It’s one of the main things that will keep you comfortable and warm at night. When you lie directly on the ground, because the ground is normally much colder than your body and very conductive heat is quickly transferred away from your body to the ground, so you get cold. Sleeping bag insulation only works when it is expanded, so sleeping bags provide essentially no insulation between you and the ground.
Heat is a form of energy, and like all forms of energy it cannot be destroyed, but it can be moved or changed into different forms. We tend to lose heat from it being transferred from us to something else and this can happen in three main ways.
Thermal conduction is the transfer of energy (heat) between two substances with temperature differences that are in direct contact with each other. You feel this when laying on a cool rock, where parts of your body touching the rock feel cold as the heat moves from you to the rock. Heat can be transferred to your body, such as when holding a hot drink. This transfer can be slowed with insulation between you and the ground, like a sleeping mat.
Convection is the transfer of heat through the movement of fluids (gases or liquids) from a warmer spot to a cooler spot. Cooler liquid or gas then replaces the warmer liquid or gas, with a continuous circulation pattern. One example is where the earth’s surface is warmed by the sun. The warm air rises and cool air replaces the warm air. When sleeping in a tent, there are small convection currents in an air mat. These currents can be slowed with small air chambers and other barriers … You can see convection above a campfire with embers and smoke lifted high above the fire.
Radiation is a heat transfer with no contact between the heat source and the heated object. Heat can be transmitted through space and some objects by thermal radiation. Examples include heat from the sun and a domestic radiator. Radiant heat can be reflected with a mirror or absorbed into another material that will then heat up, where it moves again by conduction or convection. Shiny silver coverings on sleeping mats can help reflect radiant heat back to you.
Everyone is different when it comes to preferences for sleeping mats, so make sure to try out a few different mats before making a decision. For those prone to pressure injuries, to ensure that your skin copes, test a sleeping mat at home before taking it on a bushwalk. Similarly, for people with back or neck pain, testing at home can help ensure the best pick for your walk.
Following are some examples of different types of sleeping mats with a comparison between various features.