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!

32 Answers

1952 Cape Cod


First-time poster. In the past 2 months, I’ve read a hundred or so GBA articles and comment threads; I’ve been amazed by the expertise and generosity of the community. I’ve also read extensively at buildingscience and finehomebuilding -- I’m new to but very interested in building science. Here’s why:


Asked By Emerson W | Dec 11 17
5 Answers

Is it worth it to upgrade flex duct insulation if all ductwork will be buried in cellulose anyway?

I currently have R4.2 flex duct connected to my furnace and ac in the attic (climate zone 5). I will be upgrading the ductwork soon but was wondering if it makes sense to upgrade the flex duct from R4.2 to R8 if it will be completely buried in cellulose.

The attic floor will be insulated to R60 but obviously the entire duct work won't be buried in R60 because the top of the duct sits off the floor quite a bit.

Thanks so much for your help!

Asked By BuildingNewb | Dec 14 17
6 Answers

Slab Edge Insulation and Termites in CZ 3A

My basement walls should be poured by the end of the month and I am wanting to get the details right in CZ 3A.

While slab insulation is not "required" for my climate zone, I am considering it for comfort reasons and to insure against the future (better safe than sorry). However, termites are common in my area and the house is on a wooded lot that will have plenty of food for them, so I am concerned about them coming up the edge insulation into the stud wall noted on the attached diagram.

Asked By Norman Bunn | Dec 15 17
17 Answers

Drain Water Heat Recovery

I plan to install a drain water heat recovery unit in my new home. Does anyone know of any guidelines on sizing? For example,there will normally be 2 people in the house, but on occasion that could easily double or more as we have extended stay guests (a week or even more). And we will have a 65 gallon heat pump water heater.

As the DWHR units tend to get pricey due to the copper involved, I want to make sure I get the most bang for the buck.

Asked By Norman Bunn | Dec 11 17
4 Answers

Mitsubishi Heads and the I-see function

I'm trying to determine the most efficient way to operate the above described heads. The Mitsubishi tech I spoke with just said leave the I-see functioning on and all horizontal and vertical vanes in automatic.

Asked By Mike M | Dec 14 17
4 Answers

REMOTE retrofit

I recently learned about the REMOTE/PERSIST building methods and think it'll work well on my house. I'll be removing old fiber cement siding and adding vapor barrier faced, shiplap, 4 inch polyiso (good deal on seconds from a local manufacturer). It's a small house, with only about 750 sq ft of wall space to retrofit (a newly built addition on one side). I've landed on exterior foam because I plan to replace the siding to match the addition anyway and don't want to settle for 3.5" of dense packed cellulose. The main floor is heated by a single ductless heat pump.

Asked By Pat Beurskens | Dec 14 17
13 Answers

Repair or replace sheathing behind brick veneer

I wanted to get some advice on what to do with existing sheathing material that is currently installed behind brick veneer in a 1980's home I'm currently renovating. It's located in Houston, is 2x4 wood frame construction on concrete slab foundation, and the other parts of the house have T1-11 and vinyl siding (which will all be eventually replaced), but my questions concern what to do behind the brick for now. Much of the interior has been gutted down to the studs due to issues with mold and pests.

Asked By sdcnyhou | Dec 8 17
9 Answers

Efficient shower stall design: Airflow?

So I'm kicking around ideas for efficient shower designs. Our master bath will have a shower stall that is recessed with three tile walls, and one glass wall with a glass door panel more or less flush with the side of the bathroom.

The glass wall will have three parts; two stationary panels and a door in the middle.

Asked By Lance Peters | Dec 6 17
2 Answers

True felt tar paper / grade D paper

As Martin has written many times, "felt paper" used to be made from rag, but is now made from paper. Thus when it gets wet it gets super weak.

Asked By Bryce Nesbitt | Dec 15 17
2 Answers

Insulation options with little space

Hello everyone! First time posting here. I'm working on a project and have reached the stage where I need to decide how to insulate it. Reading the information on this website, obviously one of the first tenements of insulating is that "Thicker is Better." However, I'm looking for some advice on what to do when I don't have the option to go thicker.

Asked By MayaW1010 | Dec 14 17
Register for a free account and join the conversation

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