I’ve been working on putting together a winter backpacking ensemble and one of the first steps was to get myself a warmer quilt. I ended up buying an Enlightened Equipment Enigma 10F Long/Wide ($355, 774g) but thought I’d share my research and thought process along the way.
Baseline
For three-season 2019 I’ve been using a Sierra Designs Nitro Quilt 800 20F. What I like about it is that it’s big: I can just drape it over myself like a blanket and I don’t have to fuss with straps or any other gadgets to attach it to my pad. Specifically, it’s 75 inches long with a shoulder circumference of 56 inches and a footbox circumference of 40 inches (we’ll come back to these measurements later when we’re comparing it to other quilts). It also has a closed footbox which I consider a hard requirement.
What I don’t like about it is that it’s not warm enough for shoulder season. It comes with 14.8 ounces of 800 fill power down or 11,840 “fluff” (14.8 x 800 = 11,840). The comfort rating on the quilt is 32F, however, this assumes that you’re using the built-in hood. Having used it on one particularly cold night I can safely say I’m not a fan. According to a Section Hiker interview with Therm-A-Rest the rating for a quilt without any head insulation is 4F higher so our “effective” comfort rating is really around 36F. I’d prefer something in the upper twenties for three-season backpacking and upper teens for winter use so this doesn’t cut it, both on paper and in real-world experience.
The Candidates
I went through closed-footbox offerings from several major quilt manufacturers with sizes comparable to the Nitro and compiled them into the following spreadsheet:
https://docs.google.com/spreadsheets/d/1uWbY-0K9zHPX7cUQ4DcBiya0VU6CD07zyQpqV6JxRQk/edit?usp=sharing
I also included my current quilt for comparison.
Highlights
- Only Enlightened Equipment, REI, and Therm-A-Rest actually had ready-made quilts available for sale
- The Zpacks Solo 10 and 20 and the EE Enigma are the three best quilts in terms of insulation (fluff) for the weight
- The Enigma 10 and 20 and the Solo 10 are the best in terms of just plain ol’ ounces of down. If you’re skeptical of the relative benefits of fancier 950-fill-power downs like I am then this is a good metric to look at.
- Hammock Gear’s Econ Burrow line completely dominates the insulation-per-dollar category. The closest quilt from another manufacturer is the Enigma 10. On the other hand you have to wait three weeks…
- The Enigma 20 and 10 have 25% and 50% more down than my current quilt. The 20 weighs 43g less and the 10 weighs 62g more.
Decision
I decided to go with the Enigma 10F because it was ready to ship same-day, it was one of the strongest performers in both the insulation by weight and insulation by cost categories, and it had 50% more insulation than my current quilt. In my mind there was no question that it could be used in winter down to 20F and perhaps pushed to 10F or even 0F by adding clothing or a thin synthetic quilt, respectively.
However, the Enigma 20F was a very close runner up. The temptation of a 3-season quilt that’s both lighter yet has 25% more insulation than my current quilt was hard to resist. In the end, though, I worried that the bump in insulation wasn’t going to be significant enough.
If only there were a way to know for sure…
EN Ratings vs. Fluff
Unfortunately I didn’t take time out to do this analysis before making a purchase. What follows is an investigation into whether there’s a way to actually determine just what temperature I should have expected for both the 25% and 50% bump in insulation.
Temperature Rating vs. Ounces of Down
Let’s start off with a graph comparing the manufacturer’s temperature rating vs. ounces of down:
We can see a pretty large variation in the amount of down at each temperature point. For example, the Zpacks Solo 10F has almost 5 fewer ounces of down than the Enlightened Equipment Enigma 10F. Of course, they’re using different fill powers so let’s take that into account by comparing “fluff” (ounces of down x fill power):
We have a little more agreement here (higher R-squared value) but it’s pretty obvious that we can’t usefully compare ratings across manufacturers.
Quilts and EN Ratings
The EN rating test for sleeping bags relies on the fact that sleeping bags have hoods, something which the vast majority of quilts do not have. However, the Sierra Designs quilts do have built-in hoods and as a result were the first quilts to have proper EN ratings. Later on Therm-A-Rest figured out that if you just put a hood on the testing mannequin you can get an EN rating for any quilt.
What if there was a simple relationship between fluff and EN comfort rating for the rated quilts? If there was then we could approximate the EN rating for quilts from any manufacturer, allowing us to make direct comparisons regarding warmth.
To find out, I put together a table of fluff vs. EN comfort rating for six quilts with known comfort ratings, three from Sierra Designs and three from Therm-A-Rest. I then tossed out an outlier (the Nitro 35 from Sierra Designs) to produce this beautiful chart:
Without the outlier we have a linear relationship with an incredibly high R-squared value which indicates that this should be a pretty good predictor. Of course, we are glossing over construction techniques like sewn-through vs box-baffle construction but it’s better than nothing.
We can see that the equation to convert fluff to EN comfort rating is:
EN comfort rating in F = -0.00391 x fluff + 77.3
Enigma 10 and 20 Estimated EN Comfort Ratings
Recall that the EN comfort rating for my current quilt (the Sierra Designs Nitro 20F) is 32F. According to our equation, the comfort ratings for the Enigma 10 and 20 should be 7F and 19F, respectively. That means each 25% bump in insulation was about a 12F increase in warmth – very significant! In hindsight I should have gone with the Enigma 20, reaping the 3-season weight savings and increased shoulder season comfort with the option to pair it with a Revelation Apex 40 for deep winter backpacking.