The key to staying warm in a hammock tent is finding a way to be insulated underneath. Like camping in ground tents, you are at the mercy of the temperature beneath you. But it’s even worse because even in the middle of a hot summer you can get frozen in a hammock when a breeze passes over water and acts like an evaporative cooler on your backside.
What provides the best insulation for hammocks?
There is only one reliable insulator: air. Therefore, you should judge your insulation by how much air it can hold without flushing that air out when you move around in the hammock.
The best hammock insulation will conform to the bottom of the hammock without a large gap between the insulation and the hammock bed. Pads can accomplish this, whether placed directly below your sleeping bag (or in sleeping bag sleeves such as those found in Big Agnes sleeping bags) or placed in dedicated pad sleeves below the hammock bed which some hammocks provide. However, pads can be awkward and bulky to pack and they may not always perform well in the three dimensional world of hammocking where your body weight turns a fairly flat bed into a bathtub. In addition, pads typically don’t breathe well, and may essentially seal the fabric below your back, making the hammock less comfortable.
The consensus is that insulating underquilts are superior to pads. They breathe and are built to conform to the hammock when your weight is inside. An underquilt must walk a fine line, keeping close to the hammock bed but not so close that your body weight flushes the air out of the insulation.
Underquilts come in various lengths. When you purchase a half or three-quarters size underquilt, it is usually with the understanding that your legs and feet will not need as much insulation as the rest of your body. While this is true, your heels make enough contact with the bed that you can still get cold on your feet if there is no insulation under them in frigid weather. You may find yourself relegated to a fetal position to stay as warm as you’d like with shorter underquilts. In addition, smaller underquilts can have trouble keeping cold air out when you move around in the hammock. For this reason, you should consider an underquilt that covers the entire bed of your hammock.
Consistent insulation for underquilts
There is one more hurdle for good insulation to overcome. In addition to trapping air and holding it close to your hammock bed, it must do so evenly and consistently. Otherwise, one part of your body may be a few degrees warmer than another part of your body. Even if both areas are in an acceptable range of warmth, you will go crazy at around 3:00 am just from the small disparity in temperature. You will desperately desire for your thigh to be the same temperature are your upper back.
Staying warm in a hammock when temperatures are between 32° F and 65° F (0° to 18° C)
It is very frustrating to think that most hammock manufacturers expect you to bring insulation with you on almost every trip, since most people end up in temperatures below 65° F (18° C). Clark stands out from the crowd here with its four-season hammock like called the NX Series. These hammocks have built-in pockets that, when holding gear or other items, hold out a dead air space underneath the heaviest parts of your body where you compress you sleeping bag the most. Cold breezes are then unable to affect you. The insulating pockets on the newest Clark NX models are sewn shut on the outside, with only interior access from zippers on the inside of the hammock. This means that it’s easier to keep cold air from seeping in and disrupting the stable air mass that your body is warming. These pockets are intended to keep you from having to bring a pad or underquilt on typical camp-outs where you are expecting good weather and when you don’t expect temperatures to dip below 40° F (5° C).
Down vs. Synthetic underquilts
If you are not allergic to down, then purchasing a down underquilt can be a good value since they pack tighter than synthetic and are more durable over time. However, they also cost significantly more and will not insulate you if they get wet.
Clark is the leader in cold-weather hammocking. NX models provide built-in insulation that keeps you from having to bring a pad or underquilt on most trips. They include built-in velcro to atttach full-length underquilts (called Z-Liners) that provide even and consistent warmth and can allow you to sleep down to 0° F (-17° C) if you have decent coverage inside the hammock (a sleeping bag meant for the temperatures you are sleeping in is recommended). Because Clark underquilts attach with velcro, they effectively seal out cold and won’t flush out a lot of warm air when you move around the hammock bed. Because Clark Z-Liner underquilts use the highest grade synthetic fill (ClimaShield Apex), they pack almost as tight as down and will work even if they get wet. Finally, you can install Clark underquilts on the hammock and pack them in a larger stuff sack that comes with the underquilt. After all, when your fingers are already cold, the last thing you want to do is attach an underquilt when arriving at your campsite.