First, I want to say up front that I'm not a huge fan of using this product for sleeping insulation. I know that it can provide some benefit if it is used properly but, to me, it's just not worth the bother.

How does it work?

Shiny surfaces are poor at radiating or absorbing heat. What they excel at is reflecting heat, as long as the shiny surface is not in direct contact with the heat source. That's why Reflectix has that bubble wrap - like aspect to it. The shiny side needs to be on the side away from the heat source so that the air space provided by the structure can do its job.

BUT, when the heat source is a human body which perspires, you don't want the heat source (your body) to be in direct contact with the transparent side either. There needs to be something between you and the Reflectix that will wick the moisture away. (The same thing goes for a sleeping pad.) Othereise, things are going to get damp in a big hurry.

So, if you decide to use it, make the best use of its characteristics.