Entering into the cold winter months means that feet are going to need insulation to stay comfortable and warm. Since 2015 Heeluxe has tested how boots keep feet warm in freezing environments, and we’ve learned a few tips and tricks to design the best insulation in footwear.
There are two main ways that feet get cold: from the temperature of the frozen surface we walk on penetrating through the boot (Conduction) and through our body heat escaping out of the shoe (Convection). Understanding these is critical to designing the best insulating footwear.
We lose the most heat through the top of the foot. This is because the skin is thin, with nothing to insulate the warm blood coming down from our bodies. Here we lose heat by convection. As a cold, damp, windy air surrounds the outside of the shoe it will suck the heat from the top of our foot. So our goal against convection heat loss is insulation that traps the heat on top of the foot. The best brands will insulate in two regions: the ankle (to warm the blood as it travels to the foot and toes) and the top of the foot (to keep the blood warm as it travels to the toes). Even though the toes will be the coldest part of the foot, we have seen little success in insulating the toe region alone.
Just as important as insulation is preventing areas where heat can escape. There are many shoes that use a premium insulation in the ankle and vamp but have no insulation in the tongue or lack a good gusset between the tongue and upper, allowing our precious heat to escape from the body. You’re only as warm as the least insulated part of your shoe!
On the bottom of the foot cold temperatures can penetrate through the sole and eventually get to our feet. Even though our feet have more insulation on the bottom of the foot than the top, this will eventually result in cold and uncomfortable toes. There are two strategies that are very effective at preventing cold feet from conduction. The first is the use of thermoreflective materials. These create a barrier that repels the cold temperature from the feet. While there are thermoreflective materials that can also reflect the bodies heat back to our feet, we tend to see these materials as less effective than the ones that repel cold away from the body. The second strategy is to create less surface area between the bottom of the shoe and the ground. We’ve seen women’s boots with a small heel, or work boots with a heel brake, perform better at keeping feet warm since there is less of the sole on the frozen surface.
Winter is coming and there is no reason to run and hide when you’re wearing properly insulated boots. To learn more about testing footwear for insulation (or keeping feet cool in hot environments) contact the Heeluxe team at [email protected]