Originally Posted by DivaB
No...not a good idea. It's a vapor barrier and to work right it needs to be right next to you. If you want to keep the wind from robbing your heat, try a sock, or undercover.
It's not *just* a vapor barrier it's a radiant heat barrier. In physics there are three majorly studied methods of heat transfer Convection, Conduction, and Radiation. Dead air space and insulation help in Convection and Conduction exclusively. As each of these three methods are generally approximately equal in rate of heat transfer adding a reflective surface in your arsenal could increase your comfort level significantly. As a radiant heat barrier it is possible that one of those survival blankets or some reflectix on the underside of your tarp might even have a significant effect (you would be reflecting all the heat radiating off your body back down towards yourself).