True North Blog

Staying Warm on a Cold Night

Speaking from experience, it’s seems that whenever one has to suddenly deal with an unexpected problem, rarely does it occur in perfect conditions.  This, most especially, when it involves the outdoors.  So, in this vein, my mind regularly ponders varying ways and means to effectively stay warm if one of my “day hikes” should ever turn into a overnight.  Out of this, then, let me share with you a product that you may want to consider adding to you gear inventory.

Now, of course, whenever I head out into the woods on some adventure, I am properly prepared to meet my seven priorities of survival — in particular, Priority #3 Shelter — but my concern is that even if I can protect myself from the wind and rain, it may still be hard to stay warm.

Build a fire, right?

Building a fire to dovetail with my shelter seems to be a no-brainer, and, since I am a survival instructor, it would seem to be the obvious choice, but, at the risk of appearing a heretic, I believe that there can be many downsides to placing too much emphasis on an emergency fire.  Among various other reasons: gathering kindling and fuel can expend much energy (especially when there is snow on the ground); if it’s dark outside, doing so creates a high risk of injury (like poking out an eye); it further subjects the the survivor to the elements (like rain); and gathering enough material to maintain a fire throughout the night expends much time that is probably better spent on higher priorities, like a making a shelter.

So, given a choice between a nice fire and a nice shelter, I would likely choose the latter.  At least I can simply curl up out of the elements for the night.

Besides, what if I simply cannot build a fire — For instance, my leg is broken or I am stranded in a vehicle on the interstate — what then?

Which returns me to my original question.

Use an Emergency Space Blanket, right?

Many people seem to like mylar space blankets, but I don’t.

I know that technically they work, and they are very inexpensive, but, in my view, they aren’t practical.  They seem too small, tear easily, and make a constant crinkling sound that drives me nuts.  So even at $1.98, I wouldn’t put one in my kit.

Good Idea?

However, in December of 2014, while visting the folks at Exkursion as they were closing out their retail store, I came across a mylar product that I thought too interesting to pass by.  It was the Thermo Biwak-Sack made by Ace Camp.

The product effectively looks like a mylar sleeping bag.  It’s dimensions are 7′ x 3′ and allow the user plenty of space to fully crawl inside and, if needed, close off the entry much like a cocoon.  The manufacturer states that this bag is able to reflect and retain over 90% radiated body heat for “maximum sedentary protection.”

Using our recent period of sub-zero temperatures, I finally put it to the test, and I was impressed enough to put it into my survival kit.

Dressed only in a tee-shirt, shorts, and socks, I spent an hour in it when the outside temperature was 5 degrees.  After a painful few minutes, I was surprisingly comfortable as it quickly warmed up inside.  I really think that I could have spent the rest of the night outside.  The material and seams seemed relatively rugged and any “crinkling” was relatively minor.  On top of this, there was probably enough space for two people if need be.

Here are a few points to consider, though:

  • You need to be careful to minimize any condensation in the bag.  As any moisture begins to build (from your breath, for example) it could overwhelm any warmth gained.
  • At a minimum, you should still make even a rudimentary “debris bed” to insulate yourself from the ground.  That is, if you spent the night directly on the groud, any warmth that you would gain risks being drawn out of you to the earth due to simple physics.
  • Your mobile telephone will not be able to receive or make calls while inside.  The material, I suppose, naturally blocks wireless signals.
  • Your body needs to be able to “radiate” heat.  That is, you need to be essentially warm already.  So, if one is already moderately or severely hypothermic, it probably wouldn’t be as effective.

On the whole, then, I give the product a positive review.  Moreover, at $9.95 it is quite affordable and, given its small size and very light weight, packs without too much trouble (or fit in a vehicle storage compartment).  In fact, it would seem to be a great compliment to a sleeping bag — that is, acting as a cover to the sleeping bag.

Erik Kulick leaning aginst wall with True North badge on blue shirt

About the Author

Erik is the founder of True North Wilderness Survival School. He is a police officer, EMS provider, a Wilderness EMT, and a Fellow of the Academy of Wilderness Medicine. He has been featured in national and international media, including CNN, the Associated Press, and Backpacker. To learn more about Erik, visit him on LinkedIn and be sure to follow him on Facebook and YouTube.

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