Types of Sleeping Pad Construction
Backpacking sleeping pads come in three different flavors. There are closed-cell foam, which is pretty "old school", self-inflating which is also relatively old school, and air construction, which seems to have almost completely taken over the sleeping pad market. Each of these pad designs has specific areas where they perform better than the other types, and in some cases, these pads can be used in conjunction with each other.
These products use an open-celled foam (like a sponge) sandwiched between two pieces of fabric. When the valve is open, the foam expands and inflates the pad. The foam also traps air and retains heat. It usually takes around five minutes for a new pad, but old ones with compressed foam will take longer and take more breathes from you. Keep in mind that "self-inflating" is a bit of a misnomer, as all these pads need a breath or two to reach their desired firmness. Most ultralight enthusiasts eschew the convenience of the self-inflation for the weight savings of an air constructed pad. It's best to store this type of pad semi-inflated and not compressed to extend the life of the foam.
Cons: Less durable than foam, less comfortable than air construction, can be fairly bulky
Closed Cell Foam
Closed-cell foam pads are probably what the general public thinks of when you say you're going camping. These classic camping mats are nowhere near as comfortable as inflatable air construction pads for some obvious reasons. They are constructed of a thin layer of foam, often with heat reflective material to add additional insulation. One huge advantage closed-cell foam pads have is the overall durability. Since there is no vulnerable air chamber, these pads can be abused without risk of popping and leaving you with no padding. These pads are generally very light and are a perfect solution to add additional insulation to an inflatable sleeping pad.
Cons: Bulky, uncomfortable, often difficult to brush off snow and dirt
"Air Construction" sleeping pads have taken over the backpacking pad market. There are hundreds of different models on the market fitting this description. These pads are generally plush, light, and span a vast range of insulation levels from those capable of insulating you from snow underneath to those appropriate for summer camping. While many of us remember sleepless nights out camping in the early 90s on closed-cell foam pads, now we can actually get some sleep in the great outdoors. At their core, Air Construction pads are thin laminated fabrics filled with air giving the user variability in pad firmness and much-needed loft above the hard ground and debris that previously caused some long nights.
Cons: Not as durable as foam, often take a while to set up, sometimes feel bouncy
Prioritizing Your Needs
There are a mind-boggling number of pads out there today, and having a general idea of what your priorities are will help sort through the majority of pads. Our Best Backpacking Sleeping Pads article breaks down each of the attributes represented by sleeping pads and which pads top each category. If we had to sum up the options into brief categories, it would be overall comfort, weight/packed size, durability, ease of inflation, and insulation provided. Ultimately all pads have some combination of these, and knowing your targeted climate and activity will help you zero in on which has the right combination for you.
In addition to warmth, comfort is probably the biggest reason to buy a sleeping pad. If you camp exclusively in warm climates, comfort is the only reason to buy one. We think that pads with smooth surfaces are more comfortable than those with deep baffles. Pads that are two inches thick are nice because they make sleeping on uneven ground less problematic. Deep in the backcountry, we like to have a pad that can turn a pile of pine cones or grass clumps into a cloud-like mattress. Our testers found that self-inflating pads typically felt more stable than air construction pads but often didn't provide as much cushion. Overall, we think that air construction pads are the more comfortable of the two until you start comparing them to The Best Car Camping Mattress.
Weight & Packed Size
The further you plan to hike in a day, the more important the issue of weight becomes. Consider for a moment that you're working out at the gym. If you're only doing five reps, adding five pounds of weight might not be that big a deal. But if you're going for 50 reps, that five-pound increase makes a major difference. Reducing weight is important if you plan on pushing yourself to your limits. That said, not everyone will place the same importance on weight reduction. Comfort, warmth, and price are much more important metrics for many casual outdoor enthusiasts. Reducing weight almost always comes at the expense of one or more of these three things. Figuring out what is most important to you will help you make the best choice.
A small packed size helps you use the smallest backpacking backpack possible. This reduces weight and lets you carry a less bulky (and therefore more mobile) backpack. The Thermarest Neoair Uberlite and Sea to Summit UltraLightare two of the most packable pads we tested, stuffing down to around the size of a coke can. Again, keep in mind that smaller packed size can come at the expense of warmth and comfort. For example, the self-inflating Exped MegaMat Lite 12 is one of the bulkiest pads we tested, but it is very comfortable. Closed-cell foam pads don't compress as much as inflatable pads, but their supreme durability allows them to be lashed to the outside of your pack without having to worry. While they are physically quite bulky, CCF pads don't take up any internal volume; in this way, foam pads could be considered the most space-efficient pads available if you don't mind having them strapped on the outside of your pack. The biggest downsides to placing your pad outside your pack occur when bushwhacking through dense vegetation, scrambling through chimneys, or hauling your backpack up short sections of rock.
In cold climates, warmth is the most important reason to bring a sleeping pad along. You must realize that your pad is just one integral component of a much broader sleep system designed to keep you alive and warm. Understanding this is critical to tailoring your set-up to be as lightweight and as warm as possible. First, think about what kind of shelter you'll sleep in the most. A double-walled tent or properly made snow cave is vastly warmer than an open bivy or ultralight shelter. Moving past your shelter choice, the next two things responsible for keeping you warm and comfortable at night are your sleeping pad and backpacking sleeping bag. Often people blame their sleeping bags for cold, sleepless nights when their pad was actually to blame! Obviously, you need a good sleeping bag to have a chance at staying warm, but don't think for a second that your pad isn't just as important - the ground can zap your heat faster than the air above you.
Further, you should think about what surfaces you're likely to sleep on (ice, dirt, snow, rock), what the ambient temperatures are, how much of your body will be contacting your sleeping mat (side sleeper or back sleeper), and how inflated your pad is (e.g., firmness vs. softness). If you frequent cold environments, you should buy a pad with as high an R-value as possible. Pads with low R-values combat frigid environments with ease when supplemented with cheap, closed-cell foam pads. For many people, the two pad combo is a great option because it is usually cheaper than a high R-value pad and will be lighter in the summer when the foam pad is unnecessary.
Before we start jumping into some of the physics behind sleeping pads, we need to first remember that cold is nothing more than the absence of heat and that heat involves the transfer of energy from warmer objects to colder objects. Got it? Great! Now let's move on to three of the primary ways we lose heat when we're sleeping: conduction, convection, and radiation. In case you don't remember thermodynamics from school, know that heat transfer via conduction has to do with you touching something colder (ex: touching metal in the snow). Convection has to do with a fluid or gas moving over you (ex: getting chilled from the wind). Radiation is heat transferred via electromagnetic waves to objects around you. The temperature difference between you and your surroundings dictates how much heat you lose by radiation. At temperatures below -20º F, heat loss through radiation becomes significant.
Most manufacturers give their pads a number called an R-value that relates to how well the pads resist the flow of heat. The higher the R-value, the warmer the pad will feel. The equation is linear, meaning that a pad with an R-value of 3 is three times better at resisting heat loss than a pad with an R-value of 1. Right about at this point in our ramblings on sleeping pad insulation, we previously would have complained about the lack of industry standardization with R-values and would have said take the company provided values with a grain of salt. Perhaps the one good thing to come from 2020 was the adoption of ASTM (American Society for Testing and Materials) F3340-18 standardized R-Values! (Insert applause emoji here). What this means is across the outdoor industry, pads with R-values listed and reference being tested via ASTM methods will be extremely similar to others with the same value.
According to an experiment performed by Backpacking Light, the level of inflation significantly affects the real world R-value of a sleeping pad. Simply, the more air you have in the pad, the warmer it is. This also means you'll be sleeping on a very firm mat, which many people will find uncomfortable.
An often overlooked component of staying warm while sleeping out is what surfaces are best for heat retention. If your choice is between snow and rock, it's better to sleep on snow. Most of that snow is air, which is a great insulator, whereas rock is incredibly good at transferring that warmth in a hurry. As a general rule, if overnight temps have been below freezing, it is likely better to bivy on snow than rock. No matter what season, if pine boughs or soft leaf litter is an option, these soft surfaces can yield comfortable and warm places to sleep.
Supplementing an Air Mattress with a Foam Pad
Throughout this review, there are mentions of using the Z Lite SOL as an adjuvant to other pads to boost R-Value. We have found this to be an extremely functional way to not only add extra puncture resistance and versatility to our sleep system but it does add a significant boost to our overall warmth. Utilizing this method also equips you with two separate pads that can be used individually for ultralight missions or warmer days when the boosted R-Value isn't needed.
At the end of the day, our experience has taught us a few simple rules of thumb when it comes to choosing a sleeping pad for warmth. First, you need to think of your pad as part of your sleeping system. If you skimp on your pad's warmth, you should use a warmer sleeping bag and vice versa. Second, we have found that pads with R-values between 2.0 and 3.0 generally work well for three-season use but should be supplemented with a foam pad for use in the winter, where an R-value of around 5 or above is ideal. Pads with R-values lower than 2 are great for summer, but you may want to supplement them with a closed-cell foam pad on colder nights in the spring and fall. Third, know how your own body works! If you know you're a cold sleeper, do yourself a favor and opt for a warmer sleeping pad.
No surprise, self-inflating mats are the easiest to inflate; they are filled with open-celled foam that does most of the work for you. After letting the pad sit for a few minutes, you'll just need to top it off with a couple of puffs.
Air construction sleeping pads are a mixed bag when it comes to how easy or difficult they are to inflate. While some have included pump bags, which often makes inflation super easy, others don't and require some serious lung labor. When looking at sleeping pads, don't dismiss the usefulness of a quality pump bag. The Exped Schnozzel, for example, is compatible with many sleeping pads and makes filling quick and straightforward. Pump bags also eliminate the moisture buildup inside air pads, which can eventually cause mildew or mold growth.
The advent of air construction sleeping pads brought with it a significant concern. The overall durability of these air-filled pads is critical, as is your technical ability to patch them in a pinch. All pads we tested came equipped with a little patch kit, and most pads came with a warranty, something worth looking into before making a purchase. As a general rule, the thicker materials comprising the laminated shell measured in "denier" with a higher number indicating thicker/more dense material. The highest denier we have seen in backpacking sleeping pads is around 75D and 15D being the thinnest.
Hopefully, we've demystified the saturated product market of sleeping pads enough to help you on your quest to find the right product. Whether you're looking for a pad that expertly balances all of the aforementioned attributes into a tidy package or perhaps are looking for the absolutely lightest and smallest package out there, numerous options will make your next adventure memorable; in a good way.