My house has hot water heating with in-wall cast iron radiators. The boiler is probably 50 years old although expansion tank and some other parts have been replaced some time ago. I am planning to install central air with duct work. Does it make sense to install hot air system along with ac and get rid of hot water heating? How much extra would I pay to install hot air along with ac? Also, comfort wise and monthly bills, does it make since to get rid of hot water system?