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!

9 Answers

Least toxic closed cell 2-part spray for DIY?

All the reading I have done, I see a lot of issues brought up with 2-part closed cell spray foam being kind of bad for you even with respirator.

I want to do the band joist in my crawlspace and with only entry door there isn't much room for ventilation. I need about 500 board feet.

Any recommendations for least toxic (fire-rated preferred) 2-part closed cell spray foam?

In Green products and materials | Asked By Apollo S | Jan 8 15
14 Answers

How long ago were 2x4 actually 4 inches?

I live in a very old house in Ontario Canada and its built with actual 2x4s, i have no idea how old the house is so i'm hoping to get some idea by finding out when 2x4s were shrunk and assuming the house was built before that.

In General questions | Asked By Alan B | Jan 6 15
5 Answers

Condensation in roof steel vs. wood vs. foam

In an unconditioned attic space above a residence, most of what I've read on GBA seems to agree that steel sheet roofing might develop some condensation on its underside, even if the ceiling below is properly sealed and insulated, just from the outdoor air warming faster than the surface of the metal, and this is part of the argument for installing steel sheet roofing over underlayment and plywood or OSB sheathing.

In Green building techniques | Asked By Jeff Cooper | Jan 7 15
2 Answers

Dricore Smartwall basement product

I'm in the process of refinishing my basement in East Lansing MI (posted previously a question about the insulation on the floor).
I found this relatively new product at the local big box store and it's a bit different in structure than some of the recommendations I've seen from Building Science on finishing a basement (specifically the addition of an internal vapor barrier).

In Green products and materials | Asked By Phylis Floyd | Jan 7 15
5 Answers

Acoustical caulk/sealant confusion

I keep hearing the term "acoustical sealant" in the context of air sealing, as in "use acoustical sealant for air sealing because it remains flexible", but am a little bit confused as to what it means. Does it refer to:

  1. Tremco accoustical sealant, the specific product?
  2. Any caulk or other sealant that exhibits the "remains flexible forever" property?
  3. Something else entirely?
In Green products and materials | Asked By Aaron Birkland | Aug 29 14
5 Answers

Better hot water source?

We built our house 11 years ago on an island off the coast of Maine - Vermont green standards, Energy Star, passive solar, 2500sf, r60 ceilings / r30 walls, with a masonry heater as primary heat source, and, oil fired radiant (tubes in the slab) as backup. We have PV panels that just about net out every year, supply vs demand, via net metering. No natural gas on the island, and LP is expensive to have delivered.

Info on house at this writeup by Homes Across America: http://homes-across-america.org/search/details.cfm?who=144&Feature=all&a...

In Mechanicals | Asked By Bob Earnest | Jan 7 15
2 Answers


I own a historically significant 1898, 3 floor town house in San Francisco with 1 inch separation from the two nearest neighbors. There is no insulation in the exterior walls, and the code in my area requires introducing insulation into the exterior walls when remodeling costs exceed ~$15K. The walls (outside to inside) consist of 9 inch wide, old growth redwood shiplap siding, 4 inch rough saw stud walls, finished with lath and plaster interior walls, all with the original wood finish in the public rooms and most bedrooms.

In Energy efficiency and durability | Asked By Richard Kadel | Jan 6 15
4 Answers

Help with flue work-around

I want to install a wood stove with a 6 inch exhaust connection vented to my 95 year old exterior wall masonry chimney which is just over 30 feet from chimney crown to firebox of stove. The chimney contains 3 flues each of which appear to be small - either 4x4 or 4x6 inches that are separated from each other by a row of vertical bricks running the length of the chimney.

In General questions | Asked By W. Timothy Ward | Jan 5 15
101 Answers

The differences between mass and insulation

The "I installed more attic insulation and now my AC runs more" thread got me thinking about the mass effect a bit.

In Green products and materials | Asked By Nathaniel G | Sep 14 14
2 Answers

I have a tongue-and-groove vaulted ceiling. How can I insulate it?

I live in Santa Barbara California. I have a tongue and groove ceiling in living room and dining room and ceiling is vaulted to about 18+feet. The shingles on the outside were applied directly to the plywood covering the tongue and grove (I guess there is that black barrier stuff/paper between). But no other insulation or barrier was applied. These are asphalt shingles.

In Energy efficiency and durability | Asked By Kathie Morgan | Jan 5 15
Register for a free account and join the conversation

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