Arctic Survival – Sleeping Bags
In extreme cold conditions only mummy bags should be used. Rectangular bags allow too much heat loss and rarely come with hoods, which are essential. Some mummy bags come with left and right zippers so couples can zip their bags together and combine their body heat.
Not all bags are equal, and generally you get what you pay for. There are several points to look out for when shopping for a new sleeping bag.
Down Vs. Synthetic
Often we think of down being a superior insulating material, but this is not necessarily the case. Both down and synthetic have pros and cons, and the better choice depends on your needs.
Down: The main advantage of down is it offers the greatest insulation for a given weight and compressible volume. There are two ratings that come with a down bag; loft and fill. Loft is the total insulating thickness when the bag is unrolled. Fill refers to the number of cubic inches one ounce of down will loft to in a uniform test. High quality down has a fill rating of 600 to 750.
The disadvantage of down compared to synthetic fill is it significantly loses insulating value when moist. Additionally, because down compresses easily, it does not insulate the underside of your body as well as synthetics because of its significant loss of loft. It is important to use a high-quality insulating sleeping mat in conjunction with down in cold conditions.
Synthetic: Synthetic fills are generally cheaper than down, and the big advantage is they continue insulating when moist. They are heavier and less compressible. There are several types of synthetic insulation including Polarguard, Primaloft, and Hollofil. Many Arctic explorers choose synthetic fill over down because of its superior functionality when wet. Some of the new fibres such as Polarguard 3D and Primaloft are almost the weight of down, but have the distinct advantages of synthetic.