Marmot Never Summer 0 Review

The Marmot Never Summer 0's large draft flaps keep warm air from escaping through the zippers. At the same time, its cozy blanket topper makes it a luxurious choice for relaxed car camping, even if its trim cut feels restrictive and limits the utility of the expandable footbox. Since you don't have enough room to adjust your upper legs and knees, you can't really take advantage of the little more room offered around your feet. That said, the expanded footbox does let you vent some heat or store your boot liners inside.

Both sides of this bag have a partial-length zipper. The lack of a full-length zipper limits the bag's utility in a rescue scenario where hypothermia is a concern.

Warmth

Our testers slept comfortably in this sleeping bag down to around 20°F. It also performed respectably in our heat retention tests, earning an above-average score. Still, it's no match for the impressive insulating qualities the top-performing bags offer in the test, landing it squarely in an average position for this metric.

The Never Summer includes 0 in its name, suggesting it's suitable for temperatures as low as zero degrees Fahrenheit. Beware, though, this number is closer to its survival temperature rating, or the lowest temperature at which the bag can reasonably be expected to prevent hypothermia. Independent ISO (International Organization for Standardization) tests found that its survival temperature is actually 5°F, while the comfort temperature was 18°F, which our testers confirmed during testing. Either way, this is not a zero-degree bag.

The Never Summer 0 wraps you in 36.8 ounces (3.8 pounds) of 650-fill power down. Fill power measures the quality of down, indicating how light and fluffy it is and how much heat it holds. At 650-fill power, this bag is considered an entry point for down winter sleeping bags. It's less expensive than many and can hold plenty of heat, but you would need more of this type of down to match the insulating properties of higher-quality options. The result is also a heavier, less compressible bag.

Design features like baffles sewn into the bag's 20-denier ripstop nylon fabric hold the insulation in place, effectively preventing cold spots. Large down baffles along both zippers and around the collar further reduce drafts and help retain warmth. Unfortunately, those baffles are less refined than similar versions in higher-scoring bags, meaning they don't perform quite as well. Our lead tester, Clark Tate, points out, “I found the Never Summer 0's collar baffles just don't cinch tightly above your shoulders to isolate your body from any cold air sneaking through the face opening.”

The large hood and face opening are also built more for comfort than heat retention. A static line around the hood and an elastic band across the top of the bag beneath your chin. Together, they let you cinch the opening to a snug 3.5 inches to hold in heat, but it's a chore to bunch up all that fabric. We gave up on a few cold nights and just layered a jacket over our faces instead.

Moisture Management

A wet sleeping bag can be dangerous in the dead of winter. That's why we test each bag's moisture management features, which include insulation, ventilation, and water-resistant fabrics. The Never Summer 0 earns average scores in this category, mixing some smart moisture managing components with less effective ones.

The bag's fabric is treated with PFC-free durable water repellent (DWR) to help water bead up and roll off before it can soak in. It worked well in our tests, successfully shedding a layer of overnight snow in our water bottle temperature test. That said, the bag only held a hot water bottle, not an entire human. If the bag were warmer and the snow had melted, it might have been more of an issue.

When we poured water onto the face fabric and liner and let it sit for a minute, the exterior fabric repelled completely. However, water soaked into the interior fabric in several locations, leading one tester to comment, “This makes me far less confident in the bag's ability to handle sweat or spills.”

On the upside, the down insulation is treated with Marmot's water-resistant Down Defender. The PFOA-free and PFOS-free chemical treatment coats the molecules of each feather to make them hydrophobic (literally, water-fearing). So, even if the entire bag gets soaked, the down should maintain its loft and insulating ability. Unfortunately, the treatment wears off after about 20 washes, according to Marmot. So, throughout the bag's life, this benefit will fade.

Aside from how well each sleeping bag stands up to external sources of moisture, we also evaluate how well the bag manages moisture from your breath or sweat. It's tempting to tuck your face inside your sleeping bag when it's cold enough. But then you're exhaling moisture directly into your bag, which can chill you to the bone. A common solution is to cinch the opening around your face to keep you warm while allowing airflow. You can do that with this bag, but as mentioned, it's a pain.

Another issue is the down baffle near the neck, which is designed to trap warmth despite the opening around your face — its design is not adjustable. The best bags in our tests let you cinch this down, keeping the condensation from your breath out of the rest of the bag. Then, in warmer temperatures, you can open it for airflow. Here, we did not have that option, exposing us to more cold air than we would prefer.

Speaking of warmer weather, if you tend to sleep hot and need to vent the bag occasionally to keep from sweating, the Never Summer 0 offers a few options. The two half-zippers on either side let you use the top as a blanket, which you can peel back for plenty of airflow. The zipper that expands the footbox also lets you dump heat when needed.

Comfort

This bag combines a few impressively comfortable features with a restrictive cut through the hips and knees. The cozy blanket topper is great for warmer temperatures, but your leg movements are limited when you need to batten down the hatches for warmth. Our testing results were mixed, resulting in an average score for comfort.

We got our hands on a size regular sleeping bag that measured in at 6 feet 7 inches long, 56 inches in circumference at the shoulders, 52.5 inches at the hips, 42 inches at the knees, and 39 inches at the feet when the zipper is closed (45 inches when open). Our tester thinks this is important, saying, “The design doesn't give you enough room to reach your feet while you're inside the bag.” We consider this a critical component of comfortable winter camping. Being able to tend to cold or injured feet while staying cozily inside your bag is essential.

There is enough room for our 6-foot tester to lie inside the bag on his back, side, or stomach. This ensures a fairly comfortable sleep, with a good amount of padding. When it's cold enough to keep every zipper closed, though, the Never Summer 0 is a tight fit unless you size up.

In warmer weather, the two zippers become a real benefit, turning the top of the bag into a blanket. This considerably improves overall comfort, allowing your upper body to move around as desired. But tester Clark Tate mentions, “Besides using it to cool down, I never found much use for the expandable toe box.” The area around the knees is so restrictive that you can not take advantage of the added space unless you use it to keep fresh socks, batteries, or boot liners warm.

Construction Quality

The Marmot Never Summer 0 fell short in our construction quality tests, receiving below-average scores. While there are a few redeeming features, the fabric and component quality leave much to be desired.

The stitches are easy to snag with a paperclip. While some are solid when you tug on them, others pull through, bunching the fabric. The higher-quality bags in the test feature much more durable stitching. The yellow and orange liner fabrics are also thin and puncture more easily than most.

The zippers, on the other hand, are pretty solid. The slider on the main zipper is wedge-shaped to limit fabric snags, and there's a stiffer ribbon of material alongside it to prevent jamming. While this system works fairly well, the ribbon is narrow, and we still ended up tangled with the delicate liner fabric more often than we'd like.

While we appreciate that both sides of the bag zip down to create a comfortable blanket feature, we wish the main zipper extended the full length of the bag. If you needed to get an injured person inside to protect them from hypothermia, this design makes the task significantly more difficult. In winter camping, safety should come first.

The hood's drawstring system, which combines a static cord in the arch above your head with a thin elastic strand below, is difficult to use. While we managed to cinch it down to about 3.5 inches from the outside of the bag, it's far more difficult to adjust from the inside. That means you would benefit from the help of a camping partner to keep your face warm in harsh conditions.

We appreciate the internal stash pocket, which is large enough to tuck your phone into to save its battery life. The strip of bright yellow fabric by the opening makes it easy to locate. The expandable footbox makes it easier to store things that need to stay warm inside the bag, but unzipping it releases heat, sort of defeating the purpose. We find that it's most useful in warm weather when you're in danger of overheating.

The included stuff sack is pretty worthless; you'll need to buy another if you do decide to take this bag into the backcountry.

Weight

The Never Summer is on the heavier end of the lineup, weighing in at three pounds and eight ounces. For this, and many of the reasons listed above, this bag is better suited for short hikes, ski tours, or car camping.

Packed Size

We tested each bag's packed size by stuffing it into a Sea to Summit 20L compression sack and cinching the draw cords as tightly as they would go. The result was a 14-inch long package with a 9.5-inch diameter, giving it a total volume of 992 cubic inches. We also measured the bag's dimensions using its lower-quality included stuff sack, resulting in 19 inches in length and 8 inches in diameter.

Keep in mind that lower-quality down fill takes longer to recover from compression and degrades more quickly than high-quality down. Over time, it may lose its ability to bounce back.

Should You Buy the Marmot Never Summer 0?

The Marmot Never Summer 0 bag is a reasonable cold-weather sleeping bag for budget-conscious campers who prioritize warmth, padding, and a comfy blanket topper over durability and premium features built for backcountry use. It's well-suited to front-country car camping in temperatures around 20°F. If you prefer a spacious feel, consider sizing up to get a bit more wiggle room.

The PFC-free DWR fabric treatment and Down Defender help manage condensation from your breath in a tent or car. It's also nice that Marmot is trying to reduce its use of toxic chemicals, which is good for your health and the planet.

What Other Cold Weather Sleeping Bags Should You Consider?

If you're considering the Never Summer bag because it looks comfortable, we'd steer you towards the Western Mountaineering Kodiak MF. Although it's far more expensive, it also has the most generous cut in the test, with a silky soft interior fabric that creates a luxuriously cozy nest for overnights. The Mountain Hardwear Lamina 0 may be a better option if you're drawn to a lower price tag. While it's not as comfortable or quite as warm, it's not far off and comes with a superior construction and synthetic insulation that deals well with wet weather.