If my (granted, very limited and anecdotal) experience is anything to go by, rather than TEMPESTifying a whole building, one rather hardens specific rooms or areas inside it.

Oh, and in those rooms bringing your own stuff from the outside is not encouraged - to the extent that I was asked to leave my disposable coffee cup outside on one occasion.

Didn’t matter much - there was an approved and vetted Moccamaster inside.