How to Stay Warm on a Cold Night
From rectangular to mummy-shaped, with or without hood, synthetic, down or both, waterproof or not - there are a great many variables to take into consideration when buying a sleeping bag. High quality models tend to be a little pricey, but it’s an investment worth making if you frequently find yourself sleeping in the great outdoors. A well-chosen bag can serve you for many years, and some of them are under warranty for as long as a decade.
By far the most important feature of any sleeping bag is its temperature rating. It’s often standardized under the European EN13537 standard, but there’s no legal obligation for brands to comply. What’s more, the rating is measured for a “standard man”, meaning that testing outcomes can vary greatly.
It’s customary for sleeping bags to be labeled with three numbers: comfort, limit and extreme temps at which the bag can be used. Consider these two examples:
Eddie Bauer Airbender 20°
Both of these bags feature Climashield insulation (HL and Apex respectively) and both retain a level of protection against the cold even in wet conditions.
The temperature estimations are usually made for sleeping with the zip fully closed, hood-on, with a sleeping pad underneath and wearing one moisture-wicking layer. However, the Airbender features a built-in inflatable sleeping pad, while most bags need to be paired with a traditional, external pad (which is more comfy at the expense of space and weight).
The temperature labels are merely a guide, so it’s very important to know your own preferences determined by your nighttime metabolic rate. If you tend to ditch all your covers and radiate heat, you’re a “warm sleeper.” If you end up feeling chilly no matter how many blankets you’re under, consider yourself a “cold sleeper.”
Cold sleepers should subtract roughly 10°F from the comfort rating. If your nighttime temperature is average, aim for subtracting 5°F. Only really warm sleepers should treat the comfort rating as accurate.
Curled up and enduring some level of discomfort, it’s still safe - although not pleasurable - to sleep at the “limit” temperature. The “extreme” rating indicates the harshest survivable conditions.
Additionally, make sure to choose the right size bag. A bag that is too small is bad for obvious reasons, but too big won’t perform either. A pocket of cold air at your feet can ruin a good night’s sleep.
As your body radiates heat, winter sleeping bags are most effective if you strip down to your undies. Alternatively, wear a single moisture-wicking, breathable layer and avoid cotton at all cost.
Opting for a silk liner will prolong the life of your bag and make it warmer by around 10°F. An appropriate sleeping pad can make all the difference and choosing one is almost as involved as finding the right sleeping bag.
The good news is that once you’ve determined your ideal setup, you’re ready for many beautiful outdoor nights spent in safety, comfort and warmth.