How To Do An Unvented Attic

Convert a vented attic to an unvented attic and insulate using one of the methods described in the description tab or similar.

How to do an unvented attic.

This can be accomplished by the installation of an air barrier system or by the control of the air pressure difference across the assembly depressurizing a building enclosure reduces the exfiltration of interior air pressurizing a roof assembly with exterior air also reduces the exfiltration of interior air. Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope. With unvented attics the air barrier vapor and thermal controls are installed at the roof deck. Making the attic a conditioned space means the space will be the same temperature as the rest of your home.

Unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e. 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. This allows you to install your bulkheads above the ceiling plane without the need for spray foam insulation. In this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within the building envelope.

Use closed cell foam insulation. This air seal will. In theory if you install a small exhaust fan in the gable wall of an unvented attic along with a passive duct or grille that allows conditioned air from the floor below to enter the attic as makeup air the humid air in the attic will be exhausted and will be replaced with less humid air from the home. This system can help you avoid.

The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling. The entire attic becomes conditioned space eliminating drafts and temperature fluctuations. 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. Close and seal all attic vents including roof deck and soffit vents.

Fibrous insulation fibrous insulation e g batt or blown in can be installed under the roof deck in the hot dry. The same conditions apply for moisture. Insulation approaches for unvented attics vary by climate. I ve calculated that i would need 5 kits to get approximately 2 inches total.

If installing insulation above the decking remove existing roof tiles or shingles and replace weather resistant barrier if needed. Total cost to do this would be around 3 500 dollars. By moving the vapor control layer to the roof deck it prevents moisture related problems.