STEP Joists™ - Retrofit under floor heating under existing floors

STEP Joists™ under floor radiant heating element is designed to provide radiant heat to existing floors by accessing the floor joists from below. This element can be ordered without slots and can be stapled or nailed through for easy installation.

The retrofit solution can be used as primary or supplementary heating and can be installed to heat under most floor coverings, including tile, stone, wood, laminate and carpet. For total heating a heat loss calculation is required.

After stapling the radiant heating elements between the floor joists and making the electrical connections, insulation is installed underneath the heating element. The insulation enhances the energy efficiency by minimizing heat loss and directing the warmth upwards through the floor.

STEP Joists™ is also available in 9" (22.9cm) width.

  • Technical Specifications

  • Features

Model: EP-30-29W-24V
Heating Element type: Positive Temperature Coefficient (PTC) semi-conductor polymer
Width: 12" (305 mm)
Length: Cut to order
Max. Element Length: 50ft (15 m)
Weight: 0.23lb/ft (0.34 kg/m)
Thickness: 3/64" (1.2 mm)
Output Wattage (at 24VAC):  9.0 W/ft (29W/m) @68°F (20°C)
8.4 W/ft (27 W/m) @86°F (30°C)
Nominal Resistance: 64 Ω/ft (20 Ω/m) @68°F (20°C)
Primary Draw on 230V: 0.039 amps per foot (0.305)
Strong, thin and flexible element
Designed to provide even and comfortable warmth in a home. A heat loss calculation is required when primary heating is expected
Install elements below existing floor between the joists without tearing up existing floor
Elements can be stapled and nailed through for easy installation
Operates on 24 volts (AC/DC); Connect to a power supply, solar or wind power
Compatible with any floor covering including, tile, stone, wood, laminate, resilient and carpet.
Self-regulating; As the material gets warmer, less electricity passes through the plastic – therefore it is extremely energy-efficient
Easy to install; cut elements to size on the job site, staple or nail elements underneath existing floor between the joists, connect wires to power supply and elements and install proper installation underneath
Maintenance-free when installed and does not require a utility room or dangerous storage of fuel or gas

About Us

Electro Plastics, Inc. dba STEP Warmfloor® is a US manufacturer of electric radiant underfloor heating, roof de-icing and snow melt systems. The company's headquarters is located in Saint Louis, Missouri, U.S.A. This 35,000 sq feet LEED registered building is a "living laboratory" as proof of the comfort properties and energy efficiency of STEP Warmfloor®. 


Our radiant heating products are ETL listed, have the CE marking and conform to ANSI/UL:

 intertek etl small    Cemark small



Contact us

  • Address: 11147 Dorsett Rd., Maryland Heights, MO 63043-3505.
  • Toll-Free: 1-877-STEPTEC(783-7832)
  • Tel: +1-314-426-3555
  • Fax: +1-314-426-3556