The electric and magnetic components of far field EMR and shielding thereof
It depends on the frequency, and the thickness of your electric shield.  You need to have several skin-depths thickness of shield.

The skin depth in copper is around 1cm for mains frequency, and 10\$\mu\$m at 50MHz. It varies with the square root of frequency.

So the normal thickness of copper foil on a PCB, 35\$\mu\$m, is thick enough for VHF (100MHz) and higher, marginal at HF (3-30MHz) at RF, and far too thin at mains frequency.