No joke. Back in the seventies, when I converted this building from a garage to a studio, I wrapped the entire thing in space blankets, to reduce heat loss, then put foam insulation and siding over that. Inside the block walls, I installed studs and foil-backed fiberglass. It worked great. The TV heats the entire building, most of the time.
Then they invented the cell phone... ooops.
I thought about insulating with space blankets myself. In fact I do have some draped on the outside wall and floor joists to keep my water pipes from freezing.
Lol. Yeah, a cellphone wont work well in that environment. I was doing some high power testing so the faraday cage was copper mesh and it was so my laptop and cellphone wouldn’t go poof.