If you make landlords pay for the heat and a/c they'll insulate their properties, but their renters will leave the heat and a/c on. If you make renters pay for the heat and a/c, landlords won't insulate. So, make renters pay 50% and landlords pay the other 50%, by law.
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make renters pay for heat and a/c and they'll prioritize insulated properties
Simpler solutions are better and this is simpler, but, Rational Walk, how many years do you think that rental property has gone uninsulated? It doesn't seem to work.