Attic walls separate the interior of the home from attic spaces, rather than the exterior. This usually occurs when there is a skylight (as shown above), or when different floors of the home have different ceiling heights. For instance, if there are raised or cathedral ceilings adjacent to areas with flat ceilings, there will be an attic wall present.

Due to the framing around a skylight tunnel, there is a high potential for thermal bridging. Continuous rigid foam board around the framing is recommended to reduce the effects of thermal bridging in skylight tunnels.

The above photo shows an example of a typical installation. Can you see any issues?

Insulating - Attic Walls

Insulating these walls can be very challenging as there is often insufficient framing to support the insulation. When insulating the gable wall against a cathedral, insulation needs to be cut to fit into the cavity created by the gable truss.

Taking the time to properly cut and fit the insulation in these areas can impact the effective R-value of the insulation, the condensation resistance of that area, as well as occupant comfort.

(The above photo shows a common way of insulating attic walls. The strapping is a good idea, BUT in this case it is causing compression of the batts and deforming them at the same time. This will lead to increased heat loss at the compressed areas and at the gaps formed.)

Installation Process:

There are two main methods used for installing insulation within attic walls.

1. Have a wall framed in order to provide a cavity to support insulation.
2. Use a method to fasten and support the insulation in the area. This can be done by wrapping the area with an air barrier product, or by using rigid or flexible strapping.

Method one is preferable as it provides a more consistent, durable, and uniform result.