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21 Answers

Interior vapour barrier with exterior XPS

I am in the initial stages of house design.

I am thinking of a double 2X4 wall construction with 2": of XPS on the outside to minimize thermal bridging.

My concern here is that building code here in Ontario requires a vapour barrier on the warm side wall

I suspect that the combination of XPS on the outside and 6 ml plastic on the inside will cause any water that might get into the wall cavity to stay there and not have any where to go .

Question : How do I get my wall to dissipate water in this design ?


In Green building techniques | Asked By Steve Babcock | Oct 3 14
41 Answers

I am using Roxul insulation for ceiling and walls in a post-and-beam barn home

I plan to use this insulation in a 2x8 ceiling and 2x6 stud walls. Roof is sheathed in OSB, with a Titanium underlayment with standing seam on top. Walls have OSB and Tyvek house wrap. My question is can I use a poly vinyl vapor barrier on the interior after installing the insulation and then cover with 1x6 tongue and groove pine board. I have seen conflicting information on this. We are in Kansas which I think is Zone 6. This is a full post and beam barn structure. It has a gambrel portion with a loft. Loft has 12' high ceilings. Lean to portion has 9' high ceilings.

In GBA Pro help | Asked By David Hauber | Sep 25 14
3 Answers

How can I improve the insulation and air sealing of my walk-in attic?

I recently decided to tackle the air sealing and insulating of my attic. The house was built in the 40s and I’m in climate zone 5 (NJ). It is a walk-in attic with a combination of vermiculite and fiberglass batt insulation on the floor and what looks like mineral wool covered (mostly) with plywood on the wall separating the finished portion of the attic with the unconditioned. In addition, there’s a “knee wall” (I may be using the wrong term here) along a portion of the attic which divides the unconditioned side from the cathedral ceiling in the living room.

In Energy efficiency and durability | Asked By Eric Barker | Oct 6 14
14 Answers

I'm getting two different opinions about foam insulation in the attic

Some say spray the roof deck-allowing the attic air to become conditioned which is great for the H&A ducts in the attic. Others say spray the attic side or the ceiling to allow the attic to vent. I don't understand this one since the attic air is now unconditioned air and the ducts a
have only a wrap of insulation..I'm confused. Sounds like there are two schools of thought going on. Are both ways OK? Is one a lot better than the other? Help!! I even heard that the house would be too tight and allow for stale air to remain in the house if you spray the roof deck..I need answers.

In Energy efficiency and durability | Asked By Rus Pearson | Sep 30 14
3 Answers

Vapor barrier in tight crawl space

I have a sloping crawl space under a 100-year-old Virginia house which does not have any termite or rot damage that I can find. At the tightest end of the house, there is less than a foot of crawl space.

There is very, very little space to move around in this crawlspace.

In Energy efficiency and durability | Asked By Randy Salzman | Oct 5 14
3 Answers

Footing insulation

I am building an energy efficient house on a slab with 6 inch of EPS insulating panel under the a 5 inch slab. My architect is asking to add a 3 X 3 footing (on compacted soil) under the slab where the posts that hold the stairway to the second floor is meeting the ground floor and a second one at the bottom of the stair.

How do we go about insulating these footing to at least the same level as the rest of the slab do we just put the same 6 inch insulation under these footing as well as their rim?

In GBA Pro help | Asked By Pierre Gingras | Oct 5 14
12 Answers

Is external polyiso worth the cost?

First, let me say, that this community is fantastic. It is good to see so many people invloved and really dedicated to making building more efficient, and thus, playing a part in saving our planet and environment. I am always pleasantly surprised at how helpful everyone is, most of all, you Advisors. Thanks for the time and effort.

In Green building techniques | Asked By Kurt Samson | May 19 10
3 Answers

Does insulating the slab in climates where cooling dominates over heating make sense?

Foot note from Martin's http://www.greenbuildingadvisor.com/blogs/dept/musings/wolfgang-feist-de... article- 1. After I published last week's blog, I had a discussion on Twitter about this issue with Steven Toomey. Along with Anne Decker, Toomey has built a Passivhaus in Bolton, Connecticut that they call the Hayfield House. Toomey kindly supplied energy budget information from two iterations of PHPP for his house in Bolton, which is a two-story house built on a raft foundation. The raft slab has an area of 1,248 square feet.

In Energy efficiency and durability | Asked By bruce john stracke | Oct 4 14
5 Answers

Out-sulation vs Double Stud Walls

I was reading some old GBA discussions about double-stud wall designs and the added difficulty of keeping the sheathing dry (relative to wall designs that place appropriate amounts of insulation over the sheathing). This prompts me to wonder why the double-stud approach has its adherents when an out-sulation approach can be used to achieve the similar R-values and protect against thermal bridging while dispensing with the uncertainty regarding moisture. Besides being of general interest to me, I am hoping the responses will help me decide the 'best' way to proceed for a future project.

In Energy efficiency and durability | Asked By Rob Shuman | Sep 16 14
18 Answers

Windows for my Pretty Good House

Hi all

Another question for the experts here at GBA--this time about what windows I should install in my Pretty Good House (PGA). I've written here before about this house and you can likely find the threads of previous questions. Basically, we're building a single level, 1700 sf house in Hood River, OR and we're trying to meet PGA and passive solar "standards". Currently, we're trying to decide what windows to put in this house, and the candidates are:

Marvin Integrity
Milgard Ultra
Intus Arcarde or Eforte

In Green products and materials | Asked By Matt Mesa | Sep 29 14
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