Unvented Attic Air Exchanger

The risk is condensation or mold on the underside of the sheathing.

Unvented attic air exchanger.

The problem that can occur in a closed attic assembly is the management of the moisture that rises and accumulates in the attic space. The energy savings touted by unvented attics can be as high as 20. Summer attic air temperatures with reflective roof peak at or slightly above outdoor air ambient. Now my house is an 1100sq ft bungelo.

Building codes require unvented attics to have air impermeable insulation in contact with the roof sheathing. Unventilated attics can help to mitigate energy loss through leaky ducts or ceiling fittings. In an unvented attic penetrations through the ceiling directly below the attic do not need to be air sealed. You see hot moist air rises the peak of the attic is the highest point and vapor drive moves from warm to cold.

No interior vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly 2009 irc. It often takes until early to mid afternoon for this peak to occur. We currently have an old 1980s air exchanger in our attic split entry home. Where wood shingles or shakes are used a minimum inch vented air space separates the.

Looking at an air to air exchanger its made by venmar its a constructro 1 5. No interior class i vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly 2012 irc 3. 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. 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.

We are going to address the idea of air exchange in closed attics that use open cell foam. 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. 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. It s most likely to occur after periods of mild wet weather followed by an overnight cold snap.

The unvented attic space is completely contained within the building thermal envelope 2. Or can we keep all in the attic. 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. I was wondering if i could just tap into the existing heat ducts and cold air return or do i run separate lines and if that s the case do vents have to be high and low or can they all be put at floor level.

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.