So you have finally decided it is time to replace that old sleeping bag that you’ve had since your were a teenager, a Boy Scout, or perhaps you have one of those sleeping bags made by the big box manufacturer that made your tent, your portable stove, your lantern and your cooler. At first, the number of variables to consider: temperature rating, shape, type of filler material, and finally weight, appear to make the job of selecting the right sleeping bag appear complicated. In this article I describe the important factors to consider when deciding on the filler material for your sleeping bag. The filler material is what creates the pockets of air that trap your body heat and prevents it from escaping. The filler materials are made of either Synthetic (man made) fibers or natural Down. In deciding between Synthetic and Down fillers, in my opinion it boils down to price and versatility.
In general, synthetic (man-made) filler materials are cheaper than natural, good quality down filler materials. Both materials will keep you warm, but pound for pound, down is going to be more expensive. The price difference of a good quality down filled bag compared to a bag filled with synthetics can be in the hundreds of dollars.
Synthetic material as a sleeping bag filler gained popularity in the 1960’s as manufacturers began working hard to replace the high maintenance and short life of a sleeping bag filled with Down. Materials such as Micro X, Techloft, Insulfil, Thermolite, Primaloft, Rteq and Thermoshield rival down in their warmth and weight characteristics and are much easier to maintain.
Down is a loose material that needs to be held in separate compartments to ensure that it is distributed evenly (and hence gives a uniform level of insulation) throughout the Sleeping Bag. There are many different construction methods used by manufactures. Stitched-through construction is cheaper to manufacturer but still allows cold spots to form. V-baffles and trapezoidal construction offer much better Down distribution and resistance to Down shift, but are much more time consuming and costly to manufacture.
In my opinion, versatility is where the differences between Synthetics and Down put the synthetic fillers on top. Synthetic bag fillers are much more forgiving after they become wet. After drying, a synthetic filler returns to its original loft and insulating capabilities. They also compress well, a factor that is important for a backpacking bag.
Down materials clump together and lose their insulating properties when wet and are slow to dry. For that very reason, down sleeping bags should not be washed in soap and water and should be cleaned by a professional, and only if absolutely necessary. If not properly cared for, your expensive down bag will have a very limited life expectancy.
Looking after your sleeping bag and keeping it in good condition increases its life considerably. You can wash your synthetic filled sleeping bag if it eventually gets dirty, but prevention is always better. You can keep the inside of your bag (synthetic or down) clean longer by investing in a thin liner to reduce the amount of natural oils your body transfers onto the bag. It is much easier to remove and wash the liner when it gets dirty.
When storing your down filled bag it is best to store it either hanging in the closet, or loosely rolled in a large cotton storage sack. This will ensure the down in your bag maintains its maximum loft. When your bag is compressed tightly into a small stuff sack, it pinches and squashes the down filling which can cause gaps which in turn result in cold spots. If you were to store your down bag like this, it could reduce the loft of your down filler and ultimately it’s effectiveness at maintaining its temperature rating. Never store your down filled bag compressed for more than 24 hours. And the first thing to do after you set up camp is remove your down filled bag from the stuff sack and shake it out.
My personal choice is a synthetic filler in my sleeping bags. Synthetic fillers are cost effective and much more versatile.