Surely it is your landlord that doesn't include the heating in the cost of rent who should get fucked, not your neighbour, a fellow renter who for whatever reason just managed to get a better deal than you did? Perhaps they are abusing it slightly, perhaps they have good reason, like an illness, that justifies them opening their window? Either way, only one of them has any impact on you, so why are you angry at the one that has none?