Well I'm not an expert, but my son has been doing this for quite some time. If you can install all new raidiant that would be your best move. You already have the main heat sorce, I'm assuming a boiler of some sort. To put it in your floor would cost you a ton in NY. People don't realize the aftermath of all that in floor heating. You mite ask about a sub floor with the in floor heating, but to mess with cement would be costly. Actually, putting in a new gas unit would be your best bet. They are cleaner, and so much more efficent. You could zone it also but it would require duct work, but with the new venting system they can run the up inbetween the walls now. They are amazing. My son has been trying to make me do it for a long time, but we have fuel fired hot water, so the cost would not be any savings on my part. Maybe this helps.......good luck...
