Dan Morrison | August 10, 2016

details // Concrete & Masonry, HVAC & Mechanicals, Plumbing, Electrical, Insulation & Air Sealing, Kitchens & Baths

Retrofitting Hydronic Heating into an Uninsulated Basement Slab


Direct the heat toward the feet


Retrofitting in-floor heat is a great way to warm up a chilly basement bathroom. But unless you have insulation under the heating system, your customers are going to spend fat stacks of Benjies heating the earth every month.


Step by step:

  • To keep the heat where you want it, cut out the slab before installing the heating system.
  • Dig deep enough to allow for gravel, insulation, and a slab on top.
  • Cover the earth with compacted gravel to support the slab and keep water from wicking in.
  • Reinforced plastic over the gravel stops water vapor.
  • Rigid insulation comes next surrounding the new slab on all five sides.
  • You will need some sort of steel reinforcement, either wire mesh or rebar and then install the hydronic tubing.
  • Pour the slab over the tubing, let it cure, and cover the whole assembly with flooring—and be confident that your customers Benjies will stay in the bank.
2012: IECC:
2015 IECC:
—From the fat-stack detail-pack of Otogawa-Anschel Design+Build, in Minneapolis, Minn. Thanks to Dr. Joe Lstiburek for the technical assistance and talking down to us so patiently. 


Slideshow and download:



We have the perfect product to do this, all you do is lay 1 inch crete heat on top of existing slab, walk pex tubing in place then pour thin layer of concrete or gypcrete.  Provides R6 and is the easiest installation. see www.barrett-inc.com/creteheat.php

Daniel Morrison's picture


Oddly enough I was reading about your product this morning. You should talk to our sales team about site sponsorship (scroll down past the editors on that list).

We are always interested in quality content about quality products.




Thanks Dan, tell me about it!

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