A sleeping pad is the foundation of your sleeping system. A pad cushions you against the hard ground, and keeps you warm by forming a thermal barrier between the ground and your sleeping bag. Without a sleeping pad, conduction draws heat out of your sleeping bag into the cold ground. The result? Your sleeping bag's performance is compromised, and you experience a colder night's sleep.
The warmth of a sleeping pad is indicated by its R-value. R-value measures a material's resistance (R) to heat loss. Higher numbers indicate greater warmth. If you're snow camping, consider combining an inflatable pad with a closed-cell pad. Two pads provide better cushioning, insulation, and protection from accidental punctures. The combination will also help keep moisture away from your sleeping bag.
Inexpensive blue foam is reasonably durable, and it insulates well. Although all blue foam looks much the same, its quality varies. Squeeze the foam between your thumb and forefinger. Inferior foam will spring back slowly, if at all.
Yellow foam (Evazote® is the best-known brand name) is stronger than blue foam and remains flexible to –70 degrees Celsius. It is also resistant to damage from abrasion and ultraviolet light.
Some closed-cell foam pads feature moulded-in hinges and contoured ridges. The hinges make for easy packing, while the ridges increase cushioning and insulation without increasing weight.
Self-inflating pads are more expensive than closed-cell foam pads, but they insulate well and are light and compact. Most contain open-cell foam, which is an excellent insulator when filled with air. Some include a layer of down or synthetic material, which adds warmth, but should be protected from water and dampness.
When inflating a foam-filled pad, it's best to open the valve and allow the pad to self-inflate. Add a few breaths later if required (or use the pump system on a down-filled pad). This will prevent moisture from accumulating inside.
Store your pad unfurled and with the valve open. If required, you can wipe off dirt with a damp cloth and allow the pad to air dry. Never store your sleeping pad if it is damp, dampness encourages mildew. You can repair a punctured pad with a dab of urethane glue or a simple patch. Read Sleeping Pad Repair for info about locating and sealing holes.