How do you insulate a non vented attic?

Two acceptable methods for insulating an unvented attic assembly in all climates are as follows:

  1. Air-impermeable insulation (typically spray foam) installed to the underside of the roof sheathing.
  2. Air-impermeable insulation (typically rigid foam insulating sheathing) installed over the roof sheathing.

Can I seal a vented attic?

If existing bath fans vent into the attic, they must be modified to vent to the outside. Any existing insulation must be removed to provide access to the ceiling plane for air sealing. The ceiling plane or attic floor should be thoroughly air sealed prior to installing insulation.

What is an unvented attic?

Unvented attics rely on an air-impermeable insulation installed to the roof deck’s underside (i.e. attic ceiling) to stop airborne moisture from reaching a cold surface and condensing inside the building envelope.

Why does attic need ventilation?

In cold climates, the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow, and to vent moisture that moves from the conditioned space to the attic (ventilation acts to bypass the vapour barrier created by most roof membranes).

How do you insulate an unvented vaulted ceiling?

In general, closed-cell foam is the best choice for unvented cathedral ceilings. It is also one of the most expensive, and most building inspectors will not allow it to be left uncovered (for fire-code reasons). Foil-faced iso-board can be cost-effective insulation for finished attics and cathedral ceilings.

Is air sealing the attic worth it?

Is air sealing worth it? Yes. Getting your home air sealed is a worthwhile investment—one that pays off in energy efficiency, comfort, and your home’s value. According to Energy Star, the EPA estimates savings of 15% on heating and cooling costs by properly air sealing and adding insulation.

What is an unvented roof?

An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. Historically, typical construction of homes in Canada and the US have vented attics between the ceiling of the interior space and the roof.

What is the minimum R-value for unvented roof parts?

In Cold and Very Cold Climate Regions where there is likely snow accumulation on roof surfaces, there is also the likelihood of ice-damming. In order to control ice-damming, heat flow from the interior to the roof cladding must be minimized. In Cold Climate Regions the minimum total R-value for the entire unvented roof assembly should be R-40.

What is the potential for condensation on an unvented roof?

Figure 4: Potential for condensation in Dallas, Texas with unvented roof and insulating sheathing-there is no potential for condensation on the underside of the roof sheathing until moisture levels exceed 40% RH at 70°F; rigid insulation is recommended iin this roof assembly to raise the condensation potential above 50% RH at 70°F.

Does an unvented roof assembly have insulating sheathing?

This roof assembly has no insulating sheathing installed above the roof deck. Figure 4 shows the potential for condensation of an unvented roof assembly in Dallas, TX. Dallas, TX is located in a Mixed-Humid Climate Region. Note that this roof assembly has rigid insulation installed above the roof deck in order to control the condensation potential.