Sleeping pad

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Rolled sleeping pad Mattress.jpg
Rolled sleeping pad

In camping, a ground pad, sleeping pad, thermal pad, sleeping mat, or roll mat is lightweight pad, common among hikers, backpackers and budget travelers, 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.

Contents

In its simplest form a sleeping pad consists of a foam-like material that is about half a centimeter thick (about a quarter of an inch). The dimensions of the pad are usually about the same length as a sleeping bag and a little wider. Slight variations in design can be found, such as rippling in the foam, but these do not significantly affect the pad's thermal properties.

A common misconception is that the pads are primarily for creating a more comfortable sleeping or sitting area. Instead, the primary purpose of the pad is to prevent the loss of body heat into the ground while sleeping. The materials used are typically filled with air pockets, slowing down the conduction of heat through the pad, as air is one of the best (and cheapest) insulators.

Types

Manually inflated

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.

Self-inflating

An example of a self-inflating mattress made from diamond ripstop. The black high-volume valve can be seen in the left foreground. Self-inflating mat.jpg
An example of a self-inflating mattress made from diamond ripstop. The black high-volume valve can be seen in the left foreground.

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 [1] 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.

Foam

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 self-inflating 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 manually inflated and self-inflating 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.

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:

Air/ground
Temperature
R-value for standard
malefemale
5 °C (40 °F)56
−7 °C (20 °F)78
−18 °C (0 °F)910
−30 °C (−20 °F)1113

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) [2] 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/ modelR-valueApproximate cost
Common air mattress0.7US$10
Common 10 mm (3/8 in) closed-cell foam pad1.4US$10
Advanced foam pad3.5US$40
25 mm (1 in) self-inflating mat3.4US$70
Advanced air mattress6US$200
Down-filled air mattress9US$200
50 mm (2 in) folding DIY EPS foam [3] 10US$15

See also

Related Research Articles

Thermal insulation Minimization of heat transfer

Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.

Wetsuit Garment for thermal insulation from water

A wetsuit is a garment worn to provide thermal protection while wet. It is usually made of foamed neoprene, and is worn by surfers, divers, windsurfers, canoeists, and others engaged in water sports and other activities in or on water. Its purpose is to provide thermal insulation and protection from abrasion, ultraviolet exposure, and stings from marine organisms. It also contributes extra buoyancy. The insulation properties of neoprene foam depend mainly on bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, providing buoyancy in water.

Sleeping bag Insulated covering for a person

A sleeping bag is an insulated covering for a person, essentially a lightweight quilt that can be closed with a zipper or similar means to form a tube, which functions as lightweight, portable bedding in situations where a person is sleeping outdoors. Its primary purpose is to provide warmth and thermal insulation through its synthetic or down insulation. It also typically has a water-resistant or water-repellent cover that protects, to some extent, against wind chill and light precipitation, but a tent is usually used in addition to a sleeping bag, as it performs those functions better. The bottom surface also provides some cushioning, but a sleeping pad or camp cot is usually used in addition for that purpose. The bottom surface of a sleeping bag may be moderately water repellent, but a plastic tarp or groundsheet is often used to protect against moist ground.

R-value (insulation) Measure of how well an object, per unit of area, resists conductive flow of heat

In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions.

Dry suit Watertight clothing that seals the wearer from cold and hazardous liquids

A dry suit or drysuit provides the wearer with environmental protection by way of thermal insulation and exclusion of water, and is worn by divers, boaters, water sports enthusiasts, and others who work or play in or near cold or contaminated water. A dry suit normally protects the whole body except the head, hands, and possibly the feet. In hazmat configurations, however, all of these are covered as well.

Soundproofing Methods to reduce sound pressure

Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.

Air mattress Type of mattress

An air mattress is an inflatable mattress or sleeping pad.

Mattress Large pad for supporting the reclining body, used as or on a bed

A mattress is a large, usually rectangular pad for supporting a lying person. It is designed to be used as a bed, or on a bed frame as part of a bed. Mattresses may consist of a quilted or similarly fastened case, usually of heavy cloth, containing materials such as hair, straw, cotton, foam rubber, or a framework of metal springs. Mattresses may also be filled with air or water.

Glass wool

Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties. Glass wool is produced in rolls or in slabs, with different thermal and mechanical properties. It may also be produced as a material that can be sprayed or applied in place, on the surface to be insulated. The modern method for producing glass wool was invented by Games Slayter while he was working at the Owens-Illinois Glass Co.. He first applied for a patent for a new process to make glass wool in 1933.

Memory foam Component primarily utilized for making cushions or mattresses

Memory foam consists mainly of polyurethane with additional chemicals that increase its viscosity and density. It is often referred to as "viscoelastic" polyurethane foam, or low-resilience polyurethane foam (LRPu). The foam bubbles or ‘cells’ are open, effectively creating a matrix through which air can move. Higher-density memory foam softens in reaction to body heat, allowing it to mold to a warm body in a few minutes. Newer foams may recover their original shape more quickly.

Therm-a-Rest is an American outdoor product company specializing in camping mattresses, sleeping bags, camp chairs, hammocks, cots, and pillows. Therm-a-Rest began as a line of self-inflating camping mattresses, invented in the early-1970s by two former Boeing engineers and avid backpackers. The company was initially named Cascade Designs, which is now the parent company of Therm-a-Rest and other outdoor brands.

Building insulation Methods of minimizing heat transfer in constructions

Building insulation is any object in a building used as insulation for thermal management. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.

Ultralight backpacking Style of hiking

Ultralight backpacking is a subset of lightweight backpacking, a style of backpacking which emphasizes carrying the lightest and least amount of gear. While no technical standards exist, some United States hikers consider "ultralight" to mean an initial base weight of less than 4.5kg. Base weight is the weight of a fully loaded backpack at the start of a trip, plus the gear inside and outside it, excluding consumables such as food, water, and fuel. Base weight can be lowered by reducing the weight of individual items of gear, or by choosing not to carry that gear. Ultralight backpacking is most popular among thru-hikers—those hikers on extended trips requiring resupply.

Hammock camping

Hammock camping is a form of camping in which a camper sleeps in a suspended hammock rather than a conventional tent on the ground. Due to the absence of poles and the reduced amount of material used, hammocks can be lighter than a tent, though this is not always the case. Most hammocks will also require less space in a pack than a similar occupancy tent. In foul weather, a tarp is suspended above the hammock to keep the rain off of the camper. Mosquito netting, sometimes integrated into the camping hammock itself, is also used as climatic conditions warrant. Camping hammocks are used by campers who are looking for lighter weight, protection from ground-dwelling insects, or other ground complications such as sloped ground, rocky terrain and flooded terrain.

Building insulation materials

Building insulation materials are the building materials which form the thermal envelope of a building or otherwise reduce heat transfer.

Cellulose insulation

The word cellulose comes from the French word cellule for a living cell and glucose which is a sugar. Building insulation is low-thermal-conductivity material used to reduce building heat loss and gain and reduce noise transmission. Cellulose insulation is plant fiber used in wall and roof cavities to insulate, draught proof and reduce free noise.

Spray foam

Spray foam is a chemical product created by two materials, isocyanate and polyol resin, which react when mixed with each other and expand up to 30-60 times its liquid volume after it is sprayed in place. This expansion makes it useful as a specialty packing material which forms to the shape of the product being packaged and produces a high thermal insulating value with virtually no air infiltration.

Pipe insulation

Pipe Insulation is thermal or acoustic insulation used on pipework.

Rigid panel

Rigid panel insulation, also referred to as continuous insulation, can be made from foam plastics such as polyurethane (PUR), polyisocyanurate (PIR), and polystyrene, or from fibrous materials such as fiberglass, rock and slag wool. Rigid panel continuous insulation is often used to provide a thermal break in the building envelope, thus reducing thermal bridging.

Foam glass

Foam glass is a porous glass foam material. Its advantages as a building material include its light weight, high strength, and thermal and acoustic insulating properties. It is made by heating a mixture of crushed or granulated glass and a blowing agent such as carbon or limestone. Near the melting point of the glass, the blowing agent releases a gas, producing a foaming effect in the glass. After cooling the mixture hardens into a rigid material with gas-filled closed-cell pores comprising a large portion of its volume.

References

  1. Lea et al. 1979. Method of making a self-inflating air mattress. 4,149,919.
  2. "Thermal Conductivity of common Materials and Gases". www.engineeringtoolbox.com.
  3. sweerek (12 September 2015). "Diy sleeping pad, eps accordian, 27mar15".