Sleepmat Inside or Outside Sleeping Bag?

[Requiem]

I got a bit chilly on a wild camp I did a few nights ago, the ground started to frost and I felt the chill through my bag - a mate I was sharing the hilltop with suggested that he always slept with his mat INSIDE his sleeping bag as it kept him warmer?


Anyone else do this?


Roy

[gunwharfman]

Not me I keep my mat on the outside. I have to anyway, because I use a sleeping quilt and not a sleeping bag, my quilt has no back and no hood. I lie directly on my mattress (A Thermarest Neo Air), OK, I admit to using a fitted sheet!

Not knowing anything about what mat you use, but could it be that its not good enough to stop the cold come from up from the ground, through your mat, through your sleeping bag and through to your skin?

My Thermarest is so good I've never experienced this problem. For me, from ground level, I have my groundsheet, my tent bottom layer, my mattress and then my skin. If its a bit chilly I wear my baselayer, sometimes my sleep leggings and if its really cold I may put on some form of warm jacket to get me comfortably through the night.

As regards me getting cold from the ground itself, sorry never happened to me yet.

[fernman]

I don't see the logic in having the sleepmat inside the sleeping bag because you are then not getting the benefit of the insulation that is on the underside of the bag which would normally be directly under the body, while at the same time the underside of the bag is in direct contact with the groundsheet and cold ground beneath it, which is the reason a sleepmat is normally placed there.

[Requiem]

Yeah, I can see the logic now as I've tested it out on the kitchen floor - the warmth being stored in the mat seems to stay against your body and is 'held-in' by the bag around it - I might try it out in the next couple of days as I'm waiting for some clear skies before heading up to Greenside Mine above Glenridding to take some photos so might see if it works better

[NeilC]

No way would I get my mat inside a sleeping bag so can't try that out.


Warmth-wise I can see it working about as well as being outside it so worth a shot if your bag is that big/mat that small.

[Slogger]

A sleep mats function is to insulate you from the ground, not to keep you warm. Without a sleep mat the ground will attempt to bring your temperature down to its level (equalising). The insulation of your sleeping bag between you and the sleep mat is what keeps you warm. Not saying that the mat inside your bag wont keep you warm, but that's not what its designed to do and seems pointless to me. You certainly wouldn't do it when bivvying, although some do put the mats inside the bivvy bag.

[NeilC]

A sleep mats function is to insulate you from the ground, not to keep you warm. Without a sleep mat the ground will attempt to bring your temperature down to its level (equalising). The insulation of your sleeping bag between you and the sleep mat is what keeps you warm. Not saying that the mat inside your bag wont keep you warm, but that's not what its designed to do and seems pointless to me. You certainly wouldn't do it when bivvying, although some do put the mats inside the bivvy bag.

The thing is, you're not without the sleeping mat. You've got exactly the same amount of insulation from the ground - a mat and the bottom of the bag. They're just in a different order. Exactly what difference that makes is hard to guess at. Probably would also depend on the type of mat. I can imagine that it's possible that it might help with an uninsulated air mat which tend to be cold due to circulating air currents transferring heat very efficiently between the warm top and cold bottom. Maybe having the whole lot in the bag enables the air in the mat to warm up and there not be quite such a temp difference between top and bottom so less currents? It would certainly reduce heat loss from parts of the mat not normally covered by the sleeping bag, including the sides.


It's also possible that a ridged sleeping mat would not crush the bag's insulation so flat compared to a human body would so increasing it's insulation value a touch.


Or it might be worse as you're not lying on warm insulation.


I reckon it's something you'd need to try. I'm betting it makes little to no difference in comparison to something like a simple thin sheet of closed cell foam on top of the mat which definitely works.