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.
- Section 402: Building Thermal Envelope
- R502.1.1.1: Building Thermal Envelope (existing building)
- R 502.1.1.2 Heating and Cooling Systems (existing building)
—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.