Attic Knee Wall Sheathing

Radiant barrier wall sheathing can be attached to the attic exterior side of a knee wall to cut down on radiant heat gain or heat loss in the winter.

Attic knee wall sheathing.

On one wall that is partially exposed to the outside but mainly in the attic the original builder used fiberboard. Ventilating knee wall attics is challenging. There is bare insulation just hanging between the 2x4 s so an air barrier looks to be needed. There are two ways to insulate triangular attics behind kneewalls.

It is recommended that insulation be encapsulated on all six sides with a rigid air barrier like sheathing or foam board. The best way to handle a knee wall area is to move the thermal barrier to the roofline left and stand up the knee walls after the ceiling has been drywalled. So companies like norbord started creating tallwall windstorm panels to help alleviate this. We live in a cape cod style home and i d like to install an air barrier on the second floor knee walls.

The death of the 8 sheet one of the biggest items when sheathing a wall vertically is that the sheathing has to be continuous 602 10 4 5 which meant that an 8 sheet wouldn t cut it in many places so longer ones were required. 1 a continuous air barrier can be installed on the exterior of the kneewall framing from the top of the knee wall down to the attic floor including the spaces between the attic floor joists from the bottom of the knee wall to the ceiling deck below or 2 a continuous air barrier can be installed along the underside of the attic roofline from the top of the knee wall to the top plate of the home s exterior wall. Sometimes though there are no soffits. Here are the three keys to sheathing an attic kneewall properly.

Cover the whole wall. The airflow in the ducts suffers from friction losses and the air loses heat to the cold attic space as it makes its way to the room. So after we seal up the insulated air barrier for the bonus room knee wall we install a thick blanket of cellulose insulation around the duct. Sheathe the kneewall during framing for new construction.

A leaky kneewall also can provide a pathway for escaping warm air to heat up roof sheathing which can contribute to ice dams. Cover the whole wall. This helps keep the supply air coming into the room nice and warm. Here are the three keys to sheathing an attic kneewall properly.

There are two ways to block off this air flow. Sheathe the kneewall during framing. Seal all the edges penetrations and seams. Seal all the edges penetrations and seams.

For production builders who may have less control in scheduling trade partners the knee wall can serve as the thermal barrier right as long as sheathing is installed on the back side.