Open Or Closed Attic

A spray insulation is referred to open cell or closed cell because of the difference between the small bubbles cells that make up the foam.

Open or closed attic.

Closed cell works the best to encapsulate and stop air travel though. It even rained and the sill got wet but not the floor. Closed vents during the summer. Although air should circulate year round through the attic your house will probably be more comfortable if you cover the foundation vents in the winter.

In general most closed cell foam and many open cell foam products can be installed without the need of an intumescent coating in an unvented attic and therefore can go bare provided a drywall ceiling 15 minute thermal barrier directly below the attic exists. To provide background the house has a hot unfinished attic with blown cellulose and fiberglass insulation beneath the floor and no insulation along. If you end up installing open cell spray foam in your attic in spite of my advice you should a make sure that there is a forced air register in your attic to introduce cool air in the summer and warm air in the winter and b install a hygrometer in your attic to monitor the indoor relative humidity rh martin holladay. My parents house has two small windows in the attic that open.

Would it be better to keep them closed to keep out rain or open to allow ventilation. You do see closed cell used in attics from time to time and it s being used more often but mostly open cell. After leaving the attic window open overnight it was amazing how cool it got in there. My home has a whole house fan installed in the upstairs hallway ceiling when its cool at night that thing can suck the heat out of the house in record time.

This makes the foam a softer more flexable material. An alternate to spray foam insulation in an unvented attic is plenum trusses which allow you create a reverse bulkhead above the ceiling plane that is insulated. I think it s mainly cost. The r value of closed cell is 6 5 per inch and the density of the foam is 2 lb per cubic foot.

In other words the cells are deliberatly left open. Another study s computer model indicated that open cell foam insulation is riskier than closed cell foam in all us climate zones. As long as they re properly installed both closed cell and open cell foam insulation act as an effective air barrier in your attic. Typically it s open cell that s used around here.

Closed cell spray foam insulation is more dense and provides a better r value than open cell.