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!

5 Answers

Vicwest AWIP R-value

I'm insulating using foam from factory rejects of Vicwest AWIP roof panels. They are ridiculously cheap (7 cents per board foot) and the seller claims an R value per inch of 7.5

According to the manufacturer's specs, the panels are injection moulded polyisocyanurate and R per inch is 7.9 at 40F and 7.1 at 75F. This contradicts research cited here that polyiso loses R value with colder temperatures and starts around R6/inch. Vicwest seems to have the temperature coefficient backwards.

In Green products and materials | Asked By Jonathan Dalton | Feb 11 14
9 Answers

Minimalist on top of slab insulation options

Hi all,

I have an existing 1970s structure with a 42" below grade basement slab. I'm re-doing the flooring in the basement (settled on cheap laminate over expensive stained and polished concrete) and am wondering about getting a tiny bit of insulation on top of the slab before I install the laminate.

I have a 91" ceiling height. so I don't have the head height to consider any of the lovely options described in the lovely GBA q&a here such as 2" of XPS and an inch of plywood.

In Green building techniques | Asked By Keith H | Mar 17 14
3 Answers

ERV a bad choice for a tiny house near Toronto?

I am building a 187 square foot tiny house for my family of 3 in Barrie, Ontario and have some questions about ventilation. The house is decently well insulated and airtight, with 6 ½” inches of XPS on the walls and roof, 5 ½” in the floor, and a Solitex Mento 1000 exterior membrane.

In GBA Pro help | Asked By Travis Marttinen | Mar 25 14
11 Answers

Insulating a 1929 craftsman bunglow in San Diego

The exterior walls have no insulation, vapor retarder or barrier. Is an exterior barrier/retarder required when insulating walls? If so, what products are available that doesn't require removal of siding to install?

In Green products and materials | Asked By patrick owen | Mar 24 14
13 Answers

Looking to do away with my oil heat

Hello all, I was looking up information on Air Source Heat Pumps/Ductless minisplits, and stumbled upon this website, what a great find. Anyways, I’m hoping to get some information/advice as the best way to cut WAY down on my oil heat, so bear with me as this might get a little long.

In Energy efficiency and durability | Asked By Khouri Rice | Mar 24 14
11 Answers

Do bulb replacement programs save energy in heating climates?

My question is specifically about heating climates with a predominance of electric heat.

If a house is heated with 100% efficient electric heat, such as baseboard or panel radiators, does replacing incandescent bulbs with CFL or LED bulbs save electricity? Can anyone point to a study that has looked at this issue?

If a house is heated with <100% efficient electric heat (i.e. an electric furnace with ducts in the crawl space with the (perhaps) typical ~30% duct leakage, could bulb replacement actually be a step in the wrong direction?

In Energy efficiency and durability | Asked By David Meiland | Mar 21 14
4 Answers

Radiant heat improvement?

I have an ongoing renovation of my own house but any info will certainly apply to other projects that fall into this same scenario or possibly another job that I or others may encounter.

The current conditions are:
1. Hydronic radiant heat installed under existing 3/4" board sheathing which is under two layers of wood flooring for half of the area, the second half is tile underway, same build-up thickness.
2. 5 loops cover 925 s.f of first floor area, fairly equally sized loops.

In Mechanicals | Asked By Robert van Wert | Mar 24 14
4 Answers

Uninsulated barn with wood siding: does a radiant barrier make sense?

I have a 20x30 barn with wood siding (pine boards) and asphalt shingles over 3/4" T&G decked gambrel roof. The 2nd floor loft has a 17ft height at the ridge with zero insulation. I read your article about radiant barriers and an example of an uninsulated barn with steel siding and roof was mentioned. Would a barrier be functional toward reducing air temperature in my barn and if so, where exactly should it be installed? I would try to do this myself. Thank you.
Rob Cramer

In GBA Pro help | Asked By Rob Cramer | Mar 24 14
3 Answers

Getting heavy condensation on the inside of the exterior boards.

I'm in a 50s bungalow in southeast michigan that has a walk in closet built into one of the attics. The closet was recently gutted when my wife discovered mold on the drywall on the only exterior wall of the closet. The exterior wall was poorly insulated and I figured that's why it was wet. I left it open for two weeks to dry out, which it did so I installed r-13 faced fiberglass insulation and left it for a week. I pulled back the insulation a week later to find the wall was soaked again.

In General questions | Asked By Adam Karavas | Mar 23 14
3 Answers

Effect of adding cellulose insulation on top of existing R-19 fibergass batts

My builder has installed R-19 fiberglass insulation (with vapor barrior) in the attic of the 2000 square foot one-story house he is building for me in Maine. He now plans to add 13-14 inches of blown Green Fiber cellulose insulation on top of this. Cellulose insulation being as heavy as it is, my concern is that it will compress the fiberglass, diminishing its loft and hence diminishing its R-value. Does anyone have any data on the relationship between compression and loss of R-value with fiberglass insulation?

In General questions | Asked By Robert King | Mar 23 14
Register for a free account and join the conversation

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