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3 Answers

XPS vs EPS — Below-grade slab insulation

Home Depot now sells pink XPS from Owens Corning. A 10 foot sheet by 2 feet wide was only $10 per sheet. The R-Value was R-5 per inch of foam.

I like the way XPS is easy to score and break without having EPS snow everywhere. The XPS also carries a higher R-Value per inch.

Which is better to use below grade under a slab? Which can carry the higher concrete loads of a slab?

In Green products and materials | Asked By Peter L | Aug 7 16
6 Answers

Can cellulose insulation be used on a foundation wall?

We are renovating a basement with a cider-block wall -- some above grade, some below. We put a watertight membrane on the outside and were planning on putting foam panels against the wall, taped, and then shoot cellulose to add insulation. A new cellulose subcontractor tells me that he never does that, and that we should only use rockwool. It seems to me that the foam will prevent condensation.Any thoughts?

In Green building techniques | Asked By William Murray | Aug 6 16
5 Answers

What is the roof raised heel height for R-60 insulation value?

What is a typical heel height to achieve R60 insulation value?

Wondering opinions on a somewhat standard height that I can tell my truss manufacturer. And what type of insulation you achieve this value with....blown-in cellulose, fiberglass, etc.


In Energy efficiency and durability | Asked By Adam Peterson | Aug 8 16
2 Answers

Best way to insulate raised floor over crawlspace

This doesn't seem to exactly correlate with any previous questions that I have found, but feel free to direct me to previous answers I may not have found myself.

In Energy efficiency and durability | Asked By Jim Erdman | May 18 16
3 Answers

Thermal break wall hydrant?

Dos anyone make a fiberglass, or other non thermal conducting material, freeze proof wall hydrant?

In Mechanicals | Asked By Calum Wilde | Aug 5 16
12 Answers

Zone 7 (Saskatchewan) — new four-season garage / workshop

Apologies if this has been asked before, I have read a lot of similar designs but have not found someone using this same assembly in a very cold climate. Here is the plan:

Exterior to interior:
5/8" Fiber cement board siding (Hardie Plank)
3/4" (1x4) wood furring strips (to hold insulation and act as vented rain screen)
3" Mineral wool (2 layers of 1.5" roxul comfort board 110, staggered seams). R=4.2*3=12.6
1/2" Fiberglass gypsum (GP DensElement, with PROSOCO fast flash to act as ARB and WRB). R=0.5
5.5" (2x6) wood studs with DP cellulose in cavity. R=18

In Plans Review | Asked By Craig Hoehn | Aug 1 16
16 Answers

Dehumidifier: running too much OR poor energy efficiency?

I just installed a 30 pint dehumidifier in the basement of my single story 900sqft house.

It uses about 4kWh per day to maintain a set-point of 55%, as measured by a Kill-a-watt.

I'm in Chicago, Zone 5.

My electricity bill without the dehumidifier from March-April was about 200 kWh/month.

Last month, with the dehumidifier turned on midway through saw a usage of 240kWh/month. A/C has not been used yet.

How can I determine if that 4kWh energy usage is due to it just running too much (e.g., too small for conditions?) or if the equipment just takes too much energy to run?

In General questions | Asked By Jeff Watson | Jun 6 16
8 Answers

Which way should the polyiso foil face when installing over drywall?

I plan to install 1-1/4" polyiso foamboard over existing drywall, then 3/4" furring strips, then 1/2" of drywall. Should the foil face towards the interior or the exterior?

If it matters, this is for Austin, TX 78722 where we need more cooling than heating, and I'll be using two layers of polyiso (1/2" + 3/4"), because I can't find 1" polyiso locally. I do plan to tape the edges to prevent degradation of the foamboard. Thank you for your help.

In Green building techniques | Asked By Michael Bluejay | Jul 30 16
9 Answers


I see GBA is being attacked by spam. I don't want to give this more attention than it deserves, but can someone tell me why this occurs? What benefit is there to whoever fills the Q and A with this content? If my question is some way aids them, please delete it.

In General questions | Asked By Malcolm Taylor | Apr 21 16
1 Answer

Anyone have an opinion of Rhino headers?

Are they worth considering?

In Green products and materials | Asked By charles CAMPBELL | Aug 6 16
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