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!

5 Answers

Outdoor mini split condenser unit in an insulated ventilated box indoors?

I need to cool (summer) and heat (winter) one room which is total 16.7 x 12.2 x 8.5 feet (1731 cubicfeet) (5.10m x 3.70m x 2.6m). I would need a unit between 2 or 3 tons.

Unfortunately I am not able to install the outside condenser unit outside of the building. That is the reason why I need expert advice.

Asked By purpleAnt | Mar 20 18
3 Answers

Ideal window depth to minimize window perimeter thermal bridging through frame

I am replacing the windows and redoing building envelope in my 30 year old house. Currently have 2x6 framed wall, covered with 5/8 tentest type fibreboard and then wood siding. Windows are original 30 year old solid wood. I am replacing windows with the following: Basic flush mount vinyl high efficiency windows, 4 5/8 thick with interior jamb slot for interior trim to be added to.

Asked By Clark | Mar 21 18
0 Answers

Best way to insulate an existing pole barn that has metal siding and no wrb?

I have read many versions of this question (as well as many answers) on your site, and at this point I am looking for the most current responses and solutions to this age old problem. I am well aware of the inherent pitfalls associated with pole buildings but it is what i have and i am hoping to make the best of it.

Asked By Darryle Mendes | Mar 21 18
11 Answers

Taping of Roof Sheathing / Wall to Ceiling Vapor Barriers

We building in climate zone 6A. We have planned unvented cathedral ceilings and we are planning to do 4" (or maybe just 2" depending on cost) of closed cell spray foam applied to the underside of the roof deck. We are then going to net and blow in fiberglass to the remainder of the cavities between the 16" TGI's.

I'm planning on the closed cell foam being my air and vapor barrier on the roof. On the walls the my air barrier will be the taped sheathing and the wall vapor retarder will be latex paint.

Two questions:

Asked By Steve Mackay | Mar 21 18
1 Answer

Retrofit duct sealing (sealing on all sides)

I've read through the Tape vs. Mastic article and have looked at various how-to guides for duct sealing, but I feel like I'm missing something.

In our home, most of the ducts run along the basement ceiling, including some within floor joists.

It makes sense how I'd apply tape to the sides and bottom, since those are easily accessible, but how would the tops get sealed?

Asked By Timothy Tucker | Mar 21 18
28 Answers

Insulate this!

This one-room addition has no foundation. There is insulated in walls (likely R11) and ceiling (likely R19 - certainly no more), but not in the floor. As you can see, outdoor air can simply pass through the open space under the floor. When the flat EPDM roof needs to be replaced in 5-10 years, we will install exterior foam board outside the roof deck. Heating is primarily warmed air from rest of house or propane fireplace. Cooling is AC from rest of house.

I'm considering digging 2' out under the floor, and sealing the underside with foam. What approach would you take?

Asked By Emerson | Dec 21 17
9 Answers

What is the minimum depth a water line must be in zone 6 and pure medium to course sand?

I know there must be code requirements but there must also be some scientific way to know at what minimum depths a well water line will not freeze, because I'm thinking the soil composition would be a significant factor. I am in zone 6 in Traverse City, Michigan in pure medium to course sand and on a hill 35 feet above a small lake. The sand is very dry.

Also, can I use Pex underground from the well to the house? I have heard that it is somewhat flexible and resistant to cracking or bursting if the water freezes.

Asked By user-6992381 | Mar 20 18
1 Answer

inside connecting walls

Hello again,
I'm still looking for an answer ... Are connecting/joining walls inside the house also double stud?

Asked By BR9 | Mar 21 18
2 Answers

Does Double-stud include all walls,interior and exterior?

I'm interested in finding out more about double-stud green building.
I've looked in several sites, but have been unable to find the answers I need.
Would it be possible for you to clarify for me if all walls are included when double-stud homes are built (i.e. : walls between rooms, hallways and kitchen, dining and/or living areas).
I do understand that all exterior or load bearing walls are double -stud (which that makes complete sense), but what puzzles me is the other walls.
I would really appreciate it if you could clarify this for me.

Asked By BR9 | Mar 21 18
6 Answers

Open cell spray foam under roof deck

A couple years ago we converted our vented attic to an unvented/conditioned attic with open cell spray foam applied under the plywood roof deck. We even installed an HVAC vent in the attic to keep the RH in the attic similar to the rest of the house. So far everything seems fine but I've recently read about issues with open cell under roof decks, including one article on this website. I live in climate zone 4, asphalt roof over plywood deck. Should I be concerned about having a wet roof deck?

Asked By Michael Mohr | Feb 7 17
Register for a free account and join the conversation

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