roof sheathing.

It doesn t fill the cavity though so spot checks may be required to check you don t get shorted. With enough closed cell spray foam under the deck or enough rigid above the deck interior moist air can t condense if the there is no condensation you don t need drying thus no need to vent. There are fewer reports of problems with closed cell spray foam than with open cell spray foam. Closed cell or open cell foam.

I plan to use the closed cell spray foam insulation on 3 4 inch sheathing. Closed cell spray foam is made of cells that are encapsulated and pressed tightly together to prevent air and moisture penetration inside the foam. This roof assembly is often referred to as a cold roof and is the antithesis of a hot roof. Closed cell foam has a higher r value per inch and installers generally spray 2 in walls and 3 in roof lines to meet the energy code requirements of r 13 and r 19 respectively.

Closed cell spray foam uses blowing agents with a high global warming potential and open cell spray foam needs a. Not long ago someone even told me that in florida roofing companies won t let their workers go up on roofs with open cell spray foam because the roofs are so spongy the guys fall right through. Todd miller isaiah industries inc. Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while.

Instead i like to build a fully vented roof assembly that is insulated with closed cell spray foam. Since you have already arranged to have 2 inches of closed cell spray foam installed in your floor assembly it seems clear that there is at least one insulation contractor in your area who is willing to install closed cell spray foam. It rots roofs people have told me. Unless you live in climate zones 2b or 3b desert area s in texas new mexico arizona california the codes and common sense will point you to closed cell foam.

With two strategies employed the airtight vapor impermeable foam plus the ventilation as a safety valve you might call this a belt and suspenders approach to building.