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

[Click map to enlarge]

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

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

Rigid foam roof insulation and polyethylene vapor barrier inside — problem?

Was planning on a r-25 insulated roof deck for a ski house in lower zone 6 NH with cold roof (strapping with plywood) on top of that to help prevent ice dams.
Existing cathedral ceiling is actual 8" rafters framed 24" o.c. with 6" paper faced fiberglass batts. In exploring the original construction (circa 1980) I also found a layer of POLY as an additional vapor barrier....which sabotages my R-25 rigid foam roof plan.....damn.

Asked By Dirk Gently | Mar 27 15
10 Answers

Fresh air distribution for hydronically heated house?

Currently have a leaky hydronically-heated house.

I plan on removing the siding, installing blueskin VP peel-and-stick, then 2 layers of Roxul R6 ComfortBoard IS from the roof right down to the footings.

Because this should really improve the air leakage, how should I get fresh air in/out of the house to control humidity / air quality / etc?

Do people run a set of air ducts throughout the house from a HRV?

One of the appeals of using hydronic heating is that sound / dust transmission is significantly reduced.

What would you recommend??

Thanks!
.../j

Asked By John Charlesworth | Mar 26 15
2 Answers

JM Spider overhead

I was planning on using JM Spider on the underside of my structural roof deck. (There is a layer of peel and stick and 5.5" of polyiso foam board above the deck so no worries about vapor permeable insulation inside). The installer is having problems with getting the Spider to stick overhead. The installer says JM changed the fiber recently and they are having difficulties with some wall installations too. While they are working with JM, I was wondering:

Has anyone here had JM Spider installed overhead recently?

Asked By Eric West | Mar 27 15
3 Answers

Alternate cathedral ceiling retrofit

I have a project related to a thread titled "How can I best retrofit and insulate an existing cathedral ceiling?" In my case, the zone 4b semi-arid west texas 1978 home's cathedral area has low density glass batts (or none) along with 1x10 or 12 deck boards over 2x12 rafters. The shingles above this unvented space have some blistering, and I was going to replace them along with resetting two skylight curbs that are incorrectly installed and caused some sheet rock damage from skylight leakage.

Asked By Glen Poklikuha | Mar 27 15
4 Answers

Old house, wet brick

The picture pretty much says it all. We had terrible ice damming this year, as did just about everyone in my area; houses both old and new saw wet walls and rainy windows for the first time ever. My house was built in 1850, and I have to imagine this has been a problem before. But this was our first full winter here. I'll try to explain the situation as best I can:

Asked By Chris Ermides | Mar 26 15
1 Answer

XPS as interior insulation on a plank wall

Architect's plan calls for 2" of "rigid" on interior side of a plank wall in Williamstown Ma (zone 5). Even if we tape the seams and air seal as best as possible, I am still concerned that moist air will get to the back of the planks and create moisture issues. The exterior is not being touched and I assume that there is no kind of air space between the planks and the siding. The space will be air conditioned in the summers and the 2" of xps (class II vapor retarder) gives me some drying capacity to the inside. Is that enough? How risky is the assembly?

Asked By Joseph Carry | Mar 27 15
11 Answers

Non-typical insulation of barn / garage

I live in Interior Alaska Zone 7/8. I have a rather large barn pole barn that needs to be insulated so it can be heated. Since it is rural there is no code but i want to ensure that i do not do something that damages or ruins the building over the long term with that said money is not unlimited. The space is intended to be heated to just above freezing 35 to 40 typical with the ability to warm even more during use. Not a business just personal use during the week.

Barn size is 50x60 with 14 foot walls.

Asked By James Williamson | Mar 22 15
10 Answers

Insulating scissor truss

Hi, I am building my first house, what a project that has turned out to be but that's for another day. Anyways, our great room has scissor trusses for a nice pitched ceiling. I would like to have at least 24" of insulation to keep things nice and toasty in the winter. There is a 4' overhang outside on either end. I nailed a 24" high plywood leaving a vent space above where the red is on the layout. My question is what material and how to go about it. To use the high density cellulose is has to be contained by some mesh? Any input appreciated.

Asked By Tom Smith | Jul 19 14
7 Answers

Attic insulation reality check

It's time to get my attic air sealed and re-insulated and I've committed to hiring it out since the 6/12 pitch truss attic is a horrible place that I hate to work in. I'm having trouble finding people willing to blow cellulose. Everyone around here seems to want to blow fiberglass. Is this a major issue?

The first bid I've gotten is $3.20/sf for attic floor air sealing and R-30 worth of blown fiberglass. Sane/insane?

Asked By Nathaniel G | Mar 26 15
8 Answers

Porch posts

We are building a wrap around porch that extends 6'. Since we know, because of code we have to use 6x6 for the posts for the deck, I have question about the posts that supper the roof.

One way is to use the same 6x6 and extend it from footer to header. We think that since these posts will be 6' apart going around the porch it might seem a bit too bulky.

Does code allow you to replace 6x6 posts with a PVC reinforced porch posts (they are turned and look like traditional porch posts)? Or do we have to stick with 6x6 lumber?

Asked By Matt Cibula | Mar 25 15
Register for a free account and join the conversation


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