Q&A: A Forum for Green Building Experts and Beginners

Q & A Instructions

[Click map to enlarge]

The GBAGreenBuildingAdvisor.com web site has a wealth of articles on a wide variety of construction topics. Before posting your question, you may want to check out the articles on this page: How To Do Everything. You just might discover an article there that provides the information you seek.

Please register for a free account or sign in to ask and answer green building questions.

If you want to post a question, the usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration: Under the box labeled “More explanation,” look for the words “File attachments.” Click that, and you should be able to attach a photo.

Thanks for joining the conversation!


4 Answers

Should I tape the bottom edge of the VaproShield with this wall buildout?

Hello!

Where we live (Atlantic Canada) it is not uncommon for drifting snow to pile against the sides of our home in winter.

Our foundation is skinned in rigid foam insulation, and the walls are wrapped down to the foundation in VaproShield (orange frogskin). The interior wall cavities are sprayfoam insulated, so our concern here is not really with air seals.

The exterior wall buildout is as follows:

In General questions | Asked By Benjamin Wooten | Apr 14 16
1 Answer

Is a WRB on both sides of the foam okay?

I'm re-assembling a wall to change the windows from innies to outies, and to add a rainscreen gap. To do this, I have to remove the 3/4" polyiso foamboard in order to remove the windows (foamboard is on top of the flanges). The foamboard is glued to asphalt paper with foamboard adhesive, and probably won't come off without damaging the foamboard. My plan is to reinstall the paper/foamboard combo to the sheathing, then put new housewrap over the foamboard, which will mean I have a WRB on both sides of the foamboard.

In Green building techniques | Asked By Michael Bluejay | Apr 14 16
9 Answers

Subfloor thickness, joist spacing, cost, and performance ratio

I did some searching and couldn't find anything about my question so feel free to point me to another thread if this has been asked which I am sure it has.
I am looking for some discussion about how 24" OC I-joist floor systems are performing, what drawbacks they have, and what should be avoided, mitigated, etc.

This is a durability, cost, functionality, and energy efficient question.
Primarily I want to know peoples thoughts on the following or more (please specify if you are talking about OSB or Plywood):

In Energy efficiency and durability | Asked By Spencer Burnfield | Apr 10 16
13 Answers

Bathroom venting through soffit?

Martin, you have several times stated your strong preference that bathrooms be vented through the roof, and not through the soffit. I ask again because I am not sure your earlier remarks would apply in this case.

In GBA Pro help | Asked By David McNeely | Apr 9 16
2 Answers

Under-slab vapor barrier under footing?

Greetings. First I would like to say that I am awed by the knowledge and expertise on this forum. I have purchased a steel building and am going through the process of a slab/footing-piers. I believe the foundation design is sound( had to go back to mfg. as local concrete guys were speccing different and woefully inadequate foundations)

In General questions | Asked By Ken Cohenour | Apr 13 16
12 Answers

Insulation value of snow

We are building a house in Truckee, CA. Elevation is approx 6500 ft. Our plan is to use R38 unfaced fibreglass insulation under the structural roof deck, 2" rigid foam insulation over the structural roof deck, then with 1" vent channels from the eaves to the roof vent, and then another layer of plywood sheathing to attach the asphalt shingles. My question is when estimating the condensing temperatures, prior discussions that I have read seem to ignore the insulating factor of snow.

In General questions | Asked By Burt Hoffmann | Apr 12 16
2 Answers

Conditioning an existing attic in a 1900s Queen Anne wooden home

conditioning an existing attic in a 1900s queen Anne wooden home.
Location: coastal South Carolina
Facts:
two story wooden home built 1901
attic dominations: 22'x46'x(10'at peak of roof)
planed usable newly conditioned attic space 10’x46’
2 gable end vents & ridge vent.
no gable end sheathing or sheathing on first or second floors.
roof is a standing steam installed over asphalt shingles.
rafters are true 2x4 and roof decking is true 1x6 tongue and groove.
HVAC for upstairs is located in the attic with duct work through ceiling of second floor space.
Plan:

In Plans Review | Asked By Woody Truluck | Apr 13 16
11 Answers

Drawbacks to air-sealing gable walls?

Am about to start air-sealing the attic in my 1950s brick home. There are two large gable walls, and in the attic, I can see down into the framing about two feet, until it reaches some blocking. There's about an inch of open space between the temlok sheathing attached to the framing and the inner face of the brick exterior. I can feel quite a lot of air rushing up into the attic at every stud bay.

In Green building techniques | Asked By dave williams | Apr 12 16
7 Answers

Phased insulation plan for a 1960s home

Long time reader, first time question.

I've got a 1960s raised ranch in Chicago (zone 5) that we have been renovating. As we renovated rooms, we would open the walls and replace the inch or two of original fiberglass insulation with XPS and/or closed cell spray foam. We did this because it was the best insulation we could cram in the stud bay and our home is cold and drafty. Eventually I'd like us to be net zero and my wife would like to be comfortable, so we thought this was a good first step.

In Green building techniques | Asked By Dan H | Apr 11 16
43 Answers

Air sealing and the point of diminishing returns

I'm curious at what point does it no longer make sense to spend more time/money on tightening up a house. We had our house blower door tested unfortunately after construction was completed. The house is closed cell spray foam walls and ceiling.

I was shocked that the first test was 3.2 ACH50. The test along with thermal imaging allowed us to locate some major problem areas that we addressed, most of which were behind timbers in corners that did not get sealed well. (House is a timberframe hybrid).

In Energy efficiency and durability | Asked By Jeremy Kovac | Mar 10 16
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!