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!

21 Answers

Foundation capillary break & waterproofing

My wife and I are building a small home (First Day Cottage) on a full foundation with a walkout on the downhill end. I read about having a capillary break between the footing and foundation wall and it makes sense to me. When I asked the concrete contractor about it he said he's never done it (though he did remember one other customer who asked about it a couple years back). I get the impression they won't leave me much time to do it myself between pours.

In General questions | Asked By Martin Frank | Jun 30 15
3 Answers

Revisit: Insulating a wall from the outside — but for a 200-year-old home

I stumbled upon a question from a fellow who wanted to insulate his walls from the outside and add more foam board too. This intrigued me as it was inline with my thoughts on a similar project. The problem was, I could not ascertain from the feedback whether it applied well to my situation.

So, I wanted to throw the question out there.

In General questions | Asked By Les Newsom | Jul 16 15
1 Answer

Polyethylene or peel-and-stick membrane?

I am working on a cathedral ceiling with exposed rafters. (Rafters, Tongue and groove, 5/8 plywood, 6" of polyiso, 1/2 OSB, underlayment and metal roof).
I have available a 10 mil' polyethylene roll that would cover the entire roof area in one piece. Is this an acceptable method for air sealing the system? I know this material doesn't have the advantage of "self healing" around fasteners. Would that be a concern?
I am in Austin, Tx.

In Energy efficiency and durability | Asked By Harold Orozco | Jul 17 15
2 Answers

"Designing for Durability"

Martin and others: I just read the article in Fine Homebuilding ( September 2015, #253) on the new HUD guide for building a durable house. I do not understand the "overhang ratios" given in the chart on p. 58., and am wondering if they have made an error. On a 9' wall( single story house) the 0.5 ratio required to get excellent protection in a "Damp" or "Wet" climate means an overhang of 54" . That's one hell of an overhang!

In Energy efficiency and durability | Asked By KEVIN ZORSKI | Jul 16 15
5 Answers

Caulking with closed cell insulation

I am building a new home with R30 and R 50 walls and ceilings. We will have 3" of closed cell in the basement walls.
What are best management practices for caulking?
Thanks in advance.
Peter Whitman

In Green building techniques | Asked By Peter Whitman | Jul 15 15
13 Answers

Spray foam on top of upstairs ceiling?

Getting down to the details now on my design (Upstate NY Zone 5 near Zone 6). I plan a cold attic with vented soffits, baffles protecting the upwards airflow, and no ceiling intrusions like wiring, lights, outlets ducts or holes/hatches for access from inside. My plan is to build a fake ceiling and soffited sheet rock below the original ceiling WITHIN the envelope, in which to run my ducts and put a few ceiling lights or fans up there. I plan on building a door on the gable peak large enough to get into the attic by removing some screws that will hold it in place.

In Green building techniques | Asked By Joe Suhrada | Jul 14 15
1 Answer

Need to know how good Prodex insulation is for under metal roofing?

Thinking about using Prodex insulation under metal roofing need advice.

In Green products and materials | Asked By Troy Tubbs | Jul 16 15
1 Answer

Can spray foam help?

My home originally had an open front porch which, at one point, was enclosed. I recently had the enclosure torn off and reconstructed so that the area would serve as an addition to the home's front room. The new "addition" sits atop a "coal bin." Would spray foam help insulate the front room from any moisture and drafts from the coal bin?

In General questions | Asked By Kevin McArdle | Jul 16 15
3 Answers

Spray foam under outdoor space. Good or bad idea?

I've got a outdoor patio, about 300sq/ft. Its got a hallway on one side, and covered patio on the other.

The hallway already has sprayfoam on the underside of the roof deck, in the wall cavity and under the slab. Its represented by area in blue (see attached).

The covered patio area currently has nothing for insulation in it. I was planning on doing T&G fir on the underside of the covered patio under the vault.

I'm wondering if there is any benefit to putting spray foam or any insulation under the covered patio even though the area is not heated?

In General questions | Asked By Mark Helmrich | Jul 15 15
1 Answer

Is a heat-pump water heater in Zone 7 worth it?

I'm currently designing a highly efficient 2 bedroom 1080 sqft house. Right now I am wondering if a heat pump water heater would pay itself off before it needs to be replaced. Also, the mechanical room would only be 3'6" x 7'6", not big enough size for manufactures recommendations of 10'x10'x10'

My question is how could I run the numbers to see if buying one is a good investment?

In Energy efficiency and durability | Asked By Matt Berger | Jul 15 15
Register for a free account and join the conversation

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