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!

3 Answers

Questions on creating a conditioned attic

I've been reading through the other questions and articles by Martin and I think I have something of a handle on my options, but I really feel like I need some expert advice before I proceed. I'm in a suburb of Chicago (Zone 5a) and just bought a house with a attic that was basically built as a 3rd floor complete with a set of stairs coming up to it. It has 8" rafters and is currently vented. As it is, it's pretty hot in the summer, easily over 120 degrees. The floor of the attic is insulated and has plywood over it so the current thermal envelope is to the ceiling of the 2nd floor.

In Energy efficiency and durability | Asked By John Daves | Aug 22 16
8 Answers

Insulating rim joists

Hello. I've been reading q&a on this website for a long time and have always found the content very helpful. This is my first time posting a question and hope someone has some information for me.

In General questions | Asked By P Coyne | Aug 18 16
0 Answers

Flat roof installer in Wisconsin

I have a cold flat roof, which is currently vented. I'm thinking of installing a warm roof and making it an unvented roof. Does anyone know of a good contractor for this kind of project?


In General questions | Asked By Betina Chaon | Aug 22 16
3 Answers

Pex size for hose bibs?

I have a very long ranch house...
All of my potable water has been plumbed with uponor manifolds 3/4 supply, 1/2 home runs to each fixture.. (two manifolds for each side of the house).

I want to run my hose bib's before my water softener.

the question I have is can I use the same method.. a home run of 3/4 pex... attached to a manifold with 1/2 off of that to multiple hose bibs?

I was planning on using woodford model 19's.

I imagine using 3/4 all the way would give me more volume at the hose bib..

In General questions | Asked By Dean Sandbo | Aug 21 16
51 Answers

Mooney floor

I want to put insulation on top of a concrete floor.
A layer of foam + plywood bolted to the concrete has been suggested. (By Dana I think)
While that looks an good option I've been exploring more low cost options.

What about a Mooney wall, flooring variation.
Thinking about 2x4 + 2x4, filled with blown in cellulose. Likely GreenFiber or InsulMax.

Is that a good alternative?

In Green building techniques | Asked By Tony Tibbar | Aug 6 16
5 Answers

Use foam "fluff" as attic insulation?

A facility near me apparently cuts up a lot of XPS foam and advertises the remains on craigslist for free. They have huge bags of about 4"x4"x1.5" chunks and others they refer to as "fluff". They're just very small, finely ground up pieces of the foam. Since this is free, I was wondering if the "fluff" could be used almost like cellulose in the attic or if the fact that it is no longer solid would greatly diminish its insulating abilities? Thanks for any advice.

In General questions | Asked By Ryan Cornelius | Aug 22 16
1 Answer

How far should poly run up the edge of a monolithic slab on grade?

How far should polyurethane run up the edge of a monolithic slab on grade? If it doesn't run all the way up (as I've seen in some details), should the edge be painted with damp-proofing?


In General questions | Asked By John Ranson | Aug 21 16
3 Answers

Cathedral ceiling vs. standard ceiling: Insulation issues

I'm building a 20x20 detached garage with a finished loft area. Loft area will have 2 foot knee walls and a 14/12 roof pitch to maximize space where I won't hit my head on the ceiling. I'm trying to decide whether the loft should just have a cathedral ceiling, or if I should add in framing for a standard 8' ceiling.

In General questions | Asked By Aun Safe | Aug 20 16
2 Answers

Adding a second story

Is adding a second story harder than a first?

In General questions | Asked By John Chavege | Aug 21 16
2 Answers

Spray foam in roof deck — Is lower R-value than minimum code recommendation OK?

I am remodeling a 106-year-old home in Climate Zone 4A where the minimum recommended attic value is R-38. A local spray foam contractor, with a large national company, told me that with spray foam a much lower R-value is OK. He quoted the job at R-20 for the roof deck. I know that air sealing is of paramount importance but it seems R-value also is important.

Is R-20 really enough?

In Green building techniques | Asked By Ross Williams | Aug 21 16
Register for a free account and join the conversation

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