Foam pads and air mattresses are important because no matter how inexpensive or sophisticated your sleeping bag is, without proper insulation beneath you, you can be cold in many conditions, such as dampness and frost. There are two main types of foam pads:Closed Cell (Ermolite or Volarafoam)-- Very thin, but offers excellent insulating qualities. Even makes sleeping on snow possible! light-weight, rolls very completely, and won't get water-logged.
Open Cell--Thicker and softer, which makes it more comfortable but also bulkier. Can get water-logged, rendering it useless.
The term air mattress still conjures up pictures of heavy, cumbersome rubber monsters that invariably are hard to inflate and deflate. There are air mattresses on the market that have separate tubes that inflate quickly and easily, and stuff into a small stuff sack. These air mattresses provide some of the cushioning that a closed cell foam pad lacks, but at a higher price.
