I found the perfect sized plastic storage boxes — roughly shoe box size — to fit under the kitchen sink. One has my first aid and toiletries, one has emergency candles, batteries, matches, etc — and in that pile of stuff I found three of those dollar-tree, aluminum-foil-looking emergency blankets, still in their little wallet-sized packages.
I put one in the box and set two aside. Later, I found an old flat sheet nobody uses (we are duvet people) and laid out the emergency blanket on top of it. I rolled up all four sides in a makeshift hem and used staples (friend Joe calls them “Man stitches”) to “sew” the hems. I rolled the whole thing up and put a rubber band around it, and will see if it is a suitable replacement for the popular but expensive reflective covers sold to top the bed-end canvas roofs on a pop up. http://www.popupgizmos.com/bunkcoverpage.htm
Updates when I camp in an unshaded spot. They are supposed to lower the inside temp by a considerable amount. I thought about sewing them together in crosswise strips like a quilt but I suspect the thin reflective stuff would tear. So we’ll see.