On 2008-03-30, CJT wrote:

You want to keep one side that adjoins free air clean. I don't think
it really matters whether it's the shiny side or not.

Yes, it need to be the shiny side. A radiant barrier is a shiny
surface with an air gap next to it (so there is no conduction). If
the shiny surface gets dusty, then you no longer have a radiant
barrier.

Cheers, Wayne