To ensure that you will be warm when you sleep (especially when the ground is colder), it is essential to know how well your sleeping mat resists heat loss into the ground. This resistance is known as an R-Value.
A laboratory-tested R-value is the only way to measure resistance to heat loss. Sea to Summit has always provided independent lab-tested R-Values for its sleeping mats.
Since January 1, 2020, we are using the new industry standard ASTM F3340-18 test to provide R-Values for our mats.
In some mats, the new test protocol means changes to previously published R-Values. Where values do change, it doesn’t signify a drop or increase in warmth—it simply means they have been tested using a slightly different scale. The packaging may still carry the pre-2020 R-Value.