Q&A: A Forum for Green Building Experts and Beginners

[Click map to enlarge]

Please register for a free account or sign in to ask and answer green building questions.

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

Options for air sealing T&G ceiling with no air barrier installed

Hello all,
I apologize if this question appears a repetitive one, as I have read through a good bit of the Q&As here, but still cannot determine my best course of action.

In General questions | Asked By Rob Leonard | Sep 14 14
5 Answers

Effectiveness of Roxul "flash and batt" - irregular closed-cell spray foam causing air gaps?

I have a spray foam crew coming Thursday to convert my attic to "unvented" (2x8 rafters). They want customers to do 5". My plan though was to do 4" and then 3.5" Roxul batts to fill followed by a layer of the Roxul board to reduce bridging on the rafters.

In Green building techniques | Asked By Chuck Swanberg | Sep 16 14
4 Answers

Trying to determine best assembly to insulate an old church roof being converted to office

We are looking to keep the existing roof decking and rafters exposed in a church in Atlanta, Climate Zone 3. We have read Martin Holladay's FHB Article about unvented, Super Insulated Roofs, and Joe LUtiburek's article BSI-036 Complex 3D Air Flows talking about the subject. One of the big differences (really somewhat minor) I see between the two recommended details is the best place to locate the fully adhered air barrier. Martin shows placing it at the outermost layer right on top of the new sheathing, right below the roofing material. In this case asphalt shingles.

In Energy efficiency and durability | Asked By Eric Kronberg | Sep 16 14
4 Answers

Sill slope? Sealant tape?

How much slope is recommended for window sills? The house isn't in an coastal or otherwise very exposed location, but isn't in an arid or especially sheltered place either.

I'm planning on using beveled siding, placed on a flat plywood window buck, to help move water away from the opening; the exterior face of the window frame will be set about 4 - 5" back from the outside of the exterior sheathing. I'm trying to figure out how much extra room (vertically) to include in the rough opening.

In General questions | Asked By Graham Fisher | Sep 16 14
5 Answers

Air sealing question: Assistance requested for 6th side of building envelope

My husband and I are homeowners who are working on a very deep energy retrofit of our 1860's house, almost a total rebuild. We have learned so much from this website and the Q's and A's from everyone's contributions, so many thanks to all readers and contributors. We had already started the building process when we learned of this site, and are now attempting to make accommodations for deficits in our education and processes during the early stages of our build.

In Green building techniques | Asked By Howard Lederman | Sep 14 14
13 Answers

Retrofit heating system

We recently bought a second home in the Catskills, which was built in the 1930s. Current heat system is oil furnace forced air with a pretty new high end furnace. We had an energy audit done and found that the house was not well insulated at all and are in the process of takin advantage of energy efficiency programs to upgrade.

In Mechanicals | Asked By Carole Florman | Sep 15 14
4 Answers

Out-sulation vs Double Stud Walls

I was reading some old GBA discussions about double-stud wall designs and the added difficulty of keeping the sheathing dry (relative to wall designs that place appropriate amounts of insulation over the sheathing). This prompts me to wonder why the double-stud approach has its adherents when an out-sulation approach can be used to achieve the similar R-values and protect against thermal bridging while dispensing with the uncertainty regarding moisture. Besides being of general interest to me, I am hoping the responses will help me decide the 'best' way to proceed for a future project.

In Energy efficiency and durability | Asked By Rob Shuman | Sep 16 14
6 Answers

Raising a sunken floor

I am planning on leveling an 18” deep sunken living room (15 ft x 15 ft ) with the surrounding area and then install travertine flooring. To save some concrete, I am planning on using EPS to fill the first 14” of the sunken room and then poor a 4" thick concrete slab. I read an answer to a similar situation posted a few years ago that lead me to believe that the concrete slab my not be needed, and that I could possibly install plywood or hardy baker board on top of the foam with foam compatible adhesive.

In General questions | Asked By Andres Ferro | Sep 5 14
15 Answers

Spray foam & wood roof deck

100 year old residence is located in Zone 5 w/i 50 ft of ocean/bay & has a 100 mph design wind load requirement. It is located high on a hill & completely exposed. Vented eave ridge is not advisable in this area do to high driven rains. The home will not be the primary residence, therefor optimal heating, venting & dehumidifying will not be maintained 24/7.

The energy code requires 49R roof assembly for the proposed occupied attic w/ cathedral ceiling. 49R requirements & existing 2x8 rafters, limits choice of insulation to closed cell spray foam.

In Energy efficiency and durability | Asked By Sheila Sullivan | Sep 12 14
3 Answers

Is Thoroseal good for the capillary break on footing?

I'm looking for something that can be applied to green concrete (7 days after pour ok) that would provide the capillary break on top of the footing before the foundation wall is poured. Is Super Thoroseal (or regular Thoroseal or Thoroseal foundation coating) going to work?
Thanks!

In General questions | Asked By e c | Sep 15 14
Register for a free account and join the conversation


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