You can sleep directly on the ground in your bag but you’ll lose heat to the cold ground. Forget about comfort and a good night’s sleep. Many people think they need a new warmer sleeping bag but what they really need is a new sleeping pad to decrease conduction from the ground. No sleeping bag provides much insulation or cushioning from the ground because the fill is compressed under your body weight.
Most of the time when you’re sleeping outdoors, more of your body heat is lost to the ground underneath you than the air around you. Depending on the surface you’re sleeping on and how cold it is, you can lose heat to the ground – that’s why the insulation you get from your sleeping mat is so important. The primary function of a sleeping pad is to minimize conductive heat loss. In a lot of cases, you’re retaining more warmth thanks to your sleeping pad than you are through your sleeping bag, so it’s important to choose the right one. In summer weather, some people manage without a pad, putting clothing or their hiking packs under them if it’s cold, but most people use a pad year-round.
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Types and important features of sleeping pads
The most luxurious and expensive air mattresses are filled with waterfowl down. Pump these up and they form a supportive and warm bed.
There are also sleeping pads filled with synthetic. They are less expensive but heavier than down-filled ones and not as warm as them.
Conduction of heat to the cold ground will suck the warmth right out of you. Moreover, your own body weight compresses the insulation in your sleeping bag making the insulation rating between you and the ground the worst insulated part of your entire bag. Having a good R-value sleeping pad helps make up some of that insulation loss and keeps you warm. In the cooler or winter months, R-rating makes a significant difference in how warm you stay.
Each pad is given an R-value, which is a rating of how much insulation it provides. R-value measures a mat’s resistance to heat flow. The higher the R-value, the more insulation the sleeping pad will provide. You can generally draw the line between three-season and winter mattresses at an approximate R-value of 3.0. In sub-zero temperatures, most people require an R-value of 4 or more in order to feel comfortable. When the temperatures are higher, sleeping mats with R-values of 2 to 3 should suffice.
R-value is useful in comparing mattresses, however, there is no standard methodology for testing the R-value of sleeping pads. R-Values given by manufacturers have no standard and are completely arbitrary. This is especially problematic when comparing pads made by different manufacturers.
There are three types of sleeping pads: closed-cell foam, self-inflating, and air. As with other product categories, there is no single best pad. To gain some advantages – e.g., warmth, comfort, durability, weight, and cost – compromises have to be made in terms of which properties are most important.
Closed-cell foam pads
They are lightweight, reasonably inexpensive, and hardwearing. These pads are made from foam that is either pressure blown or chemically blown; the first is warmer, more durable, and resists compression better than the second, but the two types look identical, and manufacturers rarely tell you which is which. The big advantage of closed-cell foam is that it’s waterproof, since the air pockets in the foam are sealed inside, so it doesn’t suck up water the way open-cell foam does.
Closed-cell foam pads are pretty indestructible, too, though if strapped on the outside of your pack, are prone to get caught or tear when hiking through overgrown terrain. Although they’re efficient insulators, they don’t provide much cushioning, and you can feel stones through them. Additionally, closed-cell foam pads are bulkier. Closed-cell pads come in different lengths, widths, and thickness, and you can easily cut one down to the shape you want. The thickest, longest, widest pads can weigh 20 ounces or more.
They combine the comfort of air mattresses with the insulation of foam pads and are relatively luxurious to sleep on. Self-inflating pads are lightweight, compact, provide better insulation in the cold, and offer great comfort. Some models made of thinner materials can be utilized as a makeshift frame sheet by doubling them over and placing them against the back of your pack’s interior. Needless to say, using self-inflating sleeping pads doesn’t bring only advantages but also some disadvantages. They are (in general) heavier, and more expensive (than closed-cell foam pads), and there is a risk of puncture.
Self-inflating pads have a tough waterproof coated nylon shell bonded to an open-cell polyurethane foam core that sucks in air and inflates when you open the valve at one corner. That’s the theory. However, in reality, it takes a few puffs of breath. Once the pad has reached the desired thickness, you close the valve to keep the air from escaping. To deflate a self-inflating pad you open the valve and slowly roll the pad up, either on a ground cloth or on your thighs, squeezing out the air as you go. The deflated pad can then be rolled or folded as you choose. At home, self-inflating pads should be stored uncompressed with the valve open. This also allows moisture from breath to escape. When the pad’s valve is opened, the open-cell foam expands and creates a vacuum, which causes air to rush in.
Air sleeping pads
They are suitable for use in the summer and pair well with both sleeping bags and hammocks. Traditional air sleeping pads are very comfortable but also cold, since there’s no fill to hold the air in place, so it moves around and conducts ground cold upward. Air sleeping pads are useless when flat. Once an air mattress like this deflates, you’re left lying on two thin strips of nylon with no cushioning and little Finding a pinhole leak in a pad isn’t a simple task and a repair in the wilds isn’t easy to do. One curiosity with air mattresses is that they can appear to lose some air during the night even though there is no leak. What is actually happening is that the air in the mattress is cooling down and contracting. A few breaths are usually all that’s needed to restore it to the thickness you want. If it goes completely flat, then there is a leak.
To minimize convective and radiant heat loss, they are filled with down or synthetic insulations. To improve stability, additional structures or materials are used to minimize air displacement. Air pads have unrivaled thickness, compactness, and often warmth. But they are far from perfect. Air sleeping pads are the most expensive, especially the insulated versions, and they are prone to leaks and delamination. Those filled with down or synthetic insulations must be inflated with a pump because moisture-filled breaths will adversely affect the insulation’s warmth; the lifespan of synthetic insulations is also relatively short-lived; and in cold conditions, they need to be reinflated after lung-warmed air cools down and condenses.
A comfortable sleeping pad is one of the most critical pieces of gear on any trip. As we highlighted in our guide about the types of sleeping bags, having a good sleeping pad is as important as having a good sleeping bag. A good night’s rest will easily offset the extra weight if you choose to carry a heavier and more cushioned sleeping pad on your next hike. Fine-tuning everything in your pack, and making sure you sleep well every night, will make a big difference in the way you feel on your next adventure.