For when you've gone soft and don't want to sleep on the ground
This is another item that has a range of options available. They have two functions, to make sleeping on the ground more comfortable and to keep you warm. Most people often don't understand how important the insulation underneath them is. If you've ever been camping on a cold night, and it felt like your sleeping bag wasn't warm enough, it is more than likely it was because you didn't have enough insulation underneath you. Think of it this way: (1) around 40% of your body is touching the ground while you sleep (if you lie on your back); (2) the ground is far, far more conductive than air, meaning it will conduct heat from your body a lot faster; (3) your sleeping bag does not provide any insulation underneath you because your weight is compressing it; (4) therefore, putting more insulation underneath yourself is a very effective method of retaining heat.
There are basically three types:
Closed cell foam mattresses – these are not inflatable and are just a layer of foam to sleep on, they are durable, cheap, moderately light, and can just be thrown on the ground without too much fuss. However, they normal $10 ones are not very warm or comfortable. Probably the best foam matt on the market is the Therm-a-Rest Z Lite SOL.
Air pads – these are hiking versions of standard air mattresses. Good ones can be very light, thick and comfortable, and have the most potential for warmth (it depends if they are insulated or not), and are very compact. However, they are more expensive, if they puncture they deflate and take longer to set up. There is an excellent price range in air-pads, you can spend anything from around $100 to around $500. As you spend more, they tend to get warmer and/or lighter.
Self-inflating air pads – these are stupid inventions do not buy one. They are heavy, not that comfortable, quite large and bulky, and usually don’t even inflate properly. They always have some form of insulation. How they 'self-inflate' is the insulation inside will naturally loft up (increase in size), when it is not compressed, thus increasing the thickness. They are not as thick or light as regular air pads.
General Buying Tips:
You can spend anything from very little to quite a lot on sleeping pads. Basically, as price increases they get more warm and comfortable. A $10 foam mattress will be more comfortable than the ground, but not by much. A more expensive foam mattress can be moderately comfortable, and quite warm (~$80).
On better pads you will often see something called an R value quoted, this is basically how well it insulates. Values between 0-3 are not that warm, 3-5 is quite warm, and above 5 is very warm. At 5, there is no net heat loss through the ground. Foam mats typically have an R value between 0-2.5. Air pads have the whole range.
For three season trips (late Spring – early Autumn) any insulation is fine. Any insulation in the mat reduces the amount needed in the sleeping bag, BUT it is only worth investing in a decent mat if you are going to be camping a lot.
For Winter trips, a mat with insulation is essential if you are camping. You ideally want something with at least an R value of above 3, and preferable 5 or higher.
Common Questions people ask about sleeping pads:
Won't an air pad pop or puncture easily? Most models are actually quite difficult to puncture. You would probably have to try quite hard to do it accidentally. I've used a few different inflatable pads for the last 7 years and I've never had one puncture. As long as you don't lay it down on a nail or a sharp stick and then sit on it, it should be fine. If they do puncture, they're usually quite easy to fix.
Is it really worth the money to get a good quality pad? It depends on how much you're going to use it. If you are going to use it frequently, I would say yes. If you are going to use it for cold weather camping it is most definitely worth spending some money. Past a certain point, you will usually get more warmth for your money by buying a good sleeping pad versus a warmer sleeping bag.
Do air mats take long to blow up? They're certainly not as hard to blow up as people might think. To blow up my full length Therm-a-Rest takes me about 2-4 minutes. Sure, there's that light headed feeling at the end, but my reward is a warm and comfortable sleep that night.
Your realistic choice should be between a foam matt and an air pad. Aside from price, many people choose a good quality foam pad because they like not having to inflate it in the evening and deflate it in the morning, and are worried about it puncturing. On the other hand, air pads pack down a lot smaller, have the potential to be much warmer, and are much more comfortable.