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3 Answers

Can closed-cell spray foam be applied to the underside of the decking of a flat roof that has rigid insulation & EPDM above it?

I am from Winnipeg, Manitoba (Climate Zone 7a).
I'm planning to build a cottage with a low-slope roof (0.5:12).
I was planning the layers like this (top to bottom):

  • EPDM (fully bonded)
  • 1.5" HD Isoboard
  • 5.5" rigid XPS insulation
  • 3/4" T&G plywood decking
  • 12" I-joists with 3" closed-cell spray foam applied to underside of plywood
  • drywall

I'm assuming that that the close-cell spray foam will be acceptable as a vapour retarder.

In Building Code Questions | Asked By Jake Harms | Feb 19 15
3 Answers

I am considering using double stud walls in building a net zero house in Charleston, SC

I cant find any information on the best Exterior Wall system for a Hot & Humid Climate, does anyone have experience building in that environment?

In Energy efficiency and durability | Asked By Rick Fetter | Feb 18 15
10 Answers

Longterm durability of Youker system 1.5" thin slabs

John Seigenthaler describes thin slab concrete systems that can be used as thin pour slabs over subfloors. There is a specific mix (which I intend to follow) along with some control cracks.

Gypsum is not preferred due to thermal conductivity and cost.

Does anyone he any long term experience in the longevity of these pours? I was more concerned with making sure my subfloor was designed with little deflection of L/480 or L/600 to minimize the root cause of the cracking, floor the subfloor not supporting the floor evenly.

In Green building techniques | Asked By Michael McArdle | Feb 13 15
2 Answers


Does anyone have any rough ideas what kind of cost premium PERSIST and REMOTE are over standard upper end construction? By upper end I'm thinking well sealed/insulated standard 2x6, 3.0 ACH50, $300/sq ft overall, etc. Just trying to get an idea if we're talking 5% extra or 20%.


In Green building techniques | Asked By Walker Angell | Feb 19 15
8 Answers

What combination of foam insulation for this wall?

I've got a wall that has seen substantial water damage, and the existing fiberglass insulation is destroyed (along with the studs, sheathing, and sill, but that part I've got covered).

The existing wall was:
1/2" sheetrock, paper-faced fiberglass between 2x4 16oc, 1/2" ply sheathing, 1/4" EPS, aluminum siding

I despise fiberglass insulation. The contractor who is doing the repairs asked me what I would like instead of fiberglass, but I'm not sure what to spec.

I'm in central NJ.

I would prefer 3.5" foil faced polyiso.

In Green building techniques | Asked By David Pfeffer | Feb 18 15
1 Answer

To French drain & sump crawlspace next to full basement or not?

In my Frankenstein of the house I have three basements. Original one from 30s (concrete foundations and floor - full height) in the center of the long house. Also on one side I have 70s basement, that I want to finish at some point, since it has more than enough head room.

Both 30s and 70s basements have a sump. 70s basement has perimeter footer French drain that drains into sump pit with two pumps. 30s basement does not have footer drain, just the sump with lots of holes in the liner.

In GBA Pro help | Asked By Apollo S | Feb 18 15
10 Answers

Vapour barrier is installed...should I remove it?

My insulators have finished and installed a 6 mil vapour barrier....they blew in fibreglass insulation in the 2 by 6 cavity .I have 2 layers of EPS totalling 5 inches on the outside walls and have staggered the seams. The building inspector has passed the insulation .My builder is unsure of the need for an interior vapour barrier . The inspector said it's there now so leave it. My advice from this forum is to get rid of it or slash it to make ineffective . The house is being built in zone 6 climate in Canada .

In Building Code Questions | Asked By bob holodinsky | Feb 17 15
7 Answers

Converting Vented Attic to Nonvented Attic

I've been researching several methods to insulate my attic. First, some background.

I live in Maryland and own a house that has the HVAC system in the attic. Currently the attic is vented and has zero insulation anywhere. Not ideal!

From my research, it looks like the best option is to make the attic a conditioned (nonvented) space. I'm unsure of what to do, and I'm unsure of the most economical way to do it. The attic is fairly small at about 1,000 sqf total.

Option 1:

In General questions | Asked By Samuel Burton | Feb 10 15
4 Answers

What is the desired RH in a house to prevent the woodwork from cracking and splitting and what is best way to humidify the air?

I was recently hired as an owner's rep for a 7,000 sq new construction house that is being heated with hydro air and radiant heating. For the past year they have been working on the molding, doors and wall panels around the house that is starting to show cracking and splitting in various areas. Although I have never tested the humidity levels in the house, the temperature is constantly set to 70 degrees. The painter is claiming that the cracking is due to low humidity levels in the house. If that is true, what is the minimum humidity level and how is the best way to increase the humidity?

In General questions | Asked By Joseph Samsonowitz | Feb 17 15
5 Answers

Insulating behind a wood burning stove in a basement.

I'm in the process of finishing off my basement. Generally it stays pretty dry other than the occasional gutter malfunction. I built a 2x4 stud wall with r13 batts. Behind the studs and in front of the block is a layer of plastic sheeting. For the 1/2 of the basement that has been done for years, I don't seem to have many moisture issues. However, I've decided to incorporate the wood burning stove into the finished section. Same deal, 2x4 studs with unfaced batts in this section covered by concrete board and eventually will cover that with stone.

In General questions | Asked By Mike Marino | Feb 16 15
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