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

Weeping tile (French drain) access or cleanout?

I am installing a drainage mat in a small section around my foundation. While i am installing it, I am wondering if there is any real word advantage of creating a "clean out" or or inspection pipe that leads to the surface.


In General questions | Asked By cory shwartz | Jun 9 13
2 Answers

Footing depth?

The location I'll be building has a " frost depth" requirement of 42". I'm planning on "insulated" footings set on a drainage layer of coarse crushed rock. My question is exactly what needs to be 42" below finished grade? Is that the bottom of the drainage layer, ie undisturbed soil? Is that the bottom of the insulation, ie top of the drainage rock? Or worst possibility the bottom of the poured concrete?

In Building Code Questions | Asked By Jerry Liebler | Jun 20 13
14 Answers

Hi, I'm a new real estate agent and I would like to sell energy efficient, clean and safe homes.

I've never spoken with a builder before but would love to learn how to sell these homes. I really want to feel good about the homes that I help sell. Any advice or opinions that you give are welcome. Thanks.

In General questions | Asked By Telia Rivers | Jun 16 13
5 Answers

Car fumes in the coach house

Hey there - I have a design question. My company is renovating a detached coach house which will have 2 cars parked on the main floor and a living space above. It will have radiant heating in the main floor slab, which will be the coach house's only heat source. Any suggestions on how to air seal the main floor "garage" area from the living space but still allow heat to transfer up? Is there a spray foam with no R value that still air seals?


In General questions | Asked By Steve Hull | Jun 20 13
1 Answer

Earth Tubes to Cool Roof

I know there is some debate about the benefit of earth tubes, such as air quality issues and cost/savings. If the trenching for the tubes was already a "sunk cost", would it make any sense (or cause any problems) to run the tubes up the exterior wall (or inside the exterior wall) and into the roof soffit in order to vent the roof with cooler air? To extend the idea further, would this help the efficiency of roof mounted PV panels (or laminate PV) by keeping the PV panels cooler?

In Energy efficiency and durability | Asked By Bill Greene | Jun 20 13
1 Answer

Thin-film solar laminate

We're in the process of designing a home in zone 4A, and leaning towards a metal roof. I'm hoping this question is too open-ended, but I'm wondering what your experiences are with thin-film solar laminates (link below)? From what I've been able to find, they seem to be more expensive per watt and not as efficient as tradition PV panels, but they sure look much better! Is it possible to install these after the roof is installed, perhaps once the cost is down and/or efficiency improves? Is the product durable enough to survive its payback period?

In Green products and materials | Asked By Bill Greene | Jun 20 13
7 Answers

Insulate PEX?

If all plumbing lines are within the envelope, and a recirculating pump is installed, what might the payback period be for insulating PEX hot water lines?

Because the advantage of PEX is that the pipes are easily curved around obstacles etc., I bet insulation coverage wouldn't be more than 90% in even careful installations.

In any case, insulation would serve no purpose whenever the wait between uses exceeded a couple of hours, no?

Is this one of those cases where the money would be better spent on more insulation elsewhere?

In Energy efficiency and durability | Asked By David McNeely | Jun 18 13
2 Answers

Question regarding rigid foam under slab (for Martin)

I'm building a home in Ottawa, On. (zone 6)

I'm laying 2 inches of EPS under the slab (R-8) and 4 inches of EPS on the interior foundation walls. (R-16)

I will be installing Rub-R-Wall and Geo Wrap over the exterior of the walls.

From reading previous posts, I will be adding my poly directly above the foam, directly below slab.

Question: Can I tape up all the seams with recommended foam tape? Will this help? just so we can walk over the foam while installing the foam on the walls.

In Green building techniques | Asked By Stephane Vizzari | Jun 19 13
11 Answers

Best way to insulate a bonus room over the garage?

We live in a 7 year old ranch house near Raleigh, NC. There is a 350 sq ft unfinished room over the 2 car garage and an adjacent large unfinished second floor attic area. An open stairwell leads from the first floor (has a door at the first floor level) to the room over the garage. The unfinished room has plywood flooring and batt insulation separating it from the garage. The rest of the attic has blown in cellulose insulation but is not floored (except for a small storage area). The room over the garage is about 10’ wide and 35’ long with 5’ kneewalls and a cathedral ceiling.

In General questions | Asked By Rob Silbajoris | Jun 6 12
15 Answers

Closed-cell foam on underside of roof with no AC: Do I need to vent?

I am working with a local energy efficiency contractor. They are replacing my old roof (which badly needs replacing) with a new roof. They will be spraying five or so inches of closed cell foam directly against the decking. This will fully seal my attic. My question is, how does this work if you do not have air conditioning in the house, other than window units in the bedrooms and one in the living room.

In Green building techniques | Asked By Rob Graff | May 7 13
Register for a free account and join the conversation

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