Replies

1. 
   belmanliving | Mar 13, 2013 01:04am | #1

   If you are building a new home with this style of roof, then either spray foam should be used in the sidewalls at least in the upstairs portion of the house.
   The flat attic should be insulated with cellulose insulation.

2. GBA Editor
   Martin Holladay | Mar 13, 2013 06:21am | #2

   Bruce,
   For an existing house, the answer will depend on the framing details and the level of access.

   Your thermal and air barriers need to be continuous. Ideally, the R-value of the installed insulation will meet or exceed minimum code requirements. That's tough.

   Closed-cell spray foam insulation is certainly one option, but it is not the only option. No matter which type of insulation you choose, you may need to open up a few finished ceilings to get adequate access.

   Some of the principles used when insulating homes with kneewalls also apply to homes with gambrel roofs. This article may help you decide where you want to put the thermal barrier: Two Ways to Insulate Attic Kneewalls.

   Gambrel roofs are very difficult to insulate well. Good luck.

3. 
   BruceAF | Mar 13, 2013 06:32am | #3

   Hi Martin - I should have been more clear..this is new construction. We have not yet framed this area. I understand the continuous air barrier. I can 'draw the line' of the air barrier thru the roof line or the interior wall. The insulation material has yet to be determined by presumable CC would be used at the roof. If the wall is chosen might be cellulose. A layer of plywood or other material would be attached to the rear of the wall.

   See drawing below....the blue line would be Option 2 for the insulation line and air barrier. Red line is option 1.

   
4. GBA Editor
   Martin Holladay | Mar 13, 2013 06:58am | #4

   Bruce,
   Option 2 (following the roof line) is preferable to Option 1 (following plumb-and-level right angles), for the reasons given in the article I linked to (Two Ways to Insulate Attic Kneewalls).