Proper Foam Insulating From Soffit To Attic

Aluminum or vinyl soffits eaves installed over plywood soffits that don t have venting holes.

Proper foam insulating from soffit to attic.

It has been said that insulating with spray foam insulation at the roof line will lead to moisture problems with the roof sheathing. If the attic is insulated with fiberglass batts just pull back any that are blocking the flow of air. Earlier this year i got a question about a home that had spray foam insulation in the attic. Five common causes of poor attic venting.

Verify that there is a baffle at each soffit vent extending from the top plate to above the height of the insulation to provide a pathway for ventilation air while keeping insulation out of the soffit vents. Whereas too little spray foam insulation can leave for thermal bypass because of the complete lack of insulation in the attic. If there s blown in insulation like ours rake back the fluffy stuff with a 3 or 4 ft long 1 x 6 or use a garden rake or hoe. Just getting to the soffits requires some dexterity.

I ve researched this a bit and know that the recommended approach to seal off the soffit from the attic is to insert a square of rigid foam and spray foam over it. Then cover the foam with drywall as required for fire safety. With spray foam unlike with loose fill or batts you must cover the soffit vents they aren t needed to keep the roof cool. The soffit vents are now installed but you still need to make sure there s no insulation blocking the new vents.

Install air chutes or clear them if they re clogged photo 1. A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents. That will be a pain in our house because our roof has a shallow pitch. Moisture is also another huge issue when it comes to spray foam insulation in an attic.

Install a minimum of 1 inch of spray foam insulation over the attic floor to provide a continuous air control layer. Insulation often clogs the space between the rafters blocking air from traveling to and from the soffit area. Foam blocks airflow needs no vapor barrier and has a higher r value per inch than loose fill or batts so you ll get more protection with less depth. Baffles establish a channel for air to circulate between the insulation and the roof sheathing.

To meet all three goals insulating your finished attic ventilating the roof and maximizing headroom use a combination of dense batt insulation rigid foam sheeting and air chutes.