Hi all --

My Parents' house in Boston was built in 1913 and has a forced hot-water system (previously most likely steam). The first floor has several under-floor radiators that are located in asbestos-insulated duct boxes in the basement. The problem is this: These boxes are connected, via large duct work, directly to intake registers outside of the house. As the radiators heat, the rising heat pulls in fresh air from outside (convection?). The problem is, of course, that a tremendous amount of energy is required to heat the freezing cold air enough to keep the house comfortable.

It seems to me that the duct work should be reworked so that it feeds filtered return air from either the basement or main house to the radiators, thus reducing the radical temperature difference between the heated air and the intake air.

Does anyone have any experience in this area? What is commonly done to make this kind of system more efficient?

Looking forward to any assistance.