I am looking for some advice from the radiant gurus for a project on Long Island. I am looking at a geo retrofit project where client has a total of 4 existing zones of heat/ac. Currently heats with oil. Second story is 4-ton AC and hot water coil for forced hot air (we plan a split geo system here). Basement is a 1.5 ton AC system with hot water coil for heat. Getting a line set to the basement air handler will not be possible, so homeowner is looking to keep that system (and run the coil with hot water from geo??). First floor has two zones existing. One area is heated with radiant (existing ac load is 2.5 tons for this zone) and the second area on the first floor is heated with hot water coil / air (planning a package unit here). My big conern here is the radiant and providing hot water to the basement hot water coil. There are no design documents available for the radiant so we don't know tubing layout / spacing. It is my understanding that geo-radiants systems typically run at lower temps and may require tighter spacing between the tubing. Can we successfully retrofit the radiant with geo running at lower temps or will we need to have high temp system to match existing? At this point we are just trying to determine if the retrofit is reasonable and establish a back of the napkin budget for homeowner to consider. Also, if anyone is looking to team on this, I would be open to that also.