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!

15 Answers

Open-cell spray foam in joist areas with polyiso on exterior walls?

From all the reading I have done, am I correct that I don't want to use closed-cell and need to use open-cell spray foam in the band areas of floor joists of the basement to 1st and 1st to 2nd floor areas when I have used polyiso sheathing on the outside of the walls?

I believe that is correct because of the perm is so low for the polyiso and you don't want to use another very low-perm product like closed-cell spray foam sandwiching the Zip wall sheathing. I'm just confirming if I read everything correctly.

In Energy efficiency and durability | Asked By john bell | Sep 19 12
2 Answers

I have a slab on grade, no insulation that I want to insulate and include a vapor barrier in zone 5B. What is the best way?

This is for a summer cabin and I would like to reduce the humidity in the cabin and also reduce air conditioning costs.

In General questions | Asked By Joseph LeBeau | Sep 3 14
9 Answers

Garage wall insulation

26x40 attached garage with radiant floor heat in the slab. Standard exterior construction, i.e. 2x6 walls, sheathing and Tyvek with vinyl siding.

I am trying to plan the most effective way to keep my radiant heat in the garage so it can stay warm and help warm the bonus room above. I have several ways of doing this and would like an opinion on them:

1. Spray 2-3 inches of open cell foam into the stud cavities, then drywall.

2. Spray 2-3 inches of CLOSED CELL foam in the studs and drywall.

In Energy efficiency and durability | Asked By Anthony Hughes | Sep 4 14
4 Answers

Is it possible that using a solar-powered attic fan would be appropriate in my situation?

Is it possible that using a solar-powered attic fan would be appropriate in my situation? Would using "Reflectix BP24025 24-Inch by 25-Feet Bubble Pack" be a good choice?

I am a southern Californian living in a home built in 1955 facing an AC and Ducting Nightmare.

I read MARTIN HOLLADAY article posted oct 26 2012.... Musings of an Energy Nerd
Title: "Fans in the Attic: Do They Help or Do They Hurt?"
"Homeowners in hot climates need to understand the difference between whole-house fans and powered attic ventilators"

In Energy efficiency and durability | Asked By John Alberti | Sep 4 14
1 Answer

How would you insulate cathedral ceilings?

How would you insulate your cathedral ceilings? Rafts are 10-12 inches deep.

if you have your house insulated, how do you like it? What would you have done differently?

I had a guy over to bid on sealing and insulating the cathedral ceilings with foam spray. He suggested I go with dense blown-in fiber glass instead because it works better. I had to ask him how long he's been in business. 7 years.

I don't know what I'm missing here.

Any tips on finding contractors I can count on getting the job done right?

In General questions | Asked By Jesse James | Sep 4 14
8 Answers

Cathedral ceiling retrofit

I have a section of my house with a cathedral ceiling.

SW Michigan - Zone 5A
~50 lb snow load area
4/12 pitch.
One side of the cathedral runs up to the house.

The current ceiling is (from inside the outside):

Roof is 17' wide and 20' run, gutter to ridge.
Timber Rafters - ~6' on center, about 4'x10'
T&G boards on top of the rafters.
About R-20 (guessing it is 6-8" thick) insulation.
Roof deck and black asphalt shingles.

I have 2 problems.

Bad ice dams
Noticeable temperature change to the next room. (hotter in summer and colder in winter).

In General questions | Asked By Ian Osborn | Sep 2 14
24 Answers

Solar panels for electricity generation

I would like to decide on putting in solar panels to reduce energy costs.

I have read about the next generation solar panels not being to far off.

Question: Would it be better to install current solar panels or wait for the new type that will be coming shortly?

In Green products and materials | Asked By John Alberti | Aug 26 14
0 Answers

I am considering using Boral TruExterior trim on a new house in lieu of Azek board

I am considering using Boral TruExterior trim on a new house in lieu of Azek board. I have been told that the product offers equivalent performance for less money.

Anybody have any opinions regarding this product?

In Green products and materials | Asked By Chuck Plaisted | Sep 3 14
3 Answers

Where is the link to the free webinar about basement insulation on Sept 4?

Where is the link to the free webinar about basement insulation on Sept 4?

In General questions | Asked By Lowell Lo | Sep 3 14
6 Answers

Finishing rigid foam against an innie window

So I read the innie vs. outie window article on GBA and decided to go with the innie route as I had already made my R/O to size and didn't have time to fir out the windows before my window installer (friend) showed up. So I have my windows in with flanges against sheathing and they stick out just over 2" from the sheathing. I am putting 2' rigid polyiso on the exterior and butting it into the windows. This means there is no foam showing. Do I need to put peel and stick flashing on the exposed foam before installing it? should I leave it away from the window slightly and spray foam that gap?

In Green building techniques | Asked By jordan Saunders | Sep 1 14
Register for a free account and join the conversation

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