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

Below grade polyethylene and slab

I am questioning as to the order of polyethylene vapor barrier to foam when placed under a slab. The reason I ask is because I am currently having my house built and today I have discovered that the contractor placed the poly directly on the ground (good drainable material) with the blue board foam boards on top of it. I have read in the past that the poly should be placed on top. I am worried that it has been done incorrectly. Any thoughts to put my mind at ease as I am rather stressed out right now. Thanks in advance.

In GBA Pro help | Asked By Matthew Michaud | Jun 5 14
1 Answer

What's your favorite high-efficiency natural gas fireplace?

We're building a small house with a small heating load. Thinking about a high-efficiency fireplace with electric backup.
What unit(s) do you recommend?

In Energy efficiency and durability | Asked By brian evans | Jun 3 14
3 Answers

Recommendations for exterior trim in the Northeast?

I am replacing windows and want to install a trim that is long lasting and environmentally sustainable.

In Green products and materials | Asked By matt dooley | Jun 1 14
1 Answer

What is the going rate for an energy modeler?

My architect and I are trying to design my home around a Passive House standard. My architect has some knowledge but readily admits to not being very familiar with Passive House design standards. He is well known and has designed many homes in the area, but none to Passive House criteria. Recently, I met with a building science professor who teaches energy efficient building/Passive House and is building his own home to be a non-certified Passive House zero-energy house. He has a Masters in Building Sciences and is a licensed architect.

In General questions | Asked By scott schroeder | Jun 2 14
3 Answers

Living space

I'm planning to build a new home on Houston city limit. I would like to build a 2500 sq/ft living space house, but for not be to hard on the budget I would like to live the live unfinished 2 bedroom. In other word take all the mechanical (AC duct, electric) to the room and noting else but just framing.
The builder told me that the city of Houston will not allow that but it also could be that the builder do not want me to save money.
Can you help me with that?


In Building Code Questions | Asked By Rocco Locaso | May 30 14
1 Answer

What plumbing system is safe?

Buying house with polybutylene plumbing and read that it can leak. Is it a
health hazard re leaching chemicals into drinking water? Polytheylene (PEX)
tubing can be a health hazard and carcinogenic due to leaching chemicals. Copper has health issues from leaching copper as well.
What is the best plumbing piping that is also safe to our health? Thank you.

In Green products and materials | Asked By Katherine Webb | Jun 2 14
2 Answers

Spray foam against plywood roof decking questions

I currently have the following roofing system and am located in Northern WV in climate zone 5. Fabral standing seams metal roofing, tar paper and then plywood on 2' center bonus room trusses. I am getting quotes on insulating the underside of the roof decking with spray foam. The HVAC units and ductwork are located in the attic space beside the bonus room. Here are my questions and concerns.

1) I have a vented soffit and vented ridge vent at the moment and should I put up something to keep the air flow before spraying the foam or create a unvented attic space instead with the foam?

In Energy efficiency and durability | Asked By Brian Mallow | Jun 2 14
5 Answers

Back caulking window nailing flanges

Is it common practice to use a specific window flange caulking for back caulking the flange before installation? Does flashing tape and house wrap suffice (assuming that it installed properly) or is caulk important in the case that the tape fails. Or, are you just adding a chance for water that would happen to enter this area to be trapped and rot the framing without knowing? I would like to spare the expense and labor of more caulking if I could but don't want to sacrifice air and water sealing at this crucial junction. Thanks in advance.

In General questions | Asked By Matthew Michaud | Jun 1 14
42 Answers

Dense Packing Slopes with 11.25 " rafters. Bad idea?

I did a lot of research when I built. Bottom line is that I chose the cheaper easier method and now I'm paying for it. I continue to hear that it's OK to dense pack cellulose in a slope and not vent it or not flash it with closed cell foam. This is incorrect and I can prove it now! Moisture has collected on the back side of the roof sheeting and ice chunks have formed, mostly on the north side of the house. Any where there's snow build up on the south side I have ice formation on the inside of the roof sheathing as well.

In GBA Pro help | Asked By James ODonnell | Mar 4 14
2 Answers

Building in heat/cool/humid region

We are looking to build a new town home in Alexandria VA. According to the Passive House US site we are in the heat/cool/humid region.

In Energy efficiency and durability | Asked By Mike Dyke | May 28 14
Register for a free account and join the conversation

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