R-Value is the same for inflatable, self-inflating, and foam mattresses
As the title suggests, the R-Value is the same across all mattress types, regardless of the materials used. So, you can compare a foam mattress with an inflatable one to see which one insulates better from the ground.
However, other factors besides R-Value come into play when determining which mattress is ideal for you. We recommend checking out this buying guide on mattresses if you want to learn more and be sure you make the right choice when purchasing the one that will accompany you on your outdoor adventures.
By layering two mattresses, the R-Value can be added together
If you already have a mattress with an R-Value of 2 and you're planning a trek this winter, there are two options for keeping warm.
The first option is to buy a new mattress with better thermal insulation. This is more expensive, but you’ll have one mattress for winter and one for summer. If you buy a quality brand and take care of it, it will last you for years. The investment will be worthwhile in the long run.
The second option is to buy a second mattress with an R-Value around 2. This is less expensive but bulkier. Many hikers opt for this choice, keeping an inflatable mattress in their bag and a foam mattress folded and attached to their pack, as shown in the photo below. Then, simply layer them on the ground to achieve a total R-Value of 4.
Additionally, the second option has another advantage: the foam mattress, being more durable, will protect the inflatable mattress from any thorns or sharp objects on the ground.
It can slightly vary
Don’t worry, the variations are minimal, but they can happen for a few reasons. First, it could be due to underinflation. Losses can range from 5 to 10%. For an R-Value of 6, this could make a noticeable difference, bringing it down to 5.4.
Secondly, a mattress's R-Value naturally decreases over time due to wear and tear. Just keep in mind that not all mattresses degrade at the same rate. Again, it’s important to research the reliability of a brand before making your purchase. Sometimes, it may be worth paying a little extra for a mattress that is well-known in the outdoor community and will last longer.
Before 2020, there was no common standard
It was chaos. Each brand conducted its own tests to define the thermal insulation of their mattresses. For consumers, this meant it wasn’t a reliable indicator, and they had to rely on reviews from people who had purchased the product to get a sense of its performance.
Now, a standard has been established by the Outdoor Industry Association, in collaboration with the major manufacturers. It’s more reliable, and everyone is on the same page!
To the question, "Who tests the R-Value?", the answer is: each brand tests it with an independent laboratory. For example, Therm-a-Rest works with the Thermetrics lab. What’s important to note is that these labs are independent, and therefore reliable.
So, now you know everything there is to know about R-Value.
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