Unvented Attic Spray Foam Insulation

Air impermeable insulation typically spray foam installed to the underside of the roof sheathing.

Unvented attic spray foam insulation.

When you insulate the top of your attic with spray foam you re bringing your attic into your home s envelope. Spray foam insulation in an unvented attic assembly has been one of the most researched and widely implemented innovations of recent years. Using spray foam insulation in an unvented attic application both low density open cell and medium density closed cell spray foam can be used in an unvented attic to provide the needed thermal resistance and airtightness. Insulating unvented attics with spray foam figure 1 spray foam is a good choice for roofs that are difficult to vent like a turret with converging rafters left or a flat roof with its rafters hung between flush beams right.

Two acceptable methods for insulating an unvented attic assembly in all climates are as follows. Fibrous insulation e g batt or blown in can be installed under the roof deck in the hot dry climate zone but this will cause moisture problems in all other climates straube and grin 2010. The unvented attic space is considered the most effective and up to date building practice particularly by the spray foam industry. This is done by using what is referred to as air impermeable insulation such as rigid foam board or spray foam.

As a result you can reduce the temperature in your attic by a lot anywhere from 120 degrees to around 95 during peak summer. Spray foam in unvented attics intended for regular use helps. If you want you can even transform a spray foamed attic into a finished space. Over time feedback from builders and building owners has been and continues to be overwhelmingly positive especially in the areas of moisture performance energy efficiency and building durability.

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. Common problems found with traditional insulation in an unvented attic assembly can be mitigated with spray foam insulation like icynene. Humid or cold climates require either rigid foam insulation above the roof deck to keep its temperature above 45 f. Unvented attics sometimes called sealed enclosed or encapsulated attics feature insulation on the underside of the roof decking rather than on the attic floor.

This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation.