View Full Version : Emergency "Space" Blankets
I have a couple of these little silvery devils in a first aid kit. Are they worth carrying on the trail? For a ground cloth/warmth, anything? Do they fall apart?
Footslogger
11-30-2005, 14:50
They're actually pretty durable and not a bad idea to carry along on a cold weather hike. Only problem is that they are designed as a "single use" device. They are not very user friendly after the initial use.
'Slogger
I carry one with me. If I'm tarptenting, I use it as a ground cloth. It will rip to pieces after 20 or 30 uses, then I replace it. If I'm hammocking, I carry it as emergency and last-ditch, keeping-warm gear.
For next to no weight, they seem a good thing to have. I carried one my entire thruhike, and found it useful, spreading it out under my sleeping when whenever the nights got extra cold.
Mine was a REAL throwaway, the kind they give you at the finish line of marathons to keep from getting chilled when you stop running. But it lasted nicely and I STILL have it folded away in my gear closet.
SGT Rock
11-30-2005, 17:44
It is a poor idea for real heat retention.
I don't know how anyone can use those things as ground cloths. I tried that once and my ears are still ringing. The motion from just breathing made that thing crackle and pop like I couldn't believe.
SalParadise
11-30-2005, 19:16
It is a poor idea for real heat retention.
I carried one for a while this year and for me I could really tell that it kept in a lot of heat.
but oh, the evil eyes I got when I pulled that shiny noisemaker out in the shelter one night...
Trooper347
11-30-2005, 19:25
I don't know how anyone can use those things as ground cloths. I tried that once and my ears are still ringing. The motion from just breathing made that thing crackle and pop like I couldn't believe.
Try a "Heatsheet", they are better quality, a lot less noise, better re-folding, but the same weight as some large space blankets, under 4oz..
SGT Rock
11-30-2005, 20:11
I carried one for a while this year and for me I could really tell that it kept in a lot of heat.
but oh, the evil eyes I got when I pulled that shiny noisemaker out in the shelter one night...
Quantify a lot of heat. If the space blanket really was a great idea, we would all have sleeping bags made from them since they have very little weight and bulk
The claimed science behind it is flawed. You could keep just as warm with any vapor barrier. The reflective quality of IR heat in the atmosphere, especially when wearing any sort of clothing whatsoever, is almost none. In fact, being in contact with the membrane actually acts as a heat conductor to siphon off some heat.
fiddlehead
11-30-2005, 21:19
I remember my first marathon. It turned nasty weather and we weren't wearing much. At the finish they handed us each one of those shiny emerg. blankets to wrap up in and it sure felt warm to me. I didn't want to take it off. I used one for a ground sheet until tyvek came out. Like someone said before, it only lasted a few weeks. But i thought it was good up until it fell apart.
Toolshed
12-01-2005, 08:02
for as cheap as they are, I have always carried 1 or 2 with me. It is the devil trying to get them open and apart with cold fingers when you really need them though.
I also have the $9.99 space "bag" that I carry in the winter and think would offer better emergency protection if I were to ever need it.
MisterSweetie
12-01-2005, 09:42
I don't know how anyone can use those things as ground cloths. I tried that once and my ears are still ringing. The motion from just breathing made that thing crackle and pop like I couldn't believe.I was going to suggest the same thing. In the Grand Canyon once I was cold and so I got out the space blanket... Getting it out of the package and around me .. I felt like an old person in church opening a peppermint.
What it worked perfectly for was under the sleeping pad to reduce heat loss through the ground. I always had it either in my tent or in a shelter folded my tent under it for extra insulation. Argue if you like, I certainly noticed the difference. And sandwiched between tent and pad, noise did not seem a problem either.
Remember heat is transmitted by conduction, convection and radiation. A spaceblanket, vapor barrier, and air pocket insulation each do some things better than the others and other things less well. A combination uses the advantages of each to get as much protection as possible for a given pack weight.
I agree with Mouse. I used one under a Tarptent, but when it was muddy, I pulled it towards the door to make a little entry mat. That left the area at the low end of the tent without the mylar between floor and ground. When I would break down my stuff in the morning, there was frequently condensation on top of the floor of the tent, but only up to where the mylar started. The down sleeping bag would be damp down around my feet, but dry above the mylar.
I'll have to do a test sometime to see if any thin sheet of plastic would work as well, but I doubt it.
The crackling is pretty fierce with a new blanket, but it quiets down after a couple of uses.
Youngblood
12-01-2005, 17:46
...I'll have to do a test sometime to see if any thin sheet of plastic would work as well, but I doubt it. ...
Marta,
I think it will. In the literature that came with a Stephenson tent that has a silnylon floor, it describes what you mentioned when it talks about Ground Humidity and Floor Protection: "Although the ground under a tent generally stays fairly dry during rain storms, protected by the tent, there is still frequently a lot of humidity rising from the ground (or snow). Some of that humidity will condense on the underside of the floor, while much of it goes right thru the floor coating. Any object that covers the floor will block farther travel of the humidity and cause condensation. Where the floor isn't covered the humidity continues up and adds greatly to the humidity that vent system must eliminate, or causes condensation on the tent walls. The typical reaction to finding the bottom of your sleeping bag and pack wet is to assume the floor leaked. Amazingly, some will continue to insist that floor leakage is the cause even when they observe that the ground under the tent is dry. Any time you find it wet under objects on the floor and dry on uncovered floor areas, you will know the cause is condensation, not floor leakage.
Putting a thin sheet of polyethylene under the tent will block all ground humidity, as well as portect the floor from dirt and wet earth. ..."
I didn't pay that much attention the times I used that tent, but I did notice when I tarped a difference between using a tyvek ground sheet and a plastic ground sheet. In dry conditions the plastic ground sheet would often be damp on its bottom side while the tyvek ground sheet wasn't; the underside of my tarp would often collect condensation before I ever got under the tarp with the tyvek ground sheet while it didn't with the plastic ground sheet.
Lanthar Mandragoran
12-02-2005, 18:05
I remember my first marathon. It turned nasty weather and we weren't wearing much. At the finish they handed us each one of those shiny emerg. blankets to wrap up in and it sure felt warm to me. I didn't want to take it off. I used one for a ground sheet until tyvek came out. Like someone said before, it only lasted a few weeks. But i thought it was good up until it fell apart.
Not having ANY other insulation layer is ONE instance where the 'science' of space blankets actually works (blocking radiant heat loss).
If you have ANY other insulation, you'd do just as well with ANY wind/water blocking layer (VB, Tarp, Tent, plastic ground cloth)... having said that, the space blankets seem to be pretty durable, however don't let any self-proclaimed engineer dissuade you otherwise about the 'heat retension capabilities'...