I wanted to share some thoughts on this.
I've experimented with various concepts for blocking emf, as I am electrosensitive (or I've learned how to notice the subtle effects). EFs are the easiest to block, and perhaps are the most ubiquitous in homes with lots of electric powered devices and appliances. Dependent on the voltage of the field (which is directly related to how much power is running through the device/wire/apparatus) there are increasingly noticeable biological effects (in my experience at least) ranging from induced fatigue to general localized discomfort particularly in the abdomen to prickling of the skin to impedance of linear thought processes.
A box lined with copper mesh which is then grounded will eliminate these. I've found it necessary as well to wrap the power carrying wires in the mesh to negate the fields that build around the wire, ensuring the mesh is connected to the grounded box. Cycling between exposure to the fields directly and then when they're blocked helped me to learn the feel of the difference, as well as measurements utilizing the grounded multimeter 'human capacitor' technique and a professional emf detector.
Some devices I've found to be the worst offenders are fans, lamps, power bricks, surge protectors. Surge protectors
Wired computer networks can be disastrous emf-wise if not grounded as the eth cables tend to move voltage around when connected to powered devices like routers and computers. The solution to this is the use of shielded cat6 eth cables with metal ends on the plugs, onto which a copper wire can be wound tightly and grounded, eliminating the voltage potential of the entire wire and reducing that of the devices.
I've experimented with growing plants in proximity to EFs, and although they grow and aren't impeded as much as wifi proximate plants, there are clearly noticeable differences in terms of leaf warping and flowering stoppage. Ive only tested with morning glories and peppers so far though.
MFs are a different animal, but thankfully generally seem harder to be exposed to. I've noted them to typically exist around motors, like in fans. Distance is best for these, as there's no easy way to block them outside of some metal apparatus which can divert the fields.
I've also suspected that various metal concentrations in the body will be effected by fields as well as nervous signals, but I haven't personally experimented with this more complicated area. Probably best to ensure limited exposure to fields, good detox of 'bad' metals.