A room perimeter heating/cooling radiator with a non symmetrical elliptical transverse cross section, that utilizes low to medium temperature heat transfer fluid (generally water or water/glycol) in a new design with an enhanced ‘primary only’ heat transfer surface having an internal spiral or helix to circulate the water around the inside of the primary surface to enhance the heat transfer, and an internal conduit that provides both freeze damage protection and the ability to cross connect multiple identical radiators for increased efficiency. The primary intended location is within inches of the building windows.