What is the R value?
The R value (resistance value) is a unit of measurement used to measure how effectively a carpet resists heat loss. This is the only way to know how well the rug will prevent your body heat from escaping due to the ground temperature (which can be much cooler than the air temperature).
What is an ASTM standard?
All mats with the ASTM approval mark have been tested according to the latest global standard introduced in 2020. The standard was introduced to make it easier for the buyer to compare mats, thereby reducing the risk of purchasing a mat that does not meet the expected thermal insulation effect.
Do all manufacturers test their mats to the ASTM standard?
No, carpet production is not regulated in the sense of the law and compliance with the ASTM standard is the good faith choice of each manufacturer, so (in theory and also in practice) a manufacturer can indicate on his carpet any R-value he deems appropriate. Needless to say, values are often exaggerated.
However, all leading carpet manufacturers such as Thermarest, Sea to Summit and others who care about the well-being of their customers test their carpets to this standard to ensure the highest quality for their customers.
Which R-value rug to choose for which season?
The seasonal ranges indicated on Thermarest mats are oriented within the 4-season temperate climate zone at sea level. However, the seasons are different everywhere, besides, sometimes there are frosts in the summer and the ground is frozen in the high mountains, so we recommend choosing a mat according to the guidelines of ASTM standards:
*Translation of scheme below.
CHOOSE A HIGHER R VALUE IF:
Use the R-value guide above to choose the best match for your sleeping situation, while considering the following factors. If any of these apply to you, compensate by choosing a mat with a higher R-value.
- You know that the temperature of the earth is much lower than the temperature of the air
- You are a woman (most women are more flexible than men)
- You are a light sleeper and sleep under a thicker blanket everyday
- Where you plan to stay is prone to strong, cold winds (e.g. in the mountains)
In warm weather, will a high-R-value carpet be too hot because it heats up?
A rug with a higher R-value on a hot night may not keep you cool as effectively as a rug with a lower R-value (when the ground is cooler than the air). But it also works the other way around - if the ground temperature is warmer than the air temperature, it will be cooler to sleep.
On your own carpet carries il da - it acts as a barrier between the sleeper and the ground, preventing the heat produced by body temperature from being transferred to the ground.
So is it better to choose a carpet with the highest R-value possible?
In terms of temperature, a rug with a higher R-value will always have more varied uses than a mattress with a lower R-value. But the higher the R-value, the greater the weight and volume of the mattress.
If you only hike in warm weather and never sleep in the mountains, there is no need to get a high R-value mat. If, however, you ever think of spending the night in colder weather or in the mountains, then supplement the sleeping system with another mat, for example, a roll-out mat for the inflatable one.
On the other hand, if you are afraid of freezing and you also sleep under a thick blanket in summer, it is safer to choose a mat with a higher R-value.
*Translation of the ASTM standard scheme:
WARM . Warm air and earth.
Recommended R value: 0.5 - 1
Recommended R value for men and women: 0.5 - 2
COOL . Cool temperatures in the mornings and nights. Light frosts are possible.
Recommended R value: 1 - 2.5
Recommended R-value for men and women: 2 - 3.5
COLD . Cold temperatures in the mornings and nights. Strong frosts are possible.
Recommended R value: 2.5 - 3.5
Recommended R value for men and women: 3.5 - 4.5 and above.
EXTREME . Air temperature below 0 degrees Celsius during the day and night. Cold or frozen ground.
Recommended R value: 3.5 - 4.5 and above
Recommended R value for men and women: 4.5 and above.
