Ground or air temperature for pad selection?

sort of related, I have measured the temperature underneath my pad before going to sleep, and in the morning.  Maybe it’ll be 32F before and 60F in the morning.

the ground acts as an insulator

also, the ground has thermal mass so it takes a while to warm up

so, I think, the temperature of the ground matters.  The temperature of the air does not.

The insulation and thermal mass properties of the ground matter – if you’re sleeping on a slab of granite it would be colder.   If your sleeping on barkdust it would be better.  If you’re sleeping on snow the temperature will be 32F so that’s very bad, thus you need extra pad insulation if you sleep on snow.

I could be  cracking -up, but, it seems like mid winter snow sucks-out less heat from my pad (i.e., me) than spring snow that’s denser, left over from winter.

I think Jerry has it right.

I use a GG thinlight foam pad beneath my BA inflatable to protect it from punctures. It adds a tiny bit of R value. Maybe more than stated!

I rarely sleep on snow, if I can avoid it.

I wonder if Jerry might have a Freakonomics style analysis that would state that a thinlight pad actually causes me to sleep colder over the course of a night because it insulates the ground from my body heat? and so keeps it from warming up. Seriously!

Freakonomics/gearskeptic analysis

Well @Jscott, unless you are heating the ground so much you set it on fire, any heat used to warm up the ground is still lost…

yeah, I lose heat to warm the ground which is a bad thing

but, early in the night is when I’m heating up the ground.  At that time I have extra body heat so I don’t feel cold

Early in the morning is when I feel coldest.  By that time the ground has heated up so I feel less cold.

If I slept on a material that has high thermal mass and low insulation, like a slab of copper, it would conduct heat away so fast that the temperature at the bottom of the pad would never increase very much so I would feel colder

If I slept on a slab of styrofoam that has low thermal mass and high insulation, the temperature at the bottom of the pad would quickly rise to body temperature so I’d feel warmer

If I measure the temperature of the bottom of the pad, that says it all.  Easy to do – put a probe temperature sensor underneath.

Snow is a special case.  It has high insulation value and high thermal mass, depending on the density of the snow, but if the temperature tries to go above 32 F, it will start melting so the temperature stays at 32 F.  Phase change.

I recall feeling cold at night on a Gila Wilderness trip in Oct. Sleep system should have been adequate but just didn’t seem enough. The ground was frozen solid in places if I recall so that was definitely a factor.

On my second night I raked up a “bed” of heavy ponderosa pine nettles with a couple random logs on the sides to sort of hold it all in place. I felt considerably warmer.

“in fall: lighter pad, warmer quilt/bag

in spring: warmer pad, lighter bag/quilt.”

I’m thinking, in reality, a lot of conditions that can’t be taken into account in advance will come into play. Or anyway, the conditions are likely to change from night to night. For example, will you camp in an area with a lot of sun exposure or the contrary. North or south facing? Altitudes? In short, since I like to sleep well, I always bring a warm pad. And don’t heap up Ponderosa pine cones under my inflatable pad.

Luke did the right thing! I would have done the same. But those prickly ponderosa cones are a killer.

Pine needles can be nice. Please no pine cones in my bed!

If you layer your outer clothes (pants and shell) under your mattress only air temperature will matter.

Or you can put a layer of leaves under yer tent floor/ground cloth and get good insulation as well.

My double wall solo tents (Moment DW and Notch Li) heat up easily due to their small size.                       The Moment DW that I use for winter gives me at least another 10 F. of warmth.

We’re all familiar with unzipping our tent in the morning only to have cooler air greet us.

Well, I have some subjective experiences now,since I was thinking about this.

Did a back paint trip last. Lows were around 40 F I think. Ground was wet, sandy with plenty of leaves and pine needles.

Using my 40F quilt , wearing quite a bit of clothing, the pad (Neoair Uberlite) definitely felt a little cooler than the quilt on top.

So at least for me, and when using a quilt, the answer is: go warm on the pad too, for comfort if nothing else.

Did you use a foam pad under the Uberlite?

@Gary:

No. Why do you ask?