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jkycia
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# Posted: 29 Apr 2011 11:01pm
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Hello
I am planning to insulate my small cabin.
Wondering if this experienced group can warn me of mistakes or give advice. I would like to be able to use it year round.
At this stage I am not worried about expense. Considering the ultimate
setup. Screwing up with issues of moisture barriers and irreversibility of
foam is what worries me.
I have a small cabin. 100 sqft area on ground floor with attic (bunkie)
in Ontario.
My plan is to insulate the attic, walls and floor.
The attic has 2x8 beams 16" on centre.
The floor has 2x8 beams 16" on centre.
The wall are 2x4 beams 16" on centre.
It has three 2'x4' windows and a door on ground floor and a smaller window on top floor. (if screw up insulation I will figure something
out for winter (maybe add shutters and foam)
Ok. I have already put in a ridge vent on roof (maybe a mistake or waste) I plan to spray foam the roof beams, not use foam baffles and ignore the ridge vent. The advantage is more insulation. The worry is I am screwing up with moisture issues that I may not understand.
The other option was to put in baffles and then spray but that seems to
lose insulation value and the baffles may not be necessary.
For the floor I will spray insulate and staple in metal screen to protect from animals.
For wall I would put in fiberglass batting on inside. On outside I am considering
adding 1"foam then thin wood strips as a spacer and then cedar siding running horizontally.
Does this sound good? Any advice.
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soundandfurycabin
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# Posted: 1 May 2011 03:58pm
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If you're not worried about expense then spray foam the walls too. Since they have the least room for insulation, they will get the biggest benefit. If cost becomes an issue, then I'd put fiberglass batts in the floor instead.
You are right, you don't need the ventilation chutes in the roof if you use spray foam. This sounds like a limited use cabin, maybe weekends and a week here and there. Under those conditions, moisture isn't going to be a big concern anyway, no matter how you insulate.
With a very tightly sealed cabin, you will have to make sure there is adequate fresh air. If you install any kind of stove or heater, make sure it has its own fresh-air intake and get a carbon monoxide detector just in case.
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jkycia
Member
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# Posted: 1 May 2011 08:17pm
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Thanks for the advice.
Yes I plan to get a direct vent heater. Not sure which type yet.
I have not thought about a stove.
I will get the carbon monoxide monitor.
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bushbunkie
Member
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# Posted: 4 May 2011 05:44pm
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Hi jkycia,
Nice to know there are other cabin dwellers near by!
Follow up to your questions on my thread...
Many options/choices for insulation I found when I was exploring the issue as well...
1. I wouldn't go too crazy insulating, as a 100 sq. space is pretty easy to heat, esp. the loft where the kids get too hot!
During the day I heat with a sunburst burner on a propane tank...keep it on low. At night, i use a microfurnace 'cause I have the cabin wired for a 2000watt generator...does the job at -20C.
The generator is a whisper quite one...and is actually very quiet.
I will be installing a vented furnace, since I can't find a woodstove small enough...it would just heat you out of the cabin.
2. My walls are 2 x 4 stud on 16" centres...I used fiberglass batts and vapour barrier...worked well. Did the same for my ceiling..2x4 rafters @ 24" centres, but didn't work...moisture build up in the vapour barrier so I ripped it out. I will be putting styrofoam sheets up between the rafters...allowing for air flow at the bottom and top.
The foam board will give me 2" clearance from the roof boards for air circulation as well.
I considered foam, but decided against it. Once you foam, you can't go back and I'm not crazy about all the chemical foam stuff in such a small confined space as a 10x10 bunkie....just a personal preference.
3. For my floor...I'm insulating over my sub floor with foam board and am putting down a second floor over that. I've allowed for the extra 1.5 / 2" under the loft area...it's about 6'5" right now.
Cost was a factor with some of our decisions...but I must say, a little bunkie heats up quickly when you have even basic insulation, a few bodies inside and a heat source. My kids love it.
We put in a well last summer with a handpump...made all the difference.
Send me some pics...I'd love to see your place!!!
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jkycia
Member
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# Posted: 4 May 2011 07:13pm
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If I am doing this correctly, there should be a picture of the shed
Its floor is 8'x12'
Yes, using the spray foam is a little worrying because of how permanent it is. Your experience with moisture on the ceiling is also worrying.
I think the problem could be because you only had 2x4 on the ceiling.
That is not much insulation so the bottom of the ceiling could still have been cold. I think I have read that even 2x8 is thin if you are going to
have a cathedral ceiling settup. That is why I am thinking I need as much
insulation as I can get and skip the foam duct.
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bushbunkie
Member
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# Posted: 5 May 2011 07:56am
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looking good!
After I tore the vapour barrier down from the rafters in the loft, the loft was fine and the wood rafters dried immediately...wasn't a big deal.
After more research...the rafter size is not the issue....I made the bunkie too air tight.
This is why I'm leaving breathing space around the foam insulation in the loft rafters and will not be putting vapour barrier back.
I'm also putting a small vent in the wall at the peak.
I use the bunkie up until late fall and then go up around this time of year. Summer is great, as lake huron is at the end of the road...five minute walk. Lake access...but not the taxes!!!
Probably will never use for middle of winter to stay over...get;s too small with two boys, a dog and all the winter clothes...tried it...wasn't fun.
Long term goal is to build a 1000 sq. ft. cabin (minimum allowed)...700 ft footprint / 300 ft loft...passive solar with a woodburning stove. Stay off the grid and away from the ridiculous hydro bills...if possible!
Your place will look great with cedar siding!
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JH Fish
Member
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# Posted: 5 May 2011 02:19pm - Edited by: JH Fish
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The foamboard or plastic trays attached to the underside of the roof deck between the rafters before you put in fiberglass insulation serve to facilitate air flow from the soffit up to the ridge vent. Without that space the underside of the roof deck will sweat and cause moisture build up.
There is one thing to consider with some types of the spray and cure foam insulation - they are urethane based and can be VERY combustible. Read the data that comes with it.
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rayyy
Member
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# Posted: 6 May 2011 05:27pm
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Unless your boiling a lot of water or taking a nice long hot shower,I don't think you will have a moister problem.Moister accumulates on the coldest surfaces such as windows and any thing metal.If you were just to insulate with standard craft face insulation that would be fine.It's important to have a "vented to the outside"heater,though.NOT A VENT FREE heater.
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PlicketyCat
Member
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# Posted: 9 May 2011 03:20am
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Floor and ceiling usually need higher insulation factor than walls... so you're headed in the right direction with the 2x8 & 2x4 combo. With only 100 sqft to heat, you could probably get away with regular batt insulation. If you're using vapor barrier or spray foam in the ceiling, you may be able to get away without venting your roof since you shouldn't have too much moisture without a ton of boiling water, a humidifier or a shower and the higher insulation values should keep any moisture from condensing since the loft is a heated space.
There is still a hot debate (or rather a cold debate) on whether you need to vent a cathedral ceiling like you need to vent an unheated attic roof. The jury is still out, but we decided against venting our 2x12 rafters with dense pack blown cellulose and vapor barrier on the warm side (total of R-60). With spray foam and dense pack cellulose, the air in the rafter chamber doesn't move, so there is a very effective moisture and air infiltration layer. Venting baffles sandwiched in this layer may actually introduce more problems than they solve (although highly recommended for fiberglass batt or blown insulation).
Blown cellulose and cured closed-cell polyurethane spray foam is flame-retardant. The PU foam is really only a risk for a few weeks while it completes it's curing process. We contemplated PU over cellulose, but it wasn't an option for us DIY in the bush like cellulose was... but the insulation per inch numbers are comparable, and cellulose is a lot less expensive.
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soundandfurycabin
Member
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# Posted: 9 May 2011 04:16pm - Edited by: soundandfurycabin
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The heat loss, per square foot, depends on the inside temperature, the outside temperature, and the insulation between. In a reasonably well-insulated and sealed building, there shouldn't be much temperature difference between the ceiling and floor. The outside temperature will also be the same, and so ideally the walls and roof would have about the same level of insulation. Roofs usually get more only because there is more room for insulation in the roof than in the typical stud wall.
If a cabin is on piers and the underside is not closed in then the outside temperature under the floor will also be about the same and so the floor would also ideally have about the same insulation level as the walls and roof. But if the crawlspace is enclosed, then it will stay a bit warmer under there and the floor insulation can be reduced compared to walls and floor.
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PlicketyCat
Member
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# Posted: 9 May 2011 04:50pm
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Keep in mind that the ceiling and roof are the same thing if you have a cathedral ceiling (unless you're building a double roof system).
It's also important to adequate insulate the ceiling and the separate roof if there's unheated attic space... in the unheated attic, it's more important to highly insulate the ceiling/attic floor than the roof.
Over an open crawlspace, insulating the floor to the same R-value as the ceiling/roof is a good idea since it's a solid area with a lot of conduction. Even over a closed crawlspace/basement or an uninsulated slab, your floor should still be a little higher than the walls if you live in an area with cold winters. Up here, for instance, it's not uncommon to see insulation between the ground and the concrete slab and then more insulation in between the floor joists as well. In a warmer climate you can probably get away with the same R-value in the floor on a slab as you put in the walls.
The biggest reason that walls are usually less insulated (besides being 2x4 or 2x6 studs instead of deeper joists/rafters) is that you have doors and windows in the walls that reduce your R-value anyway... super-insulating the walls would be kinda like reinforcing the fence but leaving the gates open ;)
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