Unvented Attic Air Exchanger

Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons.

Unvented attic air exchanger. Looking at an air to air exchanger its made by venmar its a constructro 1 5. In an unvented attic penetrations through the ceiling directly below the attic do not need to be air sealed. Where wood shingles or shakes are used a minimum inch vented air space separates the. The problem that can occur in a closed attic assembly is the management of the moisture that rises and accumulates in the attic space.

We will be replacing it with an hrv shortly. This is because the top floor ceiling is no longer the air barrier for the house the spray foam at the roof deck underside in the attic is the air barrier. Summer attic air temperatures with old terra cotta colored asphalt shingles peaked at 140 to 145 at 18 above the blown in fiberglass insulation layer at the attic floor. We are going to address the idea of air exchange in closed attics that use open cell foam.

Summer attic air temperatures with reflective roof peak at or slightly above outdoor air ambient. Or can we keep all in the attic. 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 soffits etc which make it difficult to achieve an airtight ceiling plane. But what i m trying to determine is should we go out of our way to change all the duct work and install the hrv in our basement.

You see hot moist air rises the peak of the attic is the highest point and vapor drive moves from warm to cold. Now my house is an 1100sq ft bungelo. Obviously it would be way easier just to keep it all in the attic and save room but i want to do what is best. It s most likely to occur after periods of mild wet weather followed by an overnight cold snap.

The energy savings touted by unvented attics can be as high as 20. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. It often takes until early to mid afternoon for this peak to occur. The risk is condensation or mold on the underside of the sheathing.

Building codes require unvented attics to have air impermeable insulation in contact with the roof sheathing. Or if high humidity bathroom air finds its way into the attic through. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. We currently have an old 1980s air exchanger in our attic split entry home.

The unvented attic space is completely contained within the building thermal envelope 2.