The quilts I'm using in this photo are rated about 90° too conservatively for the 60°F weather during this shoot, which is why the neck closure isn't cinched shut.
Anyone who enjoys cold weather camping can tell you about its many benefits: no bugs, no crowds, and an extreme peacefulness and beauty that is difficult to experience any other time. But of course these benefits don’t come free, and the primary challenge in winter camping is the simple necessity of keeping warm, especially while sleeping.
There are a few ways to tackle this issue. Traditionalists may resort to “hot tenting” which involves using a small wood stove along with a canvas tent, though “cold campers” will most often rely on a very specialized sleeping bag rated to very low temperatures. These sleeping bags, while effective, have a serious drawback: because they’re so specialized for low temperatures and require so much insulation to be effective, they’re a very high cost item that can only comfortably be used in sub-zero temperatures.
Two of our quilts attached to the pad via the Sub-Zero Strap.
At Enlightened Equipment, we like to rely instead on a very simple yet versatile method to hit sub-zero temperatures: layering multiple quilts.
For those who only occasionally do winter trips, the first benefit is simply cost. By using two quilts- typically one summer-weight quilt, and one shoulder-season quilt- they’re actually giving themselves three temperature ratings. For example, if you have a 40° quilt for summer use and a 20°F quilt for the shoulder seasons, you can use each independently, and then in winter combine them for a -10°F rating, and often both quilts combined would still come in at a lower price than a sleeping bag rated to -10°F. For reference, below we’ve included a chart to calculate the approximate ratings of two quilts. Note that these ratings only follow down to -40°F (which is also -40°C, by the way). Use below these temperatures is possible, but using either quilts or sleeping bags below -10F requires some good experience using them, and typically some well thought-out insulation for your head/face, and a very efficient insulator underneath you.
Trace your first quilt rating from the top row down to your second quilts rating from the left column. Where they intersect is the combined rating (approximately).
Also keep in mind that a tight-fitting quilt may not loft as fully as it should to hit its temperature rating, so the quilt used on top may need to be somewhat larger to allow a good fit for the quilt below it.
This style of sleep system doesn’t necessarily need to include two quilts. Using a sleeping bag or mummy bag along with one of our quilts is also a very effective way to add some versatility to your kit. When using two quilts keeping everything in place couldn’t be simpler. In order to keep everything held together in cold weather, EE offers the “Sub-Zero Strap”, which allows you to attach both quilts to your pad at once. While any two of our solo quilts can be used, one of the most popular combinations of quilts is to use a Prodigy as the outer quilt, and a Revelation or Enigma as the inner quilt.
Shown above: Enigma inside, and Prodigy Outside. Both are 20°F rated, so would be effective down to about -30°F.
The Prodigy uses synthetic insulation, which has a few benefits over using down. Besides costing less, it also handles moisture, sweat, and oils more effectively than down does, and is easier to clean besides. This makes it a really strong option for a summer quilt, when sweat and oils are most likely to be an issue, but it also has a special use for a layered quilt system as well.
Whether awake or asleep, our skin is always releasing a certain amount of moisture in the air. When the air cannot absorb it immediately it comes out as sweat, but the rest of the time it is transferred into the air as a vapor by a process called sublimation. When sleeping under a quilt or in a sleeping bag, this water vapor cools gradually as it leaves your body, the air next to your body being warmest, and gradually cooling as it moves through your quilt and out into the air. In very cold weather this cooling happens very quickly, allowing the water to condense into a liquid form perhaps even before it is able to pass all the way through your insulation. The point where the moisture condenses into a liquid is the dew point. If the dew point falls somewhere in your down insulation will dramatically reduce its effectiveness, so it’s important where possible to make sure that if the dew point must fall somewhere inside your insulation, it’s much better for this to occur inside a synthetic insulation which can continue to offer a higher level of insulation when damp than down. That said, in many conditions the dew point will be fully outside your insulation layers, and in that case using two down quilts will work just fine.
Lastly, many users may find is surprising to even consider using one or more quilts in cold weather at all, typically for concern about drafts. A well-fitting quilt should offer enough coverage to keep drafts locked out and leave some extra space for insulated clothing layers. Because there’s no fiddly zipper (which can be very frustrating to use with gloves on), getting under and out of the quilt, or even two quilts is as simple as using a blanket at home. This makes late-night trips much less clumsy than when you’re using a tight-fitting mummy bag in cold weather, and if you’re wearing a Hoodlum or something similar, you have the added benefit of taking your head insulation with you.
Notice that two pads are being used in this photo. Not only will the foam pad help protect the air pad from sharp objects, but it will add to the R-Value, allowing this combination to be used far below 0°F.
Ultimately your kit should serve the specific trips you find yourself on. For some that will mean having a dedicated sub-zero bag, but for many of us layering quilts will be completely effective to reach those temperatures when we find we need to.