25 August, 2014
Choosing the right sleeping bag for camping, travelling, hiking or mountaineering is not an easy task. There is a seemingly overwhelming number of options to consider and the terminology used to describe sleeping bags can be quite confusing: down or synthetic; duck or goose down filling; white or black down; loft power; DWR down; tapered sleeping bags, hooded sleeping bags; EN temperature ratings; continuous baffles or side block baffles just to mention a few. If you are baffled by the lingo then read on. In this blog post I'll provide an overview of the types of sleeping bags available and help you choose the right one for your needs.
Sleeping bags offer you the most efficient way to keep your body warm, and are much warmer for their weight compared to any type of clothing. With a sleeping bag usually being the second heaviest item in your bag after a tent, selecting a lightweight sleeping bag will help to keep your pack weight to a minimum.
Sleeping bag insulation or “fill”
Sleeping bag insulation comes in two types of fillings: synthetic or down.
Synthetic insulation is generally made from a polyester filling and offers the following benefits:
- Keeps you warm when wet
- Dries quickly when it gets wet
- Is cheaper to purchase than down
- Is non-allergenic
Down insulated sleeping bags offer the following advantages over synthetic insulation:
- Is lighter and more compressible than synthetic fill
- Is extremely durable and lasts longer than synthetic fill – you can expect the down within a sleeping bag that is 30 years old to still be close to its original quality whereas synthetic filling breaks down quicker and loses its insulative power much sooner than down.
- Historically lost its insulative power when wet. Many high quality down sleeping bags now have a treatment on the down to prevent this from happening. Good quality down sleeping bags that are intended for backpacking, hiking and mountaineering will also have a water resistant and breathable material encasing down within the sleeping bag to ensure moisture does not make its way into the down filling.
What is Down?
Down is a layer of insulation found under the exterior feather of birds. It holds more insulative capacity and is lighter than normal feathers. Sleeping bags that offer a mix of feathers and down will be bulkier and less warm than if the same sleeping bag was filled with down only.
What about Grey or White Down?
Down and feathers come in various shades ranging from pure white to black-speckled grey. The colour of feathers has no relevance to the quality of down with many grades of grey down rivalling the best white down.
Duck Down or Goose Down - which is better?
Although all birds have some feathers and down, the majority of down used in bedding and sleeping bags is harvested from geese and ducks. Geese, which are larger birds, generally have bigger down clusters. As a rule of thumb, the larger the bird and the colder the climate in which they live, the larger the down cluster. High quality down can be found in both ducks and geese, as the age and climate of bird from different parts of the world dramatically effects its quality. The best way of knowing the insulative power of the down within the sleeping bag is by referring to its Loft Rating, or Fill Power which is explained below.
What is Fill Power or Loft Rating?
Loft rating or fill power of a sleeping bag is a measure of the loft or volume of the down and its ability to regain its volume after being compressed. It provides a measurement on how well the down "puffs up" and what volume it fills. The higher the fill power or loft of the down, then the better the down's insulative capacity will be (warmth to weight ratio). Technically, it is the volume (number of cubic inches) that 1 oz of compressed down, when released and uncompressed will expand or "puff-up" to fill under specific laboratory conditions. So 550 Loft or 550 Fill means that one ounce of 550 loft down, when uncompressed will fill 550 cubic inches. The higher the loft, the more insulative the down is for it's weight. So if you are wanting the most thermally efficient sleeping bag for it's weight and pack-down size, going a higher loft rating is the key.
What is Hydrophobic or DWR (Durable Water-Repellent) Down?
Down is the best insulation for lightweight camping and travel because of its loft, compressibility and durability. However, down loses it's capacity to insulate once wet. Hydrophobic or DWR down is a treatment that is applied to down to prevent down from absorbing water and allow it to dry out faster.
Sleeping Bag Shapes
Sleeping bags come in a variety of shapes: rectangular, semi-rectangular, and mummy.
Rectangular Shaped Sleeping Bags
Rectangular sleeping bags are spacious and comfortable, and provide extra space for people who like to move around in their sleeping bag. They are particularly suitable for car campers or travelling where weight and size is not an issue. These types of bags can usually be unzipped to double as a quilt also. They are bulkier and generally less thermally efficient as there is more air space in the sleeping bag around the body that needs to be heated, and more air will move around within the bag when the sleeper rolls in their sleep.
Tapered or Semi-Rectangular
Tapered rectangular bags are more thermally efficient than the rectangular sleeping bags but still offer some space in the sleeping bag for those wanting some extra room in their bag. They tend to have zips and openings in the bag so they can be opened up to be used as a doona also.
Mummy Shaped Sleeping Bags
The mummy-shaped sleeping bags are the most thermally-efficient shape of bag, with a shape that sits close to the sleeper’s body, with very little space within the bag for cold spots to form. These sleeping bags provide the most warmth for their fill, and have the least internal space. These bags will hug your body and will move with you when you roll in your sleep.
Sleeping Bag Fabrics
Sleeping bag fabrics need to fulfil a number of roles: stop the fill from escaping from the bag; allow body moisture to escape from the bag and keep moisture from entering the bag. Sleeping bag fabrics are usually made from a quick-drying material and in down sleeping bags prevent the down from coming through the fabric. Sleeping bag fabrics come in different weights, measured by the fineness of the threads making up the weave. Denier is a unit of measurement that is used to determine the fibre thickness of individual threads or filaments used in the creation of textiles and fabrics. Fabrics with a high denier count tend to be thick, sturdy, and durable. Fabrics with a low denier count tend to be sheer, soft, and silky. High performance sleeping bags use a ripstop fabric to minimize tearing, and will use lighter fabrics that feel luxurious against the skin and will pack down smaller than heavier fabrics. Waterproof, or water resistant fabrics are used on sleeping bags intended for use in wet conditions.
Sleeping Bag Construction
Down sleeping bags are made with baffles or channels that are created by sewing mesh barriers between the inner and outer of the sleeping bag. These barriers allow for air to circulate between baffles and for the sleeping bag to compress when packed down. There are two main types of baffle construction: continuous baffles, which allow you to move down around within the sleeping bag; and side block baffles, which keep the down in its place. Sleeping bags designed for use in colder conditions will tend to use side block baffle construction to keep the down its place.
A cheaper alternative to baffle construction is the sewn-through, or stitch-through technique. Sewn-through sleeping bags have the shell and liner pinched and stitched directly together to join the two layers. There's no vertical baffle wall, though the individual channels of down are commonly referred to as baffles. Sewn-through construction creates colder spots at the seams, allowing heat to escape, so it's better suited to warm weather bags.
Hooded Sleeping Bags
Many winter sleeping bags are constructed with a hood and draw-cord to minimise the amount of heat lost from your body while sleeping.
Neck Baffle or Draft Collar
Neck baffles or draft collars are an insulated tube that sits around your neck and shoulders and prevents warm air from escaping within the sleeping bag and from cold air from entering the bag. These are used predominately in winter sleeping bags.
A draft tube in an insulated tube that covers over the sleeping bag zipper to reduce heat loss.
The foot box in a sleeping bag varies depending on the style of bag, with the foot box being more tapered and filled with more down for bags designed for colder conditions.
Stuff Sacks and Storage Bags
A stuff sack is used to compress your sleeping bag down to its smallest possible size when you need to put your sleeping bag into a backpack or bag. When your sleeping bag is not in use, it's best to keep your bag in a larger storage bag to let the down fully uncompress.
Sleeping Bag Temperature Ratings
How warm you are in a sleeping bag is affected by three factors:
- The environment you are in: how cold it is outside, what you are sleeping on, if there is a breeze, etc.
- Yourself: if you a hot or cold sleeper, if you have a fast or slow metabolism, the clothing you are sleeping in, when you last ate or drank.
- The type of sleeping bag you choose.
What is EN 13537?
In recent years sleeping bag manufacturers have adopted a new sleeping bag temperature rating called 'EN 13537: 2002 Requirements for Sleeping Bags’ that was originally developed in Europe. It applies to all sleeping bags with the exception of those for extreme temperatures (comfort range below -25ºC) and sleeping bags used by the military. The test uses a copper mannequin, fitted with 20 sensors, that wears long underwear and socks, and lies on top of a thin sleeping pad and an elevated 12mm thick wood platform.
There are three ratings that you need to pay attention to when looking at sleeping bags rated using this system:
The ‘Comfort’ rating is a guide for women and is based on a ‘standard’ woman having a comfortable night’s sleep. This rating is also the one to go by if you are a male who feels the cold more - or is a 'cold' sleeper.
The ‘Lower Limit’ rating is a comfort guide for men and designates the lowest temperature at which a man can remain comfortable in the sleeping bag, providing he is wearing thermal underwear and socks and sleeps on a 2.5 cm thick sleeping mat.
The‘Extreme’ rating designates the coldest temperature you can survive in the sleeping bag without freezing to death. According to EN 13537, ‘a strong sensation of cold has to be expected and there is a risk of health damage due to hypothermia’. This is a survival rating only, and consumers should not rely on this rating for general use. The best guidelines are the comfort and limit of comfort ratings.
So there you go, I hope this post provides some helpful advice and makes your decision in selecting the right bag a lot easier. When you need to purchase a bag, check out our lightweight range of down and synthetic sleeping bags available for purchase here: https://www.sevenhorizons.com.au/collections/lightweight-sleeping-bags
- Tim Coles, Seven Horizons