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Small Cabin Forum / Cabin Construction / Insulation under cabin
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hueyjazz
Member
# Posted: 20 Jan 2015 12:28
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My cabin is elevated about three feet from the ground on piers. With the winter in Upstate NY I do lose a lot of heat from this and it takes forever to heat up the cabin on a cold day. The walls and ceiling are insulated and I have decent windows. I know I want to insulate the underside but struggle as to how to do this. I wouldn't want to do anything that would trap moisture or become a mouse/animal haven. That seems to rule out fiberglass and rigid foam. Spraying on insulation also doesn't seem like it would work. What do you think of this stuff?
http://www.homedepot.com/p/Enerflex-24-in-x-4-ft-Radiant-Barrier-50-Box-126265/202456 788?srccode=cii_13736960&AID=10368321&PID=1319015&cpncode=45-23944634-2&cm_mmc=CJ-_-1 319015-_-10368321&cj=true

ladyslipper
Member
# Posted: 20 Jan 2015 15:05
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Hueyjazz, we insulated underneath our cabin with a layer of fiberglass pink insulation held in place with Styrofoam. The pink is on top of the Styrofoam. We then put Tongue and Groove plywood over the pink. So far so good although we do plan on stapling chicken wire underneath.
insulation.jpg
insulation.jpg


Quad_Hunter
Member
# Posted: 20 Jan 2015 15:28
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Think I'd rather utilize ladyslipper's approach. Protect with Ply or OSB and chicken wire.

Wondering about the R value of it?

http://www.radiantbarrierguru.com/r-value-of-radiant-barrier/

JJHess
Member
# Posted: 20 Jan 2015 17:31
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What I have done before and will be doing in the spring on our new cabin is insulate between the joists with fiberglass and then nail 1" foam board across the bottoms of the joists. Then we put corrugated steel over (under) the foam board. We get liner panels or cover sheets pretty cheap, usually the same or less per sf than ply or osb. The steel comes in 3' widths and we can usually order it to whatever lengths we want. It has the added benefit of keeping out mice, tree rats, porcupines and other critters.

Check with local pole barn builders, materials suppliers or surplus materials dealers for the steel, and also the insulation. There is a surplus materials dealer near me that sells fiberglass insulation 40% less than I get it at the wholesaler, and the same with the foam board. The last deal I got was $6/sheet for 1" foam. It's not the brand name stuff but it works in a lot of applications without the added cost.

Borrego
Member
# Posted: 20 Jan 2015 22:12
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Use I Beam joists, drop some 3/8th ply in the bottom and fill with your insulation. Easy. Done.

MtnDon
Member
# Posted: 20 Jan 2015 22:43
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I like insulation in a floor when there is no conditioned space below the floor, as with any cabin that uses a raised floor. However, I have personal reservations about infilling the joist spaces with insulation BEFORE the walls and roof make it a dried in structure. That reservation comes from having completed the basic floor structure with subflooring and then having a week to ten days of rain every day as I tried to get the walls up and a roof on. If I had insulated the floor first I would likely have had wet insulation.

We installed insulation in the floor after the structure was dried in. We nailed plywood on the underside of the floor joists after that in order to keep the rodents out of the fiberglass. It was definitely more labor. However I was more comfortable with the end result. That has worked for us. Something to think about.

As for that radiant barrier, I do not think it is worth the expenditure or the labor. It can be effective as a radiant barrier but it does zero to stop migration of heat by conduction. I believe most of the heat transfer in a floor will be by conduction, not radiation. Primary insulation in a building should be any type that provides resistance to heat movement by conduction. That's one reason home builders use things like fiberglass, blown cellulose and foams. Radiant barriers have their places, their uses. Many of the claims the manufacturers and vendors of radiant barriers make are exaggerations to some degree.

Jim in NB
Member
# Posted: 21 Jan 2015 06:24
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I have the same issue with my place - built in 2010 and have been thinking about what to do. I use my place April - Dec (snow makes it really hard to get in Jan - Mar). The issue as I have experienced it is not so much the heat loss thru the floor but rather the wind and cold air blowing under the place which wicks the heat out and keeps the floor cold - on days with no wind the place warms up pretty good. In the summer the place stays cool and I think part of that is because of the air movement under the place.

I am going to use PT and styro insulation and make a wood/insulation skirting around the permiter. I will attach several panels with hinges so that they can be raised during the summer to eliminate the moisture issue. It will certainly be alot less money and work.

silverwaterlady
Member
# Posted: 21 Jan 2015 08:37
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Why would spray foam not work?

creeky
Member
# Posted: 21 Jan 2015 09:27
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There's a good bit of knowledge on conditioned crawlspaces I read some years back at building science. URL

Helped a buddy fix his floor where he had infill insulation between joists. Like Huey he had an raised open floor. When we pulled up the old floor we found the insulation (pink) in pretty good shape. But they had put a vapour barrier under that stapled to the joists. The vapour barrier had trapped a lot of water. Basically he had a lake under his floor. The humidity had then ruined some of the subfloor.

The general construction quality of this building and the understanding of moisture was very poor tho... luckily we fixed it in time. And watch out where the vapour barrier is...

The solution I use is to put rigid insulation on top of the subfloor. Works a treat. Even if it is a pain to have to pull out the doors and raise them up (renovating). And then put down a new subfloor. Not doable in some situations I imagine.

In my "great room" I have a lightly insulated floor on a raised building. In the winter I seal the perimeter of the building and it helps a lot. A real lot. An immense amount. I think Jim you'll be quite happy with the insulated perimeter. The tighter the weather seal the better is my experience.

As I understand it, the problem with insulating between joists is the exposed joists get cold. Attract moisture. Freeze. Expand. Contract. all out of sync with the rest of the floor.

So silverwaterlady. Your spray foam will work as long as you make sure that the joists are completely covered. $$$. But you'll be toasty warm.

missouriboy
Member
# Posted: 21 Jan 2015 09:30
Reply 


Mine is also about 3 feet off he ground. I used fiberglass insulation and then plywood to hold it in place and keep the mice out. I also caulked all the edges and seams. Been two years and it has worked well so far.
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chasemichelle2014
Member
# Posted: 21 Jan 2015 12:07
Reply 


OSB or Plywood would be an option. Insulate between floor joist and attach the osb panels underneath. I would also advise to drill holes in osb or material used to allow air flow.

Malamute
Member
# Posted: 21 Jan 2015 12:25
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If a vapor barrier is used, it needs to be between the living space and the insulation.

My cabin is on piers. I had the dog water freeze on the floor in my cabin the first winter. I surounded the bottom with straw bales the first winter, then used fiberglass insulation between floor joists then 1/2" OSB unbder that to keep varmints out of it. Also built an insulated box for the water line coming out of the ground and heat taped it with a thermstatic controlled heat tape. I skirted the cabin with OSB.

Long term plan is to dig down a bit and pour a footer between the piers, then pour a wall or fill with stone work.

Bridge Boy
Member
# Posted: 21 Jan 2015 18:41
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I would agree with MtnDon. More labor time to install insulation and sheathing, but certainly worth the time and effort. I used batt insulation, sealed the bottom with OSB and screw fasteners. Had my son to help with fitting and lifting of the sheets of OSB. Then used 1 X 2 pine around the perimeter.
I never did apply any kind of a sealer or finish but seems to be holding up well.

If I ever do build a camp in the future I would most likely go with a concrete foundation. More money, but so many advantages.

Bridge Boy

Turbogeno
Member
# Posted: 22 Jan 2015 05:03
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I have about 6" of cellulose in my floor joists. It's probably settled a bit by now. The wind and cold can blow underneath. I was up there last weekend after a week of very cold weather (Adirondacks) The fan was off all night and the next morning (5f) the floor was still pretty cold but it was 70f at chest height. I'd hate to think how cold it would have been without the insulation. I do try to remember the slippers.

Geno

MtnDon
Member
# Posted: 22 Jan 2015 10:24
Reply 


Over Christmas - New Years,after 24 hours of wood stove heating the tile floor over most of the floor area was in the mid to high 60's and higher the closer to the stove you got. The farthest corner was still in the mid 50's. Exterior temperatures were lows in the single digits and highs in the high 30's.

After another 24 hours most of the floor was in the 70's during the day. So insulation does help a lot.

CanadianNorth
Member
# Posted: 22 Jan 2015 12:17
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I like a basement or even a well sealed, crawl space. That and metal siding offers the best protection against vermin getting indoors.

Scott G
Member
# Posted: 22 Jan 2015 22:50 - Edited by: Scott G
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im going with r20 batts between the joists, tyvek under that then exterior door cutouts under that providing another r7.5 and a nice layer of metal to keep the rodents out. Peeling off the topside metal from the cutout. Ill skirt the cabin with the cutouts as well gaining another 1.5 " of foam insulation there and metal on both sides for the skirting. Should keep the wind out and work well.

laudy
Member
# Posted: 23 Jan 2015 10:07
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I agree with missouriboy on this one. My lodge is elevated on concrete columns also. I used treated plywood on the bottom of floor joists, filled with insulation and then 3/4" tongue and groove O.S.B. Caulked all joints. Seen where someone else had the insulation exposed on the bottom and it was a haven for mice not to mention coons and others chewing it apart. Spend the money and sheet the bottom.
Laudy's Lost Lodge
Laudy's Lost Lodge


TheWildMan
Member
# Posted: 23 Jan 2015 15:17
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I have a similar setup, same climate (Adirondacks), my cabin started as a 12x20 high wall storage shed. i jacked it up about 3 feet and set it down on stacks of cinderblocks (had vermin under it and too much moisture, snow melt along sides resulted pools on the floor, living in a swamp and all), i used r5 foam board with an 8 inch space between them as skirting. a pot of water under the cabin does not freeze even if its 20 below outside. the foam board does not get bothered by water

MaxWebster
Member
# Posted: 25 Jan 2015 22:51
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What about spray foam? I've been told insects and rodents don't like it. I was looking at this as an option.

Steve961
Member
# Posted: 25 Jan 2015 22:55
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I have had closed cell spray foam underneath my cabin for over 4 years now. It's held up very well so far, and I've never seen any evidence of mice attempting to chew through. I recommend it highly, if you don't mind the extra cost.

TheWildMan
Member
# Posted: 26 Jan 2015 11:30
Reply 


the reason mice like fiberglass type insulation is because they can nest in it easily, i made the mistake of using some in hard to work corners, need to keep poisoning them en mass.

i tried getting spray foam first, the problem is that your cabin needs to be within about 100 feet of where they can park a trailer or equipment truck. or buy a one time use DIY kit for a couple grand. if you can't park a tractor trailer next to your cabin, then spray foam probably won't be available (they couldn't phisically get to my place, so i had to use what i could get)

hueyjazz
Member
# Posted: 26 Jan 2015 11:52
Reply 


Thanks for all of the tips. I got my path forward. Roll insulation with vapor barrier toward warm side. I may even leave a gap between vapor barrier and underside of floor. Cap the insulation with OSB. Makes sense.
My main objection to spray foam is it will trap any moisture coming from above. Considering this is a floor any liquids that come from above would settle on the foam. We use the cabin all winter. It pretty normal for us to track in snow. Dogs knocking over water dishes, mopping floor, etc.

Don_P
Member
# Posted: 26 Jan 2015 13:59
Reply 


Open cell spray foam will not trap moisture, it drops through but still has a good bit higher R/inch and much better air sealing than fiberglass.

MaxWebster
Member
# Posted: 27 Jan 2015 21:56
Reply 


I've got some building leveling to do this summer, once complete I'll be going the spray foam route. Haven't investgated the product much but had a local guy tell me he's used it under his cabin without an issue. I believe he mentioned he left the foam exposed, closed off the perimeter of the cabin (on piers).

BaconCreek
Member
# Posted: 28 Jan 2015 18:23
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Our cabin is on piers and we insulated the floor. Using someone's idea from this forum we tacked 1/4 mesh galvanized hardware cloth on the underside of the joists and made sure there was overlap. Also used spray foam in areas that looked like they might not be overlapped enough. This has worked well for over 2 years now. NO MICE or any other varmints. The only thing I have noticed is a dead wasp or two on the underside that crawled through the mesh.
We felt in super humid Kentucky this was our best option.
The biggest problem was trying to find that size of galvanized hardware cloth. I finally ordered it off Amazon.

Rowjr
Member
# Posted: 10 Oct 2015 08:52
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Quoting: BaconCreek
The biggest problem was trying to find that size of galvanized hardware cloth. I finally ordered it off Amazon.

would you have the information or description

Julie2Oregon
Member
# Posted: 10 Oct 2015 18:51
Reply 


Ace Hardware has it on their website. 48 in. X 100 ft. is $219.99.

I previously saw it at Lowe's, too. I'm very much interested in the rodent barrier properties.

MtnDon, in regard to insulation, rodent barrier, etc. and siting the woodstove away from a wall, when and how would you install the "fresh air" pipe? While the joists/subfloor/etc. was being constructed or would you cut through everything later when the stove was being installed?

MtnDon
Member
# Posted: 11 Oct 2015 15:27
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IMO,any time you know ahead of time that a wall or floor perforation is desired at some future time you should try to fit that in before the finish floor / wall is in place. Pretty much all "after the fact" work takes longer, costs more in time and maybe in money, etc....

Julie2Oregon
Member
# Posted: 12 Oct 2015 20:09
Reply 


Thanks, MtnDon!

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