We usually only find out that our sleeping mat isn't warm enough when we're mid-trip, shivering our bits off and wishing we'd got another warm layer to pull on.
Sleeping mat R values have the potential to help us avoid cold, sleepless nights. But these numbers can be misleading, even to the most discerning of campers. Here's everything you need to know about R values and why we don't use them.
R Values are a measurement of thermal resistance – they tell you how well your sleeping mat resists heat loss. The higher the R value, the more your mat resists heat loss and the better it insulates you from the cold ground. The R value scale goes from 0.0 to 6.0 – an R value of 1.0 to 2.0 is fine for summer use but you’d need a rating of 4.0 to 5.0+ for winter camping.
We don’t currently use R values because there’s no internationally agreed standard for testing them. Each manufacturer will test for R values slightly differently which makes it very difficult to compare sleeping mat warmth between brands. Until an international standard is introduced, we reckon good, old-fashioned advice and experience is the best way to choose your sleeping mat.
Having an internationally agreed standard will make it easier to compare between mats from different companies, much in the same way we now can with EN 13537 Comfort, Limit and Extreme ratings for sleeping bags.
Without an consistent standard, brands will always choose the testing method that produces the highest R value for their mats. These test results can be mis-leading and can make it hard for us, as consumers, to choose between different manufacturers.
That’s not to say that R-values are completely unhelpful. If you’re trying to choose a camping mattress from a big range by one company (e.g. Thermarest®), the R values will still be a useful tool of comparison.
A testing standard was finally introduced in 2020 for the American market (ASTM FF3340). The bad news is that brands only have to adhere to this standard if they want to include R values on their marketing and packaging within the United States. As a result, it will continue to be difficult to compare sleeping mat warmth until an international standard is introduced.
We’re part of a working group within the European Outdoor Group (EOG) that was set up to help introduce a new international standard for R values. This standard will most likely be similar to the ASTM Standard Test Method for Thermal Resistance of Camping Mattresses. We’re eagerly awaiting its introduction as this will provide a much more accurate picture of how warm each company’s sleeping mats are.
Warmth will probably be your most important factor for deciding on a sleeping mat. Some types of sleeping mat construction are much more insulating than others. For instance, uninsulated inflatable mats will always be colder than self-inflating mats which are packed with insulating open-cell foam. Looking at the construction, depth and shape of sleeping mats should give you a good guide to how warm it will be.
Our sleeping mat range covers every eventuality from ultralight inflatable mats for summer backpacking and bikepacking, to luxuriously thick car camping mattresses. We’ve tried to make sure each mat has a particular purpose, influenced by decades of experience using sleeping mats all over the world.
There are lots of different factors that can affect whether you get a warm night’s sleep. Remember that your sleeping mat is only one part of your sleep system, along with your sleeping bag and clothing. That said, choosing a warmer mat means that your entire sleep system will be more effective when it’s time to hit the hay. Well, not hay. Don’t use hay. It gets everywhere.