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

OSB sheathing touching foundation wall : should I be cutting a 1/8-1/4" slot to prevent direct contact and wicking?

Construction is 2x6 wall, 7/16 OSB, 2 inch EPS foam (high perm), house wrap, 3/4" rain screen and siding.

Currently exterior walls are up, with a standard foam sill plate gasket and the 7/16 OSB. I am wondering if the OSB in direct contact with the concrete foundation wall will be an issue when the whole wall is completed. Drainage plane for the house wrap is right at the edge of the foundation wall, and rain screen/siding actually hangs off the wall 3/4" + siding thickness.

In GBA Pro help | Asked By Mai Tai | Jul 21 18
2 Answers

Basement walls: Encapsulate with plastic sheet, tied to interior French drain?

Hello brain-trust,
Wondering everyone's thoughts on this approach.
I'll be installing a full interior french drain in the basement (1960 house), to fix seepage around the cove joint. wondering if i should install "wall encapsulation" at the same time. Attached image shows the idea. basically, a sheet of poly is glued/fastened near the top of the foundation wall, and is run all the way down the wall, into the newly installed drainage system. in theory, and moisture behind this sheet should run down into the french drain--always staying out of the basement.

In Green building techniques | Asked By Corry Daus | Jul 18 18
2 Answers

Ventilation baffles over lean-to?

My father is building a detached garage, and we are planning to put insulation in the ceiling within the next couple weeks. I know that we will need ventilation baffles on one side where the roof meets the walls. But on the other side, the roof has a lower slope and forms a lean-to. When I talked with the builder today, he said that we don't need to install ventilation baffles on that side, as there is adequate space between where the top of the insulation will be and the rafters. Can I trust his judgment?


In Energy efficiency and durability | Asked By Dylan Hillman | Jul 20 18
27 Answers

Help with air-source heat pump sizing

We are looking into getting minsplits to take care of most of our heating and provide some cooling. We currently have no AC and have a steam boiler which also heats our water. We live in Concord, MA, west of Boston. My concern is about correct sizing of the units. Our house is 1462 square feet not including the basement. Main floor is about 800 square feet so upstairs is about 600. Upstairs is a finished attic with probably average insulation. Walls are 2x4 construction and are insulated. House was built in 1950. We have 2 pane low e windows.

In General questions | Asked By Lyell Slade | Jul 4 18
21 Answers

Triple glazing or high-end double glazing?

I have decided on Milgard fiberglass windows for our house. I like the price point and warranty but I'm trying to buy their best window. The rep has tried to talk me out of the triple glaze but I think it's because he is not familiar with them in this area. He says the high end double pane with their best coatings have better u values and they can't or don't put that coating on triple pane. The cost is about the same. Triple seems to be better to me but I could use some advise. The house is in Missouri. Thanks!

In Energy efficiency and durability | Asked By User-7088022 | Jun 12 18
0 Answers

Entry door replacement, millwork and design

I'm replacing my entry door in a double wall assembly, with windows on the same elevation.

In Green building techniques | Asked By Todd Stout | Jul 21 18
8 Answers

Hybrid insulation: rockwool + foam board (and canned foam for airtightness and extra R-value)

This my first home, very hand have done remodels and stuff before. I wanted to use spray foam but it is out of the question cost wise. I have a 1900 house with plaster. I will be going room by room removing plaster to wire, insulate, drywall and replace windows. I have not found a lot of info on making a home air tight yet. So here is 2 plans not sure how they work work out:

Note 1 The plaster wall should give me 4-4.5 inch of stud bay depth.

Note 2 will be pulling down vinyl siding to put up 1 inch r5 foam board outside, then hopefully reusing siding.

Plan 1:

In Energy efficiency and durability | Asked By NewHomeOwner95 | Jul 20 18
7 Answers

Insulating conventional corner

I’m converting our 2car attached garage into conditioned shop. I’ve began weather sealing and am trying to decide what to do with the conventional corners box corners. Not sure what the proper term is for that but I’m referring to how the last and first stud in a corner of two perpendicular walls meet so that they essentially form a post, or a situation where there is an empty cavity facing the exterior and now way to access it from the interior.

I’m thinking I should:
-cut out one stud out and toenail it back to the sheathing so it’s oriented like a “California corner”?

In GBA Pro help | Asked By kevek101 | Jul 19 18
16 Answers

N.Y. Times article on dealing with heat wave

I read this article


And while most of it is silliness it did get me wondering if white or reflective window coverings would make an appreciable difference. Assuming high SHGC windows of course (not sure if my windows are or not).

Your thoughts?

In Energy efficiency and durability | Asked By Alan B | Jul 16 18
12 Answers

Is it necessary to insulate the ground in a Zone 5B crawlspace?

Small, 192 sf building with a ventilated crawl space, zone 5b, Central Oregon, ground freezes in the winter. My plan is to seal vents and convert it to a conditioned space using rigid foam - R15 on walls, R20 at the rim joist. No cavity insulation between floor joists. Building has 24" stemwalls and a 6" tall footing. The footing and stemwall were poured flush with each other on the interior, and the dirt floor inside is level with the bottom of the footing.

In Energy efficiency and durability | Asked By KevinEJ | Jul 19 18
Register for a free account and join the conversation

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