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16 Answers

Does anyone have thoughts on this wall section in regard to avoiding moisture problems and drying to the interior & exterior?

I am an architect in Boston preparing to build a home for my family on a marshfront site in Scituate MA (Zone 5 and 110MPH winds due to coastal proximity). Energy conservation is a key goal for the project. Originally I was planning an R48 double stud wall but circumstances have changed and I am now planning a single 2x6 stud wall with cellulose cavity insulation and rigid exterior insulation - total wall R value is about R38. The thinking on vapor / air / moisture barriers and retarders has gotten so complicated in recent years.

In GBA Pro help | Asked By sean stewart | Dec 20 15
1 Answer

Flash and batt on a sloped roof

The spray foam crew started work on my house today. One of areas getting CC spray foam is the sloped portion of the roof on the room over the garage. For the sloped portion of the roof, there is roof sheathing, a ventilation baffle, spray foam, and the rest of the cavity will be filled with fiberglass batts.

In General questions | Asked By Michael | Dec 22 15
3 Answers

Plumbing penetrations in a basement

I have a few plumbing holes between basement and 1st floor -- all are tight to the wood floor, no big holes under the bathtub or big gaps next to the pipes or anything.

If these plumbing pipes definitely go only to the 1st floor and are under toilets etc, should I still air seal with spray foam? Assume the answer is 'it can't hurt' but I'd be surprised looking at them if they are major sources of air leaks.

My other plumbing holes that run to 2nd floor are already air-sealed with spray foam in the attic. Should I air-seal them in the basement too?

In Energy efficiency and durability | Asked By Justin | Dec 22 15
8 Answers

Can rigid foam be used for unvented attics on the inside?

I have a fairly old (100+) house with unvented eaves, and I am doing some work on the top floor, which used to be the attic, but was mostly finished into livable space about 50 years ago. We have a very steep roof, with standing headroom even above the finished attic space.

I have gotten some recommendations from insulating contractors which include 5.5 inches of spray foam (very costly), and in one case an inch of foam between rafters followed by dense-pack cellulose. The rafters are 2x6, and the roof has planks instead of sheathing.

In General questions | Asked By Rowan Atalla | Dec 22 15
2 Answers

A-Frame insulating

I just bought a 76' A-Frame that has 2x6 roof/wall supports. I have it gutted down to the studs right now. I am having the hardest time trying to find out how to properly insulate an A-Frame! I am not into using the spray foam technology. I live in the mountain of SW Montana so it's cold in the winter. I was thinking about using 2 layers of ridged 2" foam board. Leaving a 1.5" space between the roof sheathing and the insulation. The insulation would be flush with the roof/wall 2x6's. Then a vapor barrier over all that. Tongue and groove pine over that then.

In Energy efficiency and durability | Asked By Korey Kaz | Dec 22 15
2 Answers

New home in Delaware on the bay.

Planing cantilever decks 2nd and 3rd story. Four foot width both sides mainly for maintenance as I want to stay off ladders as I get older. Should I insulate the interior bays where cantilever joists enter interior. Cantilever decks as cost savings instead of wood pilings along both sides of home.

Thanks much for your help

Happy Holidays

Ed Serafin

In Energy efficiency and durability | Asked By Edward Serafin | Dec 20 15
3 Answers

Question about building envelope/insulation around garage and walls bordering garage

As you may recall, we put 2 layers of foam (7" XPS and 2.5" EPS) above our 1:12 roofline so the attic is conditioned space. The exterior of our house will have 2" rigid foam and EIFS. Exterior 2x6 wall cavities will be filled with blown-in cellulose.

In Green building techniques | Asked By Kevin Hoene | Dec 21 15
2 Answers

Help with re-flashing leaking windows

First off, these are outies installed in a 2x6 wall with 4" of xps on the exterior.

In General questions | Asked By Mike | Dec 21 15
6 Answers

Proper insulation installation


In Energy efficiency and durability | Asked By Greg | Dec 21 15
10 Answers

Neutral pressure plane?

Background, my house has about 15ACH50, much of it coming from a very shallow crawlspace i cannot access (never mind fix, i hope to dig it out enough to access the entire perimeter of the house and encapsulate it someday)

In Energy efficiency and durability | Asked By Alan B | Dec 18 15
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