Wool insoles | Snuitide

Wool insoles are loose inner soles in cut wool or felt that add an extra layer of insulation against cold mountain boots. A classic accessory on winter trips, winter walking and long autumn trips where the ground has frost. They weigh 30–50 g per pair and cost 80–200 kr.

When wool insoles make a difference

Wool fibres trap air, and air is the actual insulator. An extra wool insole builds 3–5 mm of still air between the foot and the toe of the boot. On a typical mountain-boot winter trip, that can be the difference between ‘cold toes after 4 hours’ and ‘fine toes through the day’.

But: wool insoles do not replace a boot that is too thin for the conditions. If your mountain boot was built for summer, wool insoles will help a little — but a winter boot with Thinsulate or Primaloft fill in the boot itself is a different league altogether.

Materials and thickness

Cut wool felt — the classic type. Thickness 4–6 mm. Dries quickly after a day in the boot, shrinks a little over time. Devold, Janus and Ulvang make these in Norway.

Thicker felt wool (8–10 mm) — for extra-cold trips. Requires that the boot has room — too thick a wool insole steals volume and reduces blood circulation, which actually gives colder feet.

Lambskin insoles — naturally water-repellent, warmer than wool, but heavier (50–80 g). Mostly used in slippers and indoor shoes, not walking boots.

Synthetic fleece insoles — a cheaper alternative. They work, but wear out faster and lose their shape.

When you need them

Winter trip from cabin to cabin — many find that a wool insole makes a noticeable difference.
Winter walking — especially combined with gaiters.
Late-autumn trips with frost at night, mild weather during the day.
Mountain boots that are slightly large — a wool insole fills volume and gives a better fit.

On a summer trip it is normally unnecessary. On a topptur in randonée boots it is not common either — these boots have their own thermal lining.

Changing and washing

Wool insoles draw moisture from the feet. On a multi-day trip in sub-zero temperatures: change to a spare pair when you get into the tent, and hang the damp one out to air. Two pairs per trip is wise.

Washing: hand-wash in lukewarm water with wool-suitable soap. Never a washing machine on a normal programme — it shrinks and felts. Dry on a flat surface, never on a radiator.

Buy or home-made

Classic wool felt is easy to cut yourself. Buy a sheet of wool felt (300–500 kr per square metre, enough for many pairs), draw round your boot on the sheet, and cut along the outline. Just as effective as industry-made ones, and you get exactly the thickness you want.

For those who cannot be bothered with the hobby project: Devold Wool Insole, Janus Ullsåler, Ulvang Wool Insole. All Norwegian, all good, all 80–200 kr per pair.

Next steps

Socks on the trail — wool socks and changes of socks are the layer nearest the foot; the wool insole builds on underneath.
Mountain boots — the boot the wool insole sits in, and which decides whether the insole makes a difference.
Gaiters — keep snow and moisture out where winter walking gets wet.
Winter clothing — warm feet are one part of an outfit that keeps the whole body warm.
Contents of a day pack for ski trips — where the spare insoles belong on a winter trip.

Learn more

Text: Snuitide (2026).