Buyers Guide to Sleeping Bags

Copyright: Mountain Equipment

How to choose a sleeping bag

A good night’s sleep is key to enjoying your time in the hills and vital for physical and mental recovery. Keeping toasty while you sleep is important because your body will naturally drop in temperature during deep rest. There are a multitude of sleeping bags available out there covering a vast price range but if you choose wisely, maintain your bag and store it correctly it could very well keep you snoozing happily for 20+ years……

Synthetic or down?

This seemingly big question can be answered easily by looking at environment, budget and weight. Where will you be using your bag most? Do you want to carry it? How much are you thinking of spending?

Generally speaking, a synthetic bag will offer a cheaper option but it could be bulkier and heavier than it’s down counterpart so may not a first choice if you are planning a lightweight expedition. If, however, you are likely to be using your bag in a humid or wet environment then a synthetic filling will keep you warmer as it maintains it’s insulation properties even when wet. Synthetic materials are insulative by design with some created in a traditional sheet form and others blown into baffles as a form of featherless down. It is these different properties that require synthetic bags to be constructed and cut differently from down bags and why they are visibly flatter than down bags of a similar temperature rating.

If, however, lightweight and packability is what you are after then slipping into a sumptuous down bag could be the answer. Down bags insulate through trapping air within the fronds of the down cluster and quite simply the higher the quality of down, the more fronds it has. Why? Because it has been harvested from an older bird. To ensure the down in your bag is sourced responsibly and to the highest animal welfare standards, we only sell brands carrying the Responsible Down Standard logo. In fact some bags come with a code allowing you to trace the down enclosed back to the farm it came from. You’ll only ever want to search “live Plucking” once to understand why you should never consider buying a cheap down garment or sleeping bag. Down bags will naturally loft higher than a synthetic bag and the quality of the down within is measured by the Fill Power; the higher the number the better quality the down, offering better warmth for weight. If cared for correctly (i.e: stored in the supplied cotton bag and aired after every use) down sleeping bags will last for up to 20 years making them well worth the investment.

Men’s or women’s?

Regardless of what you call them there are bags cut for people with a larger frame and those cut for people with smaller proportions. If a bag is too long or too wide for your body shape then your body is going to have to work extra hard to warm all of that excess air. Fit is really important!

On some women’s styles you will also find they have additional insulation in areas where women are prone to heat loss. Due to evolution, men and women carry fat differently on their bodies, around the hips in particular. Now, you would think that a fatty area of the body would be warmer BUT there are fewer blood vessels in fat than muscle so blood circulation behaves differently. Blood vessels in muscle expend more energy and therefore heat. It is this heat that warms the air in your bag keeping you toasty warm - if the muscles are effectively insulated by fat then less heat can get to the air in the bag to keep you toasty warm. The additional insulation in these areas of the bag counter night waking due to these areas becoming cold . You can read more from our Director Cathy here

Superlightweight bags designed for packability are likely to be minimalist and sometimes have a degree of elasticity in the baffle seams so they snug up against your body, trap air more readily and turn with you in your sleep. Others, designed for expeditions, may well be cut generously assuming that you will be wearing more layers when you sleep and offer a waterproof fabric in the foot to allow for wearing boots.

Whatever bag you choose, it will only work it’s absolute best if it fits you. That means watching out for any areas it feels snug because if parts of you are pushing against the internal fabric you are likely to be compacting the filling leading to cold spots. You could buy the warmest bag in the world but if it is too small or too short then parts of you are going to get cold leading to frequent waking in the night.

What is a “season” and why do prices vary so much?

To help give you an idea of how warm a bag might be they are commonly sold as 2, 3 or 4 season. In the UK, a 2 season bag will be ideal for warm summer evenings but little more. A 3 season is likely to keep you warm from late spring to early autumn and a 4 season is likely to keep you toasty all through the year. There is even a 5 season for expedition and arctic use.

Most quality sleeping bag manufacturers have adopted the European EN 13537/ISO 23537 standard. This offers a Comfort rating, a Limit rating and an Extreme rating.

To achieve these ratings the bags are tested in a laboratory environment where a heated manikin is placed inside the sleeping bag, and the sleeping bag rests on a specific foam mat. The manikin wears a thin base layer that’s typical for people to sleep in and vast quantities of science are measured to determine how well the manikin is kept warm over an 8 hour period. Manufacturers can make a bag pass the laboratory ratings in a number of different ways but laboratory conditions rarely correspond to what happens in the real world. Very few of us sleep solely on our backs without moving around and any quality sleeping bag manufacturer will allow for this with additional care taken in constructing baffles, zoning insulation and carefully sculpting the hood of the bag to minimise heat loss through warm air being pushed out of the bag while you sleep. When this happens your body chills and has to start working to heat up again, if you haven’t eaten enough to provide the fuel for it to do this then guess what – you wake up shivering and starving.

There is a HUGE amount of science combined with real world testing prior to high quality sleeping bags coming to market so that literally the more you pay – the more there is going on inside the bag designed to keep you warm.

How do I make sense of comfort ratings?

You will find three ratings on the bags that we sell because the majority are tested using the EN method (although some superlightweight and extreme bags are exempt). The Comfort Rating is defined as a temperature at which a ‘standard female’ in a relaxed posture will feel comfortable inside a Sleeping Bag. If you are female or a cold-sleeper, this is the temperature rating that is most relevant to you. The Limit Rating is defined as a temperature at which a ‘standard male’ in a curled-up posture can sleep inside the Sleeping Bag without waking for an eight hour period. If you are a male, or are not a ‘cold sleeper’, then this rating is most relevant to you. This is also the rating which is advertised most widely for most sleeping bags. Finally, the Extreme Rating indicates the minimum temperature at which a ‘standard female’ can remain for a total of six hours before risking the chance of hypothermia and damage to health. Generally, this rating should be treated as a guide to how the Sleeping Bag performs under extreme emergency situations and should not be considered a factor in making a purchase.

Why should a bag “fit” me?

Just like clothing, different bags are cut differently for a multitude of reasons. Some to minimise weight, some to fit more snugly to the body and others to allow for extra clothing inside. The cut may differ between manufacturer and certainly due to the end use the bag is designed for. In some cases, our suppliers offer a number of different versions of the same bag: Short, Long, extra large so trying one on to ensure you get the correct length is critical.

If the bag is too short then you will end up with both cold feet and a cold head because you will be compressing the insulation. The simple answer will be to go for the same bag with additional baffles so that the mummy shape fits around you in all the right places. While you are trying your bag be sure to give the zip a test from inside too – is it on the right side for you? Is it easy to reach when you need to get out of your bag in the night?

Sleeping bags are a big investment – in our shops, you are always welcome to take as much time as you like to get it right.

So do I get what I pay for?

Yes.

I brought a “warm” bag but I’m still cold at night.

You can buy the warmest sleeping bag in the world and still have a miserable cold night if you haven’t eaten or hydrated properly before trying to sleep. Your metabolism is a key factor along with what you are wearing and what you are sleeping on. How old, or dirty your bag is can make a big difference to how well it lofts and how warm it will keep you too.

It’s worth thinking of your bag as part of a sleeping system: Do you have a decent matt underneath to protect you from the damp and cold? Do you have a liner inside on a cooler night to help boost the warmth of the bag? Do you have a bivvy bag on the outside to reduce air convection – again boosting the insulation properties. In extreme environments condensation needs to be factored in too. We can help with advice on all of these questions.

What about the environment?

Now, more than ever, buying products that have a minimal impact on our environment is critical. Buying once, buying well and ideally, buying something that sits within a recycling loop (i.e: made from natural or recycled materials which can then in turn be readily composted or recycled when it comes to the end of it’s useful life) is very important and our suppliers take this as seriously as we do.

This is a work in progress for all of us and we’re all making a great start. Please see our individual manufacturers websites for information on re-furbishment, recycling and sustainability.

Top tips to make the right choice:

If you can visit the shop to look at them in person this is ideal as not only does it allow you to place bags side by side to instantly see the difference in cut and loft but it also gives you the opportunity to try the bags on. Just like clothing, they are all cut differently and often come in length options so that you can get exactly the right fit for you. These days, however, travelling long distances and meeting face to face may not be quite so straightforward so we are more than happy to talk with you over the phone to discuss which sleeping bag may work best for you. We are all active users of the equipment we sell and we have all had our fair share of miserable nights, that’s why we are all happy to share our knowledge - so that you don’t have to!

Why not take a listen to our Sleeping Bag Podcast

“Slip Into Something Silky”

full of stories, tips and technical information to help you make the right choice…….