Frost on the Footbox. Asagiri, Shizuoka.
| Tested by | TAKIBI SUPPLY, Kamakura |
|---|---|
| Date | March 6–7, 2026 |
| Region | Asagiri plateau, Shizuoka, about 800 m (2,600 ft), open grassland facing Mt. Fuji |
| Weather | Clear and dry. Light wind after 22:00. |
| Temperature | 9°C at dusk, −2°C at 05:30 (48°F to 28°F) |
| Nights used | 1 |
| Sleep system | Aurora-Tex Light 450DX. Closed-cell foam pad under a 5 cm inflatable pad. Wool base layer, wool socks, beanie. Inside a Circus TC DX+ with the door closed and the vent open. |
Asagiri is open grass with the volcano filling the whole view. Nothing to block the wind, nothing to hold the warmth. It is where you go to test a bag, not to be comfortable.
Loft
Out of the stuff sack at 17:00 the bag looked flat and a little sad. We laid it out on the pads and left it. By the time the fire was going it had risen to a loft you could sink a hand into. Ten minutes is the number we would give a friend.
Night
In at 22:30, 4°C. Warm within a few minutes, the way good down is warm: not hot, just absent of cold. At 02:00 it was 0°C outside and the feet were fine. At 05:30, −2°C. The inside of the tent wall had frosted, and so had the outside of the footbox where it touched the fabric.
This is the point of the shell. The frost stayed on the outside. The down under it was dry to the hand, and the bag lofted again as soon as the sun hit the tent. A bag without a waterproof-breathable shell would have carried that moisture into the second night.
Honest notes
- The zipper snagged twice on the draft tube in the dark. Slow hands solve it. Fast hands make it worse.
- The hood drawcord takes a moment to find the first time. After that it is one pull.
- Room: generous for a 175 cm (5 ft 9 in) sleeper who turns at night. A side sleeper with wide shoulders should look at the sizing.
- Warm to −2°C with a base layer for one of us. That is one person, one night, one wind. NANGA's temperature ratings are the reference. This note is not.
What we could not conclude
Anything below −5°C. A wet night. Moisture build-up over four or five nights, which is where the shell should earn its keep most. We will bring the same bag to a November rain and add to this log.
Tested in this note: Aurora-Tex Light 450DX (Field-Tested)
Condition gear, used but not rated: Circus TC DX+