Open Cell Foam Insulation Moisture Problems

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.

Open cell foam insulation moisture problems.

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. It s not coming from above the roof and it s not some new moisture source resulting from the spray foam. Oh and when you put it in your attic spray foam. Foil faced rigid foam insulation 2 in.

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. It s just a pathway. The spray foam insulation chemicals weren t mixed properly. Remember that open cell spray foam is also an air barrier.

50 pascals of air movement is equal to about 16 mph wind. Open cell spray foam will allow moisture to get to the metal surface. Open cell spray foam insulation doesn t store the moisture. Be sure to have that discussion with your licensed contractor and don t be afraid to double check the information before the project begins.

Lstiburek takes blame for bad language. Many homeowners love spray foam insulation and it s easy to understand why. According to frank moisture can be a concern if you construct a home and insulate it with open cell spray foam. If closed cell is used the moisture cannot make its way to the wood and present.

Open cell s vapor permeability enhances an assembly s ability to dry out via diffusion should it become wet open cell spray foam may absorb moisture if subjected to hydrostatic pressure but will allow moisture to drain through open cell spray foam will not wick water or contribute to capillary action. 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. 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. 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.

For example icynene open cell spray foam must be installed at 3 inches before an air barrier is created. Over time trapped moisture can cause serious problems.