During cool camps, cold nights, and crisp mid-day rest stops, I retain my body heat with a puffy jacket containing down or synthetic insulation. If I expect nighttime temperatures below about 30 degrees, or long camps with temperatures below about 40 degrees, I will add insulated pants to my kit.
Down- and synthetic-filled garments are far more thermally efficient (i.e. warmth per weight) than synthetic or merino fleece, making them the ultimate “stop” pieces. Both garments make my Core 13, a 13-item collection of backpacking clothing that can mixed-and-matched to create appropriate systems for any set of 3-season conditions.
Unlike sleeping bags, down- and synthetic-filled jackets and pants are not assigned temperature ratings, making it difficult to determine and compare their insulating value. Instead the best indications of warmth are:
For down, “fill weight” (e.g. 75 grams) and “fill power” (e.g. 800-fill, meaning that 1 oz of down will fill 800 cubic inches of volume). The more down and the higher the quality the down, the warmer the jacket or pants will be, assuming identical construction and sizing.
For synthetics, the weight of the insulation per square area, e.g. 60 g/m2. However, this information is not entirely reliable since synthetic insulations vary in their short- and long-term thermal efficiency. Unfortuantely, the ideal measurement — the insulation’s clo value per its weight — is rarely published.
Down versus synthetic
Down and synthetics both have pros and cons. Down is:
- Warmer for its weight,
- More compressible, and
- Less expensive,
- More humane (no live plucking), and
- Less adversely affected by moisture.
In specific regard to the issue of moisture sensitivity, I want to point out that synthetic insulations are absolutely not “warm when wet” like is often claimed. Moreover, down is so much more thermally efficient that even moisture-degraded down will be as warm for its weight as dry synthetic insulation. Finally, I’ve never had my down insulation get truly wet. Damp from high humidity, yes, but never wet from, say, having worn it in the rain or fording a river — that’s what my rain jacket and pack liner are for.
With the introduction of water-resistant down a few years ago, synthetics lost much of their wet-weather advantage. So now it’s mostly a cost and ethical consideration.
With few exceptions my preference is down. It’s the superior insulation, especially as one who tends to backpack in dry environments and as someone who can justify their purchases with extensive use. And, equally important, down is a better long-term investment — my heavily-used down pieces are almost as warm now as they were when new, whereas my synthetic-fill pieces are limp, lifeless, and needing replacement after just a season of daily use.
Fit & Features
My sole consideration in an insulated garment is its warmth relative to its weight, i.e. its thermal efficiency. It need not be capable of much — basically, I just want to be able to stand around or sleep in these pieces without getting cold.
The jacket and pants should be built slightly oversized, so that they fit comfortably when worn over a hiking shirt and mid-layer, or underwear and hiking pants. It doesn’t happen often, but keep room for a 3-season shell jacket and pants too, if you’re ever desperately cold. The jacket and pants should seal off drafts in the torso area, so the jacket should be mid-butt (requiring a lady-like hourglass cut so it doesn’t bunch up at the waist) and the pants should rise nearly to the belly-button. Thumb loops, such as those on the Sierra Designs Elite DriDown Hoody, help keep wrists and hands warm.
I avoid features that add weight without warmth like fleece-lined pockets, unnecessarily heavy zippers, stretchy underarm panels or arm cuffs, and hood and waist cinch cords and locks that are no substitute for good design.
Wispy 10- or 20-denier shell fabrics are ideal. Ignore the claims that these fabrics are “water-resistant” — when new, that’s being generous, and long-term it’s downright disingenuous. Heavier fabrics are more durable, but little durability is actually needed for this application. Waterproof-breathable fabrics are much heavier, and ironically their poor breathability leads to the insulation getting wet from trapped perspiration.
Jackets: My picks & suggestions
Normal low temperatures on my backpacking trips are in the 30’s and 40’s, with a rare summer night in the 50’s. For these conditions, I find that an insulated jacket with a hood and about 3.5 oz (100 grams) of 800-fill down is about perfect. A well executed jacket with these specs will weigh about 10-12 oz. With lower-grade down fill (e.g. 700-fill) and/or less thermally efficient construction (e.g. fleece-lined pockets), the garment will weigh more.
For consistently warmer weather, consider a jacket with less insulation and/or without a hood, like the Patagonia Ultralight Down Jacket. For consistently colder weather, look for a jacket with more insulation and perhaps even baffled (not sewn-through) construction, such as the Sierra Designs Baffled DriDown Parka.
There is a lot of competition for the title of best insulated jacket, partly because many manufacturers use essentially the same shell fabrics, insulations, and/or Asian sewing factories. While the 8-oz Mountain Hardwear Hooded Ghost Whisperer — which has a hood and 80 grams of 800-fill water-resistant down — is often listed as a top contender, I’d rather carry an extra few ounces in the form of the 11-oz Western Mountaineering Flash XR Jacket or 11-oz Patagonia Ultralight Down Hoody in order to have 25-50 percent more down insulation, which is the primary driver of the jacket’s warmth.
Pants: My picks and suggestions
Shopping for insulated pants is easy: there are few worthy options. For pure 3-season backpacking, the Western Mountaineering Flash Pants and the Montbell Superior Down Pants leave little room for improvement, each containing 2 oz of premium down and weighing less than 8 oz total.
If you wish to own just one pair of insulated pants and if you need them to serve winter-duty as well, however, I would encourage investing weight in full-length or three-quarter-length leg zippers, which make the pants easy to put on and take off while still wearing big winter boots (i.e. ski boots, mountaineering boots, snowshoe boots). At 12.5 oz, the Western Mountaineering Flight Pants would be my top pick. For a synthetic, consider the Arc’teryx Atom LT Insulated Pant, which are an ounce lighter but not as warm as the WM pants.
Synthetic-insulated pants will be heavier than comparably warm down pants, but they will be less expensive. But even if even the aforementioned Arc’teryx Atom pants are too pricey, look for the “long” version of the military’s M-65 insulated pant on eBay or a local military surplus store. For less than $20 with shipping, they are the hands-down best value.