There's no one answer on that, unfortunately.
The most powerful pulse from an EMP blast in the ionosphere, the E3 pulse, has a wavelength so long that only devices connected to the mains (wall socket) will be affected. The E1 and E2 pulses have lengths (and therefore frequencies) that depend on the design of the bomb, and the blast's distance from the active Compton effect layer. The altitude of the various layers changes based on the time of day (which is why you can hear distant AM stations at night, but not during the day).
I'd be pretty comfortable with copper or brass mesh with 10 wires or more to the inch.
You have to shield the solar panel's power cable, too, or it becomes an antenna. GROUND IT AT ONLY ONE END, not both.
You seem to have a good degree of knowledge but just to be certain:
You do understand that the wire shielding is very short of what is used for critical equipment. That is generally done with six sided solid steel plate that has been continously welded pin-hole free with wave-guide and baffles at every single penetration.
MUCH THANKS.
GREATLY APPRECIATED.
GOD BE WITH YOU AND THOSE YOU LOVE.