Air matresses

For a lot of campers, the height of comfort is still the airbed. A lot of air and a lot of comfort, which can not be all that bad, could it. Until you understand what’s actually going on inside such an airbed. An air bed is often one fat air chamber. The bottom is cold due to the contact with the ground, but at the top, the air is warm, due to your body heat. That temperature difference means that the air will circulate inside the air chamber. As the air circulates, the heat generated by your body is cooled as it passes the bottom, in effect, you are warming the ground.

So where an air mattress isolates quite poorly (priority number 1) the comfort factor is better. However due to the small number of compartments you will find in most air beds you get a destabilizing water bed effect: push on one side and the other side comes up. Finally, an air bed is pliable and requires a pump to fill. You could use your mouth to inflate the air pad but the water vapor in your breath will eventually affect the inside of the air bed.

Foam pads

Foam lends itself perfectly for making an insulating layer because its cells contain a lot of air and foam is light a feather. Foam is available in many types, where the most relevant forms for outdoor are closed and open-cell foam structures. In open-cell foam the cells are connected to each other and with the outside air. When you lie down on it, all the air is pressed out of the mat and the insulation is completely lost. That and the great vulnerability of open-cell foam are the two biggest disadvantages of this material. In addition, open-cell foam does not form a barrier to moisture so that you wake up on a wet ground sieve in the morning. An ‘egg foam’ mat provides comfort, but once out of the original packaging it is a huge package.

Closed-cell foam is another thing altogether. Here the cells form closed bubbles in which the air remains trapped when the foam is compressed. When applied to a pad, the foam retains its insulation quality when if you lie down on it. In addition, it can take a punch or two and it is also very light. The only downside is that such a mat offers very little comfort.

Open and closed cell foam can be made of different types of plastic, with significant differences in quality and durability. With regard to the open-cell variant, polyurethane foam has a very good reputation. For closed-cell foam mats, the lifetime and relative invulnerability of EVA (ethylene vinyl acetate, also used for the damping layer in running shoes) is the best choice.

Variations

A well-known variant on the foam pad is the pad that consists of an ultra-thin layer of open-cell foam coated with a reflective aluminum-colored layer. The idea is that this layer reflects the heat of a rescue blanket and allows for a very thin mat. Sounds like an interesting theory, but in reality, it is pure nonsense. Because you’re lying on top of it, the reflective layer works as a heat conductor and will make you colder. What the function of the layer of open-cell foam should be is puzzling.

Other variations are the ribbed or “recessed” closed-cell mats. They have a little more bounce and therefore a are a bit more comfortable, while the spaces between the ribs – when sealed by the body of the sleeper – hold extra air for more insulation. The nipple model can be folded up as a harmonica and does not curl up after you fold it out again.

Self-inflating mats

An air mattress is cold, an insulation pad hard. There had to be an alternative and that is what American Cascade Designs invented in 1973. Their concept has soon become world famous: you take a low open-cell foam and glue it on both sides with an air and waterproof cover with one opening closed by a valve. With the valve closed, the air cannot be squeezed when compressed, so that it stays insulated. If you open the valve, all air will be pushed out as you roll up the pad. This way a thick comfortable pad will also be reduced to a package that is smaller than a rolled up insulation mat. As you close the valve, the vacuum you created keeps the mat compressed and it is easily packed away into its pouch.

When the valve is reopened, the vacuum will fill itself (as vacuums are wont to do), sucking air in through the opened valve the foam regaining its original shape: enter the Therm-a-Rest they self- inflating mattress. The Seattle thinkers spoke about a ‘mattress’ from the beginning. The true strength of such a pad is not the self-inflating character (which does mean you don’t need a pump): the real revolution was the combination of isolation and comfort that most sleepers will appreciate.

Alternatives

Like any good idea, there are also other brands that have developed a variation on pads. Generally, cheaper alternatives though it must be said that this often is achieved by making concessions in materials selection, construction, and performance. Quality of foam and coating and the way these are bonded, quality of the valve, warranty and durability are some of the variables that differ widely.

If a manufacturer does not glue foam and lining completely or poorly, which is cost-effective, the foam is not sealed off completely. Air is allowed to circulate, resulting in poorer insulation. Such pads are self-inflating but forget the most important aspect of the mat; insulation.

There is a pad for every budget, but for something that is so essential for a good night’s rest, and through that for the success of your adventure, being too economical does not always seem to be a good choice.

As with many products the adagium “if you pay peanuts you get monkeys” is relevant in this case too.

R-value

The R-value of insulation is an important value in the insulation technology that expresses the heat resistance (and hence the effectiveness) of a particular insulation layer. The higher the R-value, the better the insulation is in blocking heat transport. (which is a good thing). If you make an insulation layer thicker it increases the overall R-value, although the extent of this increase depends on the type of material.