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Marmot Helium 15 Review

A high-quality sleeping bag that's marred by a perplexing secondary zipper
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Marmot Helium 15 Review
Credit: Marmot
Price:  $479 List
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Manufacturer:   Marmot
By Jack Cramer ⋅ Review Editor  ⋅  May 26, 2022
  • Warmth - 20% 8.0
  • Weight - 20% 5.0
  • Comfort - 20% 7.0
  • Packed Size - 15% 5.0
  • Versatility - 15% 6.0
  • Features & Design - 10% 6.0

Our Verdict

The Marmot Helium 15 is a premium sleeping bag. It has premium down insulation (800FP) and premium specs, but also comes at a premium price. For that kind of cash, we usually expect best-in-class performance. In several ways, however, the Helium didn't meet those expectations. Head-to-head against other high-end sleeping bags, its weight and packed size are subpar. The absence of a neck baffle left many of our testers feeling a draft in temperatures approaching its 15F rating. Moreover, the unusual secondary side zipper proved to be ineffective for its purpose of venting excess heat on warm nights. There is still plenty to like about the Helium. But if you're going to pay top dollar for a premium bag, there are several other models with fewer flaws.
Wide upper body dimensions
Decent warmth-to-weight ratio
No neck baffle
Narrow foot dimensions
Accessory zipper ineffective at venting

Our Analysis and Test Results

Marmot is experimenting with adding a secondary zipper to several sleeping bag designs to allow new venting possibilities. The location of the secondary zipper on the side of the Marmot Helium 15 is one of the more perplexing of these experiments, causing us to downgrade an otherwise stellar sleeping bag.

Performance Comparison

marmot helium 15 - the marmot helium is a backpacking sleeping bag with a premium price...
The Marmot Helium is a backpacking sleeping bag with a premium price tag. Unfortunately, the performance doesn't seem to match the price.
Credit: Jack Cramer


The Marmot Helium utilizes 20 ounces of 800FP down, a pretty sizeable amount for a 3-season backpacking sleeping bag. It receives a 10F lower limit temperature rating on the industry-standard EN test but Marmot markets the bag with a more conservative 15F rating. We think the conservative manufacturer rating is more accurate because this bag doesn't incorporate a neck baffle to trap heat inside the bag. Some folks may prefer the simplicity of this design but be aware that this allows considerably more heat to escape out the collar of the hood. This isn't an issue in most conditions but it becomes a problem in temps approaching the 15F rating.

marmot helium 15 - a 15f sleeping bag like the marmot helium is excessively warm for a...
A 15F sleeping bag like the Marmot Helium is excessively warm for a lot of backpacking applications. Instead, it's best suited for trips at higher altitudes or shoulder seasons in northern latitudes.
Credit: Jack Cramer


A size long Marmot Helium weighed in at 2.08 pounds on our GearLab scale. That's pretty light for most backpacking sleeping bags with this level of warmth. However, the Helium is a premium bag with a premium price. In our tests, we identified a couple of other bags that provide similar warmth while weighing as much as 25% less. So even though the Helium is light, we were disappointed with its warmth-to-weight ratio compared to the top-performers in the category.


The comfort of the Marmot Helium is enhanced by its generous upper body dimensions. Unfortunately, it tapers considerably at the foot box and some of our testers found the narrowness in this area unpleasant. We did like the supple feel of the 30-Denier nylon lining combined with its fluffy 800FP down. The hood also seems well thought out with a spacious design that can cinch comfortably to seal heat in on a cold night.

marmot helium 15 - we are impressed with how comfortable the hood was when sealed...
We are impressed with how comfortable the hood was when sealed tightly. However, this bag lacks a neck baffle so body heat still has an opportunity to escape out the collar.
Credit: Jack Cramer

Packed Size

As one of the warmest models in our backpacking sleeping bag category, the Marmot Helium 15 includes substantially more insulation than others, and its packed size understandably suffered for this reason. Although it's a bit bulky, the premium down is still highly compressible and we would estimate that it would exhibit a better than average packed size among bags supplying similar warmth. Although this bag comes with a drawstring stuff sack, we discovered that it was exceedingly difficult to stuff our size long test model inside. We do not know if the same issue would occur with a size regular.

marmot helium 15 - the stuff sack included with the size long bag we tested seemed to...
The stuff sack included with the size long bag we tested seemed to be undersized. We could barely fit the bag inside.
Credit: Jack Cramer


One of the unique features of the Marmot Helium is a secondary zipper on the right side. The intention is that you can open this zipper to vent excess heat on warm nights. In practice, however, we found it rather ineffective for this purpose. The secondary zipper is simply too short to open the bag very far. On colder nights, the Helium also seems to be ill-designed because it lacks a neck baffle to seal heat it. Due to this issue, we think this model has a rather narrow usable temperature range and it's thus not very versatile.

The Marmot Helium's main zipper to the tester's left is augmented...
The Marmot Helium's main zipper to the tester's left is augmented with a short secondary zipper to his right. The idea is that the secondary zipper allows you to vent excess heat. In reality, it's so short that it hardly seemed effective.
We like the Y-shaped zipper slide because it does a good job at...
We like the Y-shaped zipper slide because it does a good job at preventing zipper snags.

Features & Design

One of the best features on this bag is the hood which cinches down comfortably and incorporates a drawcord that's directed away from your face. The bag also includes a convenient stash pocket for keeping the batteries on a headlamp or small smartphone warm. When it comes to the broader design, we just can't get past the ineffectiveness of the secondary zipper. We believe using the extra zipper material to extend the main zipper from 3/4- to full-length would improve versatility far more. The bag could weigh the same and a truly full-length would allow it to unzip into a blanket for warm nights.

marmot helium 15 - there is a small stash pocket inside the bag. we found it big enough...
There is a small stash pocket inside the bag. We found it big enough to store a small smartphone or headlamp.
Credit: Jack Cramer


The Marmot Helium 15 is a high-end sleeping bag with a corresponding price. Its 800FP down certainly feels premium and we were impressed with its all-around construction. When you compare the Helium with other high-end models, however, its deficiencies become apparent. Other companies simply offer lighter, more packable designs that also utilize even loftier down. If you're going to splurge for an ultra-premium sleeping bag, the Helium seems like a subpar value.


On its own, the Marmot Helium 15 is a very nice sleeping bag. It's lightweight and warm, and it exhibits the quality construction you would expect from a model with its premium price tag. In head-to-head competition with other expensive bags, however, it just can't keep up. We consider the top-rated backpacking sleeping bags from Western Mountaineering and Feathered Friends to be better in nearly every way. In other words, we'd likely steer clear of the Helium at full price but give it some consideration if you find it on sale.

Jack Cramer