How to Stay Warm in a Sleeping Bag


Stay Warm in a Sleeping Bag

Ever get cold in your sleeping bag? Tossing and turning, unable to get warm. Why should you be cold and miserable! With a little work, and basic planning you can stay warm regardless of the weather.

You don’t even need to spend a lot of money. Why buy an expensive sleeping bag for no good reason? By making a few simple tweaks to your sleep system you can stay warm on even the coldest night. How do you stay warm in a sleeping bag?

Staying Warm in Your Sleeping Bag

If your sleeping bag has seen better days, there’s still hope! Staying warm in a sleeping bag isn’t difficult. Follow a few basic tips to increase the warmth of your bag. Here are my favorite strategies to prevent heat loss.

  1. Use a Quality Bag: Every sleeping bag has a different temperature rating. I recommend a 40°-50° 3-Season bag for spring, summer and winter use. Spend the extra money on high-quality brands like Big Agnes, Kelty, Marmot, Therm-A-Rest, Sierra Design, Etc. The $100-$200 range seems to be the sweet spot where bags are warm without being heavy.
  2. Fight Against Heat Loss: You shouldn’t solely rely on your sleeping bag to keep you warm. To preserve body heat, pair your bag with a liner, insulated pad and extra clothing. My Sea to Summit liner adds 25° of warmth to my bag and a cheap Coleman liner will add 12° to your bags temperature rating.
  3. Prevent Moisture: It can be hard to prevent condensation in cold weather. You need to remove wet gear and minimize outside moisture. Condensation can’t be completely eliminated, but it doesn’t have to be terrible.
  4. Wear Layers: Wear multiple layers to conserve body heat on cold nights. Extra layers add insulation between your body and the cold outside air. I like to sleep in whatever base layer I plan on wearing the following day. Something like long johns, boxer briefs, t-shirts, light jackets, etc.
  5. Alternate Heat Sources: A well thought out sleep system is the best way to stay warm at night, but there are other tricks to heat up tents. Use portable propane heaters like Mr. Heater, share a tent, buy hand warmers and add hot water bottles to a sleeping bag. Every day, campers come up with ingenious ways to get extra warmth.

FAQ About Sleeping Bags

How Do You Sleep in a Sleeping Bag?

It really doesn’t matter how you use a sleeping bag. You can sleep on your back, side, stomach, etc. Just make sure you find a way to stay warm and comfortable.

Most people pair their sleeping bags with a bag liner and lightweight sleeping pad. Using a bag liner (budget-friendly liner) will protect your bag from dirt/sweat and keep you about 10°-20° warmer.

Sleeping pads lift your body off the cold hard ground conserving body height and increasing comfort. The Therm-a-Rest Z Lite foam sleeping pad is perfect for most campers and backpackers. It’s relatively lightweight at 14oz and adds extra height in cold conditions(R-Value 2.2). For more warmth you can pair a foam sleeping bad with a lightweight inflatable pad(here’s my favorite).

How Do Sleeping Bags Keep You Warm? How Do Sleeping Bags Work?

Sleeping bags work like every other type of insulation. A sleeping bag traps the warmth produced by your body keeping you warm regardless of the weather. Just make sure you buy a sleeping bag with the right temperature rating for the camping conditions.

They use some type of lightweight yet bulky filler to separate your body from the cold air outside. This can either be a down or synthetic filling like primaloft. You might want to check out my post comparing the warmth of down vs primaloft sleeping bags.

What Temperature Sleeping Bag Should I Buy?

Think about the nighttime temperature on your most recent camping trip. Do you usually camping in the spring/summer/fall or go out in the winter?

If you only camp in mild weather you can usually get away with a 3-Season sleeping bag (50° comfort temperature rating). Adding a cheap Coleman Liner gets you another 12° or Sea to Summits Thermolite Liner can add 25° to your bag.

My Sea to Summit Liner adds a lot of versatility. I pair it with a 50° bag in the spring/fall and use it by itself in the summer. It’s kind of expensive, but well worth the money

Just remember that most camping gear is designed and tested for men. Women actually need warmer sleeping bags to maintain the same internal temperature. Check out my post further explaining sleeping bag temperature ratings.

Should You Wear Clothes in a Sleeping Bag? Can I Sleep Naked?

Unless you plan on getting frisky, you should always wear clothes in a sleeping bag. Layering in a sleeping bag adds warmth and protects your bag from sweat and body oils.

Some people like to sleep naked, but your bag will get seriously nasty after a long trip. Think about how sweaty and dirty you get after a long hike. Clothes add another layer of protection between your body and the bag.

If you plan on sleeping naked in your sleeping bag, use a bag liner. This will protect the bag and increase the amount of time you can go between wash cycles. You risk damaging the bag every time you throw it in the wash. Follow these directions to wash your sleeping bag once it starts to get nasty.

Can You Layer Sleeping Bags? Does Layering Sleeping Bags Work?

Yes, you can layer sleeping bags for additional warmth. Layering sleeping bags will add a lot of warmth, but it also takes up extra space and weight in your pack.

Backpackers would be better off using an extra warm sleeping bag liner or bag with a lower temperature rating. Car campers can carry lots of extra blankets to make up for cheap low-quality bags.

Why am I Cold In My Sleeping Bag?

There’s no reason why anybody should ever be cold in a sleeping bag. Being cold in a sleeping bag means that you aren’t using enough layers.

Wear extra layers to bed, use a bag liner and get a lower temperature rating. There’s really no reason why you should ever be cold on a camping trip. There’s either something seriously wrong with your sleep system or you underprepared for the trip.

What Do You Put Under a Sleeping Bag?

Always sleep on some type of insulated sleeping pad. It doesn’t matter if you’re using a foam, inflatable, or self-inflating pad. They all offer the same benefits with only a slight difference in weight and cost.

Sleeping pads are designed to increase both warmth and comfort. They get you up off the cold ground adding just one more layer of insulation between your body and cold outside.

Look at a sleeping pads R-Value and choose a pad that meets your weight, size and temperature expectations.

How Can I Make My Sleeping Bag More Comfortable?

Sleeping bag comfort is all about warmth and padding. Sleeping pads will offer the most bang for your buck. They’re lightweight and very comfortable, but they can be expensive.

On short camping trips you can get away with using a cheap foam sleeping pad like the Therm-A-Rest Z Lite Pad. Inflatable insulated pads like the NeoAir Xlite are lighter and way more comfortable, but expensive.

Car campers can just use a regular old air mattress. Just lay down a ground cloth or tarp to protect the air mattress and figure out a way to get power. You can always buy a power inverter for your car so you always have an electrical outlet nearby.

Start off With a Quality Warm Sleeping Bag (You Don’t Need To Spend a Fortune)

You can’t expect a 20 dollar Walmart sleeping bag to perform in cold weather. There’s just no easy way to make that work.

Start off with a high-quality bag and pay special attention to the temperature rating. Think about the last couple of times you went camping. How cold did it get on the coldest night? Buy a bag with a temperature rating 15

Choose a bag with a temperature rating 15° degrees colder than the expected weather. Going colder should cover worst-case scenarios without making the bag uncomfortably hot. Remember that you can always extend the temperature rating of your bag with a sleeping bag liner.

For more info check out my post on sleeping bag temperature ratings.

Bags Start to Feel Warm at This Price Point

The 70$+ range is where you start to get into halfway decent sleeping bags. Once you get into the $100-$200 range bags get much lighter. Anything over $200 is overkill for the average camper/backpacker.

Spend the extra money on high-quality brands like Big Agnes, Kelty, Marmot, Therm-A-Rest, Sierra Design, Etc. They’re affordable and offer a lot of warmth at a reasonable size and weight.

There are a lot of great bags available, but I like Kelty’s budget lineup of Cosmic Sleeping Bags. They come in most temperature ratings and they’re really affordable. It’s going to be hard to find a nicer down bag at such a low price point.

Does High Fill Power Down Increase Sleeping Bag Warmth?

When you get into the upper $200+ price range bags get much lighter at a given size/weight. They use high fill power down that’s light and compact.

Unfortunately, premium fill power down demands a high price point. It’s used to keep weigh and bulk down. This makes a sleeping bag light and packable without sacrificing warmth.

When overall weight and size are important go with a 750+ Fill Power sleeping bag. It will be lightweight and easy to pack but expensive. The average backpacker shouldn’t worry all that much about fill power. Just go with the lightest bag you can afford that fits your temperature rating.

Even a bulky bag becomes manageable when used with a compression sack. I really like my ALPS Mountaineering Compression Stuff Sack. It only weighs 10oz and compresses my sleeping bag down to about 25% of its original size.

Keeping Heat in Your Sleeping Bag

It’s almost impossible to heat a tent. Those thin walls don’t have enough insulation. Instead of heating the tent, you need to keep your body warmth inside the sleeping bag.

Sleeping bags are designed to trap body heat. This allows you to stay warm without needing an external heat source. Some sleeping bags are more efficient, but you should be fine if you pay attention to the bags temperature rating.

I would guess that 99% of people can get away with using a 40°-50° sleeping bag. Wear extra layers and use a bag liner and thick sleeping pad.

Keep Your Sleeping Bag Warm by Fighting Against Moisture

Never let moisture get into your sleeping bag. Moisture will not only make you colder it’s going to destroy your bag. As down/synthetic insulation get wet it loses loft reducing the overall R-Value.

To prevent moisture buildup keep your bag away from tent walls and use a sleeping pad to get it up off the ground. Never wear wet clothes to bed and store your shoes away from the bag.

Condensation Makes a Sleeping Bag Cold

If you’re not careful, condensation can infiltrate even the most expensive tent. So how do you prevent condensation in a tent? There are 3 main ways to prevent condensation.

  1. Tent Placement: Pitch your tent under trees on dry ground. Air under trees tends to be warmer than wide open fields. Condensation is going to happen on the tree foliage instead of your tent. Avoid camping near lakes, streams, rivers, etc. The extra humidity in the air will cause condensation.
  2. Remove liquids from your tent: You can’t completely eliminate humidity, but you can remove wet items from your tent. Hang up sweaty clothes outside and eliminate sources of moisture. Fighting moisture is a losing battle in the cold. Every breath you take releases moisture into the air.
  3. Ventilate The Tent: Open up your tent so that you have a gentle breeze during the day. Open the rainfly/vents and get some cross ventilation.

Sleeping Bag Liners Increase The Temperature Rating(Makes it Warmer)

Always use a sleeping bag liner. They protect your bag and increase warmth. You can get a quality bag liner for about $25-$75. You can’t beat the added warmth for the price.

Liners protect your bag from sweat, dirt and body oils. Bag liners reduce the frequency that you’ll need to wash your sleeping bag. Sleeping bags tear, clump up and become less effective with every wash cycle.

You can expect a budget sleeping bag liner like the Fleece Coleman Liner to add 10 degrees to your bag and expensive liners like the Sea to Summit Reactor Extreme to add 25 degrees.

Bag Liners Add Versatility/Warmth to Sleeping Bags

With the Reactor Extreme Liner I can actually use my 3-Season bag throughout most of winter here in Ohio. Then in the summer, I ditch my sleeping bag and only use the liner.

It adds a lot of versatility to my budget 3-Season bag. Liners just add a little bit more versatility to your sleeping bag. You never know how the weather is going to be during the spring and fall. One day it’s 40 degrees at night and the next it’s 70 degrees.

Bag liners allow you to regulate the temperature of your bag. If you get too hot unzip the bag and rely on the liner. On warm late spring nights I might even ditch my bag completely.

The Ground Sucks Warmth Away From Your Body(Use a Sleeping Pad)

When your body is close to the ground the earth will suck the heat out of you. The earth is way bigger than you, so fighting against it is a losing battle. Try to get extra space between your body and the cold ground.

Insulated sleeping pads get you up off the ground making you warmer. I like to use the blowup pads designed for the ultralight community. They inflate in minutes and increase the R-Value of your bag.

I really like my Therm-A-Rest Neoair Xlite inflatable pad. It’s really lite and has a 4.2 R-Value. You can use it all year long from winter to summer.

Foam pads are usually cheaper, but harder to carry. The Z Lite Original Pad is really nice for the price. It has a 2.2 R-Value which makes it a 3-Season pad. You can even double up your sleeping pads by pairing up an inflatable pad with foam.

Pad Inside in The Sleeping Bag

There are a lot of backpackers that swear by sleeping with their pad inside their bags. If you’re a big dude you might feel a little bit claustrophobic, but it’s a great idea for smaller campers.

Less space in the bag means less air to heat up. Plus you won’t have to worry about rolling off your bag and onto the cold ground. Considering how much I roll at night this is the only way I’m staying on the pad.

Tents Aren’t Designed to Keep in Warmth

Tents aren’t really designed to keep in warmth. The cold air around your body will quickly sap away your body heat. With that being said a 4-Season tent will do a better job at blocking the wind. Plus you won’t have to worry about your poles collapsing under a snow load.

A 4-Season tent won’t keep all the heat from escaping, but it will help prevent windchill. That breezy tent you bought for the summer might not be the best idea during colder months.

Trying to insulate a tent is a losing battle. Instead, you’ll want to focus on improving your sleep system. Spend the extra money on a nice bag, liner and pad.

Hot Water Bottles Make Your Sleeping Bag Warm

Sleeping bags are designed to trap body heat, but they can only work up to their temperature rating. Some campers recommend filling a water bottle with boiling water and storing it in their sleeping bag before bed.

This is great for warming up your bag before bed and will keep you warm throughout the night. It will also stop your water bottle from freezing overnight. You need liquid water so you don’t burn a hole in the bottom of your pot when trying to melt snow.

Just make sure you’re using a quality water bottle. Old school Nalgene water bottles are extremely popular. They’re almost impossible to destroy and shouldn’t leak.

Check out my post on using water bottles on winter backpacking trips.

Other Tips to Keep Your Sleeping Bag Warm

Most of the above tactics revolve around maintaining warmth, but there are a few ways to increase body warmth. The following tricks should help you increase your natural body heat.

  • Eat Before Bed: Eating a simple snack before bed will keep your body active throughout the night. Try to find complex carbs like energy bars and whole grains that your body can slowly digest.
  • Find a Friend: Cuddling up with your partner shouldn’t be limited to sexy times. Find a couple size sleeping bag or consider zipping two bags together to conserve body heat.
  • Exercise Before Bed: A little bit of exercise before bed will boost your metabolism throughout the night. Exercise enough to get warmed up without breaking out in a sweat.
  • Try Not to Sweat: Sweat is designed to siphon heat away from your body. So after a long hike you’re going to want to put on clean dry clothes.
  • Avoid Excessive Layers: Layering in your sleeping bag is always a great idea, but avoid overdressing. Check out my post on layering clothes in a sleeping bag.
  • Pee Before Bed: A bloated bladder will make you noticeably colder. Make sure you pee before heading to bed and get up throughout the night whenever nature calls.
  • Wear a Winter Hat: We’ve all heard the rumor that 50 percent of heat is lost through your head. While that’s definitely a myth you still want to slip on a beanie before bed.

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