Community: Green building techniques

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!


5 Answers

Rigid Foam minimum for 2x8 Stud

Zone 5 - helping with a wall design. They are using 2x8s for studs to fit in R-30 mineral wool. I am suggesting rigid foam, EPS or XPS, but I have only read that 2x6 wall needs R-7.5 But, this is a 2x8 wall, and I don't think R30 is traditional. So Will 2" of XPS or EPS be sufficient? Don't really want to have to go with two sheets and achieve 2.5" of rigid foam if 2" is sufficient with R30 mineral wool on the interior.

Is there any way to make 2" work? Such as a smart membrane installed before drywall?

Asked By Nicholas C | Dec 9 16
12 Answers

How important is a thermal break between a house foundation and an attached garage foundation?

Our footings were poured today for a new house and attached garage. The walls of the basement foundation (9') and garage foundation are scheduled to be poured next week.

Looking over the plans, our concrete sub is worried about the 7" thermal break between the basement and garage foundations (no physical connection) as currently drawn on the plans. The separation is there in order to allow us to attach 5" of Roxul Comfortboard 80 to the basement foundation (we'll be doing the same for the whole exterior perimeter of the basement foundation).

Asked By Eric Whetzel | Dec 2 16
3 Answers

Exterior Rigid Foam Under Sheathing?

In my local area there is a green building consultant that recommends a CI panel which is basically EPS foam glued to OSB. The way this is installed would be the OSB to the exterior. Almost every house I see with exterior rigid foam in my online wonderings is covered with blue and pink XPS, the OSB sheathing is nailed directly to the studs and is completely covered with the rigid foam. This leads me to the following questions:

- Is anyone familiar with these kind of CI panels?

Asked By Joshua Greisen | Dec 8 16
6 Answers

Exterior foam application and window details

Im in Phoenix about 6 months away from starting my build. I was thinking about upgrading my exterior foam from 1.5" to 3" EPS. The window detailing is where my question lies. I've read the articles here, but we will be using mostly EFIS for our exterior cladding (with some stone veneer). My thought was to nail the window to the exterior after the OSB and Tyvek stucco wrap just like you would without using foam. Then add the 3" of EPS right up to the edge of the window and just add the EFIS to the 3" return created. For the stone veneer we will just frame out the window the 3 inches.

Asked By Jeffrey Savage | Dec 6 16
2 Answers

Insulating 4-inch exterior walls

I am in the process of total gut remodel project, zone 5, 2x4 walls and installing vinyl siding.
I am trying to decide if I should use structural insulated sheathing such as Huber Zip-R and closed cell foam to fill stud cavity's. or install foam on outside exterior sheathing and use open cell foam.
any feedback would be appreciated.

Asked By Steve Karkau | Dec 5 16
3 Answers

Fill stud cavity with fiberglass insulation?

I am finalizing a house design in zone 5. Exterior walls to be insulated with R10 XPS exterior of the sheathing and R13 fiberglass in the wood stud cavity. Peel and stick will be directly applied to sheathing per REMOTE style walls.

My concern: wood studs will be both 2x4 and 2x6 construction, with 2x6s where walls are tall (10 ft.). Is R13 insulation pushed towards exterior (I'll have to figure out the best way to do that) OK or should I fill the cavity with insulation in the tall walls? Will ratio of R19 to R10 work re: moisture control?

Thanks in advance.

Asked By Joel Cheely | Dec 4 16
6 Answers

Can rigid insulation be safely used in the center of a double stud wall?

Joe Lstiburek's details for double stud walls show a layer of OSB/plywood in the center of the wall for an air and vapor barrier. Could a wall be assembled with R-13 batts in 2x4 framed walls, separated by a layer of 2"-3" rigid insulation? It seems like the first condensing surfaces of the rigid insulation would safely remain below the dewpoint, and foil faced insulation like polyiso would be a very effective air and vapor barrier. This would be built in climate zone 4.

Asked By Jason Whitacre | Nov 30 16
3 Answers

Insulating a brick wall from the inside

Hi,

We have a 100 year old row house in Montreal, (zone 5000). Most walls abut the homes on either side, but we have a bump out in the back with two exposed walls. The walls are two bricks thick, (I think), with plaster on the inside, and I think a layer of drywall on top, (judging by how the walls are actually proud of the original baseboards).

The walls in question are in our bathroom, which gets quite chilly. I'd like to add foam board insulation on top of the walls, and then drywall on top of that again (we can live with the resulting deep sills in the windows).

Asked By Sean Lewkiw | Nov 23 16
10 Answers

Attic air barrier/vapor retarder

I'd like to get some feedback on this detail (attached). Background: <700 SF seasonal home in Climate Zone 6. 2x6 at 24" walls are insulated with dense pack cellulose. Rafters are 2x12s at 16"oc (snow country) and ceiling is 2x8 T&G douglas fir laid across 2x10 (actual) bottom chord ~44" apart which are exposed to the living area below. It is 1-1/2 story (just lower level and loft) and I am venting the roof. Heat is radiant slab from tankless boiler augmented with a wood stove when we are there (the only penetration in the ceiling besides the hatch, both sealed well).

Asked By Julie Brown | Nov 17 16
6 Answers

Engineered hardwood floor in basement

We have purchased engineered wood flooring for our basement. We are are also installing it on the main level. We wanted to avoid vinyl flooring and carpet due to chemical sensitivities; tile wasn't in budget; and due to height requirements on the stairs, unfinished concrete wouldn't work. Our original installer planned to glue down with Dritac Golden Bullet 4141. Unfortunately, that installer no longer has time for our job and we are getting a lot of resistance from other installers about glue down.

Asked By Carolyn Farrow | Nov 21 16
Register for a free account and join the conversation


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