Sleeping pads insulate the same way that sleeping bags and clothing layers do. They trap and hold a layer of "dead" (non-circulating) air between your body and the cold (in this case, the cold ground). Your body gradually warms this layer of dead air and it becomes an insulating barrier.
Beneath you, though, a sleeping bag's heat-trapping loft gets compressed to almost nothing due to the weight of your body. As a result, you need a pad to buffer you from heat-depleting contact with the cold ground (this is known as "conductive" heat loss). The insulative performance of a pad depends upon how much air it holds inside and how free that air is to circulate.
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Shop REI's selection of self-inflating sleeping pads.
Length: At a minimum, your shoulders and hips need to fit on a pad. Regular (typically 72" long) and long (from 75" to 78") pads will insulate your legs and feet—a big plus on chilly fall and winter trips. A short or 3/4-length pad (usually 47" or 48") weighs less and packs smaller.
Width: Nearly every pad offers a standard width of 20". If you tend to roll around a lot, you may want a width of 25" or 30". Tapered-shape pads reduce volume a bit and pack smaller. Also, consider the size of your tent to ensure you can fit 2 wider pads side by side.
Women's pads: These pads are shorter (66" is typical), and many add insulation at the hips and feet.
R-value: Insulation is measured according to its capacity to resist (that's the "R") heat flow. The higher a pad's R-value, the better you can expect it to insulate you from cold surfaces. The R-values shown on REI.com product pages are provided by the manufacturers and range from 1.0 (minimally insulated) to 9.5 (well insulated). Thicker pads generally offer higher R-values.
Textured surface: If you're a restless sleeper, look for a pad with a textured surface to minimize slippage.
These use the same foam-and-air technology as the self-inflating pads for backpacking, but they are thicker and more comfortable.
If possible, visit your nearest REI store to try out a few different pads before deciding on a single model. This will help you get a feel for:
By Steve Tischler
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Last updated: 02/19/2014
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