To the architects’ surprise, the original radiant heated floors that were run by a single-zone system were still working throughout the year they lived in the house prior to the renovation. However, since they were more than 60 years old, Jay and Melissa abandoned the old system and installed a new radiant heating system with thermal mass polished concrete floors.  Photo 4 of 11 in A Year of Careful Study Leads to a Thoughtful Renovation of a 1949 Eichler