Finishing An Unvented Attic

The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling.

Finishing an unvented attic.

Both vented and unvented attic roof designs can be used in all hygro thermal regions. Adding unvented attic insulation like spray foam seals the building envelope and stops airflow. The acceptance of unvented conditioned attics continues to grow among builders and building officials. I have a shop in my attic for some of my hobbies and it get s very hot in the summer.

I have large attic with ridge vents and screened vents at either end of the attic to maintain air flow. Once an unvented roof is finished it s awfully damn difficult to notice roof leaks. But in many spray foamed attics it can be hard to manage humidity. To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents.

Code requirements vary across the country. As a result you can reduce the temperature in your attic by a lot anywhere from 120 degrees to around 95 during peak summer. Can i put a small swamp cooler or ventless a c unit up there to cool it only to use while i am in my shop maybe an hour or two a couple times a week. The unvented attic system or conditioned attic is the new way to make your attic energy efficient.

However the designs need to be climate sensitive. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic. The choice of the venting approach is up to the designer.

Closed cell is a vapor retarder meaning water from a leak could be trapped against the roof sheathing. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. The irc has permitted unvented conditioned attics since 2006 with certain requirements. If you want you can even transform a spray foamed attic into a finished space.

Control of ice dams moisture accumulation and heat gain can be successfully addressed by both vented and unvented attic or roof design. Unvented attic system pros and cons. During the spring summer and fall relative humidity rh in a spray. The energy savings touted by unvented attics can be as high as 20.

The roof deck in an unvented attic must be exceptionally airtight.