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!

0 Answers

Toughest vapor barrier for floor of crawl space?

We're building a new house, and plan to create a sealed conditioned crawl space. We want to be able to access the space regularly, to inspect for leaks and store a few items. Which vapor barrier would be better able to hold up to regular traffic? We'll probably put a layer of coarse sand underneath it. Unfortunately, a concrete rat slab is out of our budget.

Asked By Debra | Sep 20 17
7 Answers

I am looking for the best ideas for a project for my high school Green Building class

I have been teaching a green building course to high school kids for 4 years. We design green buildings that are enegy efficient using the 3D BIM software Revit and learn all the latest construction techniques and standards. A lot to learn!
What I am looking for is a good hands on project ideas to apply all the theory and design.

Asked By tim eberhardt | Sep 19 17
0 Answers

Insulation under floor joists in a crawl space

I have recently installed a new tile floor with electric radiant floor heating over a crawlspace and am looking for the most economical way to insulate the floor. If a radiant barrier blocks 97% of the radiant heat is it necessary to install foil faced EPS on the bottom of the joists for more insulation at three times the cost?

Asked By pickaname | Sep 20 17
0 Answers

Silverboard Evaluation or Opinions?

I was watching the new Canadian show "Sarah Off the Grid" in which designer Sarah Richardson was building a new home in Creemore Ontario.. They were using an exterior insulation product called "Silverboard".


I was wondering how this product with the added "reflective lamination" may perform or compare to other rigid exterior insulations? Do you think it may trap moisture between the board and the sheathing?

Asked By Scott Wilson | Sep 20 17
6 Answers

HVAC sizing disparity relative to HERS report

My HERS rater shows heating load of 39,500 Btu/hr and a cooling load of 22,600 Btu/hr on a high performance house I plan to build. This includes 1000 sq ft of basement, 2500 sq ft on the main floor and 800 sq ft in an office/loft area. R40 ceiling, R20 walls, R5 basement and crawlspace wall insulation plus serious air sealing (3 ACH or less).

The HVAC quote shows no system in the basement (it will be finished by me after construction), 3 tons on the main floor and two tons for the loft with all duct work in the conditioned space.

Asked By Norman Bunn | Sep 20 17
8 Answers

Insulating basement foundation


I have read a lot on GBA and a few other trusted resources online and am still not clear. I have an unfinished basement below grade in zone 4 (Minnesota). House was built in 2015. Builder sprayed a black coating on the poured concrete foundation and then applied a 1.5"-2" thick rigid foam insulation to the exterior of the foundation before backfilling (completely below grade basement).

Asked By BobTheWeekendWarrior | Sep 19 17
10 Answers

Dense pack cellulose roller: Where to get one?

As a fan of the dense packing method of cellulose in Atlantic Canada, I often run into a few key challenges from contractors:

1 - It's dusty (...not really when dense-packed)

2 - It's different and learning is required.

3 - Not wanting to use strapping (due to added cost) to manage the bulge at 3.5 lb densities.

The common response is to use a hard roller long enough to push the cellulose in. The problem is no one (myself included) knows where to get one? Can you please make some recommendations?

Thank you!


Asked By Mattbrennan4 | Sep 14 17
12 Answers

Location of solar panels on roof

Progress continues on the North Idaho ranch. I'm planning to install a 7 kW grid tie solar system that will have 2 rows of 11 or maybe 12 panels. My roof pitch is 7:12 and my orientation is 10 degrees east of true south with no obstructions. The roof overhangs 3 feet on the section that will have solar panels. I attached a crude depiction of the installation.

Asked By Steve Wolfe | Jul 17 17
4 Answers

Pros - How Would YOU Build?

This question goes out to the pros on this site; those who are builders, building science aficionados, or some mixture of the two.

Many folks, myself included, come here with some vague ideas of how they think they would like to build and then post their ideas asking for advice. Instead of starting somewhere and then working backwards, I'd like to know where the pros would start. So here we go:

Asked By Lance Peters | Sep 18 17
0 Answers

Taping OSB sheathing to ICF foam

Does anyone have experience with an effective tape for sealing OSB sheathing to the ICF stem wall foam?


Asked By Brett Greenburg | Sep 20 17
Register for a free account and join the conversation

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