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!

1 Answer

Natural Gas wall furnaces

Hi there - I am curious if the GBA community has any opinions on direct-vented natural gas wall furnaces like the Rinnai EX22CN.

I have a 500 sqft kitchen + dining room + living room space with high ceilings and it's currently heated by my massively oversized central air furnace that heats the whole first floor (60k Btu for a 1100 sqft downstairs.) The ductwork also runs through my unconditioned crawl and I'm pretty sure it loses a lot of heat on the way.

Asked By frasca | Jun 24 18
12 Answers

Air Barrier Location

I'm in the process of beginning our new home in the next few weeks. We're located up in Newfoundland, Canada, just around St. John's. We're planning on incorporating a double stud wall to increase the R-value of the home. The plan is, from outside to in, : R8 Comfortboard, Tyvek, Plywood,, 2x6 wall with fiberglass batt, 6mm poly, and 2x4 wall with fiberglass batt which will contain all of the electrical and plumbing.

Asked By Dan C | Aug 6 17
2 Answers

Bubble-wrap air space 2" below in-joist radiant floor heating

My hydronic heating supplier sold me enough foil wrap for the 1600 sq. ft, two storey addition I've put on the house. I've read conflicting accounts for and against and before I begin or return this material.
I intend to install 2" styrofoam below slab in the basement addition.
Is bubble wrap efficient/sufficient with an airspace below the radiant floor hearing followed my drywall? or should I add R12 Roxul below this? Or eliminate the bubble wrap and just go with batts?

Thanks Martin, I enjoy your posts and see them frequently in Fine Home Building mag.

Asked By user-6765846 | Jun 23 18
7 Answers

Vapor retarder for exterior walls Zone 4

Good afternoon,

The insulation guys installed un-faced batts in the exterior walls in my house in Nashville Tn. Should I install a smart vapor barrier (certainteed membrain) over the insulation?

- The house was built in 1964 with thermo ply sheathing. As seen in the image the sheathing is very
leaky. I have done my best at sealing the sheathing with caulking and great stuff foam.

Thanks! ~Bob

Asked By Bob Harshman | Jun 21 18
7 Answers

Vapor permeance of thick foam sheathing and board seams

I have read that at a certain thickness, all foam boards (eps, xps, and polyiso) lose their vapor permeance, effectively rendering them vapor retarders with very low perm ratings. Does anyone have a link to the research behind these findings and if so can I be pointed in the right direction?

I am hopeful that the effective thickness at which this condition occurs for each foam is stated on the research but I will hold further questions till I have read up on it.

Asked By Sash057 | Jun 18 18
9 Answers

Ceiling insulation for a room addition to my house

I'm planning a room addition, 16 x 16 with a 6/12 gable roof and cathedral ceiling, zone 6. I'm not yet committed to anything specific so would like to run this scenario by folks for advice and opinion. I'm wanting to avoid the 5-6 inches of exterior foam (R-25) that would be needed if I went that route. And, I would like to go unvented. Would the following scenario work?

Asked By Howard Gentler | Jun 16 18
1 Answer

Reuse old fiberglass batts?

We are gutting and rehabbing an old house. We are pulling out the old fiberglass insulation from the walls and ceilings, and we have quite a large collection of the batts. Can the insulation be reused?

Some of it is obviously in bad shape, but a lot of it is still fluffy and pink with some discoloration. I know the batts acted as an air filter for the (very) leaky house over the decades, and so they have collected dust and dirt.

How much has that degraded the effectiveness of the insulation? Would it be worth salvaging some of the insulation?

Asked By James Fugate | Jun 18 18
2 Answers

Second Heating and Air

Where would be the best place to install the second unit (basement, 1st floor, upstairs)?

Asked By user-7084153 | Jun 16 18
9 Answers

Double Stud Wall & Basement Insulation Review - Climate Zone 5A

I've read practically every article on this site and many others related to 2x4 double stud walls and moisture. I want to have a wall that is low risk for moisture issues without introducing any more expense and complexity than necessary. The following seems attainable with my budget, and doesn't seem to cause much builder concern for construction. From exterior to interior:

LP Smartside Siding
1/4 rainscreen composed of either a mesh or furring strips with an insect screen at the bottom
Tyvek Drainwrap
CDX Plywood, seams taped

Asked By Shane | Jun 15 18
3 Answers

Thermal break for in-betweenie window box?

Hi, Peter in zone 5 (Boston), considering a PGH design with double stud walls (2x3's inboard, 2x4's outboard; 2.0 SPF at the outside wall and cellulose for the remainder) with about 10" of insulation space (shooting for R-40). (See case 10 of Bldg America report BA-0903:

Asked By Peter Staecker | Jun 14 18
Register for a free account and join the conversation

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