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13 Answers

We're about to begin framing on a new house in zone 6A (Minneapolis). From months of reading and following posts here, I've devised what I think is a wall/insulation strategy that will work. Does this look right, or are there any tweaks that could make it:
a) perform better (within reason; we're going after the "pretty good" model, not a Passivhaus)
b) more cost-effective
c) easier to build

The concept (inside to out):
- Drywall
- 2x6 stud wall
- Membrain or similar (6-mil poly if the inspector insists...sigh)
- 5.5" blown fiberglass cavity insulation (BIBS) = R-23

In Plans Review | Asked By Joshua Wyatt | Jul 28 14
5 Answers

Investigation revealed 3 problems: 1) no soffit vent; 2) insulation extending beyond the end of plastic rafter vents closing off the air channel up to the ridge vent; 3) no blocking above the wall to seal up the fiberglass. I've corrected the first two and caulked the ridge on the inside, but am unable to fix the blocking. The odor persists and I fear the fiberglass is contaminated with mold that the revived air flow won't be able to dissipate. Would pulling out the fiberglass (through the soffit to avoid major deconstruction) and filling the bays with foam work?

In GBA Pro help | Asked By Michael Roland | Jul 25 14
18 Answers

Hi,

We are building a duplex in Yellowknife, Canada - climate zone 8 (design temp minus 45 - same as Fairbanks).

Our winters are long and dark so some sort of (external) insulated window shutter is a huge energy saving opportunity. Our walls are going to R50, while triple pane windows get about R4.

I'm thinking of using 2-3 inches of Roxul board sandwiched between wood. That could give up to R12.

In Energy efficiency and durability | Asked By Andrew Robinson | Jun 10 14
3 Answers

My 1907 house has 2" x 4" rafters on 34" centers. After stripping to roof to the original 1 x 4 skip sheathing, I am planning to add 6" of polyiso foam and then a layer of plywood sheathing. The scrap rate is high if I have to cut every sheet to 48 x 70". Is there a precedent for using tongue and groove roof sheathing (assuming I can find it locally) without the seams landing on the rafters in this sort of application?

In Green building techniques | Asked By Keith Richtman | Jul 29 14
4 Answers

11' X 30' room. Fujitsu 9rls2h. The specifications shows the flow pattern is long and skinny. Would it be best to install at the middle of the long wall or install at the end on a short wall? There will be ceiling fans at the midpoint and at the point farthest from the minisplit if on a short wall.

In Mechanicals | Asked By Shawn Shumaker | Jul 28 14
2 Answers

A major source of heat loss/gain are the side east and west facing plaster & lathe side walls.

I've measured the temperature of those walls; they stay hotter than outside temps well into the night, and there's 5-10 degree increase as you go up the wall from floor to ceiling. They're actually hotter than ceiling and kneewalls alot of the time. There's also some moisture coming through; the plaster is rotted through under the window apron and there are cracks in the corners.

In General questions | Asked By Tomas Bridle | Jul 28 14
8 Answers

Hello, I really appreciate this website.

I understand that powered attic ventilators have a lot of problems. But my contractor is suggesting adding one to support a whole-house fan, due to the limited attic ventilation. (I do have some passive ventilation but not quite enough, and the gables are maxed out because it's a flat roof.)

So as long as I always run both fans at the same time, and as long as the cfm of the whole house fan exceeds the cfm of the attic fan, is there still going to be a problem?

Thanks!

In General questions | Asked By Robert Shelton | Jul 25 14
3 Answers

I am planning a 30'x22' farm workshop in Eastern Ontario, Canada. I want to end up with a level floor suitable for woodworking machines (table and bandsaws, planer, jointer etc) , Floor will be on grade, location is on a small rise and I will make sure there is good drainage away from building. I will place 2" of SM insulation under floor. I will most likely frame double stud walls and insulate with 6" to 7" of Roxul.

In GBA Pro help | Asked By mark godfrey | Jul 26 14
10 Answers

Reading about rainscreen siding systems it seems that the recommended gaps are typically 1/2" to 3/4" between the housewrap and and the back of the siding. Is there any reason why one couldn't do a very large gap using thicker furring material? Maybe around 3" or 4" between the siding and the sheathing for architectural reasons on a remodel? Would there be problems with having that large of a gap?

In Green building techniques | Asked By Kevin Hardy | Jul 26 14
6 Answers

Hi All,

We are using Foamglas for insulating under our slab as well as the slab edges (monolithic slab on grade). It is a requirement to leave a 2" gap above the Foamglas on the slab edges for termite inspections. Are there any options to satisfy this requirement, but not have the thermal gap? Perhaps industrial strength velcro or something :) ?

Thank you,
Stacey Owens

In Green building techniques | Asked By Stacey Owens | Jul 18 14
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