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ALEXIKA SPORT GROUP > USEFUL INFORMATION > TEMPERATURE RATE
TEMPERATURE RATE
101
WHAT IS THE TEMPERATURE RATE
Looking at any temperature rate won’t give you enough information whether you will be sleeping
with comfort or freezing. This happens because any given sleeping bag doesn’t “warm” you
(if it doesn’t have additional heaters). You are the heat source who should produce more heat
than amount lost in order to sleep with comfort. A good sleeping bag only helps you to retain
the warmth.
So, if you were freezing during the day, didn’t have enough nutrition, got tired or drank alcohol,
you shouldn’t blame the temperature rate. In order to understand how to help yourself keep
warmth let’s find out how you lose heat and how to reduce heat loss to a minimum.
1. The greatest heat loss happens because of heat transfer by conduction (heat transfer during
actually contacting with an object). If you lay down on the ground you’ll start warming it
with your body. The ground is big and it will always bet you and take lots of heat you produced.
Sleeping bags were not developed for sleeping on the ground! In all cases use thick thermoinsulating
mat.
2. Heat transfer by convection (transfer of heat in gases etc. by flows of this gas). This works
as follows; you heat the air around you but it goes away and takes the heat. The place of warm
air is now taken by cold air, and the process starts again. When your skin evaporates sweat it
also transfers heat by convection. In order to reduce heat transfer by convection you should
accurately choose sleeping bags of special construction made of particular fabrics, fillers, etc.
Alexika pays much attention to all the elements mentioned above as you can see in description
of main features of sleeping bags (see p.30). It is highly important that you sleep in tent where
you’re protected from the wind.
3. Emission of heat, or infrared emission is kind of electromagnetic emission produced by human’s
body. We have not seen any effective technologies to reduce heat loss transferred by
infrared emission. Those advertised on means of mass communication seem fake.
Now when you understand how you lose heat we can talk about preventing or reducing heat loss.
First of all, let’s pay attention to the well-known and largely spread thermo insulator on earth.
It is air. But everyone who has slept on regular inflating mats on cold ground knows that large
layer of air doesn’t help from freezing because heat transfer by convection inside the mat is
huge. In order to solve this problem a special system of many air layers should be created. The
best insulator has thin walls between small air layers. The synthetic insulation fillers solve this
problem the best. NB! Always shake the sleeping bag several times after storing it in roll so that
the insulation filler will gain air.
There are several important things that you should pay attention to when choosing a sleeping
bag. It’s very important how the insulation fillers are situated in the sleeping bag, and also
fabric and form of the sleeping bag, loose straps, insulation collar, and lots of useful details.
Alexika sleeping bags are developed using highly effective technologies of protective shell and
soft space.
How do you know at what temperatures can you use your sleeping bag Previously every producer
made home-tests of the equipment and decided at which temperatures people can sleep with comfort
in the sleeping bags. But everyone has different perception of cold, and it is not a big secret that
alpinists and mountain climbers don’t freeze as easily as campers. If you take into consideration age
of person using a sleeping bag, nutrition and diet s/he prefers, tiredness, and possible hypothermia,
you’ll get totally different comfort temperatures. Unconscious producers of equipment invented their
temperature rates without any tests. That’s why it was decided to develop a universal test EN 13537
that will use the same methods for evaluation of sleeping bags produced by different manufacturers.
This test doesn’t claim the ultimate accuracy of results because everyone has his/her own perception
of cold but it allows comparison of sleeping bags produced by different manufacturers between each
other. So how the test is implemented
Manikin with attached temperature units and heaters is put into the sleeping bag. Temperature of the
manikin stays at the level of human body average temperature. Sleeping bag with a manikin inside is laid
on the thermo-insulation mat and left in the special camera where the temperature begins to decrease.
Heat units check and memorize the heat loss and according to the test results the temperature rate is
created. That’s how it looks:
+3 0 С -3 0 С -18 0 С
COMFORTABLE
TEMPERATURE
COMFORT LIMIT
TEMPERATURE
EXTREME
TEMPERATURE
It is always better to sweat from heat than die of cold, so maximum air temperature (T max) at which
you’ll sleep with comfort in unzipped sleeping bag may be ignored.
TEMPERATURE OF COMFORT — the lowest temperature rate at which average woman can sleep
during night (8 hours) without feeling cold.
TEMPERATURE OF COMFORT LIMIT — the lowest temperature at which average man can sleep
during night (8 hours) without feeling cold.
TEMPERATURE EXTREME — the lowest temperature at which the sleeping bag protects a person
from hypothermia. Usually at this temperature you can have 6 hours of uncomfortable sleep but
without body indices dropping to hazardous levels.
PLEASE PAY ATTENTION THAT ALEXIKA PREVIOUSLY AND NOW DOESN’T
RECOMMEND CHOOSING A SLEEPING BAG ACCORDING TO TEMPERATURE
EXTREME IF YOU VALUE YOUR HEALTH AND LIFE.
Remember, that the test described above takes into consideration that you wear thermo-underwear, you
are middle aged, your weight is 80 kg (for men) or 60 kg (for women). You feel yourself well, you don’t
have hypothermia and moreover you have good nutrition.
N B!!!
It turned out that even with this test it is possible to deceive customers. The main feature of a sleeping bag is
weight/temperature of comfort ratio. If you take part of the insulation filler from the back of the sleeping bag
(during test it lays all time on the back) and put it into the upper part of the sleeping bag, you’ll get better temperature
rate with the same total weight of the sleeping bag. Such bag instead of volume of insulation filler in
grams on square meter and number of layers will be described in catalogue as having general volume of insulation
filler in whole bag. The meaning of this figure is completely incomprehensible, but if the insulation filler is
taken from the back when you turn on your side you’ll feel that your back is freezing. You should pay attention
to the description of the sleeping bag and feel the upper and lower part of the sleeping bag. Alexika always
gives full information on its products, describes and explains every detail as you can see in this catalogue.
When Alexika was using its own temperature rate before EN 13537 test it took into consideration for
whom the sleeping bag was developed. Prepared people (alpinists, mountain guides, military people)
percept cold better that city inhabitants going on camping once a month. That’s why sleeping bags in extreme
series had lower temperatures than camping ones. We also took into consideration that teenagers
and kids have unbalanced metabolic process and that is why it is harder to tell the average temperature
rate for them. In the sleeping bags for kids and teenagers the number of insulation filler was the same but
the temperature rate was 3-4 degrees higher. We marked it in description of the sleeping bags.
In this article we explained what you should pay attention to when choosing a sleeping bag. We hope that
this information will help you feel comfort in any weather conditions.
ALEXIKA SPORT GROUP // WWW.ALEXIKA.EU