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Rifraf
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# Posted: 2 Nov 2011 08:56
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My cabin shell will rest on pressure treated runners.. on top of a gravel foundation.
I want to insulate the cabin as best I can.. what would you recommend for walls and ceiling ? I was thinking some sort of styrofoam insualtion between each stud everywhere around the cabin
would this be sufficient or do I need to wrap a plastic housewrap around the inside over everything first ?
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toyota_mdt_tech
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# Posted: 2 Nov 2011 09:14
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What is your climate like? If that way my cabin, I'd put a vapor barrier down over the ground beneath it. I'm in a colder climate, I wrapped the cabin in Tyvek then sheated the exterior, used pink insulation in the floors, walls and ceiling. Then wrapped it in clear plastic thermal barrier and its sealed tight with tape (son in law did it, he is a pro in construction). As for your floor. I'd put 2X6 over top of your floor, insulate it and sheet it again or leave it uninsulated. If you try to insulate it without being covered, you will get nothing but varmints in there and having no access means not able to service/repair it.
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Rifraf
Member
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# Posted: 2 Nov 2011 12:59
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well i cant do anything to the outside it came with treated t1-11 type siding already , my climate can get both very cold and hot somtimes humid .. im in the midwest usa.
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toyota_mdt_tech
Member
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# Posted: 2 Nov 2011 18:16
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Insulation may need a vapor barrier, especially in your area. Not sure what you can do.
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Rifraf
Member
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# Posted: 3 Nov 2011 09:44 - Edited by: Rifraf
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So perhaps I should run vapor barrier and insulation on the inside before I tack in my internal sheathing ?
after googling a bit , i see some people putting insulation then a vapor barrior, then sheathing on the inside, even in the ceiling.
Would this cause condensation at the outer edge of the vapor barrier inside and around the insulation.
I mean, ill have power outlets and media outlets that will let air pass from one side to the other in very mall amounts , wont that cause issues with barriers on the inside ?
Thanks
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razmichael
Member
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# Posted: 3 Nov 2011 13:40
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Vapor barrier "warm side in winter". This prevents the warm air inside the house/cabin from condensing out moisture in the insulation (thus reducing the insulation value and leading to mold etc). Although badly insulated houses will allow air to leak out through outlets etc, if properly done these will also be sealed with the vapor barrier behind (or a multitude of products designed for this). A house can be fairly air tight and then need some sort of air ex-changer. Same rule applies for a cabin if you want to do it right (as it sounds like Toyota' son-in-law did) - if insulating for winter, then the vapor barrier is on the "warm side in winter".
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Rifraf
Member
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# Posted: 3 Nov 2011 20:47 - Edited by: Rifraf
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ok great, thanks for the info
I think I have it. Vapor barrier everything on the inside of the house just on top of the insulation, under the inside sheathing.
Does this apply to floor as well.. My floor joists wont have insulation my plan is to have a pretty well constructed skirt around the cabin.
I want to add hard woods to the floor, so this would mean plywood then underlayment, then vapor barrier, then hardwood flooring ???
What should I do for air exchange.. would I crack a window in the loft or do I need to worry about this at all ? I wont have an attic of any sort.
thanks again, i'm very ignorant when it comes to insulation methods in general and really do appreciate your time here.
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easyshack
Member
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# Posted: 23 Nov 2011 15:54
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spray foam closed cell is best. R factobeing air th out rs dont mean zip without being air tight. fiberglass R factors are lies. the only way to get the R factor they say is put the fiberglass insulation in a glass jar with lid on it.
Before i used foam insulation i was not sure, but after 4 houses, i would never use anything else. It even add strength and also does sound barrier.
38 below zero and only used 1 1/2 cords of wood for heat all winter.
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PlicketyCat
Member
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# Posted: 26 Nov 2011 19:23
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Will you be having any air conditioning in the summer?
The "warm side" vapor barrier rule gets problematic in climates that are very cold in winter and very hot in the summer because the warm side is in the inside during the heating season (winter) but on the outside during the cooling season (summer). If you place the vapor barrier on the inside for winter, when the interior your house is cooler (from the air conditioner) in summer then the hot/humid exterior air could condense against the backside of vapor barrier inside the wall.
Proper vapor barrier application is extremely problematic in high-swing climates! In many of those cases, the recommendation (if you have an air conditioner!) is not use a vapor barrier at all, but to make sure that you use a 1-way barrier (like house wrap or tar paper) on both sides of the wall so that it keeps bulk water from entering the wall assembly but allows any vapor that may have condensed within the assembly to dry out of the wall in whichever direction it can given the season.
Moisture vapor will normally try to migrate from the most concentrated to the least concentrated, which also usually happens to be from the warm side to the cold side because warmer air can hold more moisture, but it's not 100% guaranteed. Someone who lives in a cool, wet climate could still have moisture trying to migrate into the house even though the inside is warmer because the inside air is still drier despite being warmer. This can also be a problem if you use a dehumidifier inside even though the ambient temps are the same inside and outside.
Best to check with reputable builders in YOUR area to see what they recommend... even if that defies the IRC (which is "universal" even though local climates aren't).
You need to be extra careful to seal/tape/caulk any infiltrations through the wall including the weather barrier (house wrap), insulation, and vapor barriers. Moisture migration happens at a relatively constant rate... if you're pushing 1 gallon through an entire wall assembly you probably won't have a huge problem, but if you're pushing that same 1 gallon through a single small infiltration in the barriers and insulation you will definitely have some problems.
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