Part 4 - Almost Everything You Need To Know About Winter Camping
Updated: Mar 22, 2021
In the first three parts of this series, we talk about how to dress, shelters, making fire, crossing ice and when to use traction aids such as snowshoes and crampons. Now we will cover how to sleep in the cold. From sleeping bags and pads to tips to sleep warm, we pass along the tips that have made winter camping comfortable for us.
How Warm Does My Sleeping Bag Need To Be Rated For?
The type of shelter you are using combined with the outdoor temperature will dictate how warm your sleeping bag will need to be. If you are sleeping in a hot tent then a 3-season bag rated to -10 Celsius is usually more than enough but if you are cold tenting or sleeping in a snow shelter you will be relying only on your sleeping bag for insulation so it will need to be much warmer.
When looking at your sleeping bag temperature rating you will need to understand how they are rated. If you are looking at a sleeping bag from any big mainstream brand like The North Face or Marmot they will have a standardized EN Rating. Any sleeping bag sold in Europe needs to be independently lab tested so it tends to be the big brands or European smaller brands that have submitted for the testing.
The rating will have three temperatures ratings: Comfort, Limit and Extreme. Comfort is for women or cold sleepers, Limit is for men or warm sleepers and Extreme is 6 hours without getting hypothermia or frostbite. The testing is based on wearing a long sleeve top and bottom base layer and socks so factor this into your calculations. When looking at sleeping bag ratings you will have a better understanding of what temperature level you personally need basing on how warm you are.
I like to think in terms of sleep system which is the combination of a sleeping bag, sleeping bag liner and potentially an over-shell or bivy sack. While you can get sleeping bags that are rated to very low temperatures on their own, I find them of limited utility as they only work in super cold temperatures. If you use a system of parts then you have a sleeping bag that can be used most of the year and just like clothing you add layers as needed to handle the colder conditions.
If you are on a budget and want a complete system, check out the Military Sleep System kits at an army surplus store. This kit will have a couple of different layers of insulation plus the bivy sack. You can then use the inner bag for summer, the medium bag for 3-season use and the whole thing together for winter. Like most military gear it is heavier and bulkier than specialty camping or mountaineering sleeping bags. This isn't much of an issue if you pull your kit around in a sled rather than carrying it in a backpack.
I target my sleep system to be 10 degrees Celsius warmer than the coldest temperatures you expect to encounter. So if it is -20 C then I want it to be able to cover -30 C. I use the Mountain Hardwear Ratio 15 down bag which is rated to -11 C plus a Sea to Summit Reactor fleece liner. This gives me a system that is rated to -27 C. When I add in my clothing extras on top of my base layer I can easily handle -40 which is way colder than I ever want to camp in without extra heat from a fire.
To add further warmth I can use my Moutain Hardwear 32 summer bag, which is rated to -2 Celcius inside my warmer bag as an ultra liner. The Mountain Hardwear bags are cut fairly roomy in the shoulders so the extra space allows for the extra sleeping bag. If you are going to put a sleeping bag inside another sleeping bag, make sure the zippers are on the same side as it can be more effort to get in and out of when they are on the opposite sides from each other.
When shopping for sleeping bags you want to get the right size. If it is too small you can compress the insulation on the sides reducing the thermal efficiency as well as losing the utility of putting your clothing for the next day so you don't have to put on the cold gear in the morning.
You also don't want it to be so oversized that it is hard for your body to heat up. Even if you plan to buy online, take your measurements so you know how long and wide you need.
Not only do you have cold air around you but you have the frozen ground below you. Your sleeping bag will reduce the loss of heat due to convection but you will need a thermal break to stop the loss of heat due to conduction with the ground. When you are in your bag you will compress the insulation under you which makes it a poor insulator.
If you add a thermal sleeping pad under you the temperature will seem much warmer. Plus it is more comfortable than sleeping on the ground.
You can use foam, self-inflating or insulated inflatable mat to act as a thermal break between you and the ground. The key like anything in the cold is to get enough insulation. The insulative quality of a sleeping pad is rated in R-value. The outdoor industry has recently settled on a standard so you can now compare the warmth of one brand to another and know that you are comparing apples to apples. For winter camping I recommend an R-value of 5.5 or higher.
Since insulation is additive, a way you can create a winter sleeping kit is add a foam pad to your 3-season sleeping pad. If you have a Thermarest X-lite pad which has an R-value of 4.2 and the Thermarest Zlite foam pad has an R-value of 2, you will have a kit that is 6.2 which is more than warm enough for winter. If you are a dedicated winter camper and want to keep the weight down then the Thermarest X-therm pad is the clear winner with an R-value of 6.9 while only weighing 15 oz.
Dressing To Sleep In Winter
When you are planning out your winter camping trips you will want to have a set of clothing that you use exclusively for sleeping. The aim is warm but not restrictive. When cold camping the main warmth you have will be blood circulating so if the clothing you wear to bed is too tight it can reduce your warmth, especially to the extremities.
I use a thick, thermal top and a bottom base layer that is on the loose side and a pair of thick wool socks that are a size too big. A fleece neck warmer, fleece hat and light thermal gloves round out my sleeping clothing. Depending on the temperatures I can combine my down puffy jacket and fleece mid-layer to increase the overall warmth of my system.
When I want maximum warmth I pull my hat down so it comes to the tip of my nose and the neck warmer up over my chin so the only skin exposed in my mouth and nostrils. It also helps to have a beard. If you don't have a beard and the air temperatures are below -25 Celsius then a face mask with breathing holes can help protect the skin of your face from the extreme cold.
Push the clothing you plan to wear the next day to the foot of your sleeping bag. It helps keep your feet warmer and your clothing will be warm and dry for the morning.
Tips For Sleeping Warm In The Cold
Don't go to bed cold
If you've been sitting around and have gotten chilly then you should do some exercise like squats to get your temperature up. Once in your sleeping bag, you can speed up the warming process by repeatedly tensing all of your muscles.
Fill a Nalgene bottle with hot water and put it in your sleeping bag. Nalgene bottles can safely handle boiling water so don't worry that it will melt. This will pre-warm your bag saving energy you will need to heat it up. Plus if you push the bottle to the foot of your sleeping bag you will have liquid water in the morning to cook breakfast and make coffee. Just make sure the lid is tight and doesn't leak as you don't want your water to leak in your sleeping bag.
Eat high-calorie food before bed
Your body needs the energy to generate heat so top up your fuel tank with calorically dense food like protein bars, trail mix, chocolate or pemmican.
Drink a hot drink before bed
Hot chocolate with some added fat such as coconut oil or butter can add both some warmth and calories.
Do up your sleeping bag so only your nose and mouth are exposed. This will keep the warm air from escaping while keeping the moisture from your breath from wetting out the insulation in your sleeping bag.
If you are camping with people it helps to butt up against each other to share warmth. If you are in a group of 3 or more and are the coldest in the group, make sure you are in the middle. It can be trickier to get up to pee but having someone on either side is noticeably warmer.
The Wrap Up
With the right gear and a bit of knowledge, you can sleep in very cold conditions quite comfortably. Check out the next installment to learn about camping cooking and water purification in winter.
Go to Part 1, Part 2, Part 3