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Small Cabin Forum / Cabin Construction / Reflectix and some actual numbers..
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# Posted: 9 Dec 2018 15:52 - Edited by: Gone2TheCamp

Afternoon folks. I've gathered lots of helpful info from this site, so it's time to give some back.
First off, I'm not associated with Reflectix in any way; I'm just a cheap bugger that watched someone's video about it and it seemed like a cheap way to insulate and hopefully deter rodents from wanting to set up shop in my floor.

My 'cabin'. Around here we call them camps...

12x16 - Sitting on 3 beams that run the long way, the beams are sitting on cross-piled 4x4, 2x6, etc. No skirting, the joists and the reflectix on the bottom side of the floor are exposed. The bottom edges of the joists are about 18" off the ground.

2x6 floor - typical 2x6 floor construction, then one layer of Reflectix laid on the top of the joist frame, then 3/4" t&g OSB laid over the Reflectix. I have yet to add flooring, underlay, the floor is nothing but OSB, the reflectix, then the 2x6 joists, then the great outdoors.

2x4 walls - 7/16" OSB sheeting (no siding until the spring) wrapped with house wrap. 3.5" rigid foam insulation (white), vapour barrier, then the inside of the 4 walls are finished with t&g cedar. The interior is one room, no dividing walls, etc.

Heat - Pretty simple, one propane 'Big Buddy' heater. Aside from the first hour or so after arriving at a frozen camp, the heater runs on the lowest setting. I wish it had a lower setting than low, but it doesn't. I have never run it hi or med other than the initial hour or so, and I have (currently) no means of moving heat ceiling fan, no floor fans, etc.

Okay, so I built this fall and my measurements (using the soles of my feet) told me that the single layer of reflectix was doing a darned good job of keeping the floor warm. I had replied to another person's question about Reflectix, and there were also some folks in that thread that had heard that the 'miracle' foil wasn't what it was cracked up to be and that a piece of vapour barrier and/or tarp material would work just as well. Maybe it would...who knows?

So, I decided that I'd borrow a friend's infrared thermometer this weekend, and take a series of measurements. Honestly, I really had no idea if the stuff was working or if there was a ton of heat going right out through the stuff.

I'm attaching a table of what I measured, the recorded temps, the times I took the readings. I measured in the same manner, and on the same spot each time.
Outside Temp: Taken on a tree trunk beside the camp.
Joist Temp: This spot is about 1" up from the bottom of the 3rd joist in.
Reflectix Temp: This is the bottom side of the reflectix, roughly center between joists #2 and #3 where I took the 'Joist Temp'.
Floor Temp: Took this roughly in the center of the floor, on the same point each time.
3 Feet Up Temp: About 1' away from the floor spot, 3' up the side of the bed frame.

In my opinion, after looking at the numbers, and considering that the 12x16 floor only cost $140 (plus tax) to insulate, how easy it was to install, and that the critters leave it alone....I don't see where there's a downside.
Yes, the numbers indicate that there's a little bit of heat loss, but not very darn much. Especially when I see the inside surface of the OSB at +13.6c (56 deg F), and the outside surface of the reflectix is at -15.2c (4.6 deg F). And remember, there nothing is a layer of reflectix and a piece of 3/4" OSB between those two temps.

Looking at the graph, there is a fairly consistent difference between the outside temp, and the temp of the reflectix exposed to the air, but I'd expect that. And really, it's not that much, all things considered.

Bottom line is, the single propane heater ran on its lowest setting all weekend, and the floor stayed at a reasonable 13c over the 12-hour stretch that is was as low as -19.8c. During the night while it was -20 outside, with 2 windows cracked open and the Buddy on its lowest setting, the mrs and I had to take the blankets completely off to cool down a couple times during the night. (save the jokes please..haha)

One thing to note is that I measured the temp at the ceiling over the weekend and as expected, it was always 23-25 degrees. If I had a fan of some kind to move the air around, I'd expect that the temps would be more equalized, resulting in the floor temp being even warmer.

So...Here's what I measured out over the weekend. All temps are in Celcius. When you view the image after clicking below, you can click the image and it will zoom in.
(I added a Far. equivalent in the graph picture, you know, for the 3 countries on the planet that don't use the metric system. hehe)

Temps Table

Temps Graph

Conversion Chart

# Posted: 9 Dec 2018 21:13

That's pretty impressive actually. Pretty neat how big of a difference from the heated side to the unheated side. You're making me a believer. I know you cant do the test but the reflectix website says the key for higher R value is to have air space so stapling it to the bottom of the joist but it is much easier rolling it out onto then putting your plywood on top.

# Posted: 10 Dec 2018 07:11

make me break out my conversion chart LOL
Gota love the Mr. Buddy heater, mine ran all weekend in my deer blind, Sunday morning was about 34F or 1C for those of you north of the line LOL, and for South Texas that's cold!!!
I am going to add the double layer to my cabin this summer and see how it does. Guess we will find out next winter.
Thanks for the research

# Posted: 27 Sep 2023 14:15

Update, 4 years and 9months later.....

So, the cabin is essentially finished...over top of the OSB floor I laid down that wafer thin foam underlay, then cheap click flooring that I bought used from someone re-doing their basement apartment.

I soon learned that using a non-vented propane heater puts a TON of water into the air. So, I found a small oil furnace (the drip type with the float 'carb' on the back) and my moisture problems are gone.

I've used the cabin for several winters and am 100% happy with the job that the reflectix does keeping the floor warm. I'd do it again in a heartbeat.

Also, I have mice, squirrels, and porcupines all over the place, but they have zero interest in the reflectix.

I have seen where they say it will provide even more insulation if you leave an air space, but for myself, not having critters living in my insulation is pretty high on my priority list. I feel that laying the reflectix on the bottom of the joists would be like installing a flashing neon VACANCY sign.

Anyway...5 year's 100% a win/win.

# Posted: 27 Sep 2023 14:52

Thanx for the follow-up, certainly seems worth a thought for use of the product.
Big plus is the easy install the way you did it.

# Posted: 27 Sep 2023 15:15 - Edited by: spencerin

I have a layer of it between the joists and subfloor. No, it's not as good as the real deal, but it does provide some insulation, critters appear to have no interest in it like you said, it acts as a moisture barrier between my crawlspace envelope and subfloor, and it won't disintegrate over time like fiberglass batts can.

# Posted: 4 Oct 2023 17:31

Do you think it would help keep critters out if relectix went on the bottom of 2x6 joists filled with 4" rockwool/fiberglass? I'm just brainstorming, but seems like it would be a potentially cheap way to boost R-value. Plus, there would be a nice air space and the reflectix could double as a vapor barrier?

# Posted: 4 Oct 2023 18:58

No. Vermin may not chew up Reflectix to make nests out of, but it's easy for them to chew *through*, especially if they can get into a warm, dry cavity. So, don't do that. It might help provide some additional insulative effectiveness, but it definitely won't deter vermin from trying to get into the bays.

If you're going to use fiberglass or Rockwool to insulate the floor, it's best to enclose the bottom of the joists with plywood, metal sheeting, or 1/4" (or smaller) hardware cloth. Note - plenty of people can attest to vermin having no issue with Rockwool, even if others claim they don't like it. Like some humans, some vermin will make homes wherever they can.....

If you don't want to do that, then try spray DIY spray insulation instead of fiberglass or Rockwool. No enclosing required, and a small DIY kit might actually be cheapest.....

# Posted: 4 Oct 2023 19:18

You can build the deck framing and apply ledger strips down in each bay from the top to the thickness of rigid styro you want to use. My '83-'84 build I used 1"blue Dow styro. I cut the styro on the stacked decking plywood, pressed down in the bays and when I filled enough the plywood went on. Then I just worked my way on down the bays (12x24) until done.
The 1" was not bad to cut, 2" Ive yet to do. At that thickness keeping a knife straight up/down for a clean cut might be troublesome. 2" would be better insul so you could dbl up the 1".

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