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Insulation for this addition

chrisr710's picture

Insulation for this addition (post #216143)

Hello:

I am working on this addition to my home, shown in the picture. I was wondering if anyone has some advice/insights into insulating the new rooms (it's ~ 11' x 40').

My plan was to used closed cell insulation in the 2x10 rafter bays, from my understanding I can do that and don't need to leave an airgap and use a vapor barrier (the closed cell will keep moist air from going up to the roof and condensing). I was going to use regular fiberglass batts on the floor and in the walls.

If I do that

1) what should I do about the closed-off soffit area? (area B on the pic) It is separated from the inside by blocking on all rafters. Can I just fill that up with foam too and then close off the bottom? Do I need to vent it somehow? I was going to use T&G pine boards as my soffit, and wrap the housewrap up under them before putting them on.

 

2) what should I do about the cantilevered area under the wall? (are A on the pic) It is also closed off from the inside because of blocking. I was going to cover the bottom of that up the same as with the soffit, painted T&G pine and run the housewrap under there too. Can I fill that up with either foam or fiberglass batts, and if so do I need to vent it?

 

3) Finally, the other option would be the more traditional way of using fiberglass batts on the ceiling too. Then I could use soffit vents and put an air gap above the insulation, and it would have the added benefits of ventilating the house roof (since I can't put soffit vents on the house roof now that the addition is there, the air gap could extend all the way up to the attic). 

I appreciate any advice.

Thanks! This forum has helped me build this thing so far from the ground up.

As requested, here is climage info:

  • climate zone 5 according to IECC (Northern Colorado, Weld County).
  • Minimum R38 on the roof, according our building department.
  • Weld County, Colorado gets 14 inches of rain, on average, per year

  • Weld County averages 34 inches of snow per year.
  • Summer High: the July high is around 90 degrees
  • Winter Low: the January low is 15
  • elevation ~ 5000 ft
  • roof is modified bit roll roofing, older house roof is asphalt shingles.
  • There are gable vents on each side of the existing roof.

.

Climate?? (post #216143, reply #1 of 2)

Climate??


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Climate (post #216143, reply #2 of 2)

Sorry, that would be climate zone 5 according to IECC (Northern Colorado, Weld County). It's windy, fairly dry, cold in winter and hot in summer. Minimum R38 on the roof, according our building department.

Weld County, Colorado gets 14 inches of rain, on average, per year

Weld County averages 34 inches of snow per year.

Summer High: the July high is around 90 degrees
Winter Low: the January low is 15

elevation ~ 5000 ft

Is that enough info?

Thanks

Chris