In the challenging realm of winter outdoor activities, hikers often face a dilemma: how to keep their feet warm and dry when sweat inevitably builds up inside their boots. The solution, surprisingly, might involve something as simple as plastic bags. This article explores the efficacy of vapor barrier liners (VBLs), which create an impermeable layer between the skin and socks, preventing moisture absorption and maintaining warmth in freezing conditions. While it may seem counterintuitive, especially given the discomfort of plastic in warm weather, VBLs offer a vital advantage when temperatures drop below freezing, protecting against the rapid cooling caused by wet socks.
Justin Simoni, a renowned guidebook author and long-distance athlete, highlights the critical difference between using plastic in warm versus cold environments. In summer, plastic bags would lead to excessive sweating and discomfort. However, in extreme cold, minimizing heat loss becomes paramount. As hikers exert themselves and their bodies warm up, sweat accumulates. In typical conditions, this moisture would evaporate through socks and footwear. Yet, at temperatures below 30 degrees Fahrenheit, evaporation significantly slows down, causing socks to become damp and cold, leading to discomfort and, more critically, the risk of frostbite on overnight excursions.
VBLs work by trapping perspiration close to the skin, thus creating a warm microclimate. Unlike breathable waterproof materials that allow some vapor to escape, VBLs are designed to be completely impermeable. This ensures that the moisture generated by the foot stays within the VBL, preventing it from saturating the outer sock layers. Several brands offer specialized vapor barrier socks, such as Rab and Point6, and neoprene socks are another option. However, for a cost-effective and readily available solution, many seasoned hikers opt for common household items like trash bags, bread bags, or even turkey bags, as favored by Simoni.
For those sensitive to direct contact with plastic, a layering approach is recommended: a thin liner sock, preferably wool, worn directly on the foot, followed by the VBL, then your regular hiking socks, and finally your chosen footwear. This method not only traps body heat but also ensures that the primary insulating layers remain dry. An additional benefit noted by some users is blister prevention, as the VBL can reduce friction between the foot and the sock. Furthermore, VBLs serve as an excellent indicator of your body's sweat production, signaling when adjustments to your overall layering system might be necessary.
Despite their numerous advantages, VBLs do have potential drawbacks. The added bulk, even from thin plastic, can create pressure points or compress the insulating layers within your boots, potentially reducing comfort or warmth. Simoni advises testing VBLs in less critical situations, like a day hike or a chairlift ride, to familiarize yourself with their feel and effectiveness. Always carry an extra pair of dry socks as a backup. Simoni himself integrates turkey bags into his gear for challenging expeditions, such as his frequent climbs of Longs Peak or upcoming attempt on the Nolan's 14 Route, demonstrating their value in truly cold environments. This innovative approach to foot care underscores the ingenuity required to thrive in harsh conditions, turning a simple plastic bag into an essential piece of survival gear.