What should I consider when buying a sleeping bag?
This article will concentrate mainly on down sleeping bags and is aimed at people who are going to be using their sleeping bags in tents throughout the year in the UK and who might be going to the Alps in the summer.
Buying a sleeping bag is a serious investment that should last you a number of years. With this in mind it is worth putting in some time to understand what makes sleeping bags different from one another. Your comfort and ability to rest are very important if you want to maintain the necessary level of energy and performance to operate in cold/mountain environments.
There are two types of Fill that can be used in a sleeping bag. Which is best?
Down or Synthetic?
Synthetic
Pros - Very resistant to moisture. Dries quickly and stays warm when wet. Does not require specialist cleaning. Cheaper than down bags.
Cons - Less comfortable in hot weather. Shorter lifespan than down as loft degrades faster and cannot be reinvigorated. Bigger pack size and significantly heavier than down.
Down
Pros - Best warmth to weight ratio. Packs down far smaller. More comfortable than synthetic bags in hot weather due to breathability. Down can be specially cleaned, extending bags lifespan greatly.
Cons - There are three problems with Down. It is not warm when wet, takes a long time to dry and it is more expensive compared to synthetically filled bags.
How do I compare different bags?
Synthetic bags
Fill type - The more expensive brand name insulations like Primaloft, Thermic Micro and Thermolite Extra will be better (warmer for less weight). Synthetic insulation is improving greatly at the moment -Though not as good as down synthetic fills are getting closer all the time.
Fill Weight - With synthetic insulation the heavier the fill weight the warmer it will be.
Construction - A more expensive bag will be better constructed with better cut and baffling to make maximum use of materials.
Temperature/Comfort Ratings - Treat with a great deal of caution. In no way standardised between manufacturers and in no way taking into account the individual that is going to be using the bag. A rough guide only.
Pack down size - Smaller the better
Outer fabric - Less important than with down as you will remain warm even if the bag is wet. All synthetic bags should have a good nylon or similar outer to aid wind resistance and speed drying.
Price - A more expensive bag will be better built, last longer, be lighter due to more efficient use of materials. You get what you pay for.
Down Bags
Fill Power - The volume of a tube a certain weight of down will fill with a set weight resting on top of it. Higher fill power = more loft. More loft=more trapped air in the down. More trapped air in down=more warmth.
- 400 - Budget bedding insulation
- 500 - Used in the cheaper down bags.
- 600 - More expensive due to scarcity, good quality.
- 700 - Pretty expensive, high quality goose down.
- 800 - The very best, very expensive, hard to obtain.
- 900 - So good that you should be sceptical that they are telling the truth.
Beware - The way of testing fill power is different in every country and often between manufacturers. This comes from differences in the size of tubes used, size of down samples used and the amount of weight the down has on top of it in the tube. UK designed and tested bags use the 'Lorch' test to measure the fill which means all UK bags are standardised and comparable.
How can I get around this confusion if I'm trying to compare UK designed and tested bags with international bags?
To compare different manufacturers as a consumer, you have to be careful. Go to manufacturer websites, look at their testing systems. Instead of comparing 4 x 500 fill rated bags, you need to compare 4 x manufacturer ranges. With each range find the bag that most suits your needs according to the manufacturer's specs. If you are dealing with reputable manufacturers they will make all this clear. You will still have 4 bags to compare but they might not all have the same specs on the tag in terms of fill power, loft, etc. Another way to ease comparisons is to only compare bags designed and tested in the UK where the 'Lorch' test means that all fill ratings are standardised.
Temperature Ratings/Seasons
As with synthetics should be treated very carefully. They are only a rough guide. Personnel knowledge of how hot or cold you are in combination with other bag statistics is far more useful.
Compression and Weight
The Weight of a bag in conjunction with Fill Power will be two of the better indicators of how warm a bag will be. Anyone who is going to carry their bag will be preoccupied about the weight and size of the bag. Look at the stats for pack sizes and weights.
Outer Fabric
Water resistant or water proof? Water resistant breathable fabrics are commonplace these days. The more weather proof a bag is the more it will weigh and cost. Pertex outers or similar mean that your down bag can be used in damp conditions with a bivy bag. Fully taped or partially taped waterproof outers are becoming more common but obviously at a higher price. They offer a greater degree of weather proofing and if used in conjunction with a bivy bag mean the only way water will get in is if you take it in with you. Unfortunately this can be a real problem. Thicker, more waterproof outers have the disadvantage that they slightly reduce the downs ability to loft due to the weight of the outer fabric. They also mean the down is sometimes less able to shed moisture produced by your own body in the bag. It is up to the individual to decide what the greater danger is; water from the inside or out.
Bag shape Design
This is important but especially so if you are taller or shorter than average. Bags are not all the same shape, with some being cut tighter than others. You want a bag that is snug so that there is less air for you to have to warm up and no big pockets of air between you and the insulation. A baggy bag that you have loads of room to move around in will not be as efficient at keeping you warm. If you can't find a bag to fit you it is worth looking into bespoke manufacturers of sleeping bags. Baffle design used to be a serious selling point when Trapezoid baffles were introduced. They eliminated the problem of cold patches where the baffles were stitched together. Since their almost universal adoption however it has become less of an issue.
Zip or no zip?
Zips add extra weight and allow the cold to enter. They also offer flexibility in terms of allowing you to open the bag and cool down which can be just as important in terms of sleep as warming up. Remember to get a bag with a left zip if you are right handed or a right zip if you're left handed.
Price
With down bags this really is a good indicator of what you are buying. There are aspects of production that are hard to indicate statistically on the tag. These relate to the processing of the down. An in depth look at this is beyond the scope of this article but processing has a massive impact on the effectiveness and longevity of the down in your bag. European down is often better washed, plucked, dried, sorted and blended when compared to Chinese down. It will last much longer, be much more resilient and deal with re cleaning better than cheap down.
Weight and Fill Power Combined
Before temp ratings and season indicators climbers looked at fill power in combination with bag weight. They knew a 4-500g bag was for the summer and that a 900g bag or more was for the winter. Then they would look at the fill power. If they knew they suffered from the cold they knew that a 500g summer bag was still what they wanted, but they would make sure it had a 700 fill power rating giving them a slightly warmer summer bag. This is still an excellent system. It does however rely on a degree of personal experience. If you do not have this, talk to friends and shop staff.
Image: The Bashikirov Pillar on Admiral Peak, Ak Su, Kyrgyzstan, © Neil McAdie