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Sleeping pads - summer and winter
Why | History | Now | Selection | Open vs Closed cell | Practical Results | R-value | Use | Pack fitting | Care | Repair | Summary | Car camping
Why use sleeping pads...
Sleeping pads are used for comfort and protection. They provide insulation to protect you from the ground which might otherwise be prohibitively and dangerously cold and they provide the cushioning that many of us need in order to get a good night's sleep.
Sleeping bags do not provide any cushioning or insulation below our bodies. The weight of our bodies fully compresses all the insulation that ends up below us in the bag, whether down or synthetic.
A bit of history...
Historically, backpackers didn't carry sleeping pads. When they got to where they were going to spend the night, they would cut a few soft pine boughs off trees and use those to provide a buffer between them and the hard, cold ground, or the rough "bats" that were traditionally used to construct the flooring in some trail shelters.
This was fine when there were very long stretches of trail being used by very few people. Now, with millions of users on trails like the Appalachian Trail every year, this method is environmentally unsound.
There are two primary types of sleeping pads used by backpackers today. Closed cell foam pads and self-inflating open cell foam pads. Examples of closed cell foam pads are Z-Rests, Ridge Rests, and those generic "blue" pads. Therm-a-Rest is the most commonly seen brand of self-inflating open cell foam pads though there are other manufacturers of similar technology. Brands such as Big Agnes have made inroads into sleeping pad technology with lightweight air mattresses that have little insulative qualities and must be blown up, but reduce pack weight and bulk significantly. Down air mattresses are also making inroads. These insulative pads use down rather than foam for insulation.
How to select a pad...
Different types of sleeping pads are appropriate for different kinds of sleep environments and sleep habits.
In very warm weather, the sleeping pads are purely to give your body padding. In cold weather, the pads insulate your body from the cold ground or snow.
For most three season use, you do not need to worry about the cold ground. You just have to worry about your physical comfort. As such, if you are a back sleeper you can likely get away with much less padding than if you are a side sleeper. Curvy women, especially side sleepers, tend to need more padding to cushion their more prominent pressure points.
For cold weather winter and snow use, you must insulate yourself from the ground. Otherwise, the cold ground will pull warmth from your body and require you to use a lot more energy to get through the night. This could also lead to a very cold and uncomfortable night with little restoring sleep.
Insulative qualities of open-cell vs. closed cell pads...
Closed cell foam pads will hold a lot more of your body heat closer to your body than open cell foam pads. As you are sleeping on a closed cell foam pad, your body heats the air inside the cells near your body. When you move, the trapped air stays where it is so your body does not have to reheat those cells each time you move.
With open cell foam pads, your body heats the cells near you body, but when you move, the air in the pad moves around and the warmer air may be pushed out of the area where your body is warming the pad allowing cold air to move in again. You then have to use precious calories to reheat the pad.
Doing this over and over again during the course of the night can mean a lot of calories and a cold night's sleep.
When winter camping on snow, it can be interesting to see the difference in the snow under your tent after you've had two people on different systems sleeping there. A couple of foam pads, and there's likely to still be snow under the area with the pads. Under an open cell pad like a Therm-a-Rest, you are more likely to find ice where the snow melted and refroze. Brr!
Or, you can camp with one of each... a closed cell for thermal efficiency and a Therm-a-Rest for comfort. :-) If you do this, remember to keep the closed cell foam pad on top. That's the pad that will prevent the loss of heat better.
Many manufacturers of sleeping pads will list the Thermal resistance (R-values) of their sleeping pads. At first glance, the self-inflating pads seem to be better or competitive with the closed cell foam pads. But, if you take into account the thickness and weight of the pads, the closed-cell pads are much more insulative.
If you compare two closed cell pads which each have a lower R-value than a Therm-a-Rest but together weigh the same as a Therm-a-Rest, the R-values are additive and then give the close cell foam pads an insulative boost over the Therm-a-Rests. For example, the 16 oz. Z-Rest has a 2.2 R-value and the 2 lb 5 oz LE Therm-a-Rest has an R-value of 4.1. Two Z-Rests would weigh less than one LE but given the additive R-values, the insulative capabilities are better.
Of course, this assumes you do not negate any R-value affects by using two pads. For example, when using two "egg crate" Z-Rests, do you lose insulative capability if the pad nests? Or do you gain if you can keep it from nesting?
This also doesn't take into account the compressability of the material.
I'm no scientist but if you want more information on thermal resistance, I'm sure you can find a good web site out there.
Closed cell foam pads are ready to use as soon as you unroll or unfold them. This makes them great for lounging at lunch stops. I recommend carrying them on the outside of your pack if they aren't being used as primary structural support in your pack.
Therm-a-Rests take longer to prepare to use. Generally, they aren't as useful for quick lunch stops. You need to give them time to self inflate. Get to camp, set up your tent if necessary and pull out the Therm-a-Rest and allow it to inflate while you perform all of your other camp chores. By the time you've gotten your water and started your dinner, it will probably be as fully inflated as it will get. Some people add a couple of puffs of air to make a firmer mattress.
If you ever intend to use a self-inflating pad in winter conditions, you should avoid ever blowing the moist humid air from your lungs into the pad. That moisture can freeze, prevent the pad from inflating, damage the pad, and reduce the insulative qualities of the pad.
Air mattresses require you to blow them up. They usually take a couple of minutes to inflate.
Down air mattresses require inflation but by a sort of bellows mechanism. Introducing the moisture from your breath would quickly reduce the effectiveness of the down. Manufacturers usually provide an appropriate mechanism, usually in the form of a valved stuff sack of a sort.
Frameless backpacks are often designed to make use of 3/4 length closed cell foam sleeping pads as their primary pack stiffener. If you are using a pad that is too bulky to fit in the pack, you may be able to cut off enough to form the "frame" to put inside your pack and carry the rest on the outside of the pack. When going to sleep, if the two sections don't stay in place without help, rig a velcro (or perhaps duct tape) connector to hold them together while you're sleeping.
I've also found that inflatable pads can perform the same function inside the pack. Just fold them to the right size rather than roll them. Should there be extra space in the pack, it's possible to blow some air into the pad after the pack is loaded to help the pad stiffen the pack.
Because inflatable pads can be punctured, you must take more care when packing and using them. Clear away all materials which could puncture the pad or avoid using it except in your tent or the shelter. Also, keep dirt away from the valve. A speck of dirt that can keep the valve from closing properly can mean the pad can no longer hold any air.
Open cell foam pads should always be stored uncompressed and in a self inflated state. Air mattresses without open cell foam can be stored deflated and ready to pack for your next trip.
Closed cell foam pads require no special care. They can, however, get beat up and torn if carried through brush on the outside of your pack.
Repair kits are necessary in case you puncture your pad and need to repair it en route. If you can sleep on a deflated pad until your next town stop, just bounce the repair kit along.
Large holes are often easy to find and repair. Just inflate the pad and listen and feel for the escaping air.
Smaller holes can be much more difficult to find.
I had a BA Air Core pad (the one without the insulation) with a slow leak for a long time. It was so slow, that I had a hard time convincing myself at first that it really was leaking (temperature and barometric pressure can also play havoc with how firm the pad stays overnight). But it eventually worsened to the point that I would have to give it at least one good puff in the middle of the night to reinflate it enough to sleep.
I finally used the soapy water method to find the leak. Stir some dish soap into water (you don't want too many suds), and then paint it onto the fully inflated pad. The air trying to escape will cause the suds to bubble at the leak. (It was awkward, but I managed all this in my tub - then used the shower to rinse it all off.)
My pad was leaking from where the surface cloth of the pad was attached to the plastiky part surrounding the valve stem and was obviously a manufacturing defect, and not a puncture hole. I tried to patch the area but the patch didn't take as it was too close to the edge of the pad. The manufacturer replaced the pad.
If you are looking for a pad for most three season conditions, such as those you might find on an AT thruhike, get the lightest pad you can find on which you can sleep well. For many people, a 3/4 length Ridge Rest or Z-Rest is enough. For others, a full-length Therm-a-Rest LE is the minimum to allow a good night's sleep. Try to borrow a couple of different types for short outings so you can make an informed decision.
Do not be too surprised if your needs change during a long distance hike. Some people lose enough weight and can later get by with less padding. Others lose weight and end up with more protruding bones which need more padding. Some may think they need more padding until they look at the pad they started with and realized that it has become totally compressed during the months they've been hiking. In that case, just replacing the pad with another of the same may work wonders for a good night's sleep.
For true winter hiking, a couple of closed cell pads offer the most insulation but one of each type of pad can offer the most comfort for those who need the padding.
Don't be afraid to get creative. I now use an air mattress for padding with a thin closed cell foam pad on top for insulation. It still weighs less than my Therm-a-rest but allows me to bring the combination out on much colder nights than would otherwise be allowed by either pad alone.
My closed cell foam pad is an 5mm thick Evazote pad from MEC. They sells Evazote pads in a variety of thicknesses for those relying solely on the Evazote pads for sleeping. Evazote pads can also be trimmed if necessary. The MEC web pages also include the R-value for each pad.
Car camping addendum
The popularity of air mattresses has blossomed in recent years and many car campers bring full sized air mattresses rather than sleep on backpacking pads while car camping. When doing so, you must consider that an air bed is a very large open cell pad. With their large volume, they will easily take on the temperature of the air around them, not to mention the temperature of the ground underneath you (which may be warmer than the air at night) as well as disperse any of your body heat that transfers into the air bed.
If it's cold (or even cool), you'll probably want as much insulation below you as above, keeping in mind what's below you may will be compressed under your body weight. An extra blanket and comforter may be enough if it doesn't get too cold. Put them on top of the bed. If it gets cold, you may need a closed-cell foam pad on top of the air mattress to better trap your body heat next to your body.
Last updated, December 6, 2006.
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