Closed Cell Spray Foam Insulation Vs. Open Cell – Build Attic R-Value

Stopping the flow of air from leaving living space using closed or open cell spray foam is the most important part of insulating a home. In order to start building r-value, The blocks of your home where your walls meet your attic floor have to be sealed. In most situations closed-cell spray foam is the clear winner. Compared to open-cell foam, closed-cell is much more dense and is way more ridged than open cell. Closed cell foam also blocks moisture from coming through the air penetrations, which in most cases is a good thing unless there is a place for water to pool.

Open-cell foam is a cheaper material to use and does not last as long as closed-cell. Any air sealing we do is with closed-cell foam, never with open-cell. We use it to block air from coming into vents, electrical penetrations, wall cavities, eaves, gable walls, etc. Fiberglass insulation is actually an example of an open-cell foam, it just isn’t blown into your home, it’s blown into sheets at the factory. Both of the pictures above are different grades of polyurethane.

Before we blow cellulose on top we seal EVERYTHING:  Attics aren’t the only spaces we can insulate with closed cell foam. Underneath decks, below additions that have no basement underneath, etc. Closed cell foam is so durable it can be used in outdoor applications. The closed-cell spray foam we use is a two-part foam. Each one of those tanks is connected into the central spray gun, when they touch together, they instantly harden and dry. Once the spray foam is set, we can then blow our cellulose insulation over it (“Cel-Pak Insulation”, also pictured in the green bags to the right). Building r-value with blown-in insulation lasts much longer and performs much better when the air below it is sealed. Whenever we do an insulation job we actually measure the air-tightness of the home before and after, and can make a direct correlation between that and the actual energy savings you will receive from an insulation job. Because you cannot see the work when it is being done in the attic, or afterward because the insulation is on top of the foam, it is important you hire someone you know will be diligent enough to seal everything.