Spf insulation can be open cell or closed cell.
Open cell spray foam metal roof.
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.
An open cell foam about 0 5 pound density is the most cost effective way to insulate but any opening over 1 16 could cause the foam to expand out onto the roof.
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.
How ducts in an unvented attic should be installed.
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.
Open cell spray foam.
There are some cases where i could see some challenges.
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.
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.
Moisture from indoors can diffuse through the foam and find the cold roof sheathing where it accumulates and eventually rots the roof.
Spf insulation consists of isocyanate and polyol resin that is chemically combined and applied to surfaces using a spray gun.
Strong material that can strengthen walls roofs structure.
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.
In our neck of the woods closed cell foam costs about 56 more than open cell.
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.
I prefer spraying open cell over the rafters when possible because it avoids shrinkage problems that can occur with such foams.
However i own a spray foam rig and i wouldn t bother putting more than about 8 of open cell or 5 closed cell.
One would be if someone went on the cheap and used open cell spray foam rather than closed cell.
Open cell foam provides insulation and air sealing for a building but is water and vapor permeable.
Open cell spray foam is made of open cells that are softer and flexible with the physical structure similar to a sponge shape.
Closed cell foam provides better insulation than open cell and also functions as an air barrier.