Joe wrote:
"I know there is a term for a room like this but I can not remember
it..''

The term that comes to mind for me is "screened room".

I`ve used them in shortwave broadcasting stations where they provided
excellent isolation. They were constructed of ordinary copper
windowscreen wire which solders well for good continuity. Sometimes the
rooms were double screened with wire on both sides of the supporting
structure. You`ve already been given the caveats on joints and bypassing
every conductor which punctures the structure. That`s necessary.

Best regards, Richard Harrison, KB5WZI