Moisture generated indoors or that infiltrates into the home is responsible for the bulk of the moisture in an attic insulated with spray foam on the underside of the roof sheathing.
Open cell foam insulation moisture problems.
Many homeowners love spray foam insulation and it s easy to understand why.
Lstiburek takes blame for bad language.
Open cell spray foam insulation doesn t store the moisture.
Thick applied beneath and spanning the floor joists held on with cap nails and seams taped edges sealed with a foam sealant is a tested good solution.
Open cell spray foam will allow moisture to get to the metal surface.
It s not coming from above the roof and it s not some new moisture source resulting from the spray foam.
Be sure to have that discussion with your licensed contractor and don t be afraid to double check the information before the project begins.
Over time trapped moisture can cause serious problems.
The spray foam insulation chemicals weren t mixed properly.
50 pascals of air movement is equal to about 16 mph wind.
Remember that open cell spray foam is also an air barrier.
It has a relatively high vapor permeance 3 perms at a thickness of 6 allowing water vapor to migrate to the roof decking at night and back into the attic air in the daytime.
It s the wood decking that stores the moisture though.
Choose open cell spray foam when insulating roofs since closed cell foam can trap water from a leaking roof damaging the framing material and roof sheathing.
For example icynene open cell spray foam must be installed at 3 inches before an air barrier is created.
It s just a pathway.
It is lower cost than closed cell foam and has the plus of flexing with the building but can be tricky to get good paint skin coverage.
Compared to traditional insulation whether fiberglass or cellulose spray foam has the potential to provide better performance via its air sealing properties high r values per inch of thickness and in the case of closed cell spray foam ability to repel moisture.
Sealection500 the open cell spray foam used at iowa spray foam only allows 0 001 l sm2 of air to pass through at 50ps.
Foil faced rigid foam insulation 2 in.
Oh and when you put it in your attic spray foam.
According to frank moisture can be a concern if you construct a home and insulate it with open cell spray foam.