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!

1 Answer

Furring strip inside of exterior foam or nailbase Zip sheathing?

I am working on a home envelope renovation in climate zone 7 and we are trying to add insulation to existing exterior walls.

As shown in sketch, existing exterior walls have clear plastic sheeting (probably not "smart") between studs and GWB at interior, fiberglass batt in 2x6 stud cavities, and plywood on exterior.

I am proposing 2" of foam to exterior as well as nail base Zip for a total of 4" of foam.Contractor wants to add furring strips between existing exterior sheathing and new foam.

In Plans Review | Asked By Ethan Timm | Mar 23 16
17 Answers

Confusion about window sill terms and flashing

(1) What do you call the 2x4 piece of lumber that forms the bottom of the rough opening for a window? Is that the “window sill” or the “window sill plate”, or is it the same thing (or is it something else)?

In Green building techniques | Asked By Michael Bluejay | Mar 22 16
48 Answers

How to reduce radon level in my house?

When I first bought my house a couple of years ago the radon test was conducted in the first floor (bi-level house on concrete slab, all above grade) showed 3.5. A couple of years have now passed and I have since replaced all the windows and sealed all the gaps I could possibly find. Last week I did the same test again (using the same setup as my home inspector) and it was 12.1, ouch! Does it mean I made the first level too tight? What are my options to fix it?

In General questions | Asked By Joe Blanco | Jan 22 16
3 Answers

Open-cell spray-on insulation vs. a radiant barrier

Could someone give us the pros and Cons of Open Cell R-20 Spray on Insulation VS Radiant Barrier? We live in South Florida.

In Energy efficiency and durability | Asked By Clinton Casey | Mar 23 16
22 Answers

Can't find a green-minded insulation contractor

We are building a new home in Southeast Michigan. I have been searching for months for an insulation contractor that is more "green minded." Our toddler has a lot of chemical sensitivities and respiratory issues and insulation decisions are completely overwhelming me. I can't find any contractors that I trust. All of them just want to make our house as energy efficient as possible. I would rather have a less energy efficient home and have our daughter healthy. Does any one have any recommendations?

In Green products and materials | Asked By Carolyn Farrow | Mar 23 16
5 Answers

Installation of off-size reclaimed foam

I'm trying to get my hands on recycled foam for a REMOTE wall home build. I have a potential supplier with enough brand new EPS to do my project...but it's in 8' x 19.5" and 8' x 9.5" sheets - all 3" thick. Brand new, so I can count on clean edges.

There are enough of the 9.5" sheets to do my basement walls.

There are enough of the 19.5" sheets to do my exterior walls.

My questions:

In Green building techniques | Asked By Jim Tyler | Mar 22 16
6 Answers

Leave a gap at bottom of exterior rigid foam?

I could have sworn I saw/read a "howto" on installing exterior rigid foam that recommended leaving a 1/4" gap at the bottom of your exterior rigid foam. I assume it is for allowing moisture to drain out and/or keep the foam from wicking moisture up that may find its way to the foundation. I have tried to go back and find that recommendation and absolutely can't find it anywhere.

Did I dream that up?

In Green building techniques | Asked By Clay Whitenack | Mar 22 16
32 Answers

Vapor barrier under the basement slab

I am building my own home in Idaho (climate zone 5) and have a full basement and want to put a 10mil poly under the slab. My concrete contractor is very concerned and has "never heard of this" he is asking for technical information to send him. Also he puts a sealer on the top of the concrete after it is poured, would this be a issue?


In General questions | Asked By Jeremy Monroe | Mar 8 16
21 Answers

Open cell vs Cellulose

In retrofitting walls how does open cell and dense pack compare for air tightness?

In General questions | Asked By Robert Hronek | Jan 11 11
2 Answers

New high-efficiency furnace installed

I had a high-efficiency forced-air furnace installed along with a setback thermostat.
The installer said that with these new furnaces, you just set the thermostat to one temperature.

Is that true?
I live in North Vancouver, BC where the climate is milder but I would think it is still more efficient to setback the thermostat at night.


In Mechanicals | Asked By Aaron Gatzke | Mar 22 16
Register for a free account and join the conversation

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