One would be if someone went on the cheap and used open cell spray foam rather than closed cell.
Open cell spray foam on metal roof.
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.
There are some cases where i could see some challenges.
In warm climates zones 1 through 4 low density open cell spray foam insulation is the typical choice since it is vapor permeable and will allow drying of the exterior sheathing and roof framing if they happen to get wet via diffusion into the interior of the building.
Versi foam open cell foam kits have a density of approximately 0 75 pounds per cubic foot.
Since spray foam is monolithic and closed cell it will create a watertight barrier over the entire metal roof.
That s an important consideration because if there s a leak in the roofing or the ridge cap moisture could get trapped between the roof and the insulation.
Your metal roof expands when it s hot and contracts when it s cold.
Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while.
It is 92 open cell and has an insulation r value of 4 lower than the other versi foam systems but still superior to some of the other commonly used insulation materials.
Other considerations to get the best performance out of spray foam insulation you must cover the roof rafters and surrounding areas as thoroughly as possible.
Closed cell spray foam insulation has a tendency to fill voids and gaps because it doesn t expand as much as open cell insulation.
Closed cell foam differs from open cell in that it prevents water entry minimizes moisture vapor permeability and decreases air leakage making it the preferred insulation to apply to metal panels.
If you use open cell spray foam on your roof rafters you should cover the finished application with a paint or sealant that retards water vapor.
About open cell spray foam kits.
Spray polyurethane foam insulation with metal.
Most of the time extreme heat shifts cause that leak.