Community: Energy efficiency and durability

Q & A Instructions

[Click map to enlarge]

The 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!

7 Answers

How to treat wet sandy cottage crawlspace in zone 5A/6A?

Situation: cottage on the sandy shores of a large lake in Michigan on the border of climate zones 5A and 6A. The cottage is set back from the lake front perhaps 200 feet, but is probably less than 2’ above lake level. The footings are likely below lake level. To make things worse, there is a natural drainage swale running behind the cottage that some good neighbors have effectively dammed, so there is permanent standing water about 100’ behind the cottage.

So of course the cottage is built with a crawlspace, with a sand floor and concrete block walls.

Asked By andrew c | Jul 14 18
7 Answers

Can I use 1.5” x 3” rigid foam strips between exterior wall sheathing and studs?

I bought an old RV and it had so much water damage that I ended up tearing down everything and just keeping the vehicle, which is a cut off van. I am planning the rebuild of the living space now. I think that it’s going to be an RV/tiny home crossover. What I am considering doing is the following: I would like to use zip panels as my sheathing, but have a 1.5” x 3“ foam board strip in between the sheathing and the stud as a thermal break. I would then spray foam (closed cell) the cavities until it was about 3 inches to 4 inches thick.

Asked By John Haller | Jul 14 18
17 Answers

Wall assembly help


I wanted to get some advice on two wall assemblies I am considering. I am in Iowa- climate zone 5. Cost is a factor but would like to have an efficient assembly as we are going to live in this house for a long time.

Option 1 from outside in
LP Smart side
1/2” furring strips/rain screen
1 1/2” XPs rigid foam
TyVek commercial D drain wrap
2x6 standard framing with BIBS and my insulation contractors basic air sealing package
1/2 Sheetrock latex paint

Option 2
LP smartside
Homeslicker drain mat
ZIP R sheathing 1.5” r vale 6.6
2x6 wall BIBs and air sealing

Asked By jrpritchard | Jul 10 18
5 Answers

Insulating stud bays: Spray closed-cell foam directly on 1x6 diagonal sheathing or use asphalt felt with air gap?

Hi All,

We're renovating a historic 1935 brick home. Once the interior paster was removed from the walls, we found 1x6 diagonal sheathing (in great shape). While the stud bays are open, we'd like to add insulation to the house.

The house is framed with 2x4 (1.75x3.75 actual) studs.

My original plan was to line the stud bays with asphalt felt, leaving 1/2 to 3/4 air gap to allow the stud bay to dry out, and seal it up with 1" of closed cell foam, and fill the rest of the bay out with open cell foam.

Asked By Getco | Jul 12 18
2 Answers

Can you flash and batt with the spray foam on the inside?


Asked By Fallwanderer | Jul 11 18
7 Answers

Installing a door with exterior rigid insulation

I feel comfortable installing all my windows as "outies", ...I feel I can support and anchor them comfortable, but what about a heavy sliding glass door...wouldn't that have to set on solid framing? I plan to go 2x6 walls, with 2 layers of 1.5 rigid insulation, rain screen, and cedar siding. I have been looking at youtube videos, finehomebuilding, this site and others and can't find the details on how to install a heavy sliding glass door with rigid foam on the outside...please help.

Asked By user-7005676 | Jul 10 18
5 Answers

Does applying spray foam require removing sheetrock from rafters?

We are in climate zone 3 warm-humid coastal NC and are renovating our house, including air sealing and improving the roof insulation. We have a 1.5 story house with a 14:12 pitch vented roof structure and about R-19 roof insulation in 2x8 rafters. It has knee-walls, the floor joists are open at the rafter-joist-wall intersection and we have a mini-attic insulated to ~ R-30.

Spray foam has been suggested as a way to improve the insulation and air-seal, bringing the attic and knee-wall areas inside the envelope.

Asked By Bennett G. | Jul 11 18
6 Answers

Faced direction in kneewall

Hi, I'm installing the faced pink stuff in my knee wall. Which direction do I point the face? I know generally its on the heated side, however, im in NY and the crawl space gets super hot in the summer and i might be putting an AC in, so technically the knee wall would be the heated side, no? And the humidity in the house hits can hot 60 at times, averaging 50 on the first floor (which shouldn't be an issue once the a.c. is in). But then what about the winter?


Asked By Champak | May 6 18
3 Answers

Slab vs. crawl space

Hello. I seem to have written my question incorrectly previously. I am preparing to build a 1,300 sq. ft. home in northwest Montana.

Around here crawlspaces and basements are the norm. I am researching using block frost walls (no basement) and a slab. Most of my builder friends are counseling me against this.

I want to have some wood floors and some tile. Wood floor area would be poured at a lower elevation. I would lay down treated sleepers and plywood to attach the 3/4 flooring to.

Asked By Mike Koness | Jul 10 18
8 Answers

In trying to insulate a cold, north-facing parlor of my 1890 house, rigid foam board was recommended

In trying to insulate a cold, north-facing parlor of my 1890 house, rigid foam board was recommended in this forum. Further driving revealed that only one of 7 walls (there's a bay window) had enough space for that, and for 6 of the 7 walls, there's only...

Also, there's aluminum siding over the walls with the bay window. Otherwise, the exterior is brick.

Asked By Susan Hanway | Jun 27 18
Register for a free account and join the conversation

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