Underquilt at a glance
- Feels cool from
- About 65 to 70 F
- Quilt territory
- Below about 45 to 50 F
- Full length
- Around 16 oz
- Three quarter
- Around 11 oz
- Typical price
- $120 to $230
Why a hammock needs one at all
Insulation works by trapping still air, and it can only do that while it's lofted. Lie on a sleeping bag and your weight crushes the fill underneath you flat, so the half of the bag between you and the outside world stops insulating almost entirely. On the ground that's fine, because a sleeping pad handles it. In a hammock there's nothing under you but fabric and moving air, and moving air pulls heat out of your back far faster than still ground ever does.
The result surprises almost everyone. Most hammock campers start feeling cool somewhere around 65 to 70 degrees, which is a pleasant summer night, and below roughly 45 to 50 degrees the usual advice is to stop trying to make a pad work and buy the quilt.
Underquilt or sleeping pad
A pad is the cheap answer and it does work. A thin closed-cell foam pad weighs a couple of ounces against eleven to sixteen for a quilt, and costs a fraction as much. The problem is that it won't stay put. In a single-layer hammock a foam pad folds around you and slides out through the night, and inflatable pads are worse still, because they're slick and nothing is holding them.
Two things fix that. A double-layer hammock has a sleeve between its two sheets of fabric sized to hold a pad exactly where you put it, and that's the cheapest real solution. The other option is to move the insulation outside the hammock altogether, which is what an underquilt is. Out there nothing ever compresses it, so it delivers its full rating at a weight no crushed bag can match.
Full length or three quarter
Full-length quilts run head to foot and weigh around sixteen ounces in a 40-degree rating. Three-quarter quilts stop short of your feet and save about five ounces, on the reasoning that a pack or spare clothing under your calves covers the gap. Prices generally start near $120 and climb past $230 once you're buying from the well-known makers.
Fit matters more here than it does with a top quilt. An underquilt has to sit snug against the hammock's underside along its whole length, because any gap turns into a channel of moving air. Hang it too tight, though, and it pulls the hammock out of shape. Most come with adjustable shock cord at each end for exactly that reason.
What this means when you're choosing
- Full length versus three quarter, which is roughly five ounces either way
- Suspension shock cord at both ends so you can close gaps without distorting the hang
- A temperature rating you can compare, and whether it is comfort or limit
- Whether it fits the length of hammock you actually own
Underquilt vs Backpacking quilt
| Underquilt | Backpacking quilt | |
|---|---|---|
| Where it goes | Outside the hammock, underneath you | Over you, like a bag with the back removed |
| What it replaces | The sleeping pad, in a hammock | The sleeping bag, on the ground or in a hammock |
| Why it works | Nothing compresses it, so the loft is always live | Removes the fill you were compressing anyway |
| Used on the ground | No, it needs something to hang from | Yes, that is its main use |
Which to pick: These two work together rather than competing. A cold-weather hammock setup usually wants both, an underquilt below and a top quilt above. Buy the underquilt first, because that's the side the cold is coming from.
The common mistake
Bringing the tent sleeping bag and nothing else
A bag rated to 30 degrees on the ground isn't rated to 30 degrees in a hammock. Half of it is crushed flat under you, and the wind has free access to your back. It's one of the most common reasons a first hammock trip ends early, and it happens at temperatures that feel mild.
Common questions
Can I use a sleeping pad in a hammock instead of an underquilt?
Yes, and it's much cheaper. A thin closed-cell foam pad weighs a couple of ounces and works fine, as long as it stays put. In a single-layer hammock it usually won't, and inflatables are the worst offenders. A double-layer hammock with a pad sleeve solves that for far less than a quilt costs.
At what temperature do I need an underquilt?
Earlier than you'd expect. Most people start noticing the cold underneath them around 65 to 70 degrees, and below roughly 45 to 50 degrees experienced hammock campers stop improvising with pads. What does the damage is the air moving under the hammock, more than the air temperature itself.
Do I still need a top quilt or sleeping bag?
Yes. An underquilt only covers the side your weight would otherwise have crushed. You still need insulation over you, and a top quilt is the usual choice, because it's the same warmth minus the flattened underside and minus a zip to fight with inside a hammock.
Where this is defined
- EN ISO 23537-1:2022, sleeping bag thermal requirements, International Organization for Standardization
- Leave No Trace Skills: Hammock Camping, Leave No Trace Center for Outdoor Ethics