How to Choose the Right Sleeping Pad

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The below article is forwarded from http://www.rei.com/expertadvice/articles/right+sleeping+pad.html

How to Choose the Right Sleeping Pad
Sleeping pads perform 2 important functions -- first, they keep you comfortable when you're sleeping on hard, uneven ground. Second, they provide an important layer of insulation between you and the ground (to cut down on conductive heat loss).

How do they work?

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.

The insulative performance of a pad depends upon how much air it holds inside and how free that air is to circulate.

Step #1: Consider Your Plans

The primary variables to consider when choosing a pad are:

Insulation
Comfort
Weight/Bulkiness
Durability

To decide which of these variables are most important to you, consider your outdoor plans. Think about:

The kinds of weather you expect: if you're a fair-weather camper/backpacker, comfort will probably be more important than insulation. But if you hit the trail year-round or enjoy early spring or late fall trips, make sure you get a pad that provides protection from cold and wet conditions. It is recommended that you use two pads in snow or frozen conditions.
The level of comfort you want while sleeping: some people prefer to save money, space and weight by sticking with very basic pads. Other prefer to spend (and carry) a little more to stay as comfortable as possible in the wilderness.
How much extra weight you want to carry with you: Thicker, more comfortable pads can be heavy, which can cause problems on long backpacking trips. But if your trips are short or you're a car camper, weight will be less of an issue.
How much space you have for storage: If you're backpacking with a full gear load, a light, compact sleeping pad will be far easier to pack. Space will be less of a problem if you're carrying all of your gear in your car, or boat.

Step #2: Consider Your Options

Air mattresses: basic, inflatable air bladders Positives: They're comfortable, adjustable and inexpensive. Negatives: They tend to be heavy, bulky and they can be punctured/ripped easily. Air inside is free to circulate, so they tend to be poor insulators.
Open-cell foam pads: sponge-like foam pads made up of tiny, open air cells Positives: They're comfortable, lightweight and inexpensive. The tiny foam cells restrict air circulation, so they are also more effective insulators than air mattresses. Negatives: Open-cell foam is absorbent, which can cause problems in wet conditions. It's also less insulating than closed-cell foam (it must be cut about four times as thick to get the same insulation). Open-cell foam tends to be bulky, difficult to compress (for packing) and not very durable.
Closed-cell foam pads: pads made out of dense foam filled with tiny closed air cells Positives: They're cheap, durable (won't pop when tromped on) and extremely insulative (almost no circulation of air in pad, so they can be cut thin yet still provide good insulation). Closed-cell foam is also non-absorbent. Negatives: They're relatively stiff and firm, with far less cushioning than open-cell foam (so you'll need a thicker, heavier piece to be as comfortable).
Self-inflating pads: open-cell foam pads wrapped in air-tight, waterproof nylon shells. Positives: They're as comfortable as open-cell foam, but much more insulating (the nylon shell limits air circulation, while also protecting against water absorption). They're adjustable (built-in air valves let you control the amount of air inside and thus the firmness of the pad) and they're extremely compact when rolled up. Negatives: They're more expensive than the options listed above. Can be punctured or ripped (though field repairs are not difficult). Heavier than open- or closed-cell pads.

Step #3: Try Before You Buy

Sleeping pads come in a variety of styles, shapes and lengths. If possible, try out a number of different pads before deciding on a single model. This will help you get a feel for:

How much cushioning you need to be comfortable
How long and/or wide you want your pad to be (many models are cut short to save weight and packing space)
How easy the pad is to inflate, deflate, and/or pack away

Step #4: Consider the Extras

Finally, consider any extra pad features that might affect your decision -- like multiple air chambers (for a more custom adjustment), built-in pillows (for comfort), textured pad surfaces (for better insulation, less slip and more comfort) and tapered pad shapes that cut down on weight and bulk.