Modeling the Nitro 30 after on an overnight igloo camping trip.
My preference for an ultralight sleeping system that will handle occasional unexpectedly cold nights is a 30 F rated mummy-style down sleeping bag with enough girth so I can wear extra clothing inside to extend its warmth when needed. Backpacking Light will publish a series of three articles in spring 2010 covering the insulated components of an ultralight three-season sleeping system for colder temperatures. This review is a separate evaluation of the Sierra Designs Nitro 30 sleeping bag.
When selecting sleeping bags to include in my upcoming state of the market article on ultralight three-season down mummy-style sleeping bags, I at first rejected the Sierra Designs Nitro 30 because it weighs 26 ounces. The lightest bags in this category weigh in at 19 to 23 ounces. Then I noticed that the Nitro 30 (size Regular) contains 12 ounces of down, while the lighter bags contain 10 ounces of similar quality down. That’s 20% more, which should translate to more loft and more warmth. The Nitro 30 has some other features that also should contribute to warmth, so how does the slightly heavier Nitro 30 stack up compared to the lightest 30 F (-1 C) rated sleeping bags?
Sierra Designs’ Partial Stretch technology is similar to MontBell’s Super Stretch Down Hugger technology, in which a proprietary elastic thread is used in the seams to provide enough elasticity to draw the bag up so it gently hugs the sleeper’s body. Sierra Designs puts the flex in the location where it is most needed – the widest part of the bag (shoulders to hips) – where excess volume requires more body heat to warm it up. To be specific, there are 7 inches of flex in the top of the bag from your chin down to your knees, so the shoulder girth expands from 53 to 60 inches and the hip girth expands from 50 to 57 inches.
The Nitro 30 (women’s Spark 30) is a member of Sierra Designs’ Ultralight Series of bags that feature a unique jacket-style hood, half-length zipper, partial flex technology (upper top of the bag), and lots of 800 fill-power down.
All Sierra Designs bags feature a Snag-Free Zipper Track to prevent zipper snags. The key component is a stiff piping (white) on both sides of the zipper that creates a barrier between the bag’s lining and the zipper track. The bag also features a large down-filled draft tube next to the zipper to prevent cold spots.
The Nitro 30 has Sierra Designs’ unique Jacket Hood (left), which is exactly what it says – it looks like the hood on a down parka when open, and it’s well insulated. The bag’s zipper angles from the side to the base of the hood. The hood draws down like a sleeping bag hood to expose only your nose and mouth. The gap below my mouth is explained in the next section.
The Nitro 30’s footbox has an 8-inch zippered vent (left) to provide extra ventilation when needed. There are two removable Pad Locks (thin straps that pass through loops on the bag) to attach the bag to a sleeping pad (right) to prevent slide off.
Winter camping using the Nitro 30 bag inside an igloo at 9,500 feet elevation on a cold January night.
I measured the loft of the Nitro 30 to be 6 inches (double-layer; single-layer loft is 3 inches). That’s one-third more than the lightest sleeping bags with the same temperature rating. Obviously, not all 30 F rated sleeping bags are created equal! Additionally, the bag has continuous baffles, so it’s possible to shift more of the down to the topside, if desired.
Verification that the Nitro 30’s double-layer loft measures 6 inches.
According to our table of estimated temperature ratings based on measured loft (read our Backpacking Light Position Statement on Sleeping Bag Temperature Ratings), 1.8 inches of single-layer loft translates to a 30 F (-1 C) rating and the Nitro 30’s 3 inches of single-layer loft translates to a 0 F rating. Please read the referenced article and Ryan Jordan’s article entitled Sleeping by Faith: Bag Temperature Ratings and realize that sleeping bag warmth depends on a number of factors.
So, how warm is the Nitro 30? I would hesitate to sleep in it on a 0 F (-18 C) night, but I had no problem staying warm down to 28 F (-2 C), wearing microfleece long johns and sleeping in a single-wall solo tent with a Therm-a-Rest NeoAir pad and RidgeRest foam pad under me. This is the first sleeping bag I have tested that actually exceeds its claimed temperature rating!
Next I wore a lightweight down jacket and pants (plus appropriate headwear and footwear) inside the Nitro 30 to see how much I could extend its warmth, and stayed warm down into the single digits (3 and 6 F / -16 and -14 C) on two occasions, and 15 and 19 F (-9 and -7 C) on other nights (yes, as explained in the above referenced articles, sleeping bag warmth is affected by a lot of variables). That’s remarkable for a 30 F rated sleeping bag! You are probably wondering what clothing I wore inside the bag, but that’s the subject of an upcoming article, so I will save that information for later.
One disappointment with the Nitro 30 is the bag length is shorter than expected. Sierra Designs specifies that size Regular fits a person up to 6 feet tall; I am 6 feet tall and I press against both ends of the bag. I was able to “get by” with a size Regular, but it was less than comfortable, and I constantly wished for a couple of extra inches in length for a better fit. Notice in the hood photo above that there is a gap under my chin. That resulted from the bag being too short for me; when I extend my legs the gap opens up, but when I bend my legs the gap closes and the hood seals around my mouth.
The bag’s girth, regardless of its stretch technology, is on the slender side. Note in the specifications table that the extended shoulder girth is 60 inches, which is the same as the Mountain Hardwear Phantom 32 and less than the Marmot Hydrogen’s 62-inch girth. I found the girth to be perfect (for me) when wearing light sleeping clothing, but snug when wearing additional down clothing.
I noticed on several occasions that the bag’s shell fabric wets out from condensation from my breathing at night (left), so I tested the bag’s water resistance with my “puddle test.” I put an eighth of a cup of water on a seam (right) and allowed it to stand for one hour. No water soaked through the seam or fabric.
My fall-winter testing period for the Nitro 30 did not provide an opportunity for me to test the bag’s foot vent, but I assume it works well to compensate for the half zipper on warm nights. I personally don’t have a need for additional features like a zippered foot vent, but some people do.
The bag’s pad attachment straps are useful for a back sleeper or hammock sleeper. As I’m a side sleeper, I had no use for the pad attachment straps because I want the bag to turn with me.
A lightweight (0.6-ounce) stuff sack is provided with the Nitro 30 that is properly sized to stuff the bag without over compressing it. Actually, it’s a little extra roomy, which I don’t mind a bit.
The following table compares the Sierra Designs Nitro 30 with some popular 30-32 F (-1 to 0 C) rated ultralight mummy style down sleeping bags. All of the bags have baffled construction, and all data are manufacturer specifications for a size Regular bag.
Rating (F / C)
Layer Loft (in / cm)
(oz / g)
|Fill Power||Total Weight|
(oz / g)
|Sierra Designs||Nitro 30||30 / -1||3.0 / 7.6||12 / 340.0||800||26 / 737||289|
|MontBell*||UL Spiral Down Hugger #3||30 / -1||1.9 / 4.8||10 / 283.5||800||19 / 539||229|
|Mountain Hardwear||Phantom 32||32 / 0||2.0 / 5.1||10 / 283.5||800||22 / 624||290|
|Western Mountaineering||SummerLite||32 / 0||2.0 / 5.1||10 / 283.5||850+||19 / 539||315|
|Marmot||Hydrogen||30 / -1||2.0 / 5.1||11 / 311.8||850+||25 / 709||319|
|The North Face||Beeline||30 / -1||2.4 /6.1||10 / 283.5||850+||22 / 624||279|
*Note: A size Regular MontBell bag fits to 5 feet 10 inches, while the other bags fit a 6 foot tall person.
Interpreting the data, the Nitro 30 has 2 extra ounces (57 g) of down compared to the lightest bags, giving it exceptional loft, though it weighs a bit more too. Its US$289 cost makes it a good value (considering its extra warmth) compared to the other bags, but the MontBell Spiral Down Hugger at US$229 remains the best value despite it being less warm.
The Sierra Designs Nitro 30 is warm!! The bag has 20% more down than a typical 30 F rated sleeping bag, giving it a full 6 inches (15 cm) of double-layer loft, one-third more than many other bags. Factors that contribute to the bag’s warmth are its extra down, flex technology that eliminates extra inside volume to keep warm, half zipper with a large down-filled draft tube, and jacket-style hood. For comparison, the MontBell Spiral Down Hugger #3 does not have a down-filled draft tube, has 2 ounces (57 g) less down, and lighter shell and lining fabric, which reduce weight, but the MontBell bag is clearly less warm, although it has the same temperature rating.
That extra warmth comes with some extra weight, 4 to 7 ounces (113 to 198 g) more than to the lightest bags. Two ounces (57 g) of the extra weight is the additional down insulation. The half zipper saves weight, but its Snag-Free Zipper Guard uses a heavier webbing-like material on both sides of the zipper, which adds weight. There is also extra fat in the bag’s foot vent, sleeping pad attachment straps (but they’re removable, saving 0.3 ounce), and 1.0 oz/yd2 shell and lining fabrics.
Overall, the Nitro 30 is an excellent choice for hikers who want to have an extra measure of warmth and for three-season camping in colder climates where a warmer sleeping bag is needed. Another way to look at the Nitro 30 is that its loft and warmth are equivalent to many bags that have a claimed rating of 15 F, so one might say it’s a very light and less expensive 15 F rated bag.
Specifications and Features
|Sierra Designs (https://www.sierradesigns.com/)|
|2009 Nitro 30|
|Hooded mummy with half-length zipper|
|Sleeping bag, stuff sack, cotton storage bag|
|800 fill-power down, 12 oz (340 g) size Regular, 14 oz (397 g) size Long|
|5.5 in (14 cm) straight wall continuous baffles, flex technology in upper half of bag, ergonomically shaped footbox, six-chamber jacket hood|
|6 in (15 cm) average double-layer loft|
Manufacturer specification not available
Manufacturer Claimed Temperature Rating
|30 F (-1 C)|
|17 x 7 in (43 x 18 cm)|
|Size Regular tested, measured weight: 1 lb 9.6 oz (726 g)|
Manufacturer specification: 1 lb 10 oz (737 g)
|Regular 53-60/50–57/35 in (135-152/127–145/89 cm)|
Long 55-62/52–59/37 in (140-157/132–150/94 cm)
Measurements are relaxed-extended
|Regular fits to 6 ft (1.83 m)|
Long fits to 6 ft 6 in (1.98 m)
|Shell is 22 denier 1.0 oz/yd2 (35 g/m2) ripstop polyester with DWR|
Lining is 22 denier 1.0 oz/yd2 (35 g/m2) ripstop polyester
|Half-length zipper with one pull, anatomical footbox, continuous baffles, large down-filled draft tube, snag-free zipper track, jacket hood, partial flex, zippered footbox vent|
Disclosure: The manufacturer provided this product to the author and/or Backpacking Light at no charge, and it is owned by the author/BPL. The author/Backpacking Light has no obligation to review this product to the manufacturer under the terms of this agreement.