Questionable radiant heat installation
 

My wife and I are looking at making an offer on a house that has radiant heat on the 1st floor. When we went to the basement, you can see the tubing below the floor joists. It is a staple up job, but what is weird is the tubing is not stapled directly under the subfloor and channeled with metal plates, but rather runs through holes in the joists and just hangs below your typical 8" thick pink fiberglass insulation. My 1st thought was how the heck is that very efficient if the tubes are not in direct contact with the subfloor and even if it is, the heat still has to transfer through 8" of insulation. Then I noticed (2) 275 gallon oil tanks, which is the fuel source for the oil burner/hot water tank. I know mod/con boilers are the way to go with radiant, but this house was built 9 years ago, so I guess they went with an oil burner at the time. I've asked the selling agent to get me the oil bills for this past winter, so we'll see, but I was curious about how well this system really works. I wish I looked harder cause maybe I was just seeing a run of tubing going to another room and maybe there was actual contact of the tubing with the subfloor in spots, but it sure didn't look like it.

It should be against the bottom of the subfloor hidden by the insulation. Maybe what you saw was a return line?

I agree!

Look closer to determine if it is a return line or crossing an obstacle, as it should be up against the underside of the floor, ideally with transfer plates.
Is it pex or onix, or something else?

If all you saw was one line, it's probably just a return line. If they're all around, it's probably a poorly designed basement ceiling radiant system.