What is the proper spacing for installing 1/2" PEX tubing under 3/4-inch oak floors for radiant heat? I am putting the PEX piping into U-shaped aluminum, mounted on 3/4-inch plywood strips over a plywood sub-floor. Thank you in advance.
Robert ~ Glen Cove NY
Hi Bob. Placing radiant heat under your hardwood floors can be a great upgrade for an older home and may avoid the expense of a more complicated new HVAC installation. PEX piping doesn't transfer heat very efficiently so using the aluminum tracks is a good idea. The amount of spacing between the rows of piping is largely a matter of personal preference and how much warmth you would like your radiant heat to generate. Many radiant heat flooring contractors recommend spacing from 6 to 10 inches, but I would think that with the cold winters in Glen Cove, 6 to 8 inches might be ideal.
If you haven't already started the project, there are several companies that manufacture panels for radiant heat that can be nailed directly onto the room's subfloor. The panels have grooves already cut that accept the PEX piping in various spacing configurations. The panels can be used with hardwood flooring and most other types of finished flooring materials. The advantage of using the panels is that they keep the change in height to the room's floor to a minimum -- usually under 3/4 inch. This may help you avoid having to adjust trim and cut the bottoms off of doors due to the increase in the floor's height. Many of these panel systems use 5/16 inch Pex piping rather than the 1/2 inch you have planned.
Regardless of which route you take, I'm sure the radiant heat should be a big improvement for your home -- especially during those chilly Glen Cove winters.