200 liters of air weighs about 240 grams and heats up about as fast as 240 grams of sleeping bag, or 240 grams of yoga mat, I mean in a short time.
It was reported that the air never heated up much though. Well that was because the air was moving around and dumping heat into the ground, as still air is one of the best insulators.
If a bony person lays ...
Your friend isn't thinking clearly. Imagine they had asked the question:
On a cold night, is sleeping naked and unprotected better than sleeping in a sleeping bag?
Everyone intuitively knows that you will be far warmer inside a nice, lofted sleeping bag. The insulation retains your body-heat and prevents the cold air outside from reaching your skin to ...
Happened to see this and had to register just to reply because I have first hand info. I was fixing up an old mobile home and had removed the skirting and slept on a air mattress in a room with a wood stove. I thought it would be ok but since the floor was the outside temp the air mattress became ice cold. The air in the air mattress just gets colder and ...
Some more factors here:
1) Even if the air in the air mattress was the same temperature as the outside air it has much less thermal capacity and thus will take your heat away slower.
2) An air mattress will spread the pressure more evenly--your sleeping bag won't be as compressed at pressure points and thus heat will escape from them slower.
Effectively, it isn't much better to sleep on an air mattress that isn't specifically made to insulate from the ground than on the ground itself although it does make a slight difference.
The main takeaway is that you should always avoid sleeping directly on the ground so even a poorly insulated air mattress will be better than nothing.
Your friend isn't ...
There is an old adage
One blanket underneath is worth two on top.
but I can find little support for this idea except a mention on mumsnet.
The reasoning is, that the floor or the ground underneath is solid, and has a much higher thermal capacity than the air above, and so will draw a lot of heat away from your body. It's not just the temperature of the ...