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4 Answers

Thermo-Ply under drywall?

I am working on a ranch style house. We have pulled all plaster and insulation from the ceilings in the house. As we start to put the ceilings back together, can I use a product like Thermo-Ply on the underside of my ceiling joist and drywall over that? That gives me the advantage of being able to put the ceilings partly back together, re-insulate the attic with blown insulation, and then drywall at my leisure.

I am putting blown-in to R-36, and will have an air space above to vents. No storage in the attic, and no mechanical.


In Energy efficiency and durability | Asked By Ralph Vickers | Apr 29 14
8 Answers

Roxul batts and Roxul Comfortboard insulation without plywood?

I'm building a timber frame house in Vermont and was thinking of using Roxul batts in the 2x4 stud walls (studded between the posts). Then putting 2" of Comfortboard on the exterior, then strapping vertical and horizontal for cedar shingles.

One question I have is that since I've made the timber frame so rugged and stiff, (I have hardwood 3x5 bracing going from close to the post tops down to the sill, it is not moving), I decided not to have plywood or rough-cut boarding on the frame. Is there any problems with this with air or vapor passing through?


In General questions | Asked By Seth Kelley | Apr 28 14
4 Answers

Manual J questions

I had a Manual J performed recently and also did one myself with http://www.loadcalc.net/ .

A few questions arose that I didn't have good answers to. Some of these questions might help other people doing a Manual J in the future.


  • Should the truss/joist space be included in the height of a room? I personally assumed yes if the truss was in the conditioned space but no if it was behind a good air barrier (roof, etc).
In Mechanicals | Asked By Keith H | Apr 29 14
3 Answers

Beginning of a big (for me) project

Looking for some input. It feels like I've done too much research and have started to confuse myself with all the options out there (icf/persist/remote/double stud/ radiant/ gshp, mini splits/ oil fired boiler, windows, siding, choices), So I'll at the beginning looking for some insight from the pro's.

The house will be in upstate NY CZ6A 99% temp of -6f, 43* lat. building on a hill overlooking a lake (lake is due east of building site) prevailing wind is from the west. I plan on doing as much of the work as possible (to keep the price in reason budget is pretty tight).

In Plans Review | Asked By Trevor Chadwick | Apr 28 14
5 Answers

Badly executed heat, what to do now? (To mini or not to mini)

Hi all,

I'm performing some repairs on my house and discovered that most of the central heating duct work was poorly executed and needs rework Or does it?

I have a fundamental question to decide that I think the GBA community could help me with:
- Should I repair the central heating system
- Should I largely abandon it for mini splits?

House Basics:
- 1976 split level (~6 elevations)
- Climate 5b
- Low slope black epdm roof (relevant to cooling)
- Furnace: 95% 2 stage ECM variable. 75k/115k btu. Fan rated 1100 to 2000 cfm.

In Mechanicals | Asked By Keith H | Apr 29 14
20 Answers

Pretty Good Wall Design - Maybe

The attached file shows a wall design concept for a new house build near Minneapolis, Mn. I'm trying to design a wall that is both easy to build and has good performance.

In Plans Review | Asked By Karl Overn | Apr 20 14
2 Answers

Roof SIPs - Zone 4B - (Is Joe Lstiburek in the house?)

When doing an OSB roof SIP with a polyurethane core in a Zone 4B climate. If one tapes the interior seams with a building tape and uses a peel & stick Butyl membrane on the exterior OSB.

Does one still need a "cold roof" above the roof SIP?

I am under the impression that with both seams (interior and exterior) are sealed with a vapor barrier (interior tape and exterior peel & stick), one can place a standing seam metal roof directly onto the Butyl membrane & roof SIP without needing a cold roof. My concern is of course the "SIP rot" issue.

In GBA Pro help | Asked By Peter L | Apr 28 14
2 Answers

Where to buy EPS foam (25 psi, termite-treated) for use under a concrete slab in West Virginia?

If someone could assist me it would be much appreciated. I have spent several days calling and searching the net. I am building a house with a large basement using superior walls. I want to insulate under the slab with 2 inches of eps foam but I cannot find anyone near that sells it. I want eps not xps. The house is being built near Charleston wv. I would not care to drive 1-2 hours to pick it up, but would like to find a company that could deliver it to the construction site. Closest I could find was a 6 hr drive and they would not deliver. Thanks for any help.

In Green products and materials | Asked By Chris Burgess | Apr 28 14
1 Answer

Custom polyiso roof-vent baffles + traditional unfaced fiberglass batts + poly vapor barrier (conditioned space) = Success?

If I build custom roof-vent baffles with polyiso board then fill the remaining cavity with traditional unfaced fiberglass batts, can/should I also install a Poly vapor barrier prior to dry-walling? If so what mil thickness would be recommended?

I am concerned that the PolyISO board would create a vapor barrier and then the poly roll would create another barrier and any leaks could cause moisture to become trapped in the batts and rot the rafters.

In Energy efficiency and durability | Asked By Logan MacKinnon | Apr 28 14
2 Answers

Crawl space fans


Does anyone have a recommendation for crawlspace exhaust fans?

Would an appropriately sized Panasonic be the simplest option?

In Mechanicals | Asked By Jill Neubauer Architects | Apr 21 14
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