I worked in a large research lab, they made a single room into a Faraday cage for electron microscopy shielding.
Surprisingly to me, it was 3/8 inch thick aluminum plate. Walls floor, ceiling, all-welded. With elaborate traps on the air vents and doors, filters on power lines.$$$
And they still had complaints about worker’s machinery in nearby areas?
The foil stuff may not be effective?
I bought an EMP room 10 x10 x8 copper screened 8’by 2ft panels bolted together room with panel for wire through wall and 80# copper door army surplus from ft. Riley in 04. cheap