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!

4 Answers

In-Floor Heat System - Electric Energy Source - Hydronic or Electric Resistance?

I am planning a remodel of a 100+ year old house in Seattle. We are planning on removing the existing forced air furnace and replacing with in-floor heating. The energy source will be electricity. It seems to me the most efficient method would be electric resistance instead of hydronic. Wouldn't there be a loss in efficiency (and a more complex system) if you use electricity to heat the water in a hydronic system versus the near 100% efficiency of electric resistance? The only benefit I could see to having a hydronic system would be to possibly tie it in with a solar water heater.

In Mechanicals | Asked By Sean McClintock | Dec 8 12
4 Answers

Cellulose batts; experience with?

I just found these, and my curiosity is piqued. Anyone have any experience w/ them? I'm curious about how they are for general fit (tight? gappy?) and how they are for cutting around oddities. I am really leaning hard toward cellulose now, the more I read here and elsewhere. Batts, blown-in, or some combination thereof, depending on costs and what you get out of it. thanks. j

In Energy efficiency and durability | Asked By jklingel | Mar 8 10
26 Answers

Vertical Rain screen wall in climate zone 4C

I am an architect designing a house on Salt Spring Island which is in Climate Zone 8. The code mandates rain screen and the client desires vertical red cedar ship lap boards. The house has very high ceilings at 14' and 12' which requires a fire break at 10'. My questions are to do with how to best design the wall to mitigate humidity inside the house and create the most energy efficient house possible for the owner.

My current wall build up is:

1/2" Wallboard with latex paint
2x6 stud wall construction with R21 Owens Corning fiberglas insulation

In Energy efficiency and durability | Asked By Marcus Springer | Dec 6 12
1 Answer

Insulation seasonal room

I have a outside deck that I recently enclosed. The deck has a fiberglass surface, which is now my roof ceiling. I poured a concrete floor and installed radiant tubing to attach to existing home system.
How should I insulate? Do I need to install baffles in ceiling, before insulating, or can do without. My house is spray foam and no baffles were used. I am not doing spray because to small for contractors to come out.
Any ideas

In Energy efficiency and durability | Asked By Joe Santos | Dec 9 12
2 Answers

I have some questions regarding reinforcement of garage slabs adjacent to poured concrete basement walls.

I am planning to build a retirement home with a three car attached garage. Two of the garages will be used as a shop, the other for a car. Construction procedures I plan t0 specify:
1. Insulate all garage slabs with 2" thick ESP foam board (R-10) + add 6 mil polyethylene under foam for moisture barrier.
2. Will specify re-bar grid in slab to prevent cracking + install side expansion bars adjacent to each garage slab.

In Energy efficiency and durability | Asked By Robert Weber | Dec 5 12
4 Answers

Questions, then more questions, then confusion

Love that GBA presents on so many topics. Is it possible, though at the conclusion of a thread for GBA advisors to condense many of the varying inputs into some kind of general consensus guidelines on the topic? Perhaps a detailed library could be referenced with more than drawings.

Is it just me or do other people stop when they see a thread they want to read because they're not sure if they have the time and stamina it will take to delve into all the asides and redirects that will likely leave them with more information but less resolved on the topic.

In General questions | Asked By tom ruben | Dec 8 12
5 Answers

Rigid board for cathedral ceiling

I just tore out the drywall on my cathedral ceiling on my lean-to addition and found no insulation at all...just the underside of the roof sheathing. I want to insulate before drywalling but can't seem to find any consistent information on how it should be done. I was going to go with spray foam but $1k for 96 sqft is crazy. I am thinking about going with ridged board against the bottom of the roof sheathing...maybe an R30. Will this work? Will I have any concerns with moisture?

In Energy efficiency and durability | Asked By B W | Dec 7 12
4 Answers

Is extra insulation in stud bays worth it?

I am planning to use Superior Walls “Xi Walls” for my first floor, which will be daylight on three sides. These walls are 10 ¼" thick, with 1 ¾" low-water concrete shell on the exterior, then 2 ½" of DOW Styrofoam that, according to the website, results in an R-value of 12.5. However, there are concrete studs at regular intervals that are wrapped with only 1" foam, as are the top and bottom beams.

Filling up the bay with cellulose would result in an R-value greater than 36. But given that the studs would still just have 1" of foam, would it still be worth spraying in the cellulose?

In Energy efficiency and durability | Asked By David McNeely | Dec 7 12
8 Answers

Vapor retarder on interior if exterior has vapor barrier?

This question stems from a different conversation on here and we need some more help.

We're in Zone 5A. Our exterior has plywood, tar paper, 1" of foil-faced polyiso foam, and red cedar shake. The framing is 2x6 wood construction.

The interior will be heated with wood stoves only. We know to never have 2 vapor barriers. What we're wondering is if we need an additional vapor retarder on the interior? If so, what sort of barrier do we need? (Spray foam is prohibitively expensive).

In GBA Pro help | Asked By user-1044776 | Dec 3 12
6 Answers

Ductless Heat Pump - Which one?

I am purchasing a ductless mini-split heat pump. I have had several estimates and in all cases the companies recommend a 12,000 or 15,000 BTU unit. Apparently the area I want to heat/cool falls just in the middle for their calculations. I have a 1,500 sq. ft. bungalow with a large open concept living room, dining room, kitchen and front entry which is where the head unit will be. Off the living room are 3 bedrooms (no hallways) 2 on one side and one on the other.

In Energy efficiency and durability | Asked By Robb Francis | Dec 6 12
Register for a free account and join the conversation

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