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6 Answers

Spray foam optimal or does another solution exist?

In Energy efficiency and durability | Asked By Todd Munson | Mar 6 15
2 Answers

Membrain in walls, poly in attic. OK or not?

I join hundreds of others in trying to wrap my head around the nuances of vapor retarders.

In this thread in comment #32 Martin notes that ceiling poly is unlikely to cause much trouble and then in comment #34 he observes that another person should use Membrain in their walls.

Is there ever a need for Membrain in the ceiling or can cheaper poly always be used?

One other question.

Poly in walls should be on the warm side, Martin quoted the following from the same article:

In Energy efficiency and durability | Asked By Alex House | Mar 6 15
6 Answers

Recommended taping of plywood and foam layers

I am building a small casita (500 sq. ft.) in Northern California in a mild climate with hot summers. My wall framing is 2x4 w/ 3/8 continuous plywood shear (also insulated w/ R-13 fiberglass batt insul.), which I will cover with two layers of 1/1/2" Polyiso (Firestone) insulation (has fiberglass reinforced face). I will cover everything with Tyvek housewrap and fasten 1x4 battens creating a rainscreen, and attach lath and plaster as an exterior finish to the battens.

In Green products and materials | Asked By Dan Burgoyne | Mar 5 15
1 Answer

I live in the Northeast and have ice dam issues

I am having the attic insulated. I am getting conflicting answers re the attic joists. Should they be sealed and insulated? One contractor says no as needs to stay cold to prevent ice dams. Another says yes should be sealed and a radiant barrier added then blow in insulation. Who is right?

In Energy efficiency and durability | Asked By Robert Takvorian | Mar 6 15
5 Answers

Vented & unvented in same roof plane?

Hopefully you can all see this attached glass-house view of my proposed roof.


The open attic at the bottom right of the photo allows plenty of room to super-insulate, same too with the open attic above the 2nd floor ceiling, up in the top left/center of the photo. The sloped roof though poses a problem for super-insulation levels, just not enough depth. What I'd like to minimize is a path of least thermal resistance which would circumvent the high insulation levels in the open attics and favor "Easy" migration through the sloped roof section.

In Energy efficiency and durability | Asked By Alex House | Mar 4 15
3 Answers

Condensation in (conditioned space) attic, built to "environmental standards"

I am in need of a (seasoned) building consultant, familiar with New England climate, able to make an "on site" evaluation in Guilford, Ct. 06437, for an attic space that was built to environmental standards and is a conditioned space) -- air conditioning, HRVs, etc etc., for a client that has environmental allergies -- mold, fabric softener, petrochemical products etc.

There is condensation from the attic space, with leakage of water into and onto the first floor after one year. Thank you in advance. We need help.

In Project management | Asked By herbert suesserman MD | Mar 5 15
8 Answers

Insulation around a center chimney -- cape?

How would one insulate around the chimney in the attached pics? Would I start at the ceiling and just put a bunch of Roxul around it? How could air sealing work? Fireblock foam?

Bonus question: Is it too late to double stud these walls?


In General questions | Asked By stephen edge | Mar 4 15
2 Answers

Critique of cathedral ceiling and wall design - Swedish Style

Planning on building a 1-1/2 story, well insulated home using 14” I-joists as the rafters. Then running 2 x 4” horizontally. The I joist cavity will be air sealed. The 2 x 4” cavity will not. I will have an ERV. This idea is a mix of concepts seen on greenbuildingadvisor.com, buildingscience.com and the USA new wall info provided by Gregory La Vardera’s site on Swedish framing/insulation - www.lamidesign.com

In Energy efficiency and durability | Asked By Jeff Von Haden | Mar 5 15
4 Answers

New Mitsubishi Hyper Heat multi splits have finally arrived

I was having a discussion with someone on reddit and they mentioned having a MXZ-3C24NAHZ model recommended by a contractor, which I had never seen before. Googled it and, lo and behold, I find documents published just a couple months ago (like this one) describing a whole new line of Hyper Heat multi splits, sized from 20,000 BTU/hr through 48,000, and supporting 2 to 8 indoor units. HSPF rating is generally in the 9 to 11 range.

In Mechanicals | Asked By Nick Welch | Jan 13 15
10 Answers

Airspace for solar barrier

I am adding a solar barrier between layers of an alluminum roof. The existing roof is over a covered florida room. The roof system has a lower layer that is also the ceiling. The lower layer is connected to the top layer by 3 inch alumuinum I beams. The roof is insulated with porous styromfoam which is noisy when it rains and does not stop any heat penetration at all. Impossible to aircondition! I purchased a solar barrier to place between the layers of room.

In General questions | Asked By Phillip Ragan | Mar 4 15
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