Sierra Designs BTU -20
February 18, 2011
Sierra Designs BTU -20F Sleeping Bag
http://www.sierradesigns.com/p-304-btu-20.aspx
Sierra Designs BTU -20 was provided by Sierra Designs for the purpose of this review.
Reviewed by Christopher N.
$509.95
4- Season -20 ° F / -29 ° C With 800-Fill goose down insulation and a waterproof shell, this cold-weather bag is warm, weatherproof and very compressible. Perfect for your next frigid expedition.
- Ergonomically shaped footbox
- Microfleece lined foot box
- Removable pad locks™
- Snag-free zipper tracks™
- Internal media pocket
- Draw cord at collar
- Expedition Jacket Hood™
- Draft collar
- Waterproof/Breathable fabric
- Funk!Off™
- Offset Expedition Jacket Zipper (40″)
- Partial Flex™ on the interior and exterior torso
- Includes stuff and storage sacks
Temp Rating: -20° / -29°C
Shape: Mummy
Size Regular: (also available in short and long lengths)
Fits to 6’ / 183 cm
Length: 78” / 198 cm
Zipper Side: Left
Shoulder girth: 64” / 163 cm
Hip girth: 60″ / 152 cm
Footbox: 43″ / 109 cm
Fill weight: 38 oz. / 1.1 kg
Total weight: 4 lb. 1 oz. / 1.8 kg
Stuffed diameter: 10″ / 25 cm
Stuffed length: 20″ / 51 cm
Insulation:
800 Fill-Power Goose Down
Shell material:
40D Drizone™ Nylon Ripstop
Liner material:
Funk Off™ 50D Polyester
Camping in the Boundary Waters of Northern Minnesota. January. Overnight lows forecast to be -25 F (-32 C). I have a bag rated to -40 F (-40 C) and another rated to 0 F (-18 C), but that leaves a wide gap in between. Thus, I was quite excited to try out this cold weather sleeping bag that should fit the forecast temperatures quite well.
My wife had used a synthetic “FLEX™” bag from Sierra Designs for several years, and she raves about how comfortable it was. The FLEX™ technology uses an elastic tape and elastic thread in the seams of the baffles to allow the girth of the bag to expand where necessary and to reduce constriction inside the bag as the sleeper moves around. The technology also snugs the insulation closer to the body, which offers more efficient thermal insulation. I was eager to give it a try for myself.
I was not disappointed! In sleeping bag terms, I find this bag truly luxurious! I really like how the insulation almost hugs me inside the bag. It feels almost instantly warm when I crawl inside, even with cold temperatures outside. At the same time, there is plenty of room inside the stretchy bag to accommodate items that I want to keep from freezing without crowding me. Though I generally use a vapor barrier liner inside of my cold-weather down bags, I can appreciate that the fleece-lined foot box adds a level of luxuriousness as well.
All this luxury does come at a slight cost — and I’m not talking about the very reasonable price point. While still not heavy for a cold-weather bag, it tips my scales at 4 lbs 3.8 oz (1923 g), which is about 4% more than Sierra Designs’ published weight for the regular size bag. Certainly not bad, but serious gram-counters could find something lighter. For me, a few extra ounces are worth carrying for this level of comfort — especially when I’m carrying my gear in a sled while winter camping (instead of on my back in a backpack).
I have only two criticisms of the bag that are worth calling out. The first is the zipper, which I found difficult to negotiate when inside the bag. Holding the opening of the bag closed as I zipped seemed to help, but that was not always easy to do from inside the bag. I didn’t notice the zipper actually snagging on the fabric, but it did just seem to stick every once in awhile. For what it’s worth, I did notice these issues more during actual use than I did while inspecting the bag indoors. I’m hoping that with practice and familiarization, negotiating the zipper will become easier.
The other criticism I have may be more personal preference, but I found the bag opening around the neck was too narrow when the bag was completely zipped. I can appreciate that a small opening is likely to be more thermally efficient, but I found it to be too constrictive for my comfort. When I did choose to vent by opening the hood wider, the opening right across the neck was still narrow. This feature did not allow me to really open up the neck and hood area to vent, and I was forced to contend with the challenging zipper to vent on the side instead.
Unfortunately, the mercury never dipped below -6 F (-21 C) during the three nights out, so I couldn’t push the bag to its limits. Though perception of warmth has many contributing factors and is very different from one person to the next, the bag easily provided enough insulation to keep me feeling warm in those temperatures. The warmest temperature recorded while I was in the sleeping bag was 10 F (-12 C), but with a little venting I found that I did not overheat. I would have preferred a wider opening around the neck to help increase the venting without opening the zipper, but the zipper certainly worked.
While I normally prefer to sleep under the stars if conditions allow, we opted to set up a pyramid shelter to protect us from the snow that was falling. The final night out started out mostly clear, so we decided to forego the shelter. Soon enough, more snow started falling, and by morning, at least an inch (2.5 cm) had fallen around us. Fortunately, the bag insulated well enough that very little snow actually melted on the shell. The little that did melt did not soak through and compromise the insulation — thanks to the waterproof shell.
Please check back in a month to read an update to this review.
A feature of the bag that I really appreciate is that it has a short 40” (102 cm) zipper on the side opening. The venting options are more limited than a full length zipper, but in colder temperatures, I’d rather have the greater thermal efficiency that comes with a shorter zipper. A short zipper is also a bit less weight than a full-length zipper. If I were looking for one bag with a maximum temperature range, I may lean toward a full zipper instead. Since I was seeking a bag with a more precise range, this feature is beneficial. And my experience suggests that it can still be quite comfortable over a wide temperature range.
Another feature of the bag that I appreciate is the built-in sleeping pad security loops to make sure the sleeping bag stays on top of the sleeping pad. I didn’t even know what they were at first, but once I figured it out and tried them, I think it is a genius idea. Our first two nights, our shelter was pitched on slightly uneven ground, but the security loops helped keep me on my pad (and warm) all night long. The loops add a marginal bit of weight, but it’s a fair trade-off in my estimation — especially when camping on uneven surfaces.
Even with my two criticisms, I look forward to using the bag again when the temperatures drop. I am hooked on the luxurious feeling of the FLEX™ technology! The comfort and versatility that it affords in a winter setting is very attractive, and is worth the marginal amount of extra weight in my opinion. More details to come after the bag has seen additional use.
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