If they are good enough for athletes...
 

Could foil space blankets be used to insulate your home?

If they reflect radiated heat, could they be installed as a lining to your loft, or behind radiators.

Going by this link, they are reasonably inexpensive per sqm.

Just one of my strange thoughts...

There is already insulation out there that uses a reflective layer. What is really needed is a way to apply it to the roof to decrease solar load...

Something like the reflective white roof paint?
There is also a reflective insulating paint that is Nano-something paint that reflects radiant heat and insulates at the same time.
I use reflectex insulation, it's basically bubble wrap made out of silver plastic like the space blankets are made out of, only the bubble wrap part creates air gaps that slow heat transfer as well, it comes in 50 foot rolls that are 12" wide, 16" 24" or 4 feet wide with tabs for stapling, they also make hot water heater blankets and pipe insulation rolls.

I used the foil space blankets on top of the canvas part of the roof of our pop-up camper when we were in open areas. It reduced the inside temp as much as 10-15 degrees.