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9 Answers

How to excavate trench in gravel when foam is above?

New slab on grade in Zone 4A:

I plan to have about 8” of compacted 1/2” crushed stone (no fines) with 2” of XPS sheet foam, then poly of course, then 4” slab. I will need to have two trenches of a thickened-slab type footer for bearing walls.

In GBA Pro help | Asked By David McNeely | Nov 16 15
13 Answers

Recessed Lighting / heat loss


New homeowner. I have 10 6" prescolite IC non-airtight cans atop my 2nd floor going to my attic and 11 of the same IC non-airtight cans in cathedral ceilings going to the roof. They are square housings.

I have explored all the options. The attic is covered with I believe r-30 batts and about 12" of blown-in cellulose on top of that. They put additional bats all around the fixtures like a moat but not on top of them -- not sure why, since they are IC rated.

In Energy efficiency and durability | Asked By Justin Brown | Nov 12 15
30 Answers

HRV vs. whole-house dehumidifier — Need help choosing

Hello, I have a 1700 sq ft house located about an hour North of Albany, NY. The house was built in 1998, and I just purchased it last year, it is fairly tight, but nothing exotic. It has 2x6 walls with fiberglass insulation,R-60 in the ceiling, double pane vinyl windows, and vinyl siding. The house has a few year old high efficiency forced air propane furnace and no AC.

In Mechanicals | Asked By Chris Yarsevich | Oct 26 15
3 Answers

Insulating a cathedral ceiling

I am building a cape style new house and I am trying to find a good cost effective green way to insulate the cathedral ceiling that is in half the house. I was thinking about putting roxul in between the rafters and foil faced foam over the rafters in full sheets and taping the seams to stop thermal bridging. I am in climate zone 6. Looking for any suggestions thanks

In Green building techniques | Asked By Sam Gagne | Nov 14 15
1 Answer

Garage moisture issues


Our garage is unfinished cement block, and I would like to finish it at some point with insulation and a stud wall. However, I am concerned by the amount of moisture that is currently present in the garage.

The garage is typically very damp and musty. When it rains, there are are discolorations on the walls that I assume are from water being wicked up by the cement (see photo below).


In General questions | Asked By Cory Kaufman-Schofield | Nov 16 15
2 Answers

Subfloor replaced. Now what? Insulation?

I live on the coast of south Texas and have recently replace the subfloor, will plates and some joists, all due to rot. The contractor added more vents around the house to improve moisture removal, but I'm not convinced that is all that needs to be done. The crawl space is dirt floor with numerous obstacles in place that cannot be removed (remnants of an old chiller system). I was wondering if putting up foam board under the joists would keep out moisture or should we try to encapsulate with closed cell insulation. The house was built in 1937.

In Energy efficiency and durability | Asked By William Mills | Nov 16 15
19 Answers

Accidental deep energy retrofit


I'm doing a gut renovation of a stucco-sided house in the high desert. We changed most of the window sizes to improve the passive solar performance of the house, which means a lot of stucco repairs. Now my contractor is telling me we should remove all the stucco and start from scratch, rather than trying to tie new tar paper to old tar paper at the studs. It'll cost a little more, but we'll get a better result.

In GBA Pro help | Asked By Reanna Alder | Nov 5 15
13 Answers

Exterior foam justification

I'm trying to make a determination about diminishing returns...

In Energy efficiency and durability | Asked By A W | Nov 14 15
41 Answers

XPS versus EPS Underslab Foam

Hi. I am back and forth on whether I should use XPS (blue board) or EPS for the insulation underneath my slab. I understand the qualities of each regarding water absorption and drying out, but would it (XPS particularly) affect the long term performance to the point where the slab is compromised? I also understand the pollution associated with XPS manufacturing. I have the option of purchasing 6" (house in very cold climate) of EPS (R-24) or 4" of XPS (R-20). The EPS is less expensive per inch, however, I need to pay for shipping which jacks up the price.

In Energy efficiency and durability | Asked By Matthew Michaud | May 2 14
2 Answers

Adding foam insulation to the roof on a manufactued home

I have a neighbor here in Vermont who needs a new roof on her 70's doublewide manufactured home. The roof currently has asphalt shingles on OSB. The roof is vented. I thought this might be the perfect opportunity to add some foam insulation on top of the existing sheathing. I can do metal over strapping on top of the insulation or asphalt over another layer of OSB. Which will perform better? Is the payback worth the cost? Currently heating with propane. The roof only has moderate slope. What do I do with the existing vents? Any suggestions are appreciated.

In Energy efficiency and durability | Asked By William Brooks | Nov 16 15
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