Keep Warm in a Hammock

Warbonnet Blackbird with Edge Tarp

As we continue to count down to my  “Intro to Backpacking” Seminar at Harriman State Park with “Hudson Valley Hikers.”   I’m getting more and more great backpacking questions everyday.  Kristina is very interested in Hammock Camping and asks “how do you keep warm in a hammock?”

How do you Keep Warm in a Hammock?

Kristina asks, “My question is about hammocks for backpacking – have you used one?  how do you keep from getting cold?”

CampingJay Answers:

That’s a great question. I have a hammock, but I’ve only used it a few times. My girlfriend has been using it for the last few trips and likes it.

 Yes, you need to do something to keep your butt from getting cold. Let’s talk about it.

A Little Primer on Insulation:

There are three ways that the body loses heat. Conduction is direct heat loss to another object, like the ground. Convection is heat loss to moving air: your body heats the air around it, then that air blows away. Radiation is heat loss in the form of electromagnetic energy radiating from your body into the environment.

Conduction, Convection, and Radiation
A) Conduction   B) Convection   C) Radiation

 A sleeping bag works to stop convection by trapping a layer of air between you and the environment. The air can be trapped in down or some kind of synthetic material. Your body heats up that air, but it is trapped and that heat won’t be lost to the environment as quickly. Air works as a great insulator because it is a poor conductor. We call the thickness of a sleeping bag or quilt “loft.”  The temperature rating of a sleeping bag or quilt is directly related to its loft.

The “loft” of a sleeping bag or jacket governs its warmth. According to the US Army Quartermaster, 1 inch of loft will provide about 40 degrees worth of insulation.

 When you’re lying on the ground or in a hammock, the air in the portion of sleeping bag under you is compressed out. The sleeping bag will offer you very little insulation against the ground because you’re almost in direct contact with it. We call this direct contact “conductive heat loss.”  If you’re in a hammock with just a few layers of compressed sleeping bag between you and the wind, the wind will soon start to take heat away from your body faster than you can make it and you will be cold. This is “convective heat loss.” For this reason, many backpackers have stopped carrying sleeping bags in favor of lighter, more comfortable quilts (basically as sleeping bag without a bottom.)

If you’re on the ground, you solve the problem of conduction with some kind of pad.  The pad can made of closed cell foam, which is a material that permanently traps air. Some pads put open cell foams inside a flat bladder (self inflating mattress.) When the valve on the bladder is open, the air can be compressed out so that the pad can be rolled up. If you allow the foam to expand and then you close the valve, the air will be trapped and act just like a closed cell pad. A third type of pad uses just a bladder full of air and maybe some baffles to prevent air circulation. This type isn’t self-inflating, but is much lighter and packs smaller.

Using an Under Quilt to Keep Warm in a Hammock

Pads work great on the ground, but they tend to be uncomfortable in a hammock. They also tend to keep your bottom warm, but not your sides. Pads also shift and bunch up while you toss and turn, making them uncomfortable.   For this reason, someone very clever invented the “under quilt.” The under quilt basically a down-filled blanket that hangs around you on the outside of your hammock! It works just like sleeping bag or top quilt, but its outside the hammock so your weight can’t compress it.  Under quilts are typically torso-length, enveloping just the part of your body from your butt to your head. Check out Enlightened Quipment’s very popular Revolt Under Quilt.
Enlightened Equipment Revolt Under Quilt

Using a Shaped Pad to Keep Warm in a Hammock

A less expensive option is to use a shaped pad or add wings to the pad you already have.  The wings will help insulate your sides and keep the pad from moving around as much.  Check out the Hotspot Sleeping Pad Wings from Eagles Nest Outfitters.

ENO Hotspot Sleeping Pad Wings
ENO Hotspot Sleeping Pad Wings

 Wait, we forgot radiation!

Earlier, I said there were three types of heat loss: Conduction, Convection, and Radiation.  we stopped conduction and convection by placing a barrier of trapped air between you and the environment. But what about radiation? Well, almost anything opaque (something you can’t see through) will stop radiated heat loss. Dark colors will absorb heat, while light or reflective colors will reflect it back at you. For this reason, you should try to chose sleeping bags, quilts, or pads that are light in color.  Some pads have a shiny side and a dull side.  If your cold, try sleeping with the shiny side toward you. If you’re too warm, turn it over.  If you’re selecting colors for a customer quilt, get a dark exterior color and a light interior color. The dark exterior will warm quickly in the sun, useful for drying. The light interior will reflect body heat back at you.

I hope this helps!

Recommended Reading

The Science of Cold