I live in an upper duplex. The house is so hot because the radiators are burning hot. :( I understand heat rises. The downstairs tenent is a senior, and she is always cold and tells me that her house is always feeling cold.
A plumber suggested that I take aluminum foil and tape it onto the outside of the
Radiators entirely, to cover the little slots. I have followed his instructions, but, I am still finding it extremely hot. (the system has water in the radiators, and was changed from a furnace to electric heating, but using the same radiators)

Does covering the radiators with aluminum foil really supposed to make the room less hot? I would greatly appreciate any explanations, i.e. if it is supposed to become less hot... how does this work? Where does the heat go?

Also, are there any other solutions? Thanks.

If these are cast iron radiators, the foil won't do much. If the radiation is copper tube with fins on it, wrapping the fins with foil will certainly cut down on the heat.