Last year I had 2 cast iron radiators crack from a freeze up in the crawl space just under the part of the house where these radiators are located. It is not a large area about 100sq feet in total and not an area where a lot of time is spent. My plumber bypassed these two radiators and the rest of the house was fine through the rest of the season. Is it possible to put in some kind of baseboard heat like a slant fin in this area of the house without adding a second zone and without replacing all the other cast iron radiators? Would I be better off just putting in some electric baseboard to supplement and take the chill out of this small area when needed?