Can you spray foam a roof deck?

Open-cell spray polyurethane foam or closed-cell spray polyurethane foam (ccSPF) insulation can be sprayed along the underside of the roof sheathing to provide a conditioned and insulated attic space that can be durable and efficient in all climate zones (see Figure 1).

Is open cell foam worth it?

In the case of leaks, open-cell foam will absorb water and hold it against the framing and sheathing elements facilitating mold and rot. Bottom Line: It’s a great and affordable insulation option when there is no chance of water intrusion, but you’re rolling the dice if you think it might get wet.

Is spray foam insulation on roof good?

Both papers basically came to the same conclusion: “Open-cell spray foam insulation is risky in all climate zones.” We already know open-cell spray foam is risky in cold climates. Moisture from indoors can diffuse through the foam and find the cold roof sheathing, where it accumulates and eventually rots the roof.

Does open cell foam mold?

The spray foam allows water to move through it without retaining it or losing insulation properties. It has vapor permeability. Open cell spray foam cannot sustain mold. Its blowing agent is water.

What’s the difference between open cell and closed cell spray foam?

Open cell foam is full of cells that aren’t completely encapsulated. In other words, the cells are deliberatly left open. This makes the foam a softer, more flexable material. Closed cell foam is made up of cells that are, as the name suggests, completely closed.

What is the R-value of open cell foam?

Open-cell spray foam absorbs and holds water. It has a lower R-value per inch than closed-cell foam and is vapor-permeable. The R-value is R-3.5 to R-3.6 per inch, so filling a 2×4 cavity yields about an R-13.

What happens if closed cell foam gets wet?

Closed cell spray can take water for quite some time and not be adversely affected. We have actually had a basement that we spray foamed with 3″ of closed cell foam get completely flooded for over 3 weeks. When the water receded we did a absorption test and adhesion test.