<p style=”text-align: left;”>Recently I was winter camping in southern Nevada’s Spring mountains. My buddy was using my older Thermarest 5R rated self-inflating mattress.</p>
I was using an REI clone of a Sea to Summit winter mattress. As we were drifting off to sleep it occurred to me that yeah, the down beneath me was composed and insultaing me less – EXCEPT the spaces between the mattresses’ tufts. Those spaces let my bag’s down remain thicker, thus more insulating than flat pad. Hmmmm, seems mattress design does make some difference warmth.

