I'm heating 3400 square feet no problem. I'm intensionally heating 1700 square feet. to 73*. I'm un-intensionally heating 1700 square feet of un-insulated block basement to 68* (heat off piping). The Kaa-2 would have no problem bringing the basement up to 73*, if I had radiation in the basement. I'm not heating my DHW water yet. I'm all set up for it, but need a tank. This is a simple Primary / Secondary system.lsayre wrote:Wow, a Kaa-2 heating 3,500 sq. ft., plus providing DHW! You must have some super insulation.