Unvented Attic Air Exchanger

It s most likely to occur after periods of mild wet weather followed by an overnight cold snap.

Unvented attic air exchanger.

Or can we keep all in the attic. We will be replacing it with an hrv shortly. 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.

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. We currently have an old 1980s air exchanger in our attic split entry home. However if moisture is able to enter the unvented attic space it may lead to roofing panel issues. The unvented attic space is completely contained within the building thermal envelope 2.

No interior vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly 2009 irc. Now my house is an 1100sq ft bungelo. Where wood shingles or shakes are used a minimum inch vented air space separates the. 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.

The risk is condensation or mold on the underside of the sheathing. Or if high humidity bathroom air finds its way into the attic through. Looking at an air to air exchanger its made by venmar its a constructro 1 5. It often takes until early to mid afternoon for this peak to occur.

You see hot moist air rises the peak of the attic is the highest point and vapor drive moves from warm to cold. 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. No interior class i vapor retarders are installed on the ceiling side attic floor of the unvented attic assembly 2012 irc 3. Summer attic air temperatures with reflective roof peak at or slightly above outdoor air ambient.

We are going to address the idea of air exchange in closed attics that use open cell foam. 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. In an unvented attic penetrations through the ceiling directly below the attic do not need to be air sealed. 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.

The energy savings touted by unvented attics can be as high as 20.