Hi everyone….I’m going to gut a second story on a 1910 house in northern Minnesota. The knee walls are set in at 6ft height, I want to move them down the roof line to about 4 feet. ( I think that’s the lowest allowed isn’t it?)
After the demo, I want to insulate it before closing it back up. I like to make little ‘packets’ of insulation in garbage bags, then tuck these into the joists to stop cold air movement in the balloon framing.
What I’m wondering about is laying in the first layer of insulation between the joists which is the ceiling below. Can I use Kraft faced insulation and put the Kraft side facing down (toward the ceiling below)??? Then I would come back over this the opposite way with 6in unfaced for better R value and make a solid blanket using 24 inch wide insulation.
The kneewalls will get 6inch Kraft stapled to the face of it. The slant will be firred out with 2 by 2’s so I can put in 6 inch with a Styrofoam vent on the cold side to let air go from knee wall to the cobra vent. Should I put in vents when I do the new roof to vent the knee wall area, or is the cobra ridge vent enough?
Thanks for any suggestions!
Replies
Before you move anything............the farther back the knee wall from the center of the rafter, the greater the span becomes and the lesser the load carrying capacity becomes.
Just a little food for thought.
Gabe
Good thought....I've already had an engineer friend check it out and its ok to do. The roof line is tied to a stairway channel that breaks up one string of kneewall and the other is supported by a dormer in the middle of the run.
This kind of detail is very prone to air leakage, which will more or less negate your fiberglass insulation. I would consider some type of air-movement-inhibiting system to create the thermal boundry. Sprayed in foam or Dense packed Cellulose being the two that come to mind. With either one, I would probably insulate right down the rafters to the plate, and keep the area behind the kneewalls inside the thermal boundry.
Steve
Edited 3/29/2003 8:53:12 PM ET by STEVENZERBY
I don't know about your area, but where I am, 5' finished is the shortest knee wall allowed.
Bob,
In New Jersey, the minimum kneewall height is 4' accept for hallways, and that's 7'. The last house I framed the rafters sat on a plate on top of the second floor deck and the pitch was 17/12. We had to lay out the hallway and balcony from the kneewall at 7' minimum. We had to cheat the layout measuremeants over a few inches to give us the minimum hallway and balcony with.
Joe Carola