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Turk
2005-09-11, 14:19
I stumbled across a pretty amazing product in my daily work.
I am currently testing this stuff as a replacement for my 3/4 thermarest
inside the HH.
The product is made by Reflectix Inc.

What it is is a very flexible bubble wrap, double sided with silver reflective
foil. This stuff is used to insulate everything from ductwork, to piping, to waterheaters and attics.

I purchased a roll 25" wide by 50ft long for $32.00 CAN.
This will make about 10 full length sleeping pads, so I have lots of extra for
testing.

First thing I did was cut out a slab, and roll it up. Extremely lightweight.
Being in the process of moving, my scale is packed away (somewhere in here) but right away, I note that a 5ft slab, is lighter than my 3/4 length thermarest. I will get an exact weight later.

It rolls about as well as the cheap closed cell foam pads.
I next laid the piece out and walked on it. Did not pop any of the bubbles.
I then put my shoes on and put some good pressure on the pad (not quite a full stomp) and did manage to pop a few bubbles. So the stuff is pretty tough.

I then took the pad outside and laid it out on some coarse gravel in my driveway. Rolled around on it a bit, much to the amusement of my neighbours. Only a few popped bubbles. It was quite warm and sunny out and in a matter of minutes my blinding silver pad was hot to the touch.

Took a nap on it in the HH in the backyard. Removed the pad, rolled it up and unrolled it 4 or 5 times. Checked for wear. Some small permanent creases at this point, but I actually think it is better a little worked in.

I would guess that you could get at least 2 good hard abusive week long trips out of one of these pads. And at $3.20 each, thats pretty darn good.

Interesting little note - The stuff molded well to my back shape inside the hammock and was far less slippery against the nylon of the HH.

This morning I cut a new pad and sprayed it with the garden hose with full force. Water sheets right off, absolutely no absorbancy. I thought that maybe my cut edges would be a problem area, but other than a few drips of water nothing seems likely to saturate this pad with moisture.

So far I am quite impressed.
There is another product from this company that uses a different type of insulation between the foil sheeting and I think I will pick up some of that also and see if it is any better.

Otherwise I think I have found a cheap and very serviceable reflective insulation pad.

Check out their site
www.reflectixinc.com

Lanthar
2005-09-11, 14:37
yeah, I can get that stuff at my local hardware store... I might try some as a mat for our backpacking trip with our scout troop soon...

txulrich
2005-09-11, 15:41
The only thing I don't like about reflective pads is the breathability. My sleeping bag ended up soaking wet and then I would get cold. I switched to an underquilt and life has been good ever since.

JAK
2005-09-11, 17:50
Sorry. The R-value is NO WHERE NEAR where they say it is. The website of reflectix is borderline false advertising mixed with some outright lies and misinformation. It is BAD NEWS. Don't waste your time and money.

:viking:
:viking: www.reflectixinc.com = :evil: :viking:
:viking:

If reflectix has any practical use at all, it is NOT as a sleeping pad, in a hammock, or elsewhere.

====================================

What is the r-value of Reflectix :questionm

R-value = 0.67 which is all you should expect from cheap bubble wrap. It is HALF the insulating value of a 'cheap blue foam pad' and TWICE the weight. As an added bonus it is less comfortable, more fragile, and comes in convient 25 foot rolls and narrow widths. Sorry, but that's the way it is. Not a good application for this product. As a matter of fact, if there are any good applications for this product, I can't think of one.

Reflectix:
Single Bubble: thickness= 5/32", weight = 4.23 oz/sqyd, R-value = 0.33
Double Bubble: thickness= 5/16", weight = 11.25 oz/sqyd, R-value = 0.67

Blue Foam Pad: thickness= 3/8", weight = 6.50 oz/sqyd, R-value = 1.30

http://www.glacierbay.com/reflxtest.asp

====================================

Some possible application for Reflectix Insulation:

1. Astronomy - If you wrap Reflectix Insulation around a telescope with sufficient magnification, you can see the rings of Saturn. The manufacturer recommends that you overlap each wrap by 1".

2. Household - If you carefully remove the aluminum foil from the bubble wrap you can use the aluminum foil as aluminum foil, and the bubble wrap as bubble wrap.

3. Nutrition - 4 ounces of Special K and 8 ounces of Milk in a bowl made of Reflectix, will provide ten essential vitamins and minerals and is a good dietary source of protien.

4. Personal Care - Standing on a 15" x 15" square of bubble wrap while flossing and brushing your teeth after each meal is effective in preventing cavities.

5. Automotive - Reflectix seat cushions in a Porcshe or BMW might be fairly successful when cruising for chicks.

6. Thrift - A 25 foot roll of Reflectix Insulation and 50 cents might still buy you a cup of coffee.

7. ???

8. ???

9. ???

10. ???

Turk
2005-09-11, 19:01
wow, thank god for third party product reviews.
that is one crappy R-value.

I wonder how they actually came to that conclusion.
The product does actually claim an R-8 value.

Until I can finish my ultra-small underquilt I am still going to fiddle with
pads.

The real question is what do I do with the 39 ft of this foil stuff I
still have left.

maybe a solar cooker .... hmm

JAK
2005-09-11, 20:36
wow, thank god for third party product reviews.
that is one crappy R-value.

I wonder how they actually came to that conclusion.
The product does actually claim an R-8 value.

Until I can finish my ultra-small underquilt I am still going to fiddle with
pads.

The real question is what do I do with the 39 ft of this foil stuff I
still have left.

maybe a solar cooker .... hmmThe stuff looks impressive enough doesn't it. I bought a roll six years ago when I was renovating. I ended up using it on the ceiling of my furnace room which is on the main floor of my bungalo because I have no basement. Not a bad application you might think, but it's still only R=0.67. With the insulation above the ceiling (R=40) I am not gaining anything over plain old gyproc. I have justified it in my mind because it does make the room brighter and if the furnace explodes it might blow up and not out.

Anyhow, you are not the first to be duped. :)

:damnmate:
:dito:

If you look at their website they claim R=8 for this and R=14 for that, but that always includes the R=7.33 or R=13.33 in the rest of the construction. In one case they get it completely wrong when they wrap a pipe with the stuff. Anyhow. Yeh, maybe a solar cooker. Maybe a windscreen for a stove, but again blue foam with a layer of aluminum tape would be lighter and better. Maybe a halloween costume. :biggrin:

youngblood
2005-09-11, 21:45
In comparison to standard closed cell foam pads, I haven't found Reflectix to particularly useful as an insulating pad in a hammock. The insulation we normarly use in hammocks is for conductive heat transfer and Reflectix, as you pointed out, is not particularly suited as insulation for conductive heat transfer.

Reflectix does very well for radiant heat transfer but R-values are for conductive heat transfer, not radiant heat transfer and the R-value numbers they use (or pull out of the air?) are kinda funny. Reflectix should work pretty well for the right applications; typically one where there is a gap (doesn't have to be an air gap but it can be, just need something to keep conductive or convective heat transfer from being the primary means of heat transfer) and a large temperature differential between the objects separated by the gap such that the primary heat transfer is radiant heat transfer. If you tried to compare its insulating value to standard insulation where radiant heat transfer is involved, the equivalent R-value would change as the temperature difference of the two separated objects varied, while the R-value of standard conductive insulation is fixed and doesn't depend on the temperature of the objects it insulates... so it gets really confusing to even try to assign it equivalent R-values in those applications.

But to say it doesn't do anything in any condition is not quite right either. For instance, if you were to construct a tarp type structure for heat relieve in a sunny environment, the Reflectix might look pretty good. I suspect it works well on the underside of roofs were the sun heats the roof up pretty well, because then a big part of the heat transfer is radiant heat transfer to the ceiling side of the attic-- the Reflectix wouldn't radiant near as much of the heat to the ceiling side of the attic. But, these are cases were there is something very hot using radiant heat transfer to something that isn't anywhere near as hot.

All of this heat transfer stuff, conductive, convective and radiant can be about as difficult to follow as the pea in the old shell game. The effectiveness of radiant heat barriers, reflectors, emitters, etc varies with temperature differential and gap distance. Convective heat transfer can be natural or forced, like when the wind blows. Conductive heat transfer is uniquely defined in the building industry by R-value... but in the clothing and personal insulation business it might be R-value, clo's (I think that's it) or nothing at all.

Youngblood

Just Jeff
2005-09-11, 22:03
The insulation we normarly use in hammocks is for conductive heat transfer

I thought the primary heat loss in a hammock was convection from the wind on the bottom side. Am I confused? Where is the heat conducted to?

titanium_hiker
2005-09-11, 22:36
conducts from your nice toasty warm body to the air... air moves around, you have to keep heating up more air...

titanium

youngblood
2005-09-11, 22:54
On the bottom side it is conductive heat transfer thought a pad and also your underquilt when you have 'the windows closed'; it is conductive heat transfer on the topside through your quilt or sleeping bag when they are closed off or not vented. (When you vent your insulation your are introducing convection currents which reduce the effectiveness of your conductive type insulation.) When it reaches the outside surface, it primarily becomes convection heat transfer with maybe a little radiant heat transfer as well. When the air is still you have natural convection currents on your boundry layer of warm air where the warm air rises and is replaced by cooler air; replacing your boundry layer of warm air at some rate. How much boundry layer of warm air you have depends on how much insulation you have and how cold it is... you have a distribution of temperature starting with your body, through your insulation, a layer of air immediately around your outer insulation (this is your boundry layer of warm air) and finally the outside air temperature. Wind currents cause forced convection currents, as opposed to natural convection currents, and more rapidly removes your boundry layer of warm air... this effectively reduces the effect of your insulation and if you have 'just enough insulation for no wind conditions' you may feel the cooling effect each time the wind picks up and think the wind is actually blowing through your insulation even if it is not. If you have more than 'just enough insulation for no wind conditions' you might not even realize the wind is blowing. It is probably simplier to deal with if you treat wind as lowering the temperature because if you can't get out of it you will need more insulation. Like I said before, all this can be about as difficult to follow as the pea in the old shell game. Now, if the wind actually penetrates your insulation and flushes out the warm air you have trapped, that is really going to be noticed.

Youngblood

Just Jeff
2005-09-12, 00:38
Ah...I think I get it. If I'm in a hammock with no bottom insulation, the heat is conducted through the hammock material, then the wind takes the heat away by convection. Adding insulation, the loft stores the heat and keeps it away from the convection, so the convection has less of an effect.

So (assuming we're at thermal crossover temp just to keep the variables down) the conduction occurs both on the ground and in a hammock at the same rate, but in a hammock you add the convection to the heat loss. It's not a different form of heat loss in a greater value (as I thought before); it's an additional heat loss altogether.

Right?

I guess it's academic, really...get a windblock and enough loft and you're warm.

Thanks for the lesson.

youngblood
2005-09-12, 08:44
When you are sleeping on the ground, the ground is sometimes loosely compacted dry duff, which I believe is a lose mixture of dirt and decaying vegation. This acts like a good insulator for conductive heat transfer because there are a lot of small trapped air pockets. Add to this that the ground is not always as cold as the minimum air temperature that you are exposed to and in some cases you don't need any extra insulation, just sleep right on the loosely compacted ground as it might provide all the insulation and cushioning you need.

But, that is not always the case on the ground. If it is compacted, soaking wet or a sheet of ice all that can drastically change the situation I described above. It might act like a heat sink and it might even be colder in some situations than the minimum air temperature that you are exposed to.

And then there is sleeping in the three sided shelters that you encounter on the Appalachian Trail for instance. The floor is typically elevated off the ground but sometimes they are very open underneath with gaps between the flooring... sometimes they are pretty well sealed to outside air with no gaps between the flooring. In the worst case they are pretty much like sleeping in a hammock as far as natural convection and forced convection currents are concerned. In the best case the floor might act like a pretty decent insulator, trapping a pocket of warm air between the floor and the ground.

Sometimes it is best to risk oversimplifing rather than to try to understand all the intricate details. It that spirit, sometimes on the ground you are sleeping on an insulator that helps keep you warm and sometimes you are sleeping on a heat sink that takes heat away from you. When you are suspended in the outside air in a hammock you are exposed to a heat sink that takes heat away from you.

Youngblood

JAK
2005-09-12, 09:17
Good thread. Dry ground with a sawdusty sort of texture like you say can be quite warm once its heats up a bit. Can't always count on dry duff of course. Snow and even ice are surprisingly good insulators also so the surface under your pad can be counted as no colder than 32F even if the air is colder. I think a wider pad is important though (28"). This is why I think hammocks are as good as on the ground down to 32F but then are half as efficient beyond that. Still, I am going to try a hammock this winter. I think in wet snow conditions it might be particularly good.

In desert camping where it is very hot by day and cold by night like the moon, sleeping on a large flat rock with a tarp over it would be effective because the heat will come up from the ground through the rock. No I haven't slept on the moon, or the desert for that matter. :damnmate:

One problem with reflectix or any insulation immediately under a shingled roof is you end up baking the shingles off the roof. The desert tarp is an interesting application for reflectix. It would be good by day and also by night when there is a clear open sky. Still, a single sheet of just about anthing any colour is nearly as effective and a lot lighter. But it is true that the best application for reflective coatings is when you have very high temperature differences and no other insulation. Emergency blankets, for example, are very effective when you are naked in winter, but add very little to a sleeping bag. Same with heat shields around stoves. It is difficult to improve on a thin sheet of aluminum. The more weight you add to your stove and sheild and pot and pot stand the more you have to heat up. Still, when its very cold and windy and you want to cook slow and efficient I think a 1/4" blue foam with aluminum foil on the inside might be the way to go. This might be particularly useful at high altitude where less oxygen slows combustion. The thinner reflectix might work well as a heat shield. It is less than half the weight of the thicker reflectix because it doesn't have the extra layer of glue or tape or whatever they used. I think blue foam and aluminum foil is still lighter and more insulative. You get convection currents inside the bubble wrap and bubble wrap is heavy for what you get.

In simplest terms, if you have adequate insulation all around your body there will not be much of a temperature difference left on the outside surface so radiant and even convective heat transfer is not as important even if its windy. The two exceptions to this rule are that a sleeping bag does need to breath, and the wind will increase infiltration/exfiltration. Also, clear night sky is very cold even though deep space is so far away and the outer surface of the sleeping bag can get colder that the outside air conditions. Any tarp will solve this.

youngblood
2005-09-12, 10:18
Yeah, it is an interesting thread.

I tried my silnylon tarp as a heat shield one spring when the sun was baking me in the north Georgia mountains before the leafs were out. Didn't work all that well, helped some but not enough as I could feel the heat just radiating through or from it. I just gave up and hiked on using my umbrella for some shade from the mid-day sun as I walked. In Ray Jardine's book he mentions adding mylar(?) to his umbrella for dessert hiking... I greatly appreciated that idea when I was in my hammock under that tarp on that spring day trying to get some relieve from the relentless sun. I think some type of reflective barrier would have worked much better in that envirnoment but I'm not in those conditions often enough to spend too much time or pack weight worrying about it.

About the Reflectix under the roof baking the shingles off the roof. I realize it will allow them to heat up more, but will that be enough to really bake the shingles off the roof? That would enough to piss you off.

Youngblood

titanium_hiker
2005-09-13, 16:02
I just about died laughing when you said: "ok, now what do I do with the other 9 yards?"

so, lets see... You could make a large sign to stick to your house- SGT ROCK(s!) or something. :)

titanium

Lanthar
2005-09-13, 22:45
With silnylon, the inner surface is completely uninsulated from the exterior surface so it is going to get hot and radiate heat down on you. to make an adeqaute heat shield you need an area that either insulates the exterior from the exterior or allows convective heat transfer to pull heat off of the surface...

aka reflectix (isulates) or TWO silnyl taps (space for breeze to pull off heat)... that's why trees cool so well, lots of little light/IR barriers with plenty of space for breezes to carry any built up heat away

JimM
2005-09-15, 00:11
I've used Reflectix to make pot cozies. I've used it in winter during hunting season when cooking lunch. It worked well for that purpose.
Jim