INSULATION
There are two two types of insulation:
Down: The best for weight and bulk. Most down is now treated with a water-resistant coating to maintain loft and prevent dumping when wet. Check the label to make sure the down is dry treated. Most manufacturers use down that meets the Responsible Down Standard for animal welfare.
Synthetic: A good option for prolonged damp conditions, lower budgets or where weight is less important. The bags are heavier and less compressible than down for the same warmth rating but are durable, easier to wash and they’ll be warmer when wet. High-end and budget synthetic bags are available.
FILL POWER
The fill power (or loft) of a bag indicates the insulative quality of the down in the bag. Bags with high fill power numbers, e.g. 850FP, use less down to achieve the same warmth as a bag of, say, 600FP which will be heavier and less compressible. The higher the fill power, the more expensive the bag.
TEMPERATURE RATING
Ratings are approximate, however, bags in this feature have all been tested to the temperature ratings standard EN13537 or, for bags sold outside Europe, ISO 23537-1. The temperature ratings shown are:
The temperature
