The three methods
For background on what radiant heating is and how it works, the radiant pillar page has the full system overview. This page is about installation — methods, what to expect on site, what coordination is needed with the rest of the build.
In-slab radiant
Best for: new construction, basements, garages, additions where a slab is being poured.
The process: PEX-A tubing (typically 1/2 inch) is tied to rebar or laid on rigid foam insulation before the concrete pour. Spacing is 6–12 inches on center depending on the heat-loss calculation. The tubing connects to manifolds at the edges of the slab. Once the slab cures, the entire concrete mass becomes a low-temperature radiator.
Strengths: lowest cost per square foot, longest expected life (no exposure to anything), most thermal mass for stable temperatures. Drawbacks: slow response time (the slab takes hours to warm up or cool down), tubing is permanent.
Staple-up retrofit
Best for: existing homes with accessible joist bays from below — typically over an unfinished basement.
The process: working from below, we staple PEX tubing to the underside of the subfloor with aluminum heat-transfer plates. Insulation goes below the tubing to direct heat upward into the floor. Manifolds typically mount in the basement ceiling near the joists.
Strengths: true retrofit — no tearing up existing floors. Works well with hardwood, engineered wood, and tile. Drawbacks: slightly slower response than slab; requires basement access; less effective under thick plush carpet.
Panel systems
Best for: retrofits where you can't access from below, or where you don't want to disturb existing floors.
The process: pre-routed plywood panels with grooves for PEX tubing install over the existing subfloor. Tubing snaps into the grooves. Finished flooring goes on top. The system adds about 5/8 inch of height.
Strengths: fastest response of the three methods, works without basement access. Drawbacks: highest cost per square foot, adds floor height (door bottoms may need trimming, transitions to other rooms have to be planned).
What installation looks like
Design phase
Heat-loss calculation room-by-room. Zone planning. Method selection. Manifold locations. Floor covering coordination. Quote.
Coordination
For new construction: framer, slab pour schedule, electrician for thermostats. For retrofit: floor covering installer, drywaller if work is needed.
Install
Tubing goes in per the layout drawing. Pressure tested before any covering goes over it. Manifolds set, supply and return runs piped to the mechanical room.
Commission & balance
System filled, purged of air, leak-tested at operating pressure. Per-zone flow balanced. Boiler outdoor reset configured. Owner walkthrough.
Single-room retrofits we do a lot of
- Master bathroom — the #1 single-room retrofit. Warm tile floors in winter. 2–4 days. Most common in homes with finished basements where staple-up is easy.
- Kitchen — large floor area, lots of standing time, immediate comfort upgrade.
- Basement finishing — when you're already pouring a new slab over an old basement, radiant adds remarkably little cost compared to the slab pour itself.
- Garage shop floors — heated garages for people who actually use them. Often paired with snow-melt.
"The single most common mistake we see on DIY or generalist radiant installs: oversizing the heat source and undersizing the spacing. Then they wonder why the room is hot but the floor is cold."