Manufacturer’s Website: www.bigagnes.com
Recommended 20″ x 72″ x 2.5″ Air Core Pad
The Big Agnes Zirkel is a mummy-shaped down sleeping bag with three distinctive features: no down under the sleeper, a sleeve on the bottom to hold a ground pad, and a built-in stow sack to create a fixed pillow by inserting clothing. Big Agnes intends the Zirkel for use in temperatures from 20 deg F to 60 deg F for a moderate sleeper; from 15 deg F to 55 deg F for a warm sleeper; and from 30 deg F to 65 deg F for a cold sleeper. Priced at $279 for the bag and $54 for the Air Core ground pad, it is aimed at the high-end market. It will appeal to anyone who has ever rolled off a pad at night and awakened because it was too cold. The Zirkel has a feature usually found only in more expensive and warmer bags — a “no-draft” yoke. This is a down-filled collar that drapes down from the top of the bag and seals around the neck to prevent warm air from escaping and cold air from sneaking in.
Big Agnes’ 2.5″-thick Air Core mummy pad is innovative for its lack of foam. The Air Core mummy pad weighs about one-half to one-third the weight of a similar thickness foam-filled, self-inflating mattress. The pad is contoured to fit exactly into the pad pocket on the Zirkel.
The exterior shell is 30-denier Pertex nylon microfiber ripstop with a fluorocarbon DWR treatment for a windproof and water-resistant shell. The interior lining is a soft and breathable 30-denier Pertex nylon microfiber. The bag bottom is a durable 210T DWR-treated ripstop nylon. The insulation is 775 fill-power down — the highest quality available. The bag is well sewn and the workmanship is fine with no obvious gaps. Given the high quality of materials and construction, we expect that the Zirkel will give years of service.
Our review staff made preliminary loft measurements of the Zirkel and compared them with bags of known field performance. Based on this comparison, we anticipate that the Zirkel should work down to the rated +20deg F (we will report more in future issues on the field performance of this sleeping bag).
The pillow stuff sack is a nice idea. It solves the problem of chasing your slippery nylon “pillow” that has a life of its own as it pops out from underneath your head and scoots away during the night.
The Zirkel’s cut is roomy for a light mummy: a 67.5″ girth compared to a Western Mountaineering Apache, at 61″, and a Western Mountaineering UltraLite, at 59″. Our larger and more restless sleepers liked the roomy cut — our medium-build and quiet sleepers felt that it might be drafty and a bit more bag than they needed. The larger girth offers the option of wearing a jacket inside the bag to extend its range in cold weather.
Note: When you place the Air Core mummy pad in the pad pocket, the Zirkel loses some of its roominess. The rigid pad flattens out the bottom of the bag, reducing volume and making it feel tighter than its 67.5″ girth. For this reason, some of our reviewers preferred sleeping with the pad outside of the pad pocket. Others did not have a problem with this.
The Zirkel and Air Core pad combination weighs about a half-pound less than many light down bags in this temperature range paired with a light, full-length, self-inflating pads (e.g. Marmot Pinnacle and Thermarest Ultralight). However, the Zirkel alone weighs a bit more than narrow-cut mummy bags like the Western Mountaineering Apache. The combination of the Zirkel and Air Core mummy pad weighs about pound more than a narrow cut mummy bag paired with closed-cell foam pad (e.g. Mt Washington), although the Big Agnes combo has more features and comfort.
The Big Agnes Zirkel is worth a hard look if you are in the market for a new +20 deg F bag. The Zirkel’s strengths lie in its design for comfort: a full-length pad you cannot roll off, a bit more room than most mummy bags, and a built-in pillow sleeve. It is reasonably priced in comparison with other quality light down bags. One of our reviewers appreciated the room and comfort of the Zirkel. He found it a special pleasure to sleep on a full-length pad after using a 48″ one. (The reviewer had been using a Western Mountaineering Apache and a 48″ Thermarest Ultralite pad.)