Open cell spray foam.
Open cell spray foam metal roof.
Open cell spray foam is made of open cells that are softer and flexible with the physical structure similar to a sponge shape.
As a result in iecc climate zones 5 and higher building codes require the use of a vapor retarder if you install open cell spray foam.
Open cell foam provides insulation and air sealing for a building but is water and vapor permeable.
However i own a spray foam rig and i wouldn t bother putting more than about 8 of open cell or 5 closed cell.
Strong material that can strengthen walls roofs structure.
Open cell spray foam can also be used to create an unvented attic in cold climate zones provided code requirements for a vapor retarder are followed.
How ducts in an unvented attic should be installed.
There are some cases where i could see some challenges.
Moisture from indoors can diffuse through the foam and find the cold roof sheathing where it accumulates and eventually rots the roof.
There seem to be no chemicals in spray foam that could react with steel or the galvanized protective coverings on the metal siding and roofing panels.
Less common of the two types of spray foam open cell is mostly used for residential and commercial insulation.
In our neck of the woods closed cell foam costs about 56 more than open cell.
Most steel roofing is factory finish painted which adds yet another barrier surface in the interior primer paint coat which further isolates the steel from the spray foam.
Closed cell foam provides better insulation than open cell and also functions as an air barrier.
The big picture concern is actually more about trapped moisture than whether the substances that make up spray foam insulation will corrode steel or metal sheets.
It would be better to use a closed cell 2 pound density foam because it doesn t expand as much as open cell and is more likely to fill voids but not go through them.
Spf insulation can be open cell or closed cell.
One would be if someone went on the cheap and used open cell spray foam rather than closed cell.
We already know open cell spray foam is risky in cold climates.
Open or closed cell spray foam is applied to the underside of the roof sheathing and additional fiberglass or cellulose insulation is blown in as a cost saving method for meeting high insulation requirements and filling in the cavity space between the rafters to the ceiling deck.
Some spray foam manufactures have tested primer coating products that result in the formulation of a class ii vapor retarder directly on the surface of the open cell spray foam.