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Small Cabin Forum / Cabin Construction / insulation under cabin
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sparky30_06
Member
# Posted: 27 Nov 2018 09:20
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So when I built my shack I didn't put any insulation under the floor and now i'm thinking it might be a good idea. Anyone ever used this product and installed the double layer like they show?

https://www.reflectixinc.com/applications/diy/diy-crawl-space-r-21/

SCSJeff
Member
# Posted: 27 Nov 2018 10:08
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Sparky,

Same setup. Cabin on piers. No insulation on floor. At this time floor is not finished and still walking on the plywood subfloor.

I haven't used it. But, I look at it ever time I'm at Lowes and I've watched the videos.

My concern is condensation and/or spills getting trapped in between. Especially if I end up putting sheet vinyl down inside... Although, I have that concern with other insulation methods too...

ICC
Member
# Posted: 27 Nov 2018 17:54 - Edited by: ICC
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Not a fan of reflective insulation. Especially not a fan when it is the only form of 'insulation'. I do believe it can help, in some situations, when used as an adjunct to some other form of insulation that reduces conductive heat flow. Most of those claims of big R-values have lots of fine print or are unproven.

Have a read on this link, https://www.greenbuildingadvisor.com/question/why-is-reflective-insulation-still-bein g-sold-by-hd-and-lowes-and-used-by-many-contractors

The closing paragraph from the article states, "A copy of a thorough 2010 study by the Canadian National Institute for Research in Construction is also attached. Their conclusion: In a perfect state (with no dust on the surface), a radiant barrier with an air gap increased the efficiency of insulation in a wall by 10%. In other words, if the wall was already R6, adding ‘miraculous’ foil bubble wrap added .6, for a total of R6.6."

Princelake
Member
# Posted: 27 Nov 2018 19:04
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Isn't the proper method of insulating a crawl space is to lay heavy duty plastic on the ground then insulate your skirting. Then adding a form of heating down like duct work or base heaters because heat rises. Basically treat it as a mini basement.
Now in the cabin world it's alot harder to heat that space with say a wood stove or propane heater. In a small cabin this might be a decent idea if it can actually give you r21 even if it worked out to r12 the same as a 2x4 wall itd still be a half decent product.

sparky30_06
Member
# Posted: 29 Nov 2018 11:35
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Fortunately for me I'm not dealing with nasty cold northern winters, but we did drop down into the low 40's at night and will get frost too. I'm not going to enclose it and make a crawlspace, that's just asking for critter and snake trouble down here. Last thing I need is a rattle snake home. Just looking for a little something. The floors are 3/4" TG plywood that we sanded then coated with 3 coats of floor stain & Poly. They turned out nice but need a tad bit of insulation and vapor barrier.

creeky
Member
# Posted: 29 Nov 2018 12:08
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I would skip the vapour barrier. You get enuf of that from the poly.
If it were my money I would put rockwool between the joists and then staple a good metal screen on the joists.

For your climate r14 or 3.5" of insulation.

The benefit of rockwool is the hydrophobia (ha) it repels water. Breathes. Is fireproof.

For an open to the exterior build that should work. Other folks have more experience with metal screen for critters.

Rooker23
Member
# Posted: 29 Nov 2018 12:09 - Edited by: Rooker23
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Isn't that rockwool stuff good for this type situation? Thought it repelled water and critters hated the stuff?

I think this is it on youtube

https://www.youtube.com/watch?v=zd9RKeTrdXI

snobdds
Member
# Posted: 29 Nov 2018 12:21
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I'm on piers so I went under with a spray foam kit. It was one of the messiest things I've ever did, but I put about 6 inches of foam in each joist.

To date, that has proven to be the best actual change in cabin temperature yet.

Just
Member
# Posted: 29 Nov 2018 13:26
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staple 4 in. of roxol rock wool insulation paper backed to the bottom of your floor , 90 cents sq ft .Cover the bottom of the floor joists with 1/2 in. pressure treated ply wood , 1.33 sq ft keep the verman out . Canadian prices. Don't do one without the other .

NorthRick
Member
# Posted: 29 Nov 2018 14:52
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Our cabin is on piers too. I put sheets of 2" foam board between the floor joists. Only about R10 but made a world of difference in the cabin, especially on subzero (F) mornings.

So far, haven't had any critter trouble with it.

Gone2TheCamp
Member
# Posted: 2 Dec 2018 14:45
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No idea what the best thing for your particular application, but I just build and have stayed there around 10 nights, the coldest being around -15c. My floor was nice and warm on my bare feet (It's one of the things I was anxious to test, to see if my gamble paid off.)
My floor is about 2' off the ground, no skirting yet, 3 beams on blocks, 2x6 joists, a layer of reflectix on the joists, then 3/4" t&g OSB on top of that. I have yet to lay my floor covering, so the only thing between my feet and the -15c outside was the OSB and the reflectix. The warmth of the floor turned out even better than I had hoped.

I've never used it before, and never spoke to anyone (personally) that did...I have to admit that my decision was based pretty much 100% on the advice of the guy on youtube that built 4-5 cabins and has switched to reflectix.

Word on the street is that critters leave it alone, and it makes sense....there's nothing for them to get 'in' so it's not attractive to them. In the end, I decided that I'd take a chance on the reflectix because I could always put on an extra pair of wool socks....I'll take that over lying awake all night listening to critters scurrying around. Turns out, the floors are nice and warm.

Now, maybe my success is due to the fact that I laid it out on top of the joists and essentially made a solid sheet out of it, then laid down the OSB. Possibly won't work as well if it's just added after the fact between the joists? Sorry, I don't know. But if you search youtube for: insulate cabin floor rodent free.....that's the guy that sealed the deal for me.

I don't know much about the science behind it, all I know is that each time I walk around on the OSB I'm pleasantly surprised. So far, I'm 100% sold on it.
Again, my opinion is just based on my experience so far...-15c, floor is warm.

Princelake
Member
# Posted: 2 Dec 2018 20:21
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I watched buddy's video on reflectix and it seems simple but from what I'm understanding is that for the product to work properly from the manufacturer website you need an air space. So to me stapling it to the bottom side of the floor joists will give you an r16 with air space. With the method you did and the guy on the YouTube video your only getting an r3 with no air space.

old243
Member
# Posted: 2 Dec 2018 20:42
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At our hunt camp, which is on piers about 2 feet high. We just had 5/8 plywood, as the floor. we strapped the floor on top of the plywood and added 2 inches of pink rigid insulation. Then 5/8 plywood on top of that. It made a huge difference.
In our area porkypines can be a big problem, they love to eat plywood. We bought used roofing steel and covered the bottom. We added a piece to the camp and used 2 inch rigid form between the joists held up by strips, then steel on the bottom. Camp is now not bad to heat. old243

Princelake
Member
# Posted: 2 Dec 2018 20:59
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I've been doing some more reading on this product and greening building and building sciences all are saying this " magic" reflective wraps are all scams.

SCSJeff
Member
# Posted: 3 Dec 2018 08:23
Reply 


That's the same conclusion I've seen in my research too... That it does have some value in warm clients during the summer (IE: on the roof). But, not much (if any) value by itself in cold climates.

Still... I'm tempted to buy a roll and test it under a small section of my cabin (maybe under the bedroom that always seems colder on the feet than the rest of the place)

Gone2TheCamp, Are you saying you sandwiched the reflectix between the joists and your floor?

Gone2TheCamp
Member
# Posted: 4 Dec 2018 12:22 - Edited by: Gone2TheCamp
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Yes...my place is 12' deep, 16' long, with 12' joists running on 16" centers.
I bought the $140 roll of the 4'x50' reflectix at home depot. I ran it in 4 - 4'x12' strips along the joists, using the entire roll minus the last 2'.

I ran the seams edge-to-edge along the joists and didn't overlap where they met.

Then I laid the 3/4" tongue and groove OSB over top. That's all my floor is at this point...2x6's, reflectix, then 3/4" OSB.

And I'm not kidding when I saw that I walked around on it in my bare feet at -15c outside, no skirting. I don't know how high it really is, but I could shimmy around under it on my back, and then I raised the whole place around another 8' after I was done building.

Every time I step on it I'm baffled that it's so warm. I don't have any scientific data, and don't pretend to know an R value from my elbow....but I can say with 100% confidence that my floor is warm at -15c outside.

Below (picture) is the 2x6 floor with the 4 strips of reflectix on it, followed up by the first 1/2 sheet of OSB.
In the picture it might look like the joists run the long way (side to side) but that's just the waves from it being rolled. The joists run front to back.

Oh, and we laughed at the warning on the package about being careful when working with their product in direct sunlight.....until the sun came out. I kid you not, if it's sunny out, wear sunglasses.

And the picture, yes, the floor is sitting almost on the ground, and you're thinking what's with the posts..and why is there a roof before the floor....? The roof and posts were built several years before, and a slide-in truck camper served as my cabin for a bunch of years, with the future plan to be to 'just lift the roof, build under it, set it back down on the walls'. Sounds easy when you say it, right? Anyway..that's a whole other thread.
[img=null]null[/img]
Reflectix
Reflectix


sparky30_06
Member
# Posted: 5 Dec 2018 07:59
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Gone2TheCamp
Doing what you did, did cross my mind but I wanted to glue and screw my T&G down to my joists so couldn't do that.

I'm thinking I will try the bubble route and if that doesn't work I'll put rockwool in and then close the bottom up with metal tin or plywood, just need to make sure she can breath.

Gone2TheCamp
Member
# Posted: 5 Dec 2018 09:50 - Edited by: Gone2TheCamp
Reply 


Could just leave a gap between the seams of the reflectix? Staple the edges out closer to the edge of the joist, run a bead of adhesive down the wood on the gap...? If the glue is to combat squeeking, would you get any squeaking if the T&G wasn't actually touching your joists (due to it having a layer of reflectix between them)?


Anyway, again...I don't want to say "Yes, someone should or should not do this."...because I'm not qualified to do that in the least. But, I did want to confirm that I had indeed used the product you asked about, and was/am very very happy with the results, where others had read that it was kind of 'snake oil'.

If anyone's interested, Saturday night is supposed to be -16c here. Where the camp is has some more altitude to it so it's always a couple degrees colder.
I could record some inside/outside/head-height/floor-height temps....again if anyone wanted to know....
If so, new thread, post results here? Does anyone even care? haha
Sat Night Temp
Sat Night Temp


beachman
Member
# Posted: 5 Dec 2018 10:46
Reply 


I care - also in NB but only use the place sporadically in the winter. I have no floor insulation but walls and ceiling are well insulated. Spring, summer and fall make no real difference but in winter the floor does get chilly and I may have to do something. So many other priorities, this may have to wait - although, the reflectix sounds very interesting. That said, I like to be able to get at the underneath of the cabin in the event I have to install something so maybe rock wool would be the answer? I think someone said the mice do not like this stuff very much.

Princelake
Member
# Posted: 5 Dec 2018 12:37
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I've been thinking about this and what I'm thinking is if you put any type of product close to it will have the same results. I bet if you put even vapour barrier or even tarp material it will work the exact same stopping/slowing down heat transfer with a fraction of the price. When building a new home the walls get insulated and vapour barrier put on the ceiling then drywall goes up then blow in. Before the blow in your be surprised how well just vapour barrier holds the heat. Or say those flimsy pop up ice fishing shelters it's just crappy canvas and with a little heater your in your t-shirt.

Gone2TheCamp
Member
# Posted: 5 Dec 2018 12:57
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Beachman..I looked at a couple shoreline picture in one of your posts and thought..."Hey, that looks like Lake xxxxxx." My favourite lake in the world...I'm just 'itching' to go back there again. Not to be creepy, but you're in between the point with the campground (the name would give it away), and the municipal boat 'ramp' right.....how close am I?

myself different combinations of the wife and kids have rented a cabin there several times (they're likely gone now), and camped likely a dozen times up near the...smaller lake....on what was a big piece of empty, sandy land. Likely has trees 50' high on it now. I have a ton of pictures dating back close to 20 years, if you have any interest in that sort of stuff...

beachman
Member
# Posted: 5 Dec 2018 14:16
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Gone - you've got it! The main place was there before I was born but I have been there for the better part of 65yrs. Most places in NB are beautiful. There might be a rental or two left but the little store is no more. Drop by next summer if in the area (no road - water access only). I actually live in Albert County.

sparky30_06
Member
# Posted: 6 Dec 2018 08:47
Reply 


Gone2TheCamp
I glued and screwed the floor to help flex when I move it. The land I built it on is leased land so someday i may have to move it and I designed it so it could be skidded, if i'm moving to a different part of the property, or I can winch it up on a trailer and head down the highway.

Gone2TheCamp
Member
# Posted: 6 Dec 2018 09:28
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We're in nearly the same situation...Mine also had to be built portable as I'm on land that I'm given the use of currently, with the promise that I have dibs if/when he decides to sell. Everything about the land is perfect except for a camp full of hard-partying yahoos a ways down the road. There's enough woods between us that I can't see them, and they keep to themselves and cause no problems except the noise. I can endure listening to the thump thump thump of subwoofers until 6am once in a while, but only because I can keep telling myself "The land is free...the land is free...".

smallcabin
Member
# Posted: 6 Dec 2018 17:35
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Quoting: Gone2TheCamp
Again, my opinion is just based on my experience so far...-15c, floor is warm.




Drinking a couple cups of coffee in the morning will make your feet feel warmer... OR Maybe you just have warmer FEET than others? HAHAHA

Gone2TheCamp
Member
# Posted: 7 Dec 2018 07:18
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Haha. Well, the times I've really noticed was getting out of bed at 3am to go for a wee. So I figure if there was to be cold-shock, that would be the time.
I borrowed a friend's infrared thermometer yesterday...gonna collect some real data. hehe
Car's already packed, now just have to wait for 4pm.

Asher
Member
# Posted: 7 Dec 2018 09:37
Reply 


Might not be the best method, but I just used open faced fiberglass and those metal wire braces, then covered everything with house wrap. Eventually I plan on capping it all off with a thin layer of plywood sheeting. Right now it's just the insulation and house wrap and it made a WORLD of difference. I stretched the house wrap as tight as possible and didn't leave any edges for paws or teeth to grip onto... So far (1 year) I have been lucky and not have anything penetrate the wrap (we have chipmonk, packrat, raccoon, field mice populations).

Gone2TheCamp
Member
# Posted: 9 Dec 2018 16:02
Reply 


Okay....I spent the weekend at the camp and did some measuring...
See post here:
http://www.small-cabin.com/forum/2_8723_0.html

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