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!

2 Answers

Wood wool cement acoustic panels in North America?

I came across an interesting product for acoustic control: wood wool + cement panels.

They have a great look:


but the only suppliers I've been able to find are Scandanavian:


Since it seems to just be wood + cement, I was wondering if there are any US or Canadian suppliers.
I'm outside of Portland, OR, and don't like the idea of shipping a container of wood across the world = )

In Green products and materials | Asked By Kevin Lynagh | Sep 23 16
5 Answers

Is it possible to satisfactorily detail single layer of exterior xps square edge sheathing?

Having been directed to an insulation reclaimer I have the opportunity to purchase enough reclaimed xps to sheath my exterior frame though only with a single layer since the 2.5" panel thickness satisfies my requirement. Timberframe has a 2x5 (full dimension) exterior frame that gets cellulose densepack and sheathed with xps that will get 1x4 strapping prior to siding. This foam is square edge and I'm wondering if, in the absence of multiple layers with staggered seams as well as t+g edges, the detailing to adequately seal the seams of the xps will be possible or even approachable.

In Green building techniques | Asked By daniel f. vellone | Sep 23 16
6 Answers

Why is mold/mildew growing behind my rigid foam?

So I had started to finish my basement area and read all of the articles on GBA. I was using 2'' of XPS foam on the cinder block walls and recently had to remove a bunch to access an area for the egress window. When I pulled it off, I was surprised and scared to see that I had black stuff growing on the cinder block. I don't know if it's mold or mildew, but it can't be good, right? You can even see how it's growing around the foam adhesive that I used to attach it to the wall.

In General questions | Asked By Jay Johnson | Sep 21 16
7 Answers

Fiberglass insulation

I read your article on insulation an older home that does not have sheathing behind the ceder lap siding. The house is in southern Missouri so I was planning on 0.75 inch foiled rigid foam board (foil facing the exterior siding with a 0.75 inch air space. My question is should the fiberglass batting have kraft paper or just the fiberglass batting. I was planning on 0.5 inch sheet rock for the interior walls.

Thank you for your time.


In Energy efficiency and durability | Asked By Jim Tune | Sep 6 16
5 Answers

Risk of condensation on ducts inside bathroom?

Hi all,

Getting ready to frame the soffit that will hide the ductwork that will run through the bathroom. According to what I read, insulation is not needed on ductwork that is inside the thermal envelope.

Is this true for bathrooms as well? I ask because there is obviously a lot more hot steamy air in a bathroom and I wonder about condensation on the ducts during the cooling season.

In Green building techniques | Asked By Clay Whitenack | Sep 22 16
4 Answers

Huber Zip R-Sheathing with open cell insulation

I'm involved on a project where the insulation contractor would like to use closed cell spray foam insulation in our wall cavity in order to mitigate the risk of condensation. We were originally planning on using open cell foam. Climate zone is 5/4 Marine, project is on the coast.

The wall assembly is ;
- 1-1/2" Huber Zip R-Sheathing
- 2x6 stud wall
- 5-1/2" open cell spray foam insulation
- 1/2" drywall

1. Are we at risk of condensation in our wall if we use the open cell insulation?

In Energy efficiency and durability | Asked By S G | Sep 23 16
6 Answers

Insulating a cathedral ceiling with self-adhesive roofing membrane installed

We are building a 640 sq ft cabin in CZ6. At the last minute we found a metal roof rated for down to a 1:12 pitch and made the change to a 2:12 pitch.

With that change to a flatter pitch came a recommendation from the roofing supplier to cover the roof sheathing with a self adhesive "Ice and Water Shield" type product.

So our roof (all complete) from outside to in:

24 gauge metal roof.

In GBA Pro help | Asked By Chris Harper | Sep 22 16
2 Answers

Temperature adjustment / offset on Mitsubishi minisplit

I installed my MSZ-FH12NA two months ago and the unit is performing very well and I am not experiencing the short-cycling issue that others have, but the unit seems to consistently cool (haven't used heating mode yet) past the set temp on the remote by 4-5 degrees. (If I want it to cool to 70, I have to set the remote at ~74.) Does anyone know if there is a way to offset/adjust the remote control temperature to accurately reflect the actual room temperature?

In Mechanicals | Asked By Adam Emter | Sep 22 16
16 Answers

Spray foam and a vaulted ceiling - working from the top of roof down


Thanks for all the insight on insulating vaulted ceilings - both vented and unvented.

In Green building techniques | Asked By Peter Zwarich | Sep 20 16
7 Answers

Flat roof assembly question

I am replacing the roof on a brick masonry building in NYC within the 5 borough. The building was built in 1910/11. It is a flat roof, about 40 ft long and 25ft. wide. The previous roof (a tar and gravel system) failed and my brother and I removed it, and replaced the damaged roof deck. (a mixture of plywood replaced probably 30-40 yrs ago, and the original t&g boards) with 3/4 OSB. Toward the front 10 foot or so of the building the t&g boards were dry and strong so we left them in place. A little bit of repair to the cornice "box" was necessary.

In GBA Pro help | Asked By Jacob Turetsky | Sep 22 16
Register for a free account and join the conversation

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