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!

28 Answers

Are low-e windows dangerous?

I've read a couple of articles that suggest low-e windows can cause fires. It sounds like the low-e coating (or a film, the articles weren't clear) is capable of reflecting and focusing sunlight in a way that can cause materials outside the house to combust. Does anyone have an explanation for what is going on with these windows?

In Green products and materials | Asked By Steve Knapp CZ 3A Georgia | Apr 1 18
9 Answers

Building on a rock ledge

Building a foundation is usually a pretty straight forward process in my part of the country. But I am considering a small lot that is likely more rock ledge or boulder than soil. The lot has great views in several directions, but I suspect the rock has deterred at least two previous owners from moving forward with their construction plans.

In GBA Pro help | Asked By Steve Knapp CZ 3A Georgia | Apr 15 18
3 Answers

Existing basement framing against concrete

We are looking to insulate our concrete basement foundation walls and the 18" wood framed area between the foundation top and the bottom of the floor above it that includes the sill plate. We are settling on closed cell spray foam.

When the house was built the framing for the exterior basement walls were set up against the concrete foundation. There is anywhere between 0 to 1/4" between the studs and the concrete depending on the studs and the texture of the concrete forms.

In Green building techniques | Asked By tyman00 | Apr 11 18
21 Answers

Roof underlayment for vented roof with standing-seam metal roofing

Im nearing the end of construction of a high efficiency timber frame hybrid house I'm building for my self and have a low slope roof question that I would like some opinions on. Roof pitch is 1.5/12 (7 degrees)

Our main roof structure consists of timber rafters, 20" I-joists, dense pack cellulose, 1/2" plywood sheathing taped to the walls as air barrier. We drilled holes all over the roof to dense pack the cellulose from above (as our interior finish was installed on top of the timber beams as soon as they were installed.

In Energy efficiency and durability | Asked By Scott Benson Climate Zone 7A | Apr 9 18
17 Answers

Interior walls set on top of rigid foam

I'm building a living space (750sq ft) into a building in zone 6a. The slab has a 6 mil vapor barrier and 2" foam under slab and 2" foam on slab edge. The space is completely empty now. (no interior walls). I cannot tolerate concrete floor to walk around on because of hardness and cold feeling. I would like to lay down another vapor barrier then 2" foam then 2 layers of 1/2 " plywood glued and then finished floor materials. The building sits very high and has crushed rock under slab with 2 ft overhangs and proper landscape grading. I doubt there will be any moisture issues.

In General questions | Asked By Smokey059 | Apr 11 18
36 Answers

Brick house insulation

First of all, I wanted to wish everyone Happy and Prosperous New Year!
I would like to ask for an advice regarding a wall cavity composition. I am in Westchester County, 30 miles north of New York City, climate zone 4. I am about to acquire a brick house (tiny brick, maybe 2-3 inches thick). Single wythe, I believe. I think that brick is just decorative and is not load bearing at all. Only cinder blocks in the basement support the floor joists. Second floor ceiling joists are supported by wood framing.

In Green building techniques | Asked By Sebastian Smith | Dec 29 17
5 Answers

Garage Insulation - walls and roof?


I have enjoyed learning from all of the great content on this website - it has guided me through several projects and raised my interest in building science and improving the energy efficiency of my home.

My current question has two parts - 1) should I insulate my attached garage, and 2) if yes, how can I do this correctly and in a cost effective manner?

In General questions | Asked By Eric Miller | Apr 10 18
9 Answers

Does my wall assembly seem adequate for my area?

Hi everyone! I have a question about a wall assembly I want to use at my off-grid mountain cabin. It's a 1986 build cabin but the weather and environment with a lack of previous owner's attention have made the project list somewhat large. We're overhauling our solar system so I plan to practice these wall assembly details on the powerhouse shed before attempting the main cabin.

Here's what I have planned:
1) interior insulation currently fiberglass, want to install closed cell spray foam in some areas and leave fiberglass in other areas
2) 1/2" CDX plywood
3) Delta vent SA WRB

In Energy efficiency and durability | Asked By mountaincabin | Apr 17 18
14 Answers

Dense-packed dry cellulose: any downsides?

I've been going over insulation techniques to use on a new home. Every insulation contractor that we've talked to has a different system. One in particular that is being pushed is dense pack dry cellulose. I have personally witnessed wet cellulose settling in our own home, however based on everything I have read about and heard about dense pack is that it will not settle and that our current home's insulation was not installed properly. I know that cellulose is somewhat springy so I understand the theory is it will hold true in the wall for hopefully many many years.

In Green products and materials | Asked By Css1813 | Apr 16 18
9 Answers

ZIP System R Sheathing vs Roxul Comfortboard

Building in the Canadian Rockies, so climate zone 5-6 ish.

Up until now I have been considering building a 2x6 exterior wall (with Roxul Comfortbatt in the stud bays) covered in 1/2" exterior plywood, installing a air/moisture barrier from Stogard over the exterior of the plywood sheathing and then fastening1 1/2" Roxul Comfortboards over the Stogard.

In Green building techniques | Asked By Scott Wilson | Apr 13 18
Register for a free account and join the conversation

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