Choosing a sleeping bag

Your sleeping bag should be long enough, lightweight, easily compressible, have a hood, a full-length zip, a neck/zip baffle and be warm enough for the coldest temperatures you expect. Being warm in a sleeping bag is not just due to the design and fill. Let the sleeping bag ‘loft’ up before getting into it and use an insulating mat. Exercise and eat something to get warm before getting into your bag. Fill your Nalgene water bottle with hot water and take it to bed.

Consider the following when making your choice: 

  • Mummy-style bags insulate more because there are less interior dead areas, but they can be constricting. If you camp only in warm places a rectangular bag is more comfortable.
  • There are two methods of constructing sleeping bags - sewn through and box wall. ‘Sewn through’ bags are colder than ‘box wall’ construction.

Despite continued advances in synthetic insulation technology, down is still the best choice in terms of performance, however it is more expensive and needs specialist cleaning. Down-filled bags are lighter, compress better and last longer than synthetic versions. The oils in the down mean it will recover its loft quickly and dry as rapidly as synthetic materials even after a soaking. Advances in the materials used to cover down bags mean that most will cope with drips of condensation and dry much quicker. Materials like Dri-Lite or Pertex Endurance have been specifically developed to provide weatherproof protection todown-filled products. (Use a Gore-tex bivvy bag if wetness is a problem and air the bag frequently). 

Synthetic bags are less expensive and provide some insulation even when wet and may be better if you are in a continually damp environment for days. They dry out fairly quickly and are non-allergenic, but are heavier and bulkier. They also lose their lofting ability more quickly due to constant compression as it is packed away.

Down strength

The best bags have 95 per cent Goose down with 5 per cent chopped feathers. The main way to compare the warmth of bags is by looking at the down's 'fill power'. That measures how much space a set sample of down occupies in cubic inches, and hence how much insulation it will provide for its weight - a 30 g sample of down with a fill power of 600+ will occupy a minimum of 600 cubic inches. Therefore, the higher the fill power, the better the performance of the bag. A 550 fill power is used in mid-range bags; anything over 650 is excellent. These figures are for the European fill power test and in the USA the figures are higher, but mean the same!

Caring for your sleeping bag 

Never leave it damp. Air dry it every day and after every trip. Stretch it out on a bed or floor in a dry room until you know it is dry and, to prevent the breakdown of the filling, leave it loosely packed. Washing a down sleeping bag is to be avoided because it removes duck oils but if necessary, use a small amount of down soap, a gentle cycle and rinse well. Take care with a wet bag - the shell and the baffles can rip. Don’t separate the down by hand, but use a tumble drier with a couple of tennis balls. 

Insulating mats 

Your body weight compresses a sleeping bag's insulation when you lie on it, so you need a reliable buffer between your bag and the ground. An air mattress is comortable, but will not insulate you.

Closed-cell foam mat - Made from dense foam filled with closed air cells. They're cheap, durable, non-absorbent, won’t deflate and insulate well depending on thickness. However, they are stiff and not very comfortable. To make it easier to strap to the side of your rucksack cut it into convenient strips then stitch and tape them back together.

Self-inflating mat – Expensive, very comfortable and insulate well, compact when rolled up, but are heavier. The only downside is that they can be punctured, but they are repairable (with a proper repair kit) even in remote places. Short version are fine but leave your feet to get cold. The surfaces of some models can be slippery with the result that you slide off during the night.

Down-filled mats - These offer the highest degree of insulation available without the bulk or weight but are by far the most expensive.