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Sleeping Bags for Extreme Cold Weather Conditions
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Sleeping Bags for Extreme Cold Weather Conditions

Written by: Dr. S Ariharasudhan Dr. S. Sundaresan R Senthil Kumar

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A sleeping bag is an insulated, lightweight, portable bedding designed for outdoor sleeping activities such as camping, hiking, and climbing. It is essentially a quilt that can be zipped up to form a tube, offering a cozy sleeping environment. The construction of a sleeping bag includes an outer layer, an inner lining, and a filler for insulation. The main purpose of a sleeping bag is to provide warmth and protect against cold weather by trapping air inside, which is then warmed by the body’s natural heat.

When selecting a sleeping bag, important factors to consider include the temperature rating, shape, size, fit, and insulation type. Sleeping bags are typically categorised by their temperature ratings, with most designed for use in conditions ranging from 10 to 50 degrees Celsius, catering to the popular summertime camping. Models rated for 10 to 35 degrees are ideal for spring, fall, and mild winter conditions, while bags rated at 10 degrees and lower are suitable for cold winter weather.

Table 1 Thermoregulation of Human body

Thermal Radiation

Thermal radiation is the transfer of energy through electromagnetic (EM) waves.

Breathing

In colder temperatures, the body loses heat and moisture through breathing.

Conduction

It happens when solids come into contact with one another.

Convection

It is the movement of molecules within fluids (liquids and gases) caused by heat transfer. It happens when liquid or gas molecules move apart.

Evaporation

The human body sweats in order to regulate body heat. This evaporative cooling process is an effective reaction when human body attempts to cool itself down, yet ineffective if the sweat is not able to evaporate away from human body.

Factors Influencing Thermo-regulation of Human Body

Slim or Heavy: People with greater fat reserves have better insulation potential. People with greater muscle mass also produce more heat and do not cool down as quickly. Slim people usually consume as many calories as they burn.

Gender: Women tend to generally feel cold faster than men. The average comfort value for a standard female is 5o C higher than for a standard male.

Age: Metabolic rates tend to slow down as one becomes older. The lower the metabolic rate, the less body heat a person generates.

Condition: People who are physically fit and often spend time outdoors are less susceptible to cold. In addition, when a person is exhausted their body generates less heat as well.

Energy Input & Consumption Before Going to Sleep: The amount of energy or warmth generated while sleeping is affected by a person’s activities and energy input.

Sleeping Bags – Construction

Sleeping Bags comprise an outer layer, a filling, and an inner lining. Within the sleeping bag’s shell are a number of chambers called Baffles. Baffles contain the down used to insulate. The better their design, the better the performance of the sleeping bag. To insulate efficiently the down has to loft, which means to expand as it traps warm air. Too much space in the baffle is inefficient as the down disperses. Too little space constricts the down and it cannot loft fully. There are a number of different types of baffles. All have advantages and disadvantages, which vary depending upon the type of product.

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Table 2 Types of Baffles

Stitched Through Baffles, Box wall Baffles

Used on cheap sleeping bags, extremely lightweight sleeping bags and sleeping bag quilts

V Baffles

V Baffles are the most thermally efficient baffle

Trapezoid Baffles

Has more chambers to store the down and less chance of it dispersing

Brick Baffles

Brick Baffles are used for extreme cold weather down sleeping bags

Sleeping Bags – Materials

Table 3 Properties of Outer Layer/Cover fabrics

Types

Properties

Water resistant

MVTR/g/m2 hr

GSM

PERTEX Fabrics

1,000 mm water column, after 7 wash cycles

7,000

45

TEXPED PRO

1,000 mm water column after 5 wash cycles 

22,000

41

Nylon/Polyester

1,000 mm water column after 5 wash cycles

12,600

40

Vapour Vent (V2)

1,000 mm water column after 6 wash cycles

15,500

46

Ripstop fabrics

1,000 mm water column after 5 wash cycles

13,500

42


Table 4 Filling / Insulation Layer Material

Material

Properties

Material

Cu.in

Down

It is a pure, natural, thermal-insulation product. It is grown by birds, and in cold climates, it enables them to survive severe weather conditions.

Duck down

550

Loft

It is a type of an insulation material to take in air and expand.

Chinese goose down

600

Alpine wool fibre filling

Alpine wool used in sleeping bags serves as a natural air conditioning system.

Hungarian goose down

660

Down wool

It is an innovative high-end filling made of 70 per cent down and 30 per cent specially treated wool.

Polish standard goose down (grey)

680

Synthetic fibre filling

It is very popular for sleeping bags because it has a very high level of insulation.

Polish super goose down

800

Insulation layer materials

Filling material

Fill power

Weight of down (g)

Total fill volume

Using Chinese down

600

900

18000

Using Polish diamond

870

700

20300








Table 5 Bag Liner Materials

Bag Liner Materials

Silk

Very lightweight (about 5 oz.) and compact

Cotton

Strong, durable and absorbent

Fleece and microfleece

Soft, moisture-wicking and quick-drying

Synthetics

Moisture-wicking and breathable

Insulated

It uses hollow-core fibre insulation


Table 6 Shapes of Sleeping Bags

Rectangular

These bags allow plenty of room for both legs and arms to stretch out

Semi-rectangular

Offer a compromise between warmth and roominess

Mummy

Boost warmth and cut weight, this bag style has a snug fit

Double bags

Bags made for two are the best for couples who plan to sleep together

Kid-size sleeping bags

These are simply shorter, smaller and more affordable

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Conclusion

A sleeping bag is an essential textile product that is aimed at protecting people in cool or cold outdoor environments. They are widely used in field training, rescue and relief work and are also becoming common equipment in travelling and recreation for ordinary people. Sleeping bags serve as an important protective textile product for human body while sleeping under cool or cold outdoor environments. A sleeping bag should allow the wearers to sleep for four to eight hours without feeling cold under the bags’ operating temperatures.

References:
  1. An, Y., Xu, G. and Shen, H. (2021), "Factors influencing thermal resistance of a down sleeping bag", International Journal of Clothing Science and Technology, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/IJCST-05-2020-0071
  2. Yuying An, Guangbiao Xu, Hua Shen “Factors influencing thermal resistance of a down sleeping bag International” Journal of Clothing Science and Technology, ISSN: 0955-6222
  3. W. F. Song, C. J. Zhang, D. D. Lai, F. M. Wang & K. Kuklane “Use of a novel smart heating sleeping bag to improve wearers’ local thermal comfort in the feet”
  4. Huang, J. Prediction of air temperature for thermal comfort of people using sleeping bags: a review. Int. J. Biometeorol. 52, 717–723 (2008).
  5. Goldman, R. F. Biomedical effects of sleeping systems in Handbook on clothing: Biomedical effects of military clothing and equipment systems 2nd edn (eds. Goldman, R. F. & Kampmann, B.) Ch. 6b, 1–8 (International Society for Environmental Ergonomics, 2007), Scientific Reports volume 6, Article number: 19326 (2016)
  6. Zhang, C., Lai, D. Lu, Y., Wang, F. & Kuklane, K. Smart heating sleeping bags for improving wearers’ thermal comfort at the feet. Extrem. Physiol. Med. 4, A92 (2015).
  7. Chengjiao Zhang “Smart heating sleeping bags for improving wearers' thermal comfort at the feet” September 2015Extreme Physiology & Medicine 4(Suppl 1):A92
  8. Forough Amirshirzad “Assessment of the effect of body pressure on the warmth retention in sleeping bags” The Journal of The Textile Institute, 16 Feb 2021.
  9. Meredith Schlabach “Determining temperature ratings for children's sleeping bags” International Journal of Industrial Ergonomics, Volume 65, May 2018, Pages 153-160
  10. S. D. Livingstone “The composition of air in sleeping bags” International Journal of Biometeorology volume 32, pages29–32 (1988).

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