If I turn on my spectrum analyzer in the bedroom and go turn on the microwave in the kitchen, It will show a wide band of energy around 2.4GHz leaking out. They leak RF, a lot of it, even on the frequency it was designed for. But it is enough to keep the majority of it in the oven, so its safe for us and wifi routers.
If an EMP was mostly 2.4GHz, the oven may attenuate the EMP enough for your gadgets to survive. But EMPs max out around 500MHz and contain a lot of power on lower frequencies the oven was not designed for. I wouldn't trust it.
Metal tape isn't a great idea ether. I used to think so and often suggested it, but I've used enough of it shielding RF projects (amplifiers, active probes, etc) to know the glue backing is surprisingly good at keeping the foil out of contact with what you stick it to. When considering the frequency content of the EMP (under 500MHz), the capacitive seal the glue makes is not enough to appear as a short circuit to the lower frequency components of the EMP.
Then there is the thickness issue. You have to block two fields, the electric field and the magnetic field. Aluminum foil will block the electric field if it is sealed up tight, but it takes physical thickness to block a magnetic field. Non-ferrous metals can block fast-moving magnetic fields with opposing eddy currents (skin effect), but thats not good for the lower frequency stuff. unless (my opinion here) it is at least a couple mm thick.
Where you live will strongly influence your susceptibility to an EMP attack as well, so there is a lot to consider when deciding how much shielding is enough. What will protect my equipment being this far north is different from what someone in Texas will need to do to protect their stuff from the same event..
If an EMP was mostly 2.4GHz, the oven may attenuate the EMP enough for your gadgets to survive. But EMPs max out around 500MHz and contain a lot of power on lower frequencies the oven was not designed for. I wouldn't trust it.
Metal tape isn't a great idea ether. I used to think so and often suggested it, but I've used enough of it shielding RF projects (amplifiers, active probes, etc) to know the glue backing is surprisingly good at keeping the foil out of contact with what you stick it to. When considering the frequency content of the EMP (under 500MHz), the capacitive seal the glue makes is not enough to appear as a short circuit to the lower frequency components of the EMP.
Then there is the thickness issue. You have to block two fields, the electric field and the magnetic field. Aluminum foil will block the electric field if it is sealed up tight, but it takes physical thickness to block a magnetic field. Non-ferrous metals can block fast-moving magnetic fields with opposing eddy currents (skin effect), but thats not good for the lower frequency stuff. unless (my opinion here) it is at least a couple mm thick.
Where you live will strongly influence your susceptibility to an EMP attack as well, so there is a lot to consider when deciding how much shielding is enough. What will protect my equipment being this far north is different from what someone in Texas will need to do to protect their stuff from the same event..