Reflective Film vs Insulation: What Your Underfloor Heating Really Needs

Combining reflective film with proper insulation is the key to a truly efficient underfloor heating system. While reflective film stops radiant heat from escaping downward, insulation reduces conductive heat transfer. Together, they create a thermal barrier that keeps warmth in the living space. This guide explains how they work together.

The Two Types of Heat Loss

In an underfloor heating system, heat can be lost in two main ways: radiation and conduction. Reflective film addresses radiant heat by bouncing it back upward. Insulation, typically in the form of foam boards or rolls, reduces conductive heat transfer through the subfloor. Using both together ensures that neither pathway is ignored.

Why Both Are Needed

Relying on reflective film alone may not provide enough insulation in cold climates or over unheated spaces. Conversely, using only insulation without a reflective layer may allow radiant heat to pass through gaps and downward. The most efficient systems use a reflective film layer on top of rigid insulation boards, creating a complete thermal barrier.

Key Considerations

• Insulation thickness: Choose thickness based on the subfloor condition and local climate.

• Reflective film placement: Place it on top of the insulation, facing upward.

• Joint sealing: Seal all film joints with foil tape to maintain continuity.

• Compatibility: Ensure the film and insulation are compatible and approved for underfloor heating use.

• Building regulations: Check local requirements for thermal performance.

Installation Tips

Lay rigid insulation boards across the subfloor, taping joints to create a continuous layer. Then lay the reflective film on top, with the reflective side facing up. Overlap joints and seal with aluminum foil tape. Heating pipes or fixing rails can then be installed on top. This layered approach maximizes efficiency and ensures the system performs as designed.

Conclusion

Reflective film and insulation are complementary, not competing, solutions. By using both, installers create a more efficient underfloor heating system that delivers comfort with lower energy consumption.

References

[1] Underfloor Heating Systems: Design, Installation and Performance. Journal of Building Engineering, Elsevier.
[2] Thermal Analysis of Radiant Floor Heating Systems. Energy and Buildings, Elsevier.
[3] Materials and Components for Underfloor Heating. Construction and Building Materials, Elsevier.