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3 Answers

Air seal large gap around light fixture box

I've made it to nearly my last electrical box in the attic that holds a light fixture. I've used fire caulk for all of them, but this last one has a big gap on one side, probably a half inch wide.

Caulk won't work, it just falls in. I'm thinking either fiberglass mesh and duct mastic or UL 181 foil tape.

I have both of the above, I could buy Great Stuff Fireblock foam but since that still ignites at 240 degrees I doubt that's the best idea.


In Energy efficiency and durability | Asked By Jeremy M | Apr 7 15
4 Answers

Is rigid foam as sheathing cheapest way to meet code?

I know: it depends.
I found GBA's detail of 3/4 rigid foam on the framing with 1/2" ply-osb sheathing on top. this gives an easy nailing surface for shingles. So if I can use diagonal bracing, (steel or 1 x4) and xps foam and cellulose this will give me R= 22.25. (Good for Zone 5) and also 18.5+ 3.75. My question is now I don't have to worry about the condensation point because my sheathing is outside my insulation?

In Building Code Questions | Asked By Keith McGuire | Apr 9 15
2 Answers

My client has an old 1840s home that never had any kind of vapor/water barrier

It is simply clapboard nailed to studs. He gutted the old plaster wall, and had the stud bays spray foamed directly onto the old clapboards. A few popped loose on the outside, so they re-nailed them.
My question is: will the foam retain moisture and cause the clapboards to rot, or will he be o.k.?

In General questions | Asked By roger steinbrink | Apr 9 15
7 Answers

Cold storage room in a basement and a heat-pump water heater

So I'm planning to have a cool storage type room in my basement for food. We are heating with mini-splits, and will have 9.3 kW of PV solar. I'm considering placing a 80 gal AO Smith hybrid heat pump water heater in the cool storage room. Figuring if it is going to cool a room anyways, I might as well make it a cool storage food room, and insulate the floor above so it doesn't cool the floor above.

How much space(sq ft) should I allow for room the heat pump will operate in so that it works effectively? It can also be tied into our general storage room too - to allow for more space.

In General questions | Asked By brad hardie | Apr 8 15
0 Answers

Cost of European materials going down?

With the Euro getting very weak has anyone noticed materials from Europe getting cheaper? We weren't planning on getting quotes for European windows/doors because of price, but I was thinking that with the Euro plunging, maybe some stuff could be purchased 25% cheaper than a couple years ago.

In Green products and materials | Asked By Kristopher Steege-Reimann | Apr 9 15
2 Answers

What is the best way to build a 2x8 exterior wall and achieve R-40?

I am building a house near Toronto, Ontario. Winters are cold, and we do see our share of -20 or colder weather. Summers have been somewhat hot in last couple of years.
My wall section looks like this right now from exterior to interior.
Stucco>1"rigid foam board (taped seems)>2x8 studs @ 16"OC>2" closed cell spray foam> R24 Batt>6mm poly>drywall.
I am worried about any moisture getting in the wall so that is why I am considering doing 1" rigid foam board from the outside and poly from the inside.
Can anyone tell me if they have done anything similar.

In Energy efficiency and durability | Asked By Slobo Urosevic | Apr 7 15
5 Answers

I am concerned that spray foam, once installed, can become an accelerant in the event of a fire. Have there been any studies?

There was a new mansion built in Houston that had a fire. The house was completely destroyed. Spray foam was used in all the walls. I have not heard nor read anything about spray foam and fire.


In General questions | Asked By john winkler | Apr 8 15
15 Answers

Pricing per ton for GSHP and air-to-water heat pump

Is there a general rule of thumb for pricing of a GSHP and Air to Water heat pump for a medium sized installation of ~17 tons or 200,000 BTU/hr. $/Ton or $/BUT? What products fit this market segment?

Do you also have a general rule of thumb for an energy retrofit of a home in $/Ton or $/BTU reduced heating demand?

Is there an issue with using a GSHP in a climate where little cooling is required?

In General questions | Asked By Cathleen Dalmeida | Apr 4 15
20 Answers

Roof furring questions

When it comes to furring a roof, are 1x3 or 2x4 furring strips better to use? I assume the latter because they are stronger/wider and give a better grip area to the sheathing above. Spacing should be what: 12" or 16" on center?

My other question is with the sheathing above. I read that plywood is better than OSB although there has been a lot of problems at the lumber yards with plywood cupping. The lumber yard attendants said that the QC on plywood is really bad because it is so rarely used. I assume 5/8" sheathing is ideal for a metal roof?

In Green building techniques | Asked By Peter L | Apr 6 15
3 Answers

Use scrap polyiso for inground gutters?

I have bunch of scrap 1 1/2" fiberglass-faced roofing polyiso left over from basement insulation project. Next large project I will be working on is fixing grading issues around the perimeter of the house, removing all the bushes right next to foundation, and putting down washed p-stone (likely). I have read before on GBA about those inground insulation "skirts", but there XPS or EPS is recommended with EPDM on top. Would it be bad to just use scrap polyiso under EPDM?

In GBA Pro help | Asked By Apollo S | Apr 8 15
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