Order of floor layers for optimum thermal benefit

[Glitterknickaz]

Ok... we're doing it.
Off to Scotts Farm next week for DS2's birthday. Hope we don't freeze our arses off.

We have the following:

foil blankets
fleeces
airbeds (half airic, half not)
foam camping mats

Which order should these go in for optimal thermal insulation from the ground?
I'm thinking foil blanket, foam mat, airbed, fleece. Would anyone do it differently? If so how?

Dot hose foil blanket actually work if they are under an air bed? Don't they keep warm in as opposed to cold out?Have seen them in £ shop and thought about it as i was freezing at night last August!

I find foam camping mats on top of airbeds warmest. Never tried foil blankets.

Heat moves around through:
radiation (light rays and rest of electromagnetic spectrum travelling through vacuum/air/glass/etc)
conduction (objects touching each other)
convection (flowing currents).

Foil reduces heat transfer by being very poor at radiation, so you don't glow off all your heat like a little red ember.

OTOH, foil is very good at conduction, like most metals. If it's tightly sandwiched between objects (your warm arse and the cold, cold ground), it will merrily transfer your heat away in a twinkling.

So it's basically only any use as insulation when it's facing a space. (Although a wind-proof foil blanket would also stop drafts, ie convection.)

Have a fab time with the camping, btw! Hope the weather obliges for you.

Thanks TIANC.
Foil right at the bottom could reflect the cold back though, no?

Urgh, now you're making me think!

The easy one is, No, foil would reflect back your heat, rather than reflecting cold (cold isn't really a physics entity; it's just lack of heat, which is quite well defined).

The trickier one is that I think where its in contact with something solid, the high-conduction properties of foil usually make its low-radiation properties almost irrelevant. Which would be why Space Blanket for your loft has instructions to lay shiny side up (facing the cold emptiness of your loft).

But I've just learned from Wikipedia that thermal radiation increases to the power of 4 with temperature. So if object A is twice as hot has object B, it's giving out 16 times as much radiated heat.

This is different from conduction, where if A is twice as hot, it's just transferring twice as much heat as B.

Which would lead to the conclusion that, if you do decide to use foil, you'll get a much bigger bang for your buck if it's in the warmest part of the mattress sandwich - next to your skin! Perhaps just below the fleece would be less sweaty...

Blimey, can you tell I have Important Other Stuff I Really Should Be Doing!

It's the airbed which gets cold. Insulate yourself from it - i.e. a blanket or foam mat between the airbed and your sleeping bag. I don't think there's any point putting things under the airbed, it's a big heat sink full of cold air.

If you have an airic or foam mat you shouldn't need any other insulation, they are insulated in themselves.

OMG ThisIsANiceCage you lost me!

Or what greenlotus said.