Insulating Low Pitch Attic

Using spray foam insulation in an unvented attic application.

Insulating low pitch attic.

Stop using your attic for storage. Multiple jurisdictions have indicated that even though we are utilizing 4 or more of polyiso rigid insulation on the exterior side of the roof sheathing low slope roof the 24 open web parallel chord roof trusses form an attic space and they have been requiring us to vent the low slope application. Start with the attic floor. 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.

Blow or pour in loose fill between ceiling joists and outer attic rafters behind kneewalls. Because the simplest and cheapest way to insulate an attic is to add material to the floor. Worries about the hot roof un vented cathedral ceiling designs how to. Although some builders insulate a low slope roof with the same techniques used for a house with a big attic they should be using a different approach.

Suggestions for un vented or hard to vent building roof cavities. But if the floor is covered in plywood you can t stuff enough insulation beneath it to do the job sufficiently not even in warm climates. Address air sealing and insulating an existing unconditioned vented low slope attic is to convert the attic into a nonvented conditionedspace whilethisisaviableoptionthatshouldbe considered in a broad discussion on air sealing and insulating homes for this research nonvented roofs were left out of the scope. If it is and you plan to provide heating and cooling to the finished attic space you need to remove.

Stuff rafter cavity above the kneewall and blow insulation down the rafter cavity. The attic floor which is the ceiling of the living space below often already is insulated. The most common practice is to blow in loose fill or wet blown insulation if you are insulating the ceiling where there is a cavity. If the roof is vented the ceiling must be air sealed to prevent moisture laden air from reaching the attic.