Which way up?

[Red Rock]

I've just bought a cheap (99p on e-Bay) reflective mat, to go under my self inflating sleeping mat. It's light foam and only a couple of mm thick, but one side is reflective foil.

Which way should the silver side face to provide the best thermal insulation? Towards me, or towards the ground?

[LittleSkink]

guessing that the reflective side is for radiant energy shiny side up possibly makes most sense but I suspect it wont make a lot of difference and shiny side down would be more aesthetically pleasing, maybe

curious to know why you need anything under your self inflater, they are usually good insulators anyhow so a couple of mm of foam wont do much, other than make floor of the tent warmer maybe