Sleeping Bag Temperature Ratings
More Articles Related to Survival GearWhen you are looking through a manufacturers catalog you will notice that most include sleeping bag temperature ratings. There is no standard way to calculate a temperature rating for sleeping bags but a number of parameters always come into play when it comes to having a warm sleep.
Sleeping bags are an excellent addition to your survival gear. If you want to buy a sleeping bag and choose the right one, the following is required reading
Factors In Sleeping Bag Temperature Ratings
Loft or thickness of the sleeping bag. The thicker or "fluffier" the sleeping bag the warmer it will be.
Hooded bag or hoodless. Adding a good hood to a sleeping bag aids greatly in its temperature rating
Is the bag snug or roomy. The less air space in the sleeping bag, the less you have to heat with your body.
How does the bag control drafts? Sleeping bag zippers and seams leak cold air like a sieve. There needs to be some way of blocking this cold air from entering your sleep space.
Type of insulation material and quality
Insulation construction. Methods used in the sleeping bag construction include baffled, sewn-through, and shingled.
Permeability of air through the shell of the sleeping bag. Even a small breeze can bring the percieved wind chill temperature lower. Wind can increase the amount of cold air that penetrates the material of the sleeping bag and carry away heat you have generated.
Other Factors of Warm Sleep
In addition to the sleeping bag itself, other factors that cannot easily be quantified must be considered when calculating the warmth of a sleeping bag.
Factors that may effect the temperature comfort zone of your sleeping bag are many and varied. Every person is different and conditions of both the individual and the environment differ at any any given time.
One night you may feel warmer than another night. Perhaps you are physically stressed from a strenuous day, lack of food or dehydration. Perhaps there is a stiff wind blowing or your bag is a little damp. Some people sleep cold, others hot. Men tend to produce more body heat than women, and a mans body mass tends to be higher than that of a womans and so tends to cool down more slowly.
Using Loft to Calculate Sleeping Bag Ratings
There is no clear cut way to determine the temperature rating of a sleeping bag for each individual and every environment. However, loft is a good starting point from which to calculate the warmth of a sleeping bag without actually testing it in the field.
In addition to loft, there are key perfomance features we can use to estimate the relative temperature rating of a sleeping bag as compared to other makes and models.
As a general rule of thumb, for a good mummy type bag from a reputable dealer, with insulated hood, drawstring, and draft collar at the zipper, well sewn with no exposed seams etc, when the temperature is below freezing you can expect about 10 degrees F of warmth for every one half inch of insulation above you. Insulation that is compressed underneath you is next to useless and so does not count.
Here is rough guide to sleeping bag warmth as a function of loft. Assuming 1.8 inches of loft will keep you warm at 30 degrees F:
Warmth of Sleeping Bags Loft Chart
| Temperature | Inches of loft |
|---|---|
| 30 degrees F | 1.8 inches |
| 10 | 2.3 |
| 0 | 2.8 |
| -10 | 3.2 |
| -20 | 3.7 |
| -30 | 4.2 |
| -40 | 5.2 |
Of course this is just a very rough estimate of sleeping bag temperature performance and is a starting point from which the proper bag can be selected.
Extending the Warmth of your Bag
The addition of dry warm sleep clothing, a sleeping bag liner, a tent or small windproof shelter that allows some of your body heat to accumulate, and extra sleeping pads beneath you can greatly add to the warmth of a sleeping bag.
As in every survival situation, awareness is a key tool. To select a sleeping bag properly you need to know your temperature comfort zones while sleeping in the conditions you expect to encounter while outdoors. Add a little margin for error should you be exhausted, hungry, dehydrated, or even injured.
As stated in other articles on SurvivalTopics.com, often your best bet is to use a two bag system. A main bag rated about zero degrees F and a second lighter bag rated to about 35 degrees F. Combine the two and you are set to well below zero. This gives you four season capabilites in most conditions you are likely to encounter.
You are welcome to share this Survival Topic with others. I only request that you use a short blurb (not the entire survival content) and this code to
link to the origional:
