Question about sleeping pad R-values after a cold night at Lost Creek

I camped at Lost Creek in Colorado last weekend and the temp dropped to 28F. My sleeping pad has an R-value of 3.5 and I thought that would be fine for almost any three season trip. But I woke up at 3am shivering and my back was ice cold against the ground. When I got home I looked up the ASTM standard for R-value testing and found out they test pads at around 70F in a lab. That means the real world insulation can be way different depending on the ground temp and your body heat. I read on a gear blog that you basically need an R-value of 5 or higher for temps below freezing. Has anyone else had this happen with a pad that was supposed to be warm enough?

2 comments

2 Comments

abby_palmer1mo agoMost Upvoted

Lost Creek is pretty exposed too, wind chill off that valley can make it feel colder than 28. I've been in similar spots where my 3.5 pad felt fine at 32 but totally useless at 28, and honestly I think a lot of it comes down to how much you toss and turn plus what your base layers are like. That whole thing about ASTM testing at 70F is good to know but it's not like the pad magically stops working, the ground just sucks the heat out faster when it's colder. A 3.5 is still plenty for most summer nights, I'd just layer a closed cell foam pad under it for those borderline freezing trips and save the money on a high R-value upgrade unless you're planning to push deep into shoulder season.

wesleyburns1mo ago

Really feel you on this one. I had a similar rude awakening a few years back on a trip that was supposed to hit 30 but dropped to 25 overnight. My 3.5 pad just wasn't cutting it, woke up with that cold seeping through my shoulders and hips. It's wild how much of a difference just a few degrees makes, especially with wind exposure. You're spot on about the closed cell foam trick too, that's probably the most practical solution for most folks without dropping a ton of cash. The ASTM thing is good info to have in your back pocket but real world conditions are just way more complicated than a lab test. Solid advice all around.