Adding Hydronic heat to an existing slab.

Andy Wyatt

I have torn up my old tile floor that was on an inslulated slab. I now have about 700 Square feet of rough slab floor. I would like to heat with Pex. I was planning on ripping some 5/8" plywood 8" or so, Cutting some end arcs and ram setting it into the slab, leaving a 5/8" gap to run my tubing. The house is superinsulated with a 15,000 BTU heat loss on the first floor. I plan on installing 3/8" engineered flooring directly on the plywood. Any Thoughts, Pitfalls, or errors in my thinking. Slab is insulated underneath with 4" foam.

First floor of House was heated with 40' of baseboard. hot water. 180 degrees. I built the Heat source 15 years ago. A 4500 watt element in a 3" copper pipe with controls and pump. Heated first and second floor.

hr

I would

use 3/8" PAP tube. This would get you to 3/8" pex, 1/2" plywood, and less expansion issues with the PAP tube. Limit the 3/8 pex to 250 foot or less lengths. 3 loops would get you by with 12" center. Maybe consider tighter spacing, and 4 loops.

What kind of heat load? If it is low, say below 12 btu/ ft you could just install the tube in the grooves ala the Watts Subray.

A nicer detail would be to use aluminum transfer plates for better transfer, lower supply temperature, and a nice temperature spread across the flooring surface.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Andy Wyatt

Sub Ray

Thanks for the tip. Sub Ray is just what I need. I have located a distributer here in Ohio can't wait to start.