In camping, a ground pad, sleeping pad, sleeping mat, roll mat, or iso mat is a simple device often used in conjunction with a sleeping bag. Its purpose is to provide padding and thermal insulation. All types currently available use air as their primary form of insulation.
It is usually used for camping or for the most elementary bivouac and serves to isolate from cold and humidity. It is placed between the floor and the sleeping bag or for outdoor activities such as the practice of yoga in nature.
The mats are usually made from EVA (Ethylene Vinyl Acetate), a thermoplastic copolymer with good performance in terms of insulation, flexibility and weight. The synthetic material of which it is composed can break if it is rolled in the opposite direction to the usual one. On the contrary, they are light and resistant to shock. The good mats in its lower part (the one that faces the ground) have as surface a film or silver reflective film of aluminum or similar material (for example Lúrex) that serves to reinforce the thermal insulation with respect to the ground.
The mats are usually made of synthetic materials that can emit odors when they are new or when they are stored for a long time in a hot place, for example a tent. They are not as comfortable as inflatable mattresses due to their reduced thickness, between 5 and 10 mm.
A self-inflating carpet is the best solution from the point of view of the weight & volume / insulation ratio; However, its fragility makes it risky to use a bivouac where pointed pebbles, pine needles, or blunt rubbish (metal tip, bottle glass, wooden splinter, etc.) can cause it to burst. A puncture then completely eliminates the insulation and comfort of the whole set, unlike foam mats that wear or a hole will only be damaged locally.
Insulation and Humidity
Inflatable or self-inflating solutions are an interesting solution for their insulating ability to sleep on cold or snowy ground. On the other hand, the humidity of the air (ambient or insufflated) in the cells can condense and substantially reduce this insulating potential. Moisture and condensation can also be a source of bacterial development affecting the object.
The foam mats, on the other hand, absorb little moisture because of the composition of the closed cell foam (EVA: Ethylene vinyl acetate, a thermoplastic copolymer) and restore it when they are dried in the sun or in a heated room.
There are two main types of floor mats:
The camping floor mats are composed in all cases of a foam, for its insulation capabilities and for its flexibility (comfort). Foam is a light and sparse synthetic material (less than 70 kg per cubic meter), often filled with micro-bubbles. Because of its low thermal conductivity, air is responsible for the insulation provided by the floor mat. The insulating capacity (R value) differs according to the foams used and the thickness thereof, ranging from 5 mm to 15 mm. The thickness of the floor mat is proportional to its insulation. To increase it, many manufacturers add aluminum foil to reflect infrared raysfrom body heat. High-end models work the rug shape to create small, egg-shaped cavities or grooves to trap air between the sleeping bag and the insulating material, further increasing heat retention.
Inflatable / self-inflating floor mats (and air mattresses) have the same goals as traditional models, but their constitution differs radically. These are synthetic mats which are inflated by means of a valve or which fill themselves by an internal honeycomb structure. The trapped air volume creates a thickness of between 10 mm and 40 mm, providing insulation of up to twice the foam mattresses.
There are inflatable mattresses the thickness of which can exceed ten centimeters, but their weight and volume makes them not very transportable in the frame of hiking, and the cantonment rather to sedentary uses or transports in vehicle. The thickness being proportional to the volume of air blown (up to a certain threshold), the comfort is considerably increased. Finally, the volume of the deflated carpet is restricted even if the weight is comparable.
Closely related to the air mattress, a pad of this type requires an external pressure source to inflate, typically in the form of a pump or by blowing orally. Convection of the air inside the mattress reduces the amount of insulation it provides. More complicated mattresses reduce convection by partitioning the internal cavities, or by filling the cavities with material to trap the air such as down feathers or synthetic insulation. Manually inflated pads have the advantage of offering good thickness and a great deal of comfort while being lightweight and able to pack to a small size.
An extension on the conventional manually inflated mattress, this type is capable of self-inflation due to the open-cell foam that fills the internal cavity. For many years this design was protected by various patents held by Cascade Designs and they were an unusual and premium item. But since these patents expired many other manufacturers are now producing this type of mattress and they are now commonplace. These mattresses are lightweight and pack to a small size, which make them popular amongst hikers and campers. A self-inflating mat typically measures 183x51x3.8 cm, weighs about 700 g, and packs to about 28×16 cm.
Closed-cell foam is used to produce mats that can be used without requiring any inflation. Closed-cell foam pads are lighter and more durable than their air-filled counterparts, as they are constructed of fewer materials and not susceptible to damage from accidental puncture. Many may also be trimmed to size should the user choose to do so. However, they are generally not as comfortable as air-filled mats because they are thinner, and may also take up more space in a pack, depending on the materials used. Variations include textured or shaped foam to increase the unrolled volume and/or change the stiffness of the mattress. This can also be used to trap the air within ridges or an egg-carton type of texture.
Open-cell foam, although comfortable, is rarely used in the outdoors due to its ability to absorb water (like a sponge) and its air cells are crushed in use reducing its insulation capacity.
Normal sleeping mat
An ordinary sleeping mat is made of polyethylene (PE) or ethylene vinyl acetate (EVA) foam. Depending on the purpose, there are foam mattresses in different thicknesses (usually between 5 mm and 19 mm) and a standard size of 60 cm in width and 180 to 200 cm in length, and in various forms: smooth, grooved, grooved, foldable or rollable, partly with one-sided silvery aluminum coating for additional insulating effect. For weight reduction on trekking tours also shortened sleeping pads are used, in which the legs of the sleeper are not on the mattress.
The insulating effect depends on the thickness and the density of the foam as well as on the structure (for example single-layer or double-layered).
Sleeping mats are lighter (often well below 1 kg) and usually less slippery compared to thermal air mattresses.
Air mattresses have a smaller pack size compared to mattresses and offer more comfort, but they can leak.
A self-inflating air mattress is a polyurethane foam mat surrounded by an airtight cloth wrapper. This shell has one or more closable valves. Mostly at the bottom of a smooth, dirt-repellent fabric and on the top of a slip-resistant layer, which is to prevent slipping of the sleeping on an inclined surface.
When not in use, the mat is rolled up, the foam is compressed. When the roll-up safety device and the valve are opened, the elastic foam can follow its endeavor to return to its original shape. In this case, air is sucked into the foam, which remains in it when the valve is closed. In addition, the mat can be further inflated, but this is not absolutely necessary and by the entry of (respiratory) humidity can also have negative effects – such as the colonization of microorganisms. Compared to the usual air mattress, the thermo- air mattress is lighter and thinner and offers even in not bulging filled state through the interior foam still thermal insulation.
Newly purchased mattresses should “rest” for a few days with the valve open before first use, so that the foam can expand completely. In order to maintain the swellability of the foam, thermo-air mattresses should be stored in the unrolled state, with the valve open.
Color and reflectivity have no impact on a pad’s insulating ability. Just like with clothing and sleeping bags, the interior color (flat black, shiny silver, white, or orange) makes no difference in warmth.
The price plays against the self-inflating, being more technical because consisting of several layers of materials.
One last point differs according to the floor mats: their grip on the ground. Although it is better to sleep on a flat floor, some situations do not allow it, and an inclined carpet can slip due to lack of traction, especially if it is placed on a tent floor. Self-inflating mattresses, whose casing uses smooth synthetic materials, are more sensitive to the slope than their foam counterparts, whose asperities hang on the ground thanks to the elasticity of the materials. This remark is also valid for the sleeper in his sleeping bagsliding over the night because of his movements on his floor mat. With this in mind, some manufacturers incorporate anti-slip micro-reliefs to keep both the sleeper on the carpet and the carpet on the floor.
When they stay a long time in a rolled position, the foam mats keep the ‘fold’ and will tend to wrap themselves once unfolded; and the foam that composes them can break if the mattresses are rolled in the opposite direction to the usual one.
For their part self-inflating must imperatively be stored in inflated condition so that their cells maintain this state as that of ‘rest’, and therefore spontaneously re-inflate during their installation; failing this, a self-inflating device having lost this ability will require inflating by insufflation, more tiring and source of internal moisture. They should only be compressed during transport.
Insulation / Ratings
A sleeping pads’s warmth is characterized by R-value. But unlike sleeping bags’ EN 13537 test standard and widely accepted recommendations, sleeping pad R-values lacks a simple mapping and label for ‘how much warmth’ a consumer should expect. Combining various standards and various authors’ research, an approximate R-value to temperature chart follows:
|R-value for Standard|
Same as EN 13537, a “standard man” is assumed to be 25 years old, with a height of 1.73 m and a weight of 73 kg; a “standard woman” is assumed to be 25 years old, with a height of 1.60 m and a weight of 60 kg. The sleeping bag and pad system (above, below, and sides) should provide the same insulation value all around a person, but cost, size, weight, comfort, and lack-of-knowledge often lead persons to reduce the R-value to below their personal ‘recommended R-value’. Since the pad and bag work together, a ‘warmer’ bag can compensate the a ‘thin’ pad and a ‘thick pad’ for a ‘cold’ bag. Highly heat-conductive surfaces (e.g. concrete, granite) require more insulation for the same temperature than insulating ground surfaces (e.g.snow, dry moss, loose soil, wood, etc.). More heat is lost downward when sleeping on one’s stomach vs sleeping one’s side (due to reduced contact area and cooler body parts in contact). Most persons can ‘feel the cold ground’ at approximately half the ‘recommended R-values’.
Sleeping pads R-values range from 1 to more than 10. A few category examples follow:
|Make/ Model||R-value||Approximate cost|
|Common air mattress||0.7||10 $USD|
|Common 3/8” closed-cell foam pad||1.4||10 $USD|
|Advanced foam pad||3.5||40 $USD|
|1″ self-inflating mat||3.4||70 $USD|
|Advanced air mattress||6||200 $USD|
|Down-filled air mattress||9||200 $USD|
|2″ folding DIY EPS foam||10||15 $USD|
The very first self-inflating mat was released by the American firm Cascade Designs Inc. in 1972 under the trademark Therm-A-Rest. Since self-inflating mats use the so-called “open-porous” variety of polyurethane, that is, a polyurethane consisting of cells communicating with each other and with the surrounding atmosphere (analog: kitchen sponge), self-inflating mats are well compressible for their transportation, and are also able to suck in air after pressure is released from their surface. Subsequently, Cascade Designs Inc. began to produce under the trademark Therm-A-Rest all its tourist rugs, including rugs made of ethylene vinyl acetate (from 1986 to 2005), polyethylene (since 2005), as well as inflatable mattresses, that is, litter, the filler of which is exclusively air (since 2009). Despite this, in the Russian-speaking environment the expression “termarest” is sometimes mistakenly considered synonymous with the expression “self-inflating mat”.
The expression “self-inflating” is, strictly speaking, not entirely correct, since self-inflating mats – and especially those that have a small thickness – are not able to fill themselves with the amount of air that is necessary for the total comfort of sleep, which is determined, at least, by the capacity mats provide thermal insulation and smooth out the unevenness of the soil. The volume of air can reach 93-98% of the total volume of open-porous polyurethane used as a filling of the self-inflating mat – however, the gradual self-inflating of the self-inflating mat with air, caused by the removal of pressure from its surface and the opening of its valve, leads at best to full spreading foam inside the mat, but not to increase the hardness of this foam. Concerning, The recommended (economical) way to use a self-inflating mat is the following: opening the mat valve and unfolding the rug in advance to allow it to fill itself with air (the sign of the end of the “self-inflating” rug is the crease of the folds on its surface) and a short additional inflation of the mat with the mouth (2-4 complete exhalation) immediately before bed. When inflating a self-inflating mat you can skip the “self-inflating” phase by inflating the mat with air immediately after it is deployed. Pumping of self-inflating mats with air can be carried out both by the mouth and various kinds of pumps (special packing bags-pumps, hand or foot pumps, and electric mini pumps). During long trips at very low temperatures, however,
The duration of the “self-inflating” of the self-inflating mat (from a few minutes to about half an hour) depends on many factors, the most important of which are the thickness and density of the polyurethane used in the mat, the age of the rug, and the ambient temperature. At low temperatures, the process of “self-inflating” is sometimes considerably longer than at high temperatures. The new rug, which was stored for a long time in a collapsed state, is filled with air much more slowly than a rug that has already passed a sufficiently large number of cycles “compression (transportation) – filling with air (sleep, rest) – compression (transportation).”
The cover of the self-inflating mat, made of synthetic material (nylon, polyester) and firmly bonded to the polyurethane filler of this rug, performs several functions. It prevents the absorption of water into the open cells of the foam filler of the rug (protection of the foam filler from damages due to mold), does not allow the air to leave the foam due to the pressure exerted by the sleeper’s body on the rug of the person, and also protects the carpet filler from damages.
Self-inflating mats, becoming by the mid-90s of the last century the most common type of rugs in the environment of Western sports tourism enthusiasts, keep this primacy to this day. The technology used in them was the first technology of production of tourist mats, in which the constructive scheme “water and airtight shell + solid filler” was used. This constructive scheme is also used in other, newer types of rugs – for example, in rugs filled with fluff and microfibre, as well as in rugs, the filler of which is partly composed of an airgel. Unlike rugs made from so-called “closed-cell” foam materials (that is, foams consisting of closed cells), all the rugs manufactured according to this design scheme are characterized by a decrease in thickness and thermal insulation ability in the event of a puncture. For the repair of these rugs, special repair kits are produced, which allow to produce a fairly fast and reliable repair also in conditions of a hike.
Source from Wikipedia