Serious Sleepers: Testing His-n-Hers Sea to Summit Ascent Down Sleeping Bags

We’re longtime campers. We’ve slept in tents, rooftop tents, vans, and more. Andy and I have tent camped with sleeping bags in a wide variety of conditions—all throughout the world. Until now, we’ve primarily used sleeping bags with synthetic insulation. However, as we expand our cold weather sleeping scenarios in different climates, we decided to test a pair of down variants. Would they hold up to cold weather, no matter if it’s snowing or raining? We test the Sea to Summit Ascent Down Sleeping Bag and the Sea to Summit Women’s Ascent Down Sleeping Bag, both in Regular lengths.

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Why Sea to Summit?

Andy and I have used Sea to Summit products for years. We’ve tested their inflatable Aeros pillows and bought their sleeping bag liners. We have used a wide swath of their kitchen wares, which include a collapsible pour over for coffee, their collapsible Frontier Ultralight Collapsible Dinnerware Set, Detour Stainless Steel Cutlery Set, and more. Many of these items have even crossed the globe in our quest for outdoor adventure.

So far, these products have stood the test of time and travel. That says a lot, especially from on-the-go folk like us. So, when the time came to create a new sleeping setup for our 2022 Subaru Crosstrek adventuremobile and TSD rally car, we turned to a name we know.

Sea to Summit Ascent Down Sleeping Bags

We’ve worn high-quality down jackets for years now, but haven’t slept in down sleeping bags much. The Sea to Summit Ascent Down Sleeping Bag comes in both a Unisex and Women’s specific relaxed mummy fit. Both models are offered in Regular 6’-1” and Long 6’-6” lengths. This gives sleepers extra room to move about without feeling too constricted. The Women’s specific fit is narrower at the shoulders  to reduce weight but is wider at the hips and knees to allow for a better side-sleeping position.

Both iterations boast either 30°F or 15°F lowest temp ratings, depending on which you buy. We opted for the Unisex Regular 15°F sleeper for Andy, and the Women’s specific Regular 15°F sleeping bag for me.

The Unisex and Women’s Ascent bags include a technical hood which traps heat around the head and neck. Zip up the draft-tube-protected zippers and you’re ready for cold-weather sleeping. Each bag has an internal zipper pocket near the shoulders. It’s a great place to stash keys or a smartphone.

Car Camping with Sea to Summit Down

We planned to sleep in our Crosstrek, our 1994 Mitsubishi Delica Space Gear van, as well as in tents with our new Sea to Summit Ascent Down Sleeping Bags. For us, convertibility is key.

We outfitted our Subaru Crosstrek with a Sleep Rides sleeping platform, and once deployed, used an EXPED MegaMat Duo medium sleeping mat on it as the foundation for our Ascent Down Sleeping Bags. This proved to be a comfortable and stable setup which fit our Crosstrek perfectly. While we could easily sleep in our Crosstrek with both bags as individual sleepers, we preferred to zip them together to create one large two-person down sleeping bag.

Note: The Unisex and Women’s bags have different-length zippers. Once you get the bottom footwell zipper started and zipped up together, one of the sleeping bags may be slightly longer on the bottom than the other. Bonus: Each person retains their own “foot zone.”

For Andy, the Sea to Summit Ascent Down Sleeping Bag in the Unisex style had great loft and felt very cozy. He was plenty warm as temps dropped into the 30s. Also, when he compared it to the zippers on some of his other bags, it was very easy to zip and didn’t get caught in the fabric.

I felt like I was sleeping on clouds. I snuggled up with my Sea to Summit Women’s Ascent Down Sleeping Bag like I would be on a pillowtop mattress at the Four Seasons Hotel. The down loft was evenly weighted and warm. The inside zippered pocket was stashed in a good location, although I’d prefer it larger for my Samsung S24 Ultra phone with Quad Lock case.

Does Size Matter?

By first glance, my Ascent Sleeping Bag is much bigger in size in its rectangular stuff sack vs. the Unisex Ascent bag. It also appears much more filled with down than Andy’s Unisex sleeping bag when laid out. The Unisex bag weighs 2 lbs. 4 oz. and can be compressed to 7.5 liters. However, my Women’s variant weighs a bit less at 2 lbs. 3.3 oz. and has a slightly larger compressed volume of 7.7 liters.

I asked the company about its notable difference in size and loft (when compared to other his-n-hers sleeping bag comparisons we’ve done). Here is what they said:

Both the unisex and women’s Ascent bags are built to deliver the same real-world warmth — comfort around 15°F — but the ISO 23537-1 test shows different numbers because each bag is tested on a different mannequin. The lower limit rating on the women’s bag often appears significantly lower (5°F vs. 15°F). That’s expected, and here’s why:

The ISO test uses two mannequins: one representing a standard female sleeper “cold sleeper” and one representing a standard male sleeper “warm sleeper.”

The women’s-specific bags are engineered with more down insulation, especially targeted in the torso and footbox, so they keep a colder sleeper warm at the same temperature as the unisex version.

That added insulation means the women’s bag performs better under the ISO test, which results in a Lower Limit rating that appears colder, even though both bags are designed to feel equally warm for their intended user.

In other words, the Comfort Rating is the temperature at which a standard woman would sleep comfortably for 8 hours. It shows up as 29°F on the men’s bag because that version has less insulation, so the female mannequin reaches its “comfort” threshold at a higher temperature than it does in the women’s bag. Both bags are sold and rated as 15°F bags. The women’s Ascent simply requires more insulation to deliver the same real-world warmth, and that extra fill naturally lowers its ISO test results.

It’s All About Down

The Sea to Summit Ascent Down Sleeping Bag and Sea to Summit Women’s Ascent Down Sleeping Bag offer high lofting 750+ Ultra-Dry Goose Down to keep you warm. The company says that one ounce of this down will expand to over 750 cubic inches after its compression. Note: The higher the fill power, the more the down will insulate you for a given specific weight. What this means is that less down can be used to achieve the same temperature rating in a sleeping bag. Sea to Summit states that 750+ goose down “represents a good balance between insulation and packability.”

In addition to noting the fill power of this down, it’s RDS-certified (Responsible Down Standard). This means 100% of the down used in Sea to Summit sleeping bags are independently certified to this standard. RDS certifies that this down demands better animal welfare practices when it comes to the down/ feather supply chain. RDS also tracks down from the source to the final product.

Sea to Summit down sleeping bags come with a test report from the International Down and Feather Laboratory (IDFL). They are hydrophobically treated with a non-PFAS ultra-dry down finish treatment to stay drier in damp conditions. That’s critical in our Pacific Northwest’s rainy conditions but would also help with condensation from a vehicle or tent.

Sea to Summit stuff sacks and compression bags also use a non-PFAS durable water repellent finish to help stave off water. Both sleeping bags include a 40D recycled, bluesign approved nylon compression bag.

Warm Weather Opportunities

The Sea to Summit Ascent Down Sleeping Bag works well for cold-weather conditions, but it’s also made to be used in warmer weather, too. The Free-Flow Zip system lets you unzip in different configurations for increased ventilation.

Ascent zippers unzip on each side of the bag (one fully and the other a third of the way down). Plus, Quilt Lock Snaps on each side where your shoulders are keep the sleeping bag secured while having your arms outside of it. The Ascent line-up also has a separate footbox zipper—perfect for bottom-end venting if you’re too warm. Or, if you’re so inclined, you could wear this sleeping bag like a cocoon around you at camp. Not like we’ve done that … yet. Finally, you can open the Ascent Down Sleeping Bag completely flat and turn it into a lightweight quilt if desired.

Price for either of our Ascent Down Sleeping Bag models: $449.00