Selection in the shopSelecting a sleeping mat is an important decision - it’s one of the main things that will keep you comfortable and warm at night. When you lie directly on the ground, because the ground is normally much colder than your body and very conductive heat is quickly transferred away from your body to the ground, so you get cold. Sleeping bag insulation only works when it is expanded, so sleeping bags provide essentially no insulation between you and the ground.

Heat is a form of energy, and like all forms of energy it cannot be destroyed, but it can be moved or changed into different forms. We tend to lose heat from it being transferred from us to something else and this can happen in three main ways.

Thermal conduction is the transfer of energy (heat) between two substances with temperature differences that are in direct

contact with each other. You feel this when laying on a cool rock, where parts of your body touching the rock feel cold as the heat moves from you to the rock. Heat can be transferred to your body, such as when holding a hot drink. This transfer can be slowed with insulation between you and the ground, like a sleeping mat.

Convection is the transfer of heat through the movement of fluids (gases or liquids) from a warmer spot to a cooler spot. Cooler liquid or gas then replaces the warmer liquid or gas, with a continuous circulation pattern. One example is where the earth's surface is warmed by the sun. The warm air rises and cool air replaces the warm air. When sleeping in a tent, there are small convection currents in an air mat. These currents can be slowed with small air chambers and other barriers ... You can see convection above a campfire with embers and smoke lifted high above the fire.

Radiation is a heat transfer with no contact between the heat source and the heated object. Heat can be transmitted through space and some objects by thermal radiation. Examples include heat from the sun and a domestic radiator. Radiant heat can be reflected with a mirror or absorbed into another material that will then heat up, where it moves again by conduction or convection. Shiny silver coverings on sleeping mats can help reflect radiant heat back to you.

Everyone is different when it comes to preferences for sleeping mats, so make sure to try out a few different mats before making a decision. For those prone to pressure injuries, to ensure that your skin copes, test a sleeping mat at home before taking it on a bushwalk. Similarly, for people with back or neck pain, testing at home can help ensure the best pick for your walk.

Following are some examples of different types of sleeping mats with a comparison between various features.

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R-valueThis is a lab-obtained value that conveys the insulating properties of the sleeping mat. The higher the number, the better the insulation. Since the measurement is made about the resistance of a sleeping mat to heat transfer, the larger the R-value, the better it is at retaining heat, i.e., better for winter.With the lack of standards and labelling rules there is not a great deal of R-value consistency between brands. So take the reported R-values with a grain of salt and think though the style and materials used before assuming one mat is warmer then another.

Of course, every person is different and their tolerance to cold will vary with the way they sleep and the sleeping bag they use. The R-values are what the mat can do at its extreme and not loaded with a person lying on it (this reduces insulation). Select a mat with an R-value that is higher than you expect to have a comfortable night.

SizeSleeping mats vary in size by their thickness, width and length. Generally they are about 180 cm long, and about 50 cm wide. Thicknesses varies greatly, from about 8 mm for closed cell foam mats, to about 30 mm for self-inflating mats to a very comfortable 50 mm or more for inflatable mats. Some bushwalkers prefer three-quarter or half sized lengths to save on weight. Bushwalkers may use clothes or other material to provide insulation under their feet with shorter mats, but full-length mats tend to be more comfortable. As a general rule, the thicker the mat, the more comfortable they are and the lower the likelihood of pressure points. For some people, particularly people with

some disabilities, a double width sleeping mat can make the night much more comfortable and mean they are less likely to come off the mat during the night.

ShapeSome sleeping pads are rectangular, while others are mummy-shaped, following the body’s natural shape. For instance, the Therm-a-Rest™ Women’s ProLite.

This has the advantage to save on weight due to less material.

Surface materialSome sleeping mat surfaces are really slippery, causing your sleeping bag to slide off easily, particularly if you move around a lot in your sleep. Some mats will move on the tent floor. Textured surfaces tend to have more grip and can provide a more comfortable sleep. Too much grip may make it hard to move around. Some sleeping bags have pockets to hold the sleeping mat. If you have this design, then you tend to want more slippy mats to make it easier to get in and out of the sleeping bags pocket. Also think about the noise generated by the material; in a quiet hut or campsite you can drive yourself and others crazy each time you roll over with noisy material.

Inflation time and chambersThe two factors that affect inflation time are the size of the mat and the type of valve. Some valves transport high airflow

Black Wolf 3/4 Ultralight self-inflating mat 3.8 cm

Klymit Inertia X-Lite Short Inflatable hiking Mat

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volumes, meaning that the mat inflates quickly. It's far more enjoyable to inflate these mats after a long day on the track! And of course, a three-quarter mat will be much faster to inflate than a similar full-size model. Some mats are self-inflating, while others need to be inflated by mouth. Orally inflated mats tend to be slow and over time can have mould build up inside the mat. To avoid mould growth, use a dry bag pump, as these not only make inflating mats much faster and easier but the bags can also be used to keep gear dry.

Side railsSide rails are railings on the side of a mat that make it harder for the user to roll off the mat during sleep. These are not common and I am not sure how much they help.

Baffles If this was an English lesson I would say a baffle is something that restrains or regulates, but since this a bushwalking article I will say they are fabric that joins walls and hence create chambers to minimise airflow and the loss of heat through convection. Baffles give

a sleeping mat, sleeping bag or down jacket better insulation. Generally the more baffles the better the insulation, but they also add weight due the extra material. Also, baffle design effects the comfort on the mat. This is probably more of a personal thing, so worth trying out a few designs to see how they work for you.

REI Co-op AirRail 1.5 ($90)

InsulationInsulation has really been covered above. R-value is really a measure of the overall insulation performance of the mat. Baffles play a role in this, but inflatable mats can be partly filled with down or a synthetic insulator as well, helping reduce heat loss through convection and conduction. Also, some will have reflective material to help reduce heat loss through radiation. The value of these vary greatly depends on the overall design and interplay with each type of insulation.

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Underquilt - for hammock usersAn underquilt is used with a hammock to reduce heat loss to the air under the hammock. Underquilts are made out of the same insulation material as a sleeping bag and hang beneath the hammock. The idea is to create an insulation layer underneath the sleeper that does not get crushed under body weight. Since crushed insulation is far less effective than expanded insulation, keeping body weight off the insulation material provides a far more effective insulation layer for hammock users.

Some hammock users carry sleeping mats to give them more options. For example if they camp somewhere with no hanging points, they can use a sleeping mat on the ground, where an underquilt would provide very little value. Most hammock sleepers find underquilts lighter, warmer and more comfortable then a sleeping mat in most situations.

Similar to sleeping bags, some of the key features to look out for when selecting an appropriate underquilt include the following.

MaterialThe two main material elements to consider for a hammock underquilt are the outer shell, which will be subject to dew and condensation from being out overnight, and the insulation. The shell of a hammock must be durable and water repellent. Ideally, select a hammock with a material that is non-rip (e.g. Ripstop material) to protect the underquilt from tears. Select materials with some sort of durable water repellent coating. Just like sleeping bag insulation, underquilt insulation is either synthetic or down. Down has the advantage of a great weight to warmth ratio and compacts well. Synthetic insulation tends to work better if it gets wet and is bulkier.

SizeAn underquilt should be well fitted to your hammock for maximum insulation. Size differences in underquilts generally relate to the length and width of the hammock, so check that these dimensions match the hammock you typically use. Select a size that insulates well but not so tight that it restricts your movement in the hammock.

WeightWeight is obviously a factor for comfort in overnight hiking. Underquilts range in weight from as light as 210 grams (e.g. Thermarest Slacker Hammock Warmer) through to 400 grams (e.g. the Revolt) and more.There is generally a trade-off with weight - the lighter it is, the more expensive it is! Light can also indicate that the temperature rating is not as high as heavier ones made from same materials, so make sure to check this out also.

RatingHammocks work well in a broad range of temperature conditions and follow a similar temperature rating scheme to sleeping bags. Seek an underquilt that is rated to below conditions you’ll typically be using it in. Some examples:

Thermarest Slacker Hammock Warmer

Flying Tent Underquilt 150 dark anthracite

Thermarest Slacker Down Underquilt

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Expect your sleeping mat to get a bit dirty in the bush - this is something you can deal with at home. However, there are a few things worth cleaning up immediately if they come into contact with a sleeping mat. Insect repellent with DEET can damage material, and sap from trees can stick to material and be hard to remove. Wash off with a cloth soaked in water. If the sap is hard to remove, consider using alcohol wipes from the first aid kit.

When setting up your sleeping mat, over-inflate it slightly. When you lie down, release air until the mat feels super comfortable. Roll on your side and make sure that your hip is not touching the ground. If leaving camp set up for the day, especially in warmer months, release some air or leave the valve open to avoid the mat over-inflating as the air expands in the heat.

Repairs in the fieldWhile a leaking air mat on a trip can be disheartening, to say the least, it’s usually fairly straightforward to fix with a repair kit. Remember, a repair done on a trip doesn’t have to be the final one, it’s just to make the mat functional until the end of the trip. Even if you don’t have patches designed for sleeping mat repairs, you may find that first aid kit tape suffices for the rest of the trip, and you can do a more thorough repair at home.

The first thing is to find the leak. Sometimes this is easy as you can hear the air leak or see a hole. Other times, this can be much harder, especially if there is a tiny hole or a really slow leak. In these cases, it works well to use water to identify the leak (for details, see Care and maintenance on the

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Care and maintenance at homeBack home, use a damp cloth to remove anything that has stuck to the mat such as dirt, insect repellent, or sunscreen. If left on for longer periods, these can cause damage to the material, particularly if chemicals such as DEET are in insect repellent. For stubborn stains, use biodegradable soap. Once a season, completely clean the sleeping mat to remove body sweat and dirt, as they can transfer to a sleeping bag and compromise performance. Follow the manufacturer's instructions for washing. When cleaning inflatable sleeping mats, take care to ensure that the valve is closed; drying the inside is tricky and it should not need cleaning.

After cleaning, dry the sleeping mat thoroughly (but avoid prolonged periods of direct sunlight), and open the valve. Take care to dry both the interior and exterior of the sleeping mat. Interior moisture can lead to mould and degradation of the material. Dry the interior with a hair dryer on a low setting to partially inflate the sleeping mat, then deflate and repeat a few times.

For long-term storage, follow instructions for your sleeping mat; some need to be inflated (e.g. Therm-a-Rest©), while others can be left deflated (e.g. NeoAir©). In general, self-inflating mats should be stored semi-inflated for good air circulation, whereas air mats should be stored loosely and not folded along the same crease lines each time. Choose a cool, dry place that doesn't have extremely hot temperatures.

Repairs at homeRepairing sleeping mats at home is far easier than in the field. At home you can focus on getting the job done well, with the right gear for long-lasting results.

If you can’t find the hole, fill a tub or bath with water, inflate the sleeping mat as much as possible, and look for tiny bubbles to appear from the leak. Another way is to splash water with dish washing detergent or soap onto the surface of the mat. This works best when the location is believed to be known. If you still can’t see bubbles, try gently squeezing the mat. Dry the area thoroughly with a towel, and mark the leak by drawing a circle around it with a marker pen or chalk. It is possible to have more than one leak, so keep looking even after you have found the first leak.

After finding the leak(s) follow the instructions in the paragraph above the Care and maintenance at home heading on this page.

This article was written by Matt McClelland and Helen Smith. The article is adapted from the NPA's Bushwalking101.com website and was produced in partnership with Wil dwalks.com.

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