Hate to say it, but a lot of this information is bogus too.My brother builds EMP-proof rooms, both for medical equipment (i.e. CAT and PET scanners), as well as for "bug-proof" rooms for the government, and he has commented several times about how difficult it is to get the room "right".
Oftentimes, a seemingly minor kink in the flashing or gaskets around the doors can completely undo the isolation of the room. They often spend considerable time scratching their heads, trying to figure out why the room doesn't perform as designed, before finally realizing that some minor detail wasn't quite right.
For what it's worth.
That is true for EMF, but this is EMP, similar but not the same.
Your room is going to get hit with broad spectrum energy.