Yes! That’s a common problem—shrinking sleeping bags. The darned things!

Chances are you no longer want or would be comfortable in a mummy bag, the bag you probably had in storage. Mummies are efficient because you aren’t heating up a lot of extra space inside the bag. But they can be, well, snug. Like a mummy! Full rectangular bags are much roomier and more comfortable, but they’re inefficient because you do have to warm up a lot of interior air. The solution: A semi-rectangular bag. It’s trimmer than a full rectangular, roomier than a mummy, and pretty warm.

Big Agnes makes a bag called the Encampment ($169; bigagnes.com) that would suit you. It’s a 15-degree, synthetic-filled (Polarguard Delta), semi-rectangular bag (although they call it a “rectangular") with a full hood, draft yoke around the neck, nylon shell, and other good features. The weight is not bad—three pounds, four ounces—but that’s in part because it has no insulation on the bottom side. You need to use a good-quality pad with it.

That said, the gold standard in semi-rectangular bags in your desired temperature rating is the Western Mountaineering Ponderosa MF (westernmountaineering.com). It’s a down bag, which helps make it light (two pounds, nine ounces). And it has a naturally water-resistant polyester microfiber shell. Yeah, water can be an issue, but this bag would have to be pretty soaked before it lost a lot of insulation. The Ponderosa is not a cheap bag—$420 in the model that can fit people up to six feet, six inches—but it’s a lifetime investment.

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