p>Yes, <strong>you can run what is called a ‘ground loop’ below grade to warm or cool incoming air to your ERV or HRV</strong> depending on the season. This is seen sometimes in extremely high performing homes or Passive House builds where the design phase includes trying to save every watt of energy possible.</p> <p>On the down side, there have been cases where people have spoken about debris or mold buildup inside the tubes, and that can be difficult to deal with. So it is recommended to install it on a slight slope so that any moisture that may condense on the tube walls from hot humid summer air coming in contact with the cooler surface.</p