Radiant Heat Over Concrete Slab

Choosing the Right Over Slab Radiant Heating System

If you’re installing hydronic radiant floor heating over concrete, the right approach depends on what’s under the slab. On uninsulated or poorly insulated slabs, traditional in-slab tubing can waste energy into the concrete. WBI’s over-slab insulated radiant panels, Ecowarm RadiantBoard® EPS (plywood core, 1/2″ PEX) and ThermalBoard EPS (MDF core, 3/8″ PEX), move the heat source above the concrete and place EPS insulation directly beneath the aluminum panel to reduce downward heat loss and speed response.

Already have proper underslab insulation? You can use Ecowarm RadiantBoard® or ThermalBoard (non-EPS) directly over the slab. However, EPS-backed systems are still preferred when height allows because they further limit downward losses and improve comfort at lower water temperatures.

Why Radiant Heat Over Concrete Slab?

Concrete is strong, but it’s also a massive heat sink. When you place the heat emitter at the floor surface and include a thermal break under it, more of your BTUs move up into the room. That means:

• Faster warm-up and recovery from setbacks.
• Lower supply temperatures (great for condensing boilers and air-to-water heat pumps).
• Better zoning and comfort in basements, slab-on-grade additions, remodels, and garage conversions.

Key Challenges of Traditional Methods

• Downward heat loss on uninsulated slabs: A significant share of energy migrates into the concrete before it reaches the room.
• Slow response of high-mass systems: In-slab tubing or wet overpours can take hours to heat/cool—frustrating for tight schedules or variable occupancy.
• Wet trades & curing time: Gypcrete/overpours add moisture, weight, and project delays, and can complicate transitions at doors and stairs.
• Flooring limitations: Higher surface temps sometimes needed to overcome mass can clash with certain floor goods and adhesives.
• Difficult retrofits: Cutting or trenching an existing slab introduces dust, noise, and cost, with uncertain results.

Benefits of Installing Radiant Heat Over Concrete

• Low-mass, high-control comfort: Aluminum-laminated panels deliver rapid warm-up and precise thermostat response.
• Lower operating temps: Efficient at modest water temperatures—ideal for heat pumps and modern modulating/condensing boilers.
• Integrated EPS insulation: EPS under the panel reduces (does not “stop”) downward heat flow into the slab, pushing more heat into the occupied space.
• Clean, dry installation: Adhesive + mechanical fastening; no curing or wet trades, minimal disruption during remodels.
• Slim, configurable build-ups: Multiple thickness/R-value families to meet height limits and transition needs.
• Finish-floor friendly: Works with common floor goods—tile/stone, engineered hardwood, LVP/LVT, laminate, carpet (with proper cushion), and more (follow flooring and panel guidelines).

Why Concrete Slab Insulation for Radiant Heat is Essential

Insulation is the difference-maker on concrete. Without a thermal break, heat readily conducts into the slab. Placing EPS directly under the panel:

• Creates a thermal break that reduces downward losses.
• Improves upward output so rooms reach setpoint faster at lower supply temps.
• Helps maintain flooring-friendly surface temperatures and even heat across the room.

If your slab already has proper underslab insulation, you can run Ecowarm RadiantBoard (plywood, 1/2″ PEX) or ThermalBoard (MDF, 3/8″ PEX @ 8″ o.c.) directly over the slab. You’ll still gain additional efficiency and comfort with EPS-backed versions where height allows.