best bang for buck on 5 month lake cabin

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best bang for buck on 5 month lake cabin

Postby jludman » Mon Aug 22, 2011 7:49 pm

I have a 20'x20' 1 bedroom cabin with no insulation whatsoever. It has 30 year old fake wood paneling, 2x4 studs followed by thin exterior wood with some holes and gaps. For a ceiling it has the roof - 2x6 supports, thin wood above that followed by shingles. It's zone 4, and open from May - October, but only occupied usually mid June to mid October. Our handyman calls it "the hotbox".

Since it is only open when our water supply won't freeze, I replaced our heater with a PTAC style heat pump.

My thought was to caulk as many gaps in the exterior walls as I could, and put hard foam insulation (2" seems to be R10) on the ceiling. If this is right, I have no clue as to the best way to seal the insulation to the roof or if a reflective barrier in the mix is worth it ... I don't really care if there's blue foam showing on the "ceiling". Anything that'll pay for itself in 3 years or so is worth it right now. I have to wait for longer turnaround improvements, I think.
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Re: best bang for buck on 5 month lake cabin

Postby Jackofalltrades » Tue Aug 23, 2011 10:12 pm

If you install 2" foam board (pink or blue extruded polystyrene) you can use 3" nails with plastic cap washers to hold it in place. Foam board is a dangerous material when it burns so it should be covered with 5/8" drywall or other suitable fire barrier (per code).

Is the paneling rigid enough that you can dense pack the side walls with cellulose?
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Re: best bang for buck on 5 month lake cabin

Postby jludman » Wed Aug 24, 2011 9:59 am

I didn't think about fire safety codes. Maybe there is an uglier alternative that is legal for a fire barrier? I can't find the paperwork, but we did have a quote for installing a real ceiling and insulation, and it was too much ($3,000 I think). Gross rent for the little guy is only about $5,000/yr.

I'm hoping that there's something that I can do to change the insulation in this cabin from "triple horrible" to just "really bad" for like $500 if I can do much of the work myself. I don't know anything about insulation yet.

Last season, we had total heating costs of maybe $200 with our propane furnace. I think our PTAC should reduce this cost by 50%, making it insignificant (usually just weekends when its cold). I am much more worried about reducing heat gain in midsummer (near 100% occupancy). When installing our PTAC the other day, the temperature inside was maybe 80 or a little more, while outside it was a pleasant 70. Some customers complained the main room of the cabin remained over 100 for several consecutive days (there is an A/C in the bedroom).

The ceiling/roof insulation situation is where most of the heat-gain comes from, right?

If I were to put insulation up against the roof itself, this would probably be incompatible with the future addition of a real ceiling. With a real ceiling, you want to have an air gap and soffets with temperature controlled fans to keep the air gap from getting too hot. And the insulation should be flush with the ceiling, not the roof. I think.

The roof is angled, maybe 12' in the front and 8' in the back.

Maybe I can hang some (fireproof) rigid insulation a few inches below the roof joists, so that all the air comingles up there. Then put a temperature engaged fan(s) to blow out the side of the cabin near the front, and some soffets on the back side for air flow. Center front seems best (middle of the highest point), but that's directly overhead of where people sit on the deck to look at the water.

The fake wood paneling is very insubstantial. The studs are much too far apart, and there's some horizontal ones in there for some reason. I don't want to do any insulation in the walls until I'm pretty sure I'm finished with all the wiring I need anyhow. We'll be replacing the propane stove with electric and maybe putting in a tiny electric tankless hot water heater in future years. You can't get much of a shower out of the 12 gallon hot water tank that's under the sink.

Thanks for the help.
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Re: best bang for buck on 5 month lake cabin

Postby jludman » Wed Aug 24, 2011 10:50 am

Continuing to spitball, maybe just putting the thin foil-fiberglass-vinyl directly onto the ceiling joists, and some roof venting between joists would be the most economical.
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