Choosing a sleeping bag can be confusing. Depending on your activity, there’s a lot to consider. What should it be made of? Which is the best shape? And why are temperature ratings written in hieroglyphics? Read on and we’ll reveal all!
CHOOSING YOUR SLEEPING BAG'S TEMPERATURE RATING
Most technical sleeping bags follow the International Standard ISO 23537 to communicate their temperature ratings. This includes three unique temperature categories: T Comfort, T Limit and T Extreme. When assessing a sleeping bag, look at what temperatures the sleeping bag suits based on the following:
- T Comfort: Comfort is based on a ‘standard’ adult woman having a comfortable night’s sleep. She’s wearing one base layer in a relaxed position and, you guessed it, she’s comfortable.
- T Limit (AKA the lower limit of the Transition range): is based on the lowest temperature at which a ‘standard’ adult male is deemed to be able to have a comfortable night’s sleep. He's also wearing one base layer but sleeps in a curled position to keep warm.
- T Extreme (AKA the lower limit of the Risk range): is a survival-only rating for a ‘standard’ adult woman. This is an extreme survival rating only and it is not advisable for anyone to rely on this rating for general use. There will be a strong sensation of cold which can only be endured for a limited time.
In other words, you will choose a sleeping bag based on what temperatures you are likely to experience, and look at ensuring that you will sit within that 'T Comfort' stage. It’s a lot harder to increase your warmth than it is to cool down. In short, you should always choose a sleeping bag that has a "comfort" rating that is colder than your trip's coldest weather forecast.
HOW TO CHOOSE A SLEEPING BAG SHAPE
Sleeping bags come in mummy, semi-rectangular or rectangular shapes. All come with distinct benefits. Note: Make sure you pay attention to the max sleeper height of your sleeping bag as well. As a general rule of thumb, you should add 25–30cm on top of your height for maximum comfort.
Mummy sleeping bags
Maximum insulation and minimum volume/weight.
The mummy shape is narrow at the feet and tighter around your body so there’s less space around you. This is a deliberate design decision — with less empty space to heat up, your body won’t have to work as hard to stay warm. You’ll stay warmer for longer and use up less energy. A mummy bag also has a snug hood you can pull around your head for extra heat retention.
Semi-rectangular sleeping bags
More legroom and usable as a blanket.
These bags suit a variety of uses and temperatures and have a tapered cut that still provides efficient heat retention. There’s more space for your legs for those who like to sleep on their side or who move around more in their sleep. Unlike the mummy, you can open it up and use it as a blanket which can be beneficial in warmer climates.
Rectangular shapes
Roomier, but take up more space and weigh more.
Rectangle shapes are as wide at the foot as they are at the shoulders. They give you the most amount of room and are a good choice for warmer climates, camping beds, car camping, or for when you want to share your sleeping bag with someone else.
HOW TO CHOOSE A SLEEPING BAG FILL
Feather down fill
A down sleeping bag can be appropriate for multi-day overnight hikes, cold camping conditions, world travel or alpine adventures.
Pros:
- Warmth. It offers you the very best warmth for weight on the market. Nothing will keep you quite as warm for the same weight. If you’re new to down in general, it might be worth understanding what down fill power is and why it matters.
- Lightweight. If weight is an important consideration, down is a better choice.
- Compression. Down sleeping bags are more compact and easier to carry in a backpack or on the move.
- Durability. It can last upwards of a decade, even more if you look after it properly.
Cons:
- Less water-resistant. To combat this, look for a down sleeping bag with water-repellent down that sheds water and dries quickly. A waterproof outer fabric will help too.
- Price. Typically more expensive than synthetic sleeping bags – but well worth the upfront investment.
Synthetic fill
A synthetic sleeping bag can be appropriate for a wide range of activities,including an overnight hike, camping, and travel across a range of climates.
Pros:
- Wet-weather friendly. Synthetic fill performs well even in damp conditions. The lightweight synthetic fibres are less affected by moisture and trap warm air around your body, giving you a high thermal performance even when damp.
- It’s easy to care for. You can easily wash your synthetic bag in the washing machine.
- Typically more affordable.
Cons:
- Weight. Synthetic sleeping bags are heavier, so can add additional grams to your backpack or luggage. That said, if a heavier bag is what you need on your adventure, it’s worth adding the weight to your sleeping kit and taking something else out.
- Warmth: if you're sleeping in extremely cold conditions, synthetic can't really compete with feather down. Although there are some great hybrid options that combine the durability of synthetic with the warmth of down.