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!

3 Answers

Combine 2 bath exhaust fan runs to vent outside?

I have 2 bathrooms, each with a fan. Both come into the attic as flexible metal about 3 feet from each other. They then snake around and go down to a soffit.

I realize from reaching on this site that this isn't ideal. I'm considering switching them to rigid metal or pvc once they reach the attic, have each continue up slightly about a foot above the attic floor, then slope down toward a new vent in a gable wall.

In Building Code Questions | Asked By Jeremy M | Mar 15 15
5 Answers

Air sealing/insulation on top of stairs in a bungalow

Planning my air sealing project I'm most stumped by the stairs area. I tried some photos but they don't help explain it. I've attached one of the second floor hall, the stairs top out just to the left, I'm talking about the narrow ceiling showing in the photo and the slant on top of the ceiling over the stairs.

In Green building techniques | Asked By Jeremy M | Mar 13 15
2 Answers

Insulating and heating barn

We are are about to start on a project of converting our horse barn into an office area. We are in southern Coos County NH. The area we want to heat is 900 sf, so first floor only. Half the barn has a four foot crawlspace the other is full basement. The building is post and beam about 160 years old. The walls are 6 inches deep the floors and ceilings are thicker because of the beam construction. There is no natural gas, so propane Rinnai wall furnace is what we were considering for heat. Our plan was to use closed cell urethane for insulation, but are open to other ideas.

In General questions | Asked By Ken Chester | Mar 15 15
11 Answers

1 or 2 rigid foam at top plate around attic baffle?

Just joined, hope this is the right category....Ohio is the state.

I'm going to install attic baffles from new soffit vents. I currently have fiberglass blocking the cellulose, under a plywood floor.

I've seen just the baffle, I've seen the baffle with a flat piece of rigid foam on top of the top plate and caulked, I've seen the flat piece of foam along with a vertical piece, also foamed.

Which is best and why?

(Examples attached-I hope- 1487 is my house with the fiberglass pulled back for the photo.

In Green building techniques | Asked By Jeremy M | Mar 10 15
13 Answers

Please review my floor plan

See attachment for proposed floor plan. My dear, dear wife likes most of it except the location of the pantry/utility room. I've tried to move the flexroom to the area behind the garage (see second attachment), but I end with with a smaller closet and bath in the master. She urged me to ask other people...so people...I am askin'. What's your input on that or anything else you see?

In Plans Review | Asked By Andrew Bennett | Mar 14 15
10 Answers

Insulated slab details for zone 7 walkout

My build is in Kenora Onrtario Canada (zone 7). The basement is a walkout; I need to incorporate a sewage lift station under the floor to pump (shower/toilet/sink and washing machine) water up to my septic
I need to know how to detail the insulation and poly layer under the concrete.
Do I insulate the sides and bottom of the hole the tank (110 gallon) goes into; if so do the joints have to be taped like building an foam box; I can't have the sewage freezing in the tank! Is that even a concern?

In Energy efficiency and durability | Asked By tim brown | Mar 5 15
4 Answers

Building envelope


We live in southeastern Wisconsin and are currently a year into a complete gut/remodel of a home built in 1963. We have the interior complete and are living in the home (family of 4).
We are about to have the siding installed (LP Smartside lap siding) and have a few questions/concerns.

- 2x4 wall construction (16" centers)
- interior spray foam closed cell urethane on all walls with no interior vapor barrier
- attic insulated with loose fill blown in fiberglass insulation R-50 with interior vapor barrier

In Energy efficiency and durability | Asked By Kevin Steltenpohl | Feb 16 15
2 Answers

I am insulating my cottage

I am insulating my cottage. I need to know if I need to seal all the cracks completely in the outside wall? It is wood Dutch Lap siding.

I want to use 2" blue extruded (XPS) board, and 4" fiberglass insulation with vapor barrier, for a 6" wall. And also, what about the seams in the 2" foam boards? The interior wall will be 1/4" OSB with knotty pine 1/4" paneling. Is the vapor barrier on the fiberglass enough?

In General questions | Asked By larry rummel | Mar 13 15
4 Answers

Can I still use polyiso to insulate a rim joist that is irregular?

I am about to jump into insulating rim joist in the my crawlspace, but as I am cutting pieces for it, I am starting to realize that foam often will not be 100% flush with wood and in some spots there will be resulting small cavity behind. Will that create a problem or is little bit of cavity behind fine, as long as I make sure all pieces of foam are foamed in just right?

In GBA Pro help | Asked By Apollo S | Mar 13 15
18 Answers

How would YOU insulate my new house given the conditions?

This is my first post on GBA but I think I've read every article on the site in preparation for building our new home, located in Thunder Bay, ON, Canada (40 minutes north of the Minnesota border, Climate Zone 7). I've learned a lot here, but like other posters have suggested, I might be MORE confused than when I started!

In Energy efficiency and durability | Asked By Nik Fiorito | Mar 11 15
Register for a free account and join the conversation

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