There is another source that I found that is really useful, where a padded blanket or 'moving blanket' is attached to a radiant heat blanket, and this has advantages in that it maintains the heat in the room by adding extra insulation.
Radiant Reflective material reflects up to 97% of the radiant heat. Blanket padding provides up to 1/2 inch thickness which is sufficient for the radiant heat reflecting fabric to work. The blankets are also pretty good for outdoors, being windproof and washable. The company that offers them claim they can also stitch them into specialty heat reflective covers. They run about $10 each for a 58 x 58 inch blanket, and the place I found them is a website called Moverssupplies.com
