Enhancing your Sleeping Bag

Once you have a sleeping bag that is warm enough for most conditions that you expect to meet there are still a number of things to do that will improve its performance

Wear your walking/hiking clothes

This is the simplest and cheapest option. It is also one of the best - given the weight saving.

If you are a typical modern walker then you will be wearing a wicking base layer and some sort of fleece / windproof mid-layer. These are all high performance pieces of clothing designed to keep you warm and dry during vigorous exercise. This makes them ideal for wearing inside your sleeping bag.

The only caveat is that your clothes must be dry or nearly-dry before you get inside of your sleeping bag. If you are sweaty then it is vital that you allow time for your clothes to dry. This is necessary so that extra moisture is not added to your sleeping bag

Silk Liner

A silk liner is a useful addition to any sleeping bag. Silk feels very warm and comfortable against the skin and acts as a good wicking layer. Using a silk liner will add a few degrees of extra warmth to your bag at the cost of typically a 100g. The temperature rating is marginal but the comfort increase may be worth it.

Knitted Polyester Liner

A knitted liner is supposed to be better than silk for improving your sleeping bag. It is more bulky to pack but feels warmer. It is a military item that has made it into the civilian market. The basic idea is that the liner hugs your body and provides both a snug air pocket around you and of course it has insulating properties of its own. A knitted liner will typically weigh around 240g.

Fleece Liner

A Fleece liner is even warmer than either a silk or polyester liner. A typical claim is that the liner will increase the rating of your bag by °5C which is equivalent to a full season rating. The downside is that a fleece liner will weigh around 400g and have quite a large pack volume - the size of another sleeping bag.

Cotton Liner

These are sold as sleeping bag liners. Do not even consider it. Cotton is not a good choice of material for something next to your skin when you are going to be sweating.

Windproof pertex Outer

There is no point having a really warm sleeping bag if you have chosen to use it in the middle of a gale.

The biggest sources of heat loss from a sleeping bag are the ground, airflow and moisture. Of these three, airflow is the easiest one to solve with very little weight penalty.

A lightweight pertex outer (in addition to your sleeping bag's outer) will add an extra few degrees of warmth to your bag and stop you feeling cold.