How to Stay Truly Warm in Your Sleeping Bag

You went out and bought the warmest sleeping bag you could find, expecting it would keep you warm in cold temperatures. Yet, you still ended up freezing through the night. It might not be the sleeping bag which is at fault but rather how you used it. Here’s what you need to know to truly stay warm in a sleeping bag.

First, Check the Comfort Rating

Most good sleeping bags will list their temperature rating. However, the rating you see is usually the limit or extreme temperature and not the temperature at which you will feel comfortable.

For example, the ACU Modular Sleeping Bag System (which is one of the most popular US Military sleeping bags) has a rating of -20°F. However, this is the temperature at which you’ll stay alive. The comfort rating is more likely around -10 to 0°F.

Next, Look At Your Complete Setup

A good sleeping bag won’t keep you warm if you aren’t insulated from the cold ground. You’ll need an insulated pad to put underneath you. The good sleeping bags will list their insulation value, or tell the comfort level.

Pro Tip: Have a subpar sleeping pad? Pile leaves, pine boughs, or other fluffy materials underneath you for an extra layer of insulation.

Fluff Your Sleeping Bag

Sleeping bags contain fluffy layers of insulation. Air pockets within the insulation are what trap your body heat, allowing you to stay warm. If the insulation gets compacted, it won’t have as many air pockets, and thus won’t be able to trap heat well. This is particularly true of down sleeping bags, since the feathers can clump together.

A simple solution to fix this is to fluff your sleeping bag when you set up camp. Give it several good shakes, ensuring that the insulation is “lofted” and well distributed.

Be Cautious About How You Wash Your Sleeping Bag

Residue from detergent can linger in your sleeping bag, causing insulation to clump and lose its loft. To avoid this, you should only wash your sleeping bag as instructed. Consider getting a detergent especially for tech items. Or, run an extra rinse cycle to get rid of detergent residues.

Avoid Wearing Too Many Layers

One common sleeping bag mistake is assuming that wearing layers will always keep you warmer. Yes, you need dedicated warm pajamas to wear while sleeping. However, too many layers can restrict your blood flow (making you feel cold and possibly compress the bag’s insulation (reducing its effectiveness).

Even worse, wearing too many layers can cause you to start sweating. Remember, sleeping bags work by trapping your body heat, so it can take a little while before you warm up in the bag. If you enter the sleeping bag with so many layers on that you are already warm, you will overheat once the bag traps your heat. Sweat will cause you to get wet, which in turn will make you feel cold due to evaporative heat loss.

The image below shows the US Military recommendations for sleep attire.

Warm Up Before You Get In

Instead of layering up, a better way to feel warm immediately in your sleeping bag is to do some exercise before you crawl in. Run a few laps around camp, or do some jumping jacks. Your body will produce heat and the sleeping bag will trap it, so you don’t have to wait as long to feel warm.

Never Put Your Face In Your Sleeping Bag

Another common sleeping bag mistake is putting your face inside the bag. Yes, your warm breath will make you feel warmer temporarily. As you continue to breathe in your bag, though, it will start to get damp from moisture in your breath. A wet setup is a cold setup, and you will end up freezing. Bring a full mask to keep your face warm instead when in very cold temperatures.

Get a Sleeping Bag That Fits You

If you are a bigger person and sleeping in a standard-sized bag, you will end up compressing the insulation and it won’t be as warm. On the flip side, smaller-statured people will end up with a lot of extra space in a standard-sized sleeping bag, and it won’t be able to trap heat as well.

Smaller people can solve this by filling the empty space in the bag with dry items, such as extra clothes or gear. But there isn’t a fix for larger people, so getting the right-sized sleeping bag is crucial to staying warm.