No Cold Too Cold: Vapor Barrier Boots

It was during the Korean War (1950-1953), that the U.S. Military first encountered the debilitating effects of extreme cold on the modern battlefield.

The Winter of 1950 saw many U.S. troops stuck in defensive positions, often in very cold climates, without access to appropriate cold weather gear. Frostbite casualties were rampant.

After much research and development, a new class of boot was issued to troops for dealing with extreme cold. By 1962, 2 different varieties of Extreme Cold Weather Boot were finally issued: the Type 1 and the Type 2. They would go on to remain in service, mostly unchanged, up through the 1990's and even today.

This same design sees use in places as far distant as the Amundsen-Scott South Pole Research Station.

The Science Behind the System

Most boots are breathable, in that they allow moisture from your feet to naturally wick out into the environment. These boots do not. Instead, thick layers of wool insulation are completely isolated from the outside environment using separate layers of rubber. This completely prevents heat loss from convection with the outside world.

It also greatly minimizes heat loss through conduction. The insulation is sealed in a dead space, much like modern home insulation. Moisture conducts heat faster than air, up to 25X faster in fact. This dead space ensures not a single drop of moisture transfers into that wool layer, from either your foot or the environment, to diminish its effectiveness.

The heat loss that still exists is through radiation, the slowest form of heat transfer, and the one that astronauts still have to deal with when operating in a vacuum. Versus conventional boots, this extreme cold vapor barrier blocks almost all thermal transfer between your feet and the outside environment.

The Mickey Boot

The Mickey Boot, or officially the Type 1 Boot, is designed for cold, wet climates in temperatures down to -20ºF. And due to the sealed interior of the boots this is a hard -20º, regardless of windchill. The dead space inside the Boot is filled with 2 layers of wool, and a layer of felt protects against heat loss through the floor.

The Bunny Boot

Immediately identifiable by the white exterior instead of the Mickey Boot's black exterior. Bunny Boots are designated as Type 2 boots and intended for extreme cold, dry climates. This refers to low-precipitation environments such as taiga, tundra and the cold desert climates of the Arctic and Antarctic.

Bunny Boots have 3 layers of wool, along with 2 layers of felt to protect feet from heat loss through the floor. They are meant for use in temperatures down to -60ºF, again regardless of windchill effects.

Uses of Vapor Barrier Boots

Both types of boots excel in extreme cold weather. Perfect environments include stationary use in deer stands and poorly-insulated ice houses. They can also be used for cold weather chores (such as snow clearing) as well as movement between positions in isolated environments.

They are must-haves for preparing for any potential survival situation in the extreme cold.

Because these boots do not breathe, moisture will naturally build up inside, especially during high activity.

However, the comfort level even when totally saturated with moisture is still remarkably good. Since the moisture remains at body temperature, the felt dampness is much less noticeable. And if necessary the moisture level can be alleviated simply by changing into a new pair of thick wool socks, since the Boots themselves are completely watertight.

Protecting Boots

Very little maintenance is involved in keeping rubber Vapor Barrier Boots operational. Exposure to corrosive environments will, over time, deteriorate the rubber as well as prolonged exposure to sun or long-term disuse. Punctures to the rubber will also severely impact the thermal capabilities.

The air valve present on most pairs of boots allows air exchange between the dead space inside and the outer environment. This is to reduce pressure build up when changing elevations, particularly during air transit. However, the air valve should not be left open as this allows moisture infiltration into the dead space within the boot, potentially destroying the thermal capabilities.

For dependable foot survival against frostbite in the most extreme conditions, these Vapor Barrier Boots provide a tried-and-true answer. Both Mickey (Type 1) and Bunny (Type 2) versions are regularly found here at The Guide, in both new and used versions.

Good luck and enjoy the cold!

Further Reading

The U.S. Military's struggles combating cold weather during the Korean War

Comprehensive Overview of Bunny Boots

Living at the South Pole

U.S. Military Cold Weather Training in 2018 (with photos of Mickey Boots in action)