Replies

1. GBA Editor
   Martin Holladay | Apr 21, 2018 06:59am | #1

   Emerson,
   I'm not sure what risk you're talking about. I don't think there is a risk.

   For more information, see “Two Ways to Insulate Attic Kneewalls.”

   If you do a good job of insulating along the roofline, you don't need any insulation in the kneewalls.

2. 
   Jon_R | Apr 21, 2018 10:36am | #2

   Space located part way through the total insulation can suffer from excessive humidity. Warm side vapor barriers and air sealing help, cold side makes it worse - but it can occur anyway. A small amount (depends greatly on conditions) of air flow (draw from the lower dew point side) helps. Or a dehumidifier (when warm enough). Start by monitoring % relative humidity.

3. GBA Editor
   Martin Holladay | Apr 21, 2018 11:06am | #3

   Emerson and Jon,
   There are a lot of unknowns here, but it is really hard to imagine that the triangular attic behind the kneewall will have a moisture problem under these circumstances. Anyone proposing a moisture problem has to start by answering the question, "Where do you think the moisture is coming from?"

   I guess if we want to really delve into this question, we would need to know whether Emerson (a) plans to install air-sealed blocking in the joist bays under the kneewall bottom plate, and (b) plans to install air-sealed blocking in the rafter bays above the kneewall top plate, and (c) plans to insulate the joist bays under the triangular attic behind the kneewall, and (d) plans to air seal leaks from the exterior into the triangular attic behind the kneewall.

   We would also need to know Emerson's climate zone and the proposed R-value for the kneewall and the sloped roof assembly.

   All that said, I stand by my original answer.