Learn Gear An introduction to down jackets and sleeping bags

An introduction to down jackets and sleeping bags


When temperatures drop, nothing is quite as inviting as a down jacket or sleeping bag. But what should you look for when choosing down products? This article outlines some factors to consider when investing in new down gear:

Down jackets and sleeping bags feel so warm because down (the soft under feathers from ducks and geese) is naturally very good at trapping a layer of air around your body. The more effective it is, the warmer it feels. It’s also incomparable in terms of packability, warmth for weight, longevity and resilience. Down is measured in two ways, fill power and quality. For maximum warmth, look for maximum quality:

Fill Power

This is a measure of the strength of the down or its ability to resist compression under a standard compression force, but also how well it can loft (puff up). Any down as a raw material when placed into a sleeping bag or jacket will lose a certain percentage of its fill power. This loss can be increased further depending on how the bag is stored and how dirty it gets during use, so it’s important to take good care of your down products.

Down Quality

Down is graded according to the mix of pure down clusters to small feathers. This is expressed as a ratio i.e. 96/4, or sometimes as a percentage 96%. The purer the down, the better it will be at trapping air and thus warmer.

Temperature Ratings

Sleeping bags are given temperature ratings which give an idea of comfort (although be aware that different manufacturers may use different guidelines to determine a sleeping bag’s rating). The ability of a sleeping bag to meet the given rating depends on a wide range of factors including the individual’s metabolism, level of fitness, degree of fatigue and hydration, standard of diet, climate and altitude, wind conditions, humidity and type of accommodation. These will all have a profound effect on how warm the bag is.

Construction Methods

The construction methods used in down jackets and sleeping bags are just as important as the filling quality. The best (and most expensive) methods are Box Wall (single and double), and Trapezoid. These methods use separate pieces of fabric that create individual channels in between the inner and outer fabrics of the jacket or bag. These types of construction vastly reduce the opportunity for cold spots and as such are used mainly in down sleeping bags. The main other type of construction is ‘stitch through’, which is basically two pieces of fabric sewn together. This is mainly used in down jackets, as it allows more freedom of movement combined with adequate insulation when hill walking.

Shell Materials

Shell materials provide durability and are the only real variable in producing lighter down sleeping bags, as the down itself is pretty much a fixed weight. Manufacturers use a variety of fabrics to perform different functions. One of the most important considerations is the ability of the fabric to be ‘downproof’ so that the down doesn’t escape over time. Strength is also important, and top end fabrics feature ripstop to provide additional durability. There are two main types of fabric:

Coated fabrics

These fabrics have a coating on their inside face, affording the bag more protection from wind and snow, and giving increased protection against water. Coated fabrics give the bag a higher thermal efficiency due to the amount of air being trapped.

Uncoated fabrics

These fabrics feel softer and lighter than coated ones and arguably provide a more comfortable night's sleep night after night. Advances in technology have enabled superlight fabrics to be developed, giving outstanding strength to weight ratio with a super soft silky feel - which actually allows down products to loft better.

How To Look After Down Jackets & Sleeping Bags


When packing a sleeping bag or jacket made with coated fabrics into a stuff sac, turn it inside out first. This will allow the air from the loft of the down to be squeezed out more easily, the product to pack smaller and re-loft a lot easier.

Feather Leak

If a feather from the down pokes through the fabric, never try and pull it out – pull it back into the bag or jacket from the inside. This stops the hole getting bigger and additional down escaping in future.


Always use a sleeping mat. This stops heat being lost through conduction into the ground. This is especially important when you consider that when you lie in a down bag you squash most of the insulation on the underside limiting its ability to provide any insulation.


Always store down products loose in a cool dry location. Most manufacturers supply a cotton storage sac for sleeping bags. Never keep down products in a storage sac or even worse a compressed compression sac, as this will damage the down irreversibly. Never store down damp, always make sure the bag is well aired, otherwise it will smell and the only remedy will be to have it cleaned professionally.


It is inevitable that all down bags will need to be cleaned after a time, but using a liner will reduce the amount of body oils and dirt entering the bag.


Due to the long life of a quality down bag (10-15yrs) - they will inevitably need to be cleaned at some stage. To avoid damaging them, only use specialist products designed for washing down and follow the instructions carefully. If you don’t want to take the risk of washing them at home, most suppliers of down products also offer a cleaning service which costs a fraction of the price a new jacket or sleeping bag.  [Link to sustainable steps guide with list of suppliers].

Animal Welfare

If you’d like to know more about the source of down, the Responsible Down Standard independently certifies down against animal welfare requirements and tracks it from the source to the final product.

For more information about ways to repair, recycle or upcycle old kit check out the BMC Old Gear Directory.