Radiated power drops rapidly with distance. No need to shield Romex in wall. It's too far away from the system.
The power cord, which is the last 6' of the power delivery system, seems to be an ideal place to put a tuned filter. Filtering out everything but the pure 60Hz using a power conditioner and a tuned power cord would seem to be optimal.
It seems that shielding on a power cable would keep it from radiating noise to the high impedance lines, such as the IC's. If the power has high frequency noise, it may radiate this too. Shielding is a difficult design process, however. No doubt many manufacturers just use trial and error.
Just my 2 cents (or maybe 3).
The power cord, which is the last 6' of the power delivery system, seems to be an ideal place to put a tuned filter. Filtering out everything but the pure 60Hz using a power conditioner and a tuned power cord would seem to be optimal.
It seems that shielding on a power cable would keep it from radiating noise to the high impedance lines, such as the IC's. If the power has high frequency noise, it may radiate this too. Shielding is a difficult design process, however. No doubt many manufacturers just use trial and error.
Just my 2 cents (or maybe 3).