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Max Dilthey
(mdilthey) - M

Locale: MaxTheCyclist.com
Space Blankets- Do You Carry One? on 10/10/2013 14:43:23 MDT Print View

Ok, so I'm going back out on tour (again, again, again) and I'm looking at the space blanket on my floor, thinking "What the hell do I use this for?"

I've got synthetic insulation, and the good sense not to get soaked. So will I really need this thing? It's like four ounces. I understand the science (sort of...) but I see a lot of companies putting reflective layers in stuff. Both my thermarest pads have it. It's starting to look like a gimmick to me. Am I wrong?

Does it really make a big enough difference to warrant the weight, or can I ditch it if i'm within my sleeping bag's "Extreme" range the entire trip?

Edited by mdilthey on 10/10/2013 14:44:01 MDT.

Justin Baker
(justin_baker) - F

Locale: west coast best coast
Re: Space Blankets- Do You Carry One? on 10/10/2013 14:45:49 MDT Print View

Space blankets are pretty useless for keeping you warm, the bivy space blankets are much better.
I sometimes tape a space blanket to my tarp to reflect heat from a fire. It works amazing for that.

Edited by justin_baker on 10/10/2013 14:48:18 MDT.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Space Blankets- Do You Carry One? on 10/10/2013 14:51:41 MDT Print View

A space blanket can be effective in blocking radiated heat loss, but that is less than 10% of your total heat loss. It is as effective as a good sheet of plastic for blocking convected heat loss, so it is not worthless. It is a good rain cover in a storm.

I've used one as a ground sheet when I didn't have a better piece.

--B.G.--

Brett Peugh
(bpeugh) - F - M

Locale: Midwest
kinda on 10/10/2013 15:14:53 MDT Print View

I use one above 60F for warmth and at lower temps as a VBL with my quilt.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Space Blankets- Do You Carry One? on 10/10/2013 15:16:56 MDT Print View

I've carried one for years and never used it, wonder if it wouldn't be better to leave at home.

It provides a little warmth. It provides more warmth for the weight and volume than anything else.

If you have a tent and sleeping bag it's probably not important to take. In a survival situation just use those.

If you're day hiking it could save your life in a survival situation.

Billy Ray
(rosyfinch) - M

Locale: the mountains
Re: Re: Re: Space Blankets- Do You Carry One? on 10/10/2013 15:35:25 MDT Print View

I spent a night out once down in the low 20's clothed in shorts and T-shirt.
Wished I had a space blanket or bivy back then. :)

Bill D.

John Myers
(dallas) - F - MLife

Locale: North Texas
Day hiking only on 10/10/2013 15:37:34 MDT Print View

"If you're day hiking it could save your life in a survival situation."

What Jerry said.

I've stopped carrying them when backpacking.

Dena Kelley
(EagleRiverDee) - M

Locale: Eagle River, Alaska
"Space Blankets- Do You Carry One?" on 10/10/2013 15:40:41 MDT Print View

In most instances, yes I have a space blanket. They are in my vehicle, in my PSK, and even hanging on the backside of my greenhouse (increases the internal temperature of my greenhouse). When backpacking with all my camping gear, I consider the space blanket to be redundant and don't carry it but in the winter I do carry it as a ground cloth (I use snow shelters in the winter, not tents).

Justin Baker
(justin_baker) - F

Locale: west coast best coast
blanket on 10/10/2013 15:49:13 MDT Print View

The blanket is difficult to use. It's so light that you can't wrap it around your body well, especially not if you are putting it over your bag. The bivy version is so much better.

Max Dilthey
(mdilthey) - M

Locale: MaxTheCyclist.com
Yep on 10/10/2013 16:00:23 MDT Print View

Cool. Confirms what I was thinking. Definitely useful to have in a dayhike bag, but redundant when backpacking and camping.

just Justin Whitson
(ArcturusBear)
Re: Yep on 10/10/2013 16:32:28 MDT Print View

Justin had some good suggestions, but I think where a reflective sheet is really going to shine (pun intended) would be as a partial VBL under a quilt and directly over the body during cold temps to boost ones sleep system. Think Michael L's earlier thread with using Cuben and it helping a lot, but instead using the reflective stuff. I've experimented with S.B.'s before but not quite in that way yet. But it seems clear that would be of the most efficient ways to use it besides reflecting fire heat.

Edited by ArcturusBear on 10/10/2013 16:34:13 MDT.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Yep on 10/10/2013 17:03:19 MDT Print View

"but I think where a reflective sheet is really going to shine (pun intended) would be as a partial VBL under a quilt"

This may be controversial, but I think there needs to be an air space next to the space blanket to be effective.

If there's something against the reflective layer, it will just conduct heat and reflective layer won't make any difference

If the space blanket is on the outside that works. There's an air space on the outside.

If you could have an air space and then space blanket, that would work, but how could you suspend the space blanket? The Blizzard Survival Suit accomplishes this by having an accordian fold with elastic, but that's sort of heavy.

Ken Miller
(Powderpiggy) - F

Locale: Colorado
Redundant on 10/10/2013 18:51:14 MDT Print View

+1 with Dena

Usually you'll have a fly or ground cloth or tarp for wind and rain protection.

I carry them in my day packs. Colorado is known for 40 to 50 degree temperature swings at elevation. Mix that with a little August snow fall and you might catch a chill.

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Yep on 10/10/2013 19:06:48 MDT Print View

That's interesting Jerry, i didn't know that. I would still like to test it out.

Guess Columibia is scamming folks then with their reflective liners and claims of enhanced warmth?

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Re: Yep on 10/10/2013 19:25:09 MDT Print View

Like I said, the air space to make reflective layer effective theory seems to be controversial for some reason

Don Morris
(hikermor) - F
Space Blamkets on 10/10/2013 19:29:14 MDT Print View

I tend to prefer the bivvy configuration. I use the old space blankets I have lying around for ground sheets

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Re: Re: Yep on 10/10/2013 19:32:39 MDT Print View

How does the concept work? Does it matter at all how the reflective layer is made besides the accordion part? What i mean more specifically, is i just got some SOL emergency blankets, they are reflective on one side and solid color on the other side, as opposed to the regular mylar space blankets. Would that make any difference at all, or do you just need some kind of air space?

I'm trying to figure out how this works, and my brain is just not working very well so far doing it.

Edited by ArcturusBear on 10/10/2013 19:52:04 MDT.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
re on 10/10/2013 20:11:22 MDT Print View

I prefer a blanket type vbl, less sweaty.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 21:19:17 MDT Print View

What's important is reflectiveness in the IR spectrum. It may be a solid color in visible wavelength, but reflective in IR, I don't know.

You want an air space next to a reflective surface for it to work.

I would put the solid color surface against me (my clothing) and the reflective surface facing out.

If you look on the web, you can frequently see photos of people with space blankets with a colored surface on the outside. If that colored surface is not reflective in IR, I think that won't work, they should have the shiny side out, not the colored side. Radiant heat loss is sort of obscure, so maybe they're just making a mistake in usage, which is funny since they're selling it. They should show how to use it properly.

If there's a shiny side facing you, there is some air gap because of wrinkles and such so that works some.

And, like I said, I may get some disenting opinion about this : )

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 21:43:26 MDT Print View

Ok, i think i see what you mean a little better, especially as far as the air gap. Like an air gap between you and the S.B. That part makes sense, i thought you were saying you had to have a clear air space behind the S.B. to work.

Well there are ways to create some air gaps i suppose, rolling up some clothes into a tight roll placed over your body, but then you got to sleep like the dead, so not very practical i suppose.

Why does nature hate us so, why, whhhhyyyyy..???? Can't things be easy, light, effective, and cheap?

Why are we such wimpy creatures, with so little natural adaptation? Wolves don't have to hang around gear forums figuring out, "Gggrr arff arrff ruff ruff ruff Ah oooooh(translates) "Well Bob, let me tell you, i got these new down booties, and they are dah bomb, super light, super warm, and it only cost 3 rabbits. Can you believe it?"

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 22:12:32 MDT Print View

clothes don't create air space. As soon as IR hits the surface of the clothing it gets absorbed. You need an air space that consists of air.

A blizard suit has several layers of reflective material, then they're accordianed up using elastic. So you have reflective material, air, reflective material, etc.

A neo air mattress has internal reflective layers inside, suspended so there's air space between.

In the ceiling of a house, you can suspend the reflective material between joists so there's air space

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 22:50:37 MDT Print View

Got you, got you before too, but i guess i wasn't explaining myself well. In any case, what i was saying wouldn't really be practical anyways.

Probably also not practical; I guess one could put guy outs on a S.B. (one of the stronger SOL ones) and raise it up an inch or so from your body, but what a pain in the butt.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 23:18:49 MDT Print View

My great idea is to make a tent out of reflective material

Theoretically this should work

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 23:24:48 MDT Print View

Sounds interesting, i'm guessing there's no current suitable material?

Funny enough, i have been thinking of making a reflective liner for my Tipi tent, but i don't know how to do it with the stove being set up inside same. I don't think putting it any where near the pipe would be a good idea.

But maybe i can just sort of hang some from the top sides and reflect it down. Probably don't really need it to begin with the stove in there. Get's plenty hot, but more interested in conserving the heat a little longer.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/10/2013 23:51:01 MDT Print View

The outside of a clothed or sleeping bagged body is only slightly warmer than ambient so heat loss from radiant heat loss is small - what did someone say, 20% of total heat loss?

A stove is hot. Radiant heat reflected would be a lot more.

You can buy space blankets.

Go to a store that sells stuff for growing (marijuana) plants indoors. They sell reflective material.

just Justin Whitson
(ArcturusBear)
Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: Yep on 10/11/2013 00:00:56 MDT Print View

Just got a bunch of the SOL emergency ones, a couple double sized ones and couple single sized ones. Have had and used some of the mylar space blankets, but like the SOL ones more so far. It's polyethylene instead.

Thank you for the info. If you ever build that tent, let us know.

eric chan
(bearbreeder) - F - M
VBL on 10/11/2013 00:04:07 MDT Print View

one thing that is useful when its not cold enough for a full fledged VBL ... but when you may want the occasional boost in cold nights ...

is to wrap oneself in one of the more durable emergency blankets, or one of those 4 oz bivies ... it provides a decent heat boost

of course you have to remember to put your puffy between the the blanket and the bag rather than wear it or itll get damp ... of if you wear the puffy, wrap it around your torso under yr puffy as best you can

;)

Jason Elsworth
(jephoto) - M

Locale: New Zealand
Space Blankets- Do You Carry One? on 10/11/2013 02:23:59 MDT Print View

If you wear the puffy, wrap it around your torso under yr puffy as best you can.

I did that with a small cuben groundsheet one night when I was stuck out without a sleeping mat. It worked well.

Jennifer Mitol
(Jenmitol) - M

Locale: In my dreams....
Re: Space Blankets- Do You Carry One? on 10/11/2013 08:17:20 MDT Print View

Do they really use them in space?

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Space Blankets- Do You Carry One? on 10/11/2013 08:24:23 MDT Print View

yeah, they use them on satelites to control temperature

there's no air, so no conduction, so all you have is radiation

either absorbing heat from the sun or radiating it to space

Dale Wambaugh
(dwambaugh) - MLife

Locale: Pacific Northwest
Re: Space Blankets- Do You Carry One? on 10/11/2013 11:02:26 MDT Print View

Space blankets are a "better than nothing at all" option for emergency use. IMHO, it goes in the "extra clothing" slot in the list of hiking essentials. I carry one of the bivy sack style AMK blankets for day hiking emergency shelter an long with my poncho.

What you get is an inexpensive, light and compact sheet of material that is windproof and waterproof. You can simply wrap it around yourself and sit under a tree if you are too messed up for better options. They make a good ground sheet and can be used to waterproof the roof of an improvised shelter. You can rig one as a windbreak an reflector in front of a fire.

A night spent with a space blanket might be miserable, but it can give you the edge to survive to complain about it :)

If you have your full multi-day kit, it is redundant. It may have more use as a first aid item with a group.

Some folk use them as their regular ground sheel. The Mylar ones are noisy and prone to tearing. The AMK versions are polyethylene and quieter and tougher.

Dean F.
(acrosome) - MLife

Locale: Back in the Front Range
Not for hiking on 10/11/2013 12:33:50 MDT Print View

I don't see much point in carrying a space blanket while hiking/camping, for the myriad reasons already listed. However, I do keep one in my "man-purse"- the little satchel I carry sometimes on short jaunts. It's my non-UL daily survival bag: a nalgene nested in a titanium mug, a knife, a firestarter, a windshirt, some snacks... and both a polycro groundsheet and a space blanket still in the wrappers so that they are small.

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: Re: Space Blankets- Do You Carry One? on 10/11/2013 12:48:29 MDT Print View

"Do they really use them in space?"

The Hubble Space Telescope does -

Hubble

marc D
(mareco) - M

Locale: Scotland
Space Blankets- Do You Carry One? on 10/11/2013 12:55:45 MDT Print View

I always carry one, though fortunately never had to use them. I have given a couple to people who have got into difficulties in the mountains and were needing picked up by the mountain rescue teams, it seemed to make a difference to them.

Nick Gatel
(ngatel) - MLife

Locale: Southern California
Re: Space Blankets- Do You Carry One? on 10/14/2013 21:19:26 MDT Print View

I carried one for decades. Never used it. So I removed it from my pack along with most of my first aid kit.

Greg F
(GregF) - F

Locale: Canadian Rockies
air gap on 10/15/2013 18:35:57 MDT Print View

The air gap does not affect radiative heat loss as air essentially has an emissivity of 0 and the emissivity of a material is determined by surface finish and what it is.

Air Gaps will generally decrease conduction as air is not very thermally conductive and if you restrict the air flow you will reduce convection. However it does not have an affect on radiative heat loss.

just Justin Whitson
(ArcturusBear)
Re: air gap on 10/15/2013 19:14:21 MDT Print View

Translation for us non physics, engineer, etc. types?

Are you saying that a space blanket will still work if more directly on the body with very little air gaps between your body and the S.B.?

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: air gap on 10/15/2013 20:28:01 MDT Print View

#1 - If you have body, clothing, space blanket, clothing, air - space blanket does very little

#2 - Body, clothing, space blanket, air - space blanket reduces maybe 20% of your heat loss

#3 - Body, clothing, air space (I don't know how you'de accomplish this), space blanket, air - the space blanket might reduce your heat loss 40%

#4 - body, clothing, blizzard survival suit that has several layers of air and space blanket - that would provide some real warmth, might be a good alternative to a sleeping bag

This is my opinion based on theory, measurements, looking on the internets but may be contoversial?

Greg F
(GregF) - F

Locale: Canadian Rockies
Re: Re: air gap on 10/16/2013 12:53:42 MDT Print View

I will try to explain it a little better. I was on my phone so I was farly brief.

There are 3 methods of heat transfer
- Convection - heated air moving and escaping and being replaced with cold air. A drafty window which leaks around the edge is letting heat escape through convection
- Conduction - Heat that is transferred through the medium. If you put your hand on the window glass it will be cold and your hand will become cold because the glass conducts heat into your hand.
- Radiation - Electromagnetic waves are emitted from virtually everything. These waves contain energy and as such emit heat. They are governed by equation q = esT^4A where q is the heat loss, e is the emissivity, s is a constant A is the area and T is the temperature. So looking at the equatuion the only way to increase or decrease the rate of radiation is to change the temperature of the material, the surface area, or the emissivity. If you notice in the equation that an Air Gap or thickness is not a factor. Therefore radiation is not affected my the gap.

This means in terms of radiation is does not matter where the reflective layer is. Also to determine the effectiveness of the space blacket layer vs say a layer of nylon you would just compare their emissivity.

Now this does mean what Jerry is expericing or measuring is incorrect. Its just not do to radiation. Conduction the equation is essentialy a function of thickness, and heat loss due to convection can be reduced by limiting air movement by creating multiple pockets of air that can't flow into each other.

I would suggest that what Jerry is observing is that the air gap decreases conduction and therefore is warmer.

James Klein
(jnklein21) - M

Locale: Southeast
air gap on 10/16/2013 13:12:27 MDT Print View

With no air gap (or just 'space') between emitting surface's, there will be no meaningful temperature differential and therefore no meaningful IR exchange to block.

Will Webster
(WillWeb) - M
Radiation on 10/16/2013 13:31:48 MDT Print View

Radiative heat transfer only occurs through a medium transparent to IR radiation. Put a space blanket between you and your quilt, and it just acts as a vapor barrier. Put it on top of the quilt and it will absorb heat from the top of the quilt by conduction and lose heat to the air by convection (just as the quilt itself would do), but it will not radiate IR to the inner surface of your shelter (or to the sky if cowboy camping). Suspend it above you and it will reflect the IR coming off your quilt back down.

Related to this: A lot of Reflectix's claims are regarded skeptically in the insulation community, but if you read their literature it plainly states that a minimum 1" air gap is required on both sides to get benefit from its reflectivity.

Will Webster
(WillWeb) - M
Link on 10/16/2013 13:41:15 MDT Print View

I was referred to this thread a while back when I asked about making an emergency shelter from space blankets:
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=23685

Matt Dirksen
(NamelessWay) - MLife

Locale: Mid Atlantic
Re: Radiation on 10/16/2013 13:45:47 MDT Print View

Right on!

For many years, I've installed Reflectix in client's attics to reduce solar heat gain just under the rafters. The air gap between the rafters and roof sheathing gives us the space we need for proper IR reflectivity to occur. Thats about the extent of it's use in for homes, and installing it doesn't come close to the improvement that upgrading the attic insulation to R-49 could do, performance-wise.

But because I have so much of it left over from jobs in my basement, I LOVE using it, either under the tents to keep the kids from tearing up the tent floor, or to add a little bit of "comfort" under my Neorest. I also like how I can fold it up in my pack, offering more back comfort & support.

Matt

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Re: air gap on 10/16/2013 13:46:41 MDT Print View

Yes to both James and Greg. It's the combination of conduction and radiation.

All that matters is heat loss or temperature differential, doesn't matter whether it's radiation or conduction. I believe my 4 examples are correct and pretty much charcterize what you experience.

Some day I'm going to measure the combination of conduction, radiation, and convection.

Mike Schasch
(MSchasch) - F
oh yeah on 10/16/2013 21:21:30 MDT Print View

I don't know much about the science, but I do have some real life experience with a space blanket on 3 separate occasions. Twice in November in Zion, once in February in the Panamint Mountains above Death Valley. 2 of those were in technical canyons and one was on the side of a big wall. Was truly grateful to have a space blanket on all of these day trips. Even worked somewhat to cover up myself AND a buddy on the big wall. Trust me when I say you'll be happy to have it.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
'space blankets' on 10/16/2013 22:45:09 MDT Print View

Max,
I only carry one of these products when day snowshoeing in the mountains. If I had to call for a rescue, at least it's something, in addition to whatever insulation is on me and in the day pack.

The one I carry is an envelope Adventure Medical Kits calls an emergency bivy, (all their blankets say 'SOL' on the package, although some are very different in composition). It is a breathable, water resistant, nonwoven gray polyester with a reflective coating on the outside of the envelope with Velcro closures, and rolls up into a 8"x4" stuffsack weighing just under a half pound. It is very different from the lighter polyethylene blankets also sold with the SOL label, and by Heatsheets, and totally different from the crinkly, reflective Mylar space blankets.

I'm thinking that if on deep snow, there would be plenty of airspace between me and the ground. The polyester is much easier to handle than the polyethylene and mylar materials, and if very cold and hypothermic, handling stuff can be a major problem.

Hope I never have to use it. Hope 'SOL' doesn't mean what I think it might.

Edited by scfhome on 10/16/2013 22:46:14 MDT.