Sleep Systems and Sleeping Bags

When you start to consider light and ultralight backpacking then you need to be holistic in the way that you look at things. This is especially true when you start to look at your overnight sleeping arrangements.

Your sleeping bag does not work in isolation. It is used in conjunction with your bivi or tent and your groundsheet and your sleeping mat and your clothing. Any of these items will have an impact on the performance of your sleeping bag.

The most interesting question is do you need anything at all to sleep in? If you are in the tropics then it may be that a hammock is all that you need and you can sleep in your clothes.

if you choose to wear your clothes in your sleeping bag then you can generally get away with using a lighter sleeping bag.

Before you can decide what sleeping bag to choose it is necessary to consider how and where you are going to use it. There are a list of things that you should consider:

Sleeping Bag Season Ratings

All sleeping bags are given a temperature rating - typically a comfort rating and an extreme rating. These are all subjective. For full details read 'Sleeping Bag Season Ratings'.

The summary is that you should always buy a bag that is warmer than you think you will need on the basis that you can always remove or add clothing or other layers to increase or decrease the rating of your sleeping bag by using clothing or other sleeping bag accessories.

Sleeping Bag Construction and Fit

The next thing to consider is the construction of the bag. Mummy bags will tend to be warmer than square-cut bags and bags will in-built hoods and things like zip and shoulder baffles will be warmer than bags without.

The two biggest items that will make a sleeping bag feel cold are draughts and moisture. Both of these can be engineered out of the sleeping bag design. The warmest winter bags will have no zips at all.

The construction of your sleeping bag will have a huge impact on its performance. Much more than the choice between down and synthetic fills. You can read more here.

Enhancing your Sleeping Bag

A sleeping bag does not exist in isolation from the rest of your kit. When you buy a sleeping bag you buy one that you think will be warm enough for the conditions that you will meet. If you find that this is not the case or that you want to make your sleeping bag warmer so that it can be used for large chunks of the year then there is plenty that you can do. Most of them will add weight and most will cost money but in general the increase in weight is no more than the difference between the bag you have and the next highest rating. You can read more here.

Sleeping Mats

A sleeping bag on its own is useless. You certainly cannot just place it straight onto the ground. Typically you will decide on a level of comfort that you need and a level of insulation that you need and shop accordingly. There are many options available. There is no point in spending large sums on a luxury down sleeping bag if you then sleep on a mat that is useless. You can read more here.

Shelter

The final part of any sleeping system is the shelter. The choice of shelter will make a huge difference to the actual warmth of your sleeping system. The difference between sleeping in a small 4-season tent and just sleeping on a groundsheet in the open air can easily be equivalent to adding another seasons rating to your sleeping bag. It is that important!

One of the things that it is important to be aware of is that many of the modern ultralight tents achieve their lightness by using an inner tent which is 100% mesh. This means that it will be very draughty. This in turn means that your tent will feel colder than a tent which has a fabric inner.

Likewise, the size of the tent will make a huge difference to how warm you feel. The only source of heat in a tent is you, so the larger the tent the bigger the volume of air that has to be heated and the harder it will be to keep warm.

What this all means is that if I am using a tent in the summer I will use a big spacious tent with a mesh inner tent and if I am using a tent in the winter I will use the smallest tent I can find that is suitable for my needs. It will be a tent with very little ventilation.

By considering my choice of tent and sleeping bag together I can adapt much more readily to the temperatures.

For the summer months (OK, with temperatures more than 10°C I am experimenting with just using a tarp or nothing at all (in dry weather). This is working out extremely well and saves a lot of weight over a tent.