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!

1 Answer

How to seal and insulate a crawl space in a humid environment

We purchased a second home on a lake in mid-Michigan in Winter. With Summer, we discovered a moisture problem in the very narrow (16" deep) crawl space. The previous owner had put 6" fiberglass batts under the floor to insulate the crawl space and used plastic film as a vapor barrier over some of the ground. When we crawled through this narrow crawl space, we discovered the fiberglass batts were wet and falling into the crawl space, mold was forming on the floor joists, and there was water puddling on the vapor barrier covering the ground.

In General questions | Asked By Colleen Bruning-Fann | Nov 12 14
3 Answers

What's up with ComfortTherm plastic-enclosed batting?

My contractor came home today with some fiberglass batting wrapped up in plastic that says "vapor retarder" on it. It's this stuff in the vapor retarding form: http://www.rockweilerinsulation.com/documents/JM_ComfortTherm_Batt_Spec_...

In Green products and materials | Asked By Andrew Levitt | Nov 11 14
4 Answers

Air sealing and rim joist insulation

First off, thank you everyone for the all the helpful answers I’ve received here.

This may be a pretty basic question, but how is air sealing normally accomplished at the sheathing when using OSB with no exterior foam? Can it be taped? Glued?

In General questions | Asked By Michael Geoghegan | Nov 10 14
1 Answer

What is the best method to upgrade a 3-season cathedral ceiling to 4-season in zone 7a?

From inside to out my roof consists of 1 1/4 x 5 1/4" tongue-and-groove cedar, then a layer of poly, 2x4 strapping with Buffalo board filled in the gaps (1 1/2"), then roof sheathing, then shingles. Need to upgrade this and maintain the cedar on the inside. The roof is laid on large beams inside.

In General questions | Asked By Keith Malenchak | Nov 11 14
12 Answers

28" or 32" door widths?

The door widths to the bedrooms in my home design are 32". Should I have the architect design the bathroom door widths at 32" also or leave them at the standard 28" width?

In Interior design | Asked By Peter L | Nov 8 14
9 Answers

One coat stucco over Roxul - dealing with the strapping?


I'm investigating refurbishing our 1970s home that was one coat stucco'd on XPS in the 80s. The stucco is deteriorating due to a lack of expanse joints, horizontal stucco window sills, XPS shrinkage, and a zero overhang roof line.

I'd like to use the re-stuccoing to increase the outsulation R-value. I'd like to do something like install Roxul Comfortboard IS (in either 2 3/8" or 3" for R-10 or R-12), and reinstall one-coat stucco over the comfortboard.

In Green products and materials | Asked By Keith H | Nov 9 14
2 Answers

Hydronic radiant design questions

Hello GBA,

I posted a pretty naive question last week regarding selecting the proper heat source. I'm not an HVAC expert by any stretch but as an owner of multiple degrees and a home improvement nut, I don't want to back away from this just because it is quite a bit more intricate than I realized.

In Mechanicals | Asked By Brian Gray | Nov 11 14
1 Answer

I have a detached garage with a hip roof, and the garage is open to the ceiling without rafters

I have a detached garage with a hip roof, and the garage is open to the ceiling without rafters. I had a ridge vent installed but the venting is only in the center and not extended to the hip portion of the roof. I am currently in the process of installing


In General questions | Asked By Edward Millward | Nov 11 14
19 Answers

What heating system should I install in my 150-year-old house in Connecticut? Oil boiler, ductless minisplit, or something else?

My family lives in a 2-story 2000-sq.ft. balloon-framed house in Western Connecticut (zone 5A). We currently heat exclusively with a Harman XXV pellet stove, which surprisingly keeps most of our house pretty comfortable even in the depths of our cold New England winters. Of course there are some rooms that will get down below 60 on the coldest of nights, but that just means we stay in the warm parts of the house, which works fine for us. We used to heat with a Burnham RS-111 oil-fired boiler piped through about a dozen beautiful and massive cast-iron radiators.

In Mechanicals | Asked By Rob Wotzak | Nov 9 14
4 Answers

Is there an equation that will tell me how relative humidity varies with temperature?

I live north of Seattle and the winter humidity in my partially earth berm home runs 70%. The outside air temp tonight is 45 degrees and 95% humidity. I am trying to decide between ventilation and a dehumidifier. I would like to know at what RH that outside air will have after I warm it up.

In General questions | Asked By Mike Roberts | Nov 9 14
Register for a free account and join the conversation

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