The Furnace is an impressively affordable down sleeping bag. This down insulation, however, doesn't seem to provide the weight and packed size benefits that we're used to seeing. We were surprised to discover that it's just as heavy and bulky as several comparable synthetic models. So even though we love this bag's anti-snag zipper and minimalist stash pocket, there are several other budget sleeping bags that our testers prefer at the same price point. The Kelty Cosmic is a lighter, cheaper, and more packable down option, while the Nemo Kyan offers similar advantages with synthetic insulation.
The North Face Furnace 20 Review
Cons: Heavy, bulky, no storage sack included, narrow-ish foot box
Manufacturer: The North Face
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Our Analysis and Test Results
The North Face has an extensive selection of sleeping bags. After recently testing their Cat's Meow, Hyper Cat, and Furnace sleeping bags, however, we're not sure how the Furnace fits into the mix. Read on to find out why we think it's the odd one out.
The Furnace is filled with 14 ounces of 600 fill power ProDown. With this insulation, it receives an impressive 14°F lower limit rating on the industry-standard EN test. Our testers acknowledge that it's one of the warmest 3-season budget sleeping bags out there. However, we don't think its quite as warm as its rating compared to some overachieving premium bags.
The Marmot Phase 20 and Rab Mythic 400, for example, are both filled with 14.1 ounces of much higher-quality 850+ fill power down, but receive worse EN temp ratings (19F and 21F, respectively). The Furnace is still plenty warm for most 3-season uses — but don't expect to stay toasty warm at its 14F EN rating. Its 20F manufacturer rating seems more reasonable.
Ordinarily, down insulation is used to minimize weight. At nearly 3 pounds, however, the down-filled Furnace weighs considerably more than a few comparably warm models filled with cheaper synthetic insulation. Thus, there are several other budget bags out there for weight conscious shoppers to consider.
This model is a fairly spacious mummy bag. Its 63-inch shoulder girth is among the widest in the budget sleeping bag category. The lining fabric, however, isn't as soft as the polyester taffeta in some other models. Most sleepers will still find the Furnace to be plenty comfortable, but people that sleep on their side or stomach may prefer a bag with a roomier foot box for stretching their legs.
Another reason to use down insulation is to minimize packed size. In this area, The North Face succeeds — the down compressed smaller than comparable synthetic bags in our tests with a third-party compression sack. Many of those bags, however, come with their own compression sack, while the Furnace includes only a simple drawstring stuff sack. Thus, to enjoy its superior packed size, you will need to buy an after-market compression sack.
Although down often weighs less and packs smaller than synthetic insulation, it clumps and loses its ability to insulate if it gets wet. Like a lot of modern sleeping bags, the Furnace contains down that's chemically treated to be water resistant. If exposed to real moisture, however, this treated down will still clump. A synthetic bag is thus a better choice for wet conditions.
The Furnace still provides decent versatility though. Its ¾-length zipper is effective at venting excess heat on warmer nights, while its significant insulation extends its useful temperature range lower than many other budget sleeping bags.
Features and Design
There are a couple of subtle features on this bag that we like. Although the zipper doesn't feature an anti-snag slide, the partial sleeve of stiff fabric that's sewn next to it is effective at preventing snags. The Furnace also has a convenient stash pocket for storing a phone or headlamp. It happens to be our favorite stash pocket because it's on the inside of the bag where your batteries will stay warm, and its zipperless design is ultralight.
The Furnace is one of the more affordable down bags out there. However, it's noticeably bulkier and heavier than at least a couple down bags that cost less. Meanwhile, similarly priced synthetic bags also provide similar warmth while weighing less and packing smaller. For these reasons, we don't consider the Furnace a particularly great value.
Sleeping bag makers generally use down insulation to minimize weight and packed size. The Furnace is filled with 600 fill power down, but it's not particularly light or packable. Its synthetic cousin from The North Face, the Cat's Meow, offers comparable warmth while weighing 8 ounces less. The Cat's Meow's synthetic insulation also won't lose its ability to insulate if it gets wet. Still, if you can find the Furnace on sale, it could be worth considering. Otherwise, we prefer the Kelty Cosmic 20 for a budget down sleeping bag.
— Jack Cramer