The Sea to Summit Ascent Down Sleeping Bag is a lightweight down sleeping bag with three zippers that lets you fine-tune ventilation and comfort as outside temperatures change.
To get us a closer look, Sea to Summit sent Man Makes Fire a review unit. After testing the Ascent Down Sleeping Bag in the 15-degree Fahrenheit option, a.k.a. the 15°F AcII version, this what we learned during the review process after camping and backpacking in Idaho:
Review: Sea To Summit Ascent Down Sleeping Bag
The Sea to Summit Ascent down sleeping bag series is light enough to take backpacking but roomy and versatile enough for camping.The Sea To Summit Ascent Down Sleeping Bag has a tapered rectangular design. It’s roomier than typical competitive mummy-shaped sleeping bags but not quite as roomy as full rectangular bags. The shape is aimed at versatility and comfort — and in this Sea to Summit succeeds admirably. The slight taper helps retain warmth . . . while the slight taper also gives you a bit more room to roam inside the bag. It’s a good design.
Personally, I’m only a fan of mummy-style sleeping bags when it’s wicked cold outside. I’m a relatively big guy — about 6’3″ and 220 pounds — and I tend to sleep in multiple positions each night. In addition, very often when I’m camping or backpacking in the mountains, the temperature starts out relatively warm in the evening but drops much colder around 4 a.m.
We’re very impressed with the versatile 3-zipper design in the Sea To Summit Ascent Down Sleeping Bag
The Sea To Summit Ascent Down Sleeping Bag lets me unzip multiple sides to let me fine-tune the temperature or even poke a leg or knee out.
In addition to my own experience, another Man Makes Fire gear tester appreciated the versatility of the zippers while backpacking in Idaho at around 8,000 feet of elevation in July. Most nights were warm to start out but dipped down much cooler just before dawn. “The ‘Free-Flow’ zipper system works great!” he reported.
Let’s take a closer look at the zipper system because it’s the key differentiating factor that might make the Ascent series bag right for you.
3-Way Multi-Zipper Options
The versatile zipper options give you multiple configurations for excellent warmth and ventilation as temperatures change.On one side of the bag, Sea To Summit Ascent Down Sleeping Bag gives you a half-length zipper. On the other side, you get a full-length, two-way zipper.
But wait, there’s more: You also get a separate foot box zipper. What does this all mean?
If your feet get hot, you can unzip the foot box zipper to ventilate and cool down. Similarly, you can unzip the long side zipper from the bottom end and poke a foot out if you want to. Or unzip it quite a bit and poke a leg out. Or you can keep your foot box zipped and unzip both sides half-way, which lets you fold the top down like a blanket.
The foot box zipper lets you cool down while keeping your upper body warm.Or you can zip and unzip in all sorts of different ways to accommodate however you like to sleep.
It works well and it makes the Sea To Summit Ascent Down Sleeping Bag particularly great for warm nights that turn cold just before dawn.
750+ Loft Ultra-Dry Down
The 750+ fill power hydrophobic down lofts well and delivers excellent coverage for warmth. Also note the two-way zipper.With a 750+ loft rating, the Sea To Summit Ascent Down Sleeping Bag doesn’t use the very lightest down — 850-900 fill power down is typically the best you can get. However, 750+ is very good lightweight down.
More importantly, Sea to Summit doesn’t skimp on the down when the company fills the baffles. The Ascent bag is well-stuffed with down, which helps ensure great insulation and warmth throughout. It’s also certified to the RDS standard for responsibly sourced down.
The down has a non-PFC treatment that makes it hydrophobic so that it resists moisture. This means that if your bag gets a bit wet, there’s a better chance that the down insulation will retain its loft and keep you warm. We like hydrophobic down because it tends to perform just a bit better in damp conditions. Similarly, if you’re sleeping in the same bag over multiple days, hydrophobic down is sometimes better at handling water vapor produced by your own body while you sleep.
The point is, the down used in the Sea To Summit Ascent Down Sleeping Bag is very good.
Shop the Ascent Down Sleeping Bag at Sea to Summit and get FREE Shipping on U.S. orders $50+!
Great Baffle System
Sea to Summit uses a multi-directional baffle design, along with draft baffles for the zippers for superior warmth.Sea to Summit has created a great multi-directional baffle system. The top half of the top sheet baffles are vertical while the bottom foot box baffles are horizontal. The most important element here is that the baffles aren’t too large. When they’re too big, down can shift around inside leaving you with gaps in your insulation. That’s not a problem with the Sea To Summit Ascent Down Sleeping Bag.
Better yet, Sea to Summit includes neck baffles as well as internal baffles around the zippers. This design takes a bit more work to construct, but the result is great insulation even where there are zippers.
Excellent Zipper Quality
The zippers are burly, smooth, and snag-free.With a bag with so many zippers, you would expect high-quality zippers — and Sea to Summit delivers. The zippers are smooth and usable, even at night.
Most importantly, Sea to Summit has added in a stiffer material along the length of the zippers that prevents the zipper from snagging on the soft nylon face fabric of the bag.
We’re very impressed with the quality of the zipper experience in the Sea To Summit Ascent Down Sleeping Bag.
Weight vs. Versatility
The Ascent compresses down into a stuff sack for travel or backpacking.While the Sea To Summit Ascent Down Sleeping Bag isn’t the lightest down sleeping bag in its price and quality range, it is far more versatile. Why? Zippers require a few extra ounces than less-zippered bags. However, I’m usually willing to carry a few extra ounces for the improved sleeping experience I tend to get from more versatile bags.
Basically, it comes down to this: I’d rather carry 10 ounces more after a good night’s sleep than 10 ounces less after a bad night’s sleep.
Choose the Sea To Summit Ascent Down Sleeping Bag if you prioritize the ability to move around and add ventilation when the weather is a bit warmer than expected.
Key Specifications
Sea to Summit offers three temperature versions of the Ascent Down Sleeping Bag. The three version each have a different bright green color scheme and a slightly different name that some retailers like REI use to distinguish between the version. The AcI, for instance, refers to the 25°F bag while the AcII refers to the 15°F bag. The 0°F version is AcIII. The Regular is sized to fit people up to 6′ tall while the Long is sized for people up to 6’6″ tall.
All of the bags share these materials:
Insulation: 750+ fill power Ultra-Dry Down
Shell Fabric: 20D Nylon
Shape: Relaxed Mummy/Tapered Rectangle
They also all come with a ventilated storage sack for long-term storage at home as well as a compression sack in case you want to compress the bag into a tidy size for travel or backpacking.
Weight
Check out the Sea To Summit Ascent Down Sleeping Bag series page on Sea to Summit for a complete weight chart. In general, the Long versions weigh a few ounces more than the Regular versions listed here:
Ascent 25°F: 1 lbs 14.3 oz
Ascent 15°F: 2 lbs 6.8 oz
Ascent 0°F: 2 lbs 14.7 oz
Which Version Should I Choose?
You can pair a unisex left-handed Sea to Summit sleeping bag with a women’s specific right-handed bag like the Altitude.Because the Sea To Summit Ascent bags give you so many ventilation options, you can safely choose a more insulated version compared to bags with fewer zippers. What do I mean? I’d rather have a warmer bag than I will probably need because I’ll be more comfortable if it does get cold. Conversely, for summer camping and backpacking, I tend to prefer lighter, less insulated bags . . . but because I can vent the Ascent in so many ways, I can get warm-weather comfort out of it, too.
If you want one good bag to cover a wide range of possibilities, the Ascent is a good choice.
The 15°F AcII will be the best all-around choice for most people, but if you tend to sleep cold or plan some high-mountain or spring/fall trips, the 0°F might be your ticket. I would only get the 25°F if you tend to sleep warm or plan to limit your use to warmer weather summer nights.
Shop the Ascent Down Sleeping Bag at Sea to Summit and get FREE Shipping on U.S. orders $50+!
The Bottom Line
All in the all, the Sea To Summit Ascent Sleeping Bag is a surprisingly versatile down sleeping bag. The build quality is fantastic. More importantly, the 3-zipper design delivers outstanding insulation for chilly nights but also lets you easily adjust ventilation. Last of all, the relaxed tapered rectangle shape avoids the constricting full-mummy shape in favor of a more roomy experience. Very highly recommended.
Get the Gear:
Check pricing & availability:
Backcountry.com | CampSaver | Moosejaw | REI
Pro Tip: An Insulated Sleeping Pad Makes a Big Difference
If you buy a warm sleeping bag but sleep on an uninsulated air pad . . . you’ll be cooler — sometimes much cooler — than you’ll be if you sleep on an insulated air pad. Sea to Summit has a pretty good explanation of the insulated/uninsulated sleeping pad issue here if you want to learn more.
Meanwhile, if you just want a good insulated air mattress recommendation, read our review of the Ether Light XT Insulated Air Sleeping Mat.
