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!

13 Answers

Controlling bathroom humidity & wet towels

How do you control bathroom humidity after you've left home or have gone to sleep, A/C is put on setback so it doesn't come on, and you leave your towels to dry by hanging them on the back of the door?

I can't tell during the daytime how bad the humidity gets (since the A/C pops on as we start getting home), but overnight, bathroom humidity shoots up & is consistently in the 60-70% range.

Asked By Jeff Watson | Sep 17 16
0 Answers


Editor's note: This post is part of an existing thread. I have moved the post to the thread where it belongs. Here is the link: My interior fireplace tile chipped over a year ago. Note to Gina: Please don't create a new thread every time you want to post a new comment. You should add any new comments to the same thread you created to start this discussion. Thanks.

Asked By Gina Allen | Sep 19 16
8 Answers

Vented "over-roof" sheathing

I'm building an unconditioned workshop with a cathedral ceiling (i.e., no attic) under a shed roof.
The planned roof stackup, from inside to outside:

Exposed TJI Rafters @ 24" OC
1/2" plywood sheathing w/ h-clips
fully adhered WRB, continuous with wall WRB
2 layers of 3" of Roxul ComfortBoard (R-24 total)
2x4 purlins parallel to ridge, connected to rafters via long screws (these purlins provide a ventilation channel to prevent ice dams)
Snap Lock metal roof (e.g., https://www.pac-clad.com/metal-roofing/snap-clad/) attached to purlins

Asked By Kevin Lynagh | Sep 18 16
1 Answer

Do I need a barrier between wood subfloor and lightweight concrete?

I would like to use lightweight concrete with a radiant heating system on thee second floor as the finished floor. Do I need a barrier between subfloor and concrete? What is minimum thickness of the concrete? I live in Colorado at 9,600 ft.

Asked By Todd Hebebrand | Sep 18 16
9 Answers

Homemade anchor-bolt holders

Wanting to minimize the chances that I'll mess up the last stage of my house build where what I do gets set in stone, I've been reading up on the most foolproof ways to set anchor bolts exactly where they should be in the bond beam of an 8" masonry stem wall. A great article at http://www.finehomebuilding.com/2002/07/01/precise-location-of-foundatio... describes several techniques that the author considers superior to inserting the bolts by hand after the concrete is poured, and my idea is a slight modification of one of his.

Asked By Jeff Cooper | Sep 3 16
5 Answers

House is under negative pressure. Why?

I think my house is under negative pressure. There's always a lot of dirt that builds up on the bottom flat horizontal part of my double-hung windows (this would be the surface that the bottom of the lower sash meets when you close the window). Technically it's still the exterior.

All windows experience this dirt buildup. I cleaned them all thinking that it's never been done in 50 years, but 1 month later they're all dirty again. If I wiped the surface with a wet rag, the rag pretty much has mud on it. It's not dust, it's more like soil. Windows are closed year-round.

Asked By Jeff Watson | Sep 17 16
1 Answer

What is the N.C. code requirement for R-value for roof and exterior walls? How many inches of closed-cell foam is it?

What would be recommended for the R-value and inches of closed-cell foam below living space and unheated garage space ?

Asked By Daniel Mckay | Sep 17 16
3 Answers

Gas fireplace... insulated vent chase warranted?


Asked By Jay Miracle | Sep 16 16
1 Answer

Do I need an air exchanger?

I am building a super insulated home in Massachusetts and just had my blower door test complete after the insulation was installed and registered a 0.5995 at 50 pascals and it would have been better if I had known the electricians untaped two conduits and a plumbing vent pipe was not sealed. In my spare time (nights and weekends) I completed the air sealing and my builder is an old school guy who thinks homes should breath on their own so I never expected to come close to this type of tightness.

Asked By Brandon McCabe | Sep 17 16
3 Answers

Capillary break

I am getting ready to insulate my basement in preparation for future finishing into living space. My home is located in NE Pennsylvania and was built in 1859 and sits on a field stone foundation. The foundation overall is in very good condition. It is is need of re pointing in some areas but over all in good condition. The basement is damp on two of the walls and during periods of heavy rain weeps water slowly. I have already installed a french drain to daylight around the two walls that periodically weep and are damp on the lower half for much of the year.

Asked By Ben Hardy | Sep 15 16
Register for a free account and join the conversation

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