“When the thermometer plunges, a well-insulated sleeping bag is essential to your nighttime comfort,” says the Fieldbook.
I had no idea how much of a difference it’d make when I got a cold weather bag for winter camping. Cold nights have been a thing of the past for nearly 35 years!
SLEEPING BAG TEMPERATURE RATINGS
You’ll notice labels with ratings like -10 degrees or +30 degrees, which tell you the lowest temperature at which most people will be comfortable sleeping in that particular bag. Price is affected by both the quality and amount of insulation, so price goes up as rating goes down.
“There are two main types of insulation: down, which is natural, and synthetic, which is man-made,” said the Gear Guy at Boy’s Life. Generally, goose down is warmer, lighter and easier to pack. Unfortunately, it’s typically more expensive and requires extra care. The worst part about down is it loses its ability to keep you warm if it becomes wet.
“Synthetic insulation, like PrimaLoft, is typically less expensive, requires little care and retains its warmth if the bag gets wet. Synthetic sleeping bags are heavier than down competitors, but they remain the best choice for routinely wet adventures.
“To blur the line, you can now buy water-resistant down, which retains its ability to trap heat when wet. Still, even saturated water-resistant down loses some of its ability to trap heat, and you might have trouble drying out any bag in prolonged wet weather.”
Instead of pajamas, the Fieldbook suggests adding layers of dry fleece under-clothing and mittens. They also recommend a hat and dry woolen socks. Of these, I’ve found the hat and socks to be most important. Wearing warm clothing allows you to tolerate colder temperatures while in your sleeping bag.
The Fieldbook says, “What you have beneath you at night is as important in keeping you warm and dry as what’s on top.”
Lay one or more insulated sleeping pads on your ground cloth or in the bottom of your tent. In the summer, these pads provide comfort from rocks and twigs. In winter, they are also helpful. They prevent snow from drawing heat away from your body.
Closed cell pads are my choice for winter. In fact, I have four. I bring two for me and two for a tent mate. Though these are not very comfortable in summer, they are just what you need to prevent heat loss. Inflatable pads will be colder, but some, like Thermarest come with built in insulation.
OTHER SLEEPING TRICKS
Before I got my winter bag, I used two sleeping bags, one inside another. With an additional layer, warm air is trapped and keeps you comfortable. However, the bag should not have a large opening. If it does, pull a wool blanket over and under your head and shoulders, tucking it into the opening.
The Fieldbook reminds us: “Sleeping in a tent or snow shelter prevents wind from interfering with warmth, too. Of course, insulation beneath your bag is vital; one or two foam sleeping pads work well for this purpose.”
“With all the emphasis on insulation, don’t become so warm that you perspire during the night. Sweating can rob your sleeping system of its ability to keep you cozy. Ventilate by opening the bag, taking off your hat, or removing other layers. Try not to exhale inside of your bag since water vapor can cause the loft in your bag to loose it insulating effectiveness. Instead, pull drawstring of the bag’s hood around your face, leaving just enough open-space for exhaling outside of your sleeping bag.”
For more on sleeping systems, see the Fieldbook chapter “Gearing Up,” pp.30–32
Here are some other posts in this series: