Everything you need to know about the Sleeping Bag

When we go out into nature in search of starry skies, one of the most important decisions we must make is which sleeping bag to take.

A good sleeping system for sleeping in nature pays off in comfortable and restful hours of sleep.

These are the key factors to take into account:

• Temperature ranges: It is advisable to choose a bag rated slightly below the typical/expected outdoor temperature.
• Sleeping system: In addition to the sleeping bag, it is essential to have a good insulator.
• Padding: Foam or synthetic? Several factors play a role here, such as heat containment power, compression, durability, weather conditions and humane treatment of the animals.
• Weight: A bag needs more insulation material to have a lower (i.e. warmer) temperature rating. Therefore, we should compare the weight between bags with similar temperature ratings.
• Other features: types of adjustment, fabric types, hidden pockets, pillow compatibility, etc.

Sleeping bag temperature ranges

The temperature ratings of a sleeping bag identify the temperatures for which it was designed. It is always advisable to choose a sleeping bag with a temperature rating a few degrees lower than the lowest temperature we expect to encounter. For this task, it is important to understand temperature ranges and their terms:

• An ISO or EN approved temperature range indicates that two sleeping bags can be reliably compared with respect to the manufacturer’s temperature specification. These standardized tests ensure that temperature ranges can be reliably compared between manufacturers (brands).
• Based on ISO/EN standardized tests, the bag is assigned temperature ranges: maximum, comfort, limit and extreme.
  • The “comfort” rating is the lowest temperature at which the bag will keep a cold person comfortable during sleep and is usually associated with the comfort temperature for a woman.
  • The “limit” rating is the lowest temperature at which the bag will keep a person who is not usually cold at night comfortable and is generally assigned to the comfort temperature for a man.
  • The “maximum” rating is optional and indicates up to which temperatures the bag does not generate excess heat; while the “extreme” temperature is for survival for 6 hours without going into hypothermia. Outside these ranges it is not possible to fall asleep.

Rest system

The sensation of cold when sleeping depends on many variables, including humidity, wind, type of shelter and soil conditions. However, it is the sleeping system that is critical. This system has three basic components: 1) the sleeping bag, 2) the insulation and 3) the clothing.

If we use an insulator with poor insulating power in cold temperatures, the sleeping bag will not live up to its rating. The rating of a sleeping bag is based on a person wearing full-length underwear and socks, along with an insulator for extreme conditions.

Insulation, clothing and bag work together. In this table, we show you how they should be complemented, depending on the weather conditions:

*The value of R is a measure of how well a surface barrier, i.e. a layer of insulation, resists the heat-conducting flow.

Recommendation: if you usually feel hot when sleeping, take into account the “limit” temperature of the range. If you usually feel cold when sleeping, go for the “comfort” temperature.

Fillers

These are the most important differences between feather and synthetic fillings:

Some additional details about each type of filler: Feather: On average, it is more expensive than synthetic fillers, lighter and more durable. When comparing qualities, we can focus on these points:

• What doesfill powermean? It is a specification that indicates the quality of the material. If the number is higher, it is because it generates more warmth.
• Is there such a thing as water resistant down? Yes, some manufacturers use feather fillings that have a water repellent treatment.
• What is RDS/TDS and how does it relate to the humane treatment of animals? Indicates that bag manufacturers have taken steps to ensure the humane treatment of the ducks and geese that produce the material through the following programs: RDS (Responsible Down Standard) and TDS (global Traceable Down Standard).

Synthetic: Offers solid performance at an affordable price. Unlike down, it continues to keep you warm when wet, making it the best choice for humid climates. Most of these fillings are polyester-based.

The filler is what determines the size of the bag when compressed. Therefore, we must compare “compressed volume” specifications to understand the size differences between bags.

Weight of the sleeping bag

The most important factors are the filling and shape. Advanced synthetics and feathers with high filling power provide more warmth for less weight. Fill weight: The total weight of the bag is what matters when carrying a bag in a backpack. However, some manufacturers also indicate the weight of the filler, i.e. the insulating material of the bag. In non-approved bags, we can use this value as an indicator of the warmth capacity (if it has more padding, it will be warmer). Bag shape: Sleeping bags come in three basic shapes.

• Mummy: In order to increase warmth and reduce weight, this bag has a slim fit, with a contoured hood that can be adjusted. The fit is ‘to the body’ and, if we turn to change position, we will do so next to the bag.
• Semi-rectangular: Also known as “modified mummy” or “barrel”. Offers a balance between warmth and comfort.
• RectangularCamping bags: Generally, these are camping bags. They offer comfort of movement when sleeping, but are heavier.

All sleeping bags keep you comfortable, because they retain the air heated by your own body. But this task is easier in a small space like a “mummy” bag, and more difficult in a large space, as is the case with rectangular formats.

Finally, we must consider what is the most appropriate size. Most bags come in regular and long sizes, although there are shorter variations for smaller people.

Additional features

Adjustable hood: Provides extra warmth, especially when the collar is adjusted around the head and only the nose and mouth are uncovered. Draft blocking: Air tubes run the length of the bag behind the zipper to prevent warm air from escaping. Anti-zip closure: Some bags protect the closures with a full-length zipper protector. Left or right zipper: Intended for ‘joining’ sleeping bags. One person has a bag with a zipper on the left, the other has a bag with a zipper on the right, and a special zipper joins the two bags together. However, it creates additional air space inside and limits the comfort of movement. Hidden pocket: Generally located on the chest, it is useful to protect items such as a watch, headlamp, GPS and extra batteries from the cold. Pillow pocket: Some bags include this pocket in the hood that allows you to tuck clothing inside. Sleeping bag outer shell: Usually made of rip-stop nylon or polyester. Some are treated with a durable water repellent (DWR) finish to keep out moisture.

Accessories

Compression bag: These are cloth bags with straps to easily compress the bag. Resting bag: Leaving a sleeping bag compressed for long periods of time affects its ability to insulate. For that, large bags are used where the bag can be stored without being compressed. Thermal bag liner: This is a cylindrical fabric envelope that slides inside the bag, helping to minimize wear and tear and keep the bag clean.