04 December 2024

Retrofitting Underfloor Heating

Retrofitting underfloor heating (UFH) systems that lay on top of the existing flooring is becoming a popular option, particularly for homes that want the benefits of underfloor heating without the disruption and cost of lifting and replacing floors. Here’s how this approach fits into the comparison:

 

Retrofitting Underfloor Heating (On Top of Existing Flooring)

This type of UFH is specifically designed for retrofit projects, often involving low-profile systems that can be installed directly on top of an existing floor without needing to excavate or lift the original surface. There are two main types: electric (dry) systems and water-based (wet) systems, both of which have options suited for retrofits.

Pros:

  1. Minimal Disruption:
    • Because these systems are laid on top of the existing floor, there’s no need to dig into the floor structure. This reduces the disruption associated with traditional UFH installations.
  2. Lower Installation Costs (Compared to Traditional UFH):
    • While still more expensive than radiators, low-profile UFH systems that sit on top of existing flooring have a lower installation cost compared to fully integrated systems, as they don’t require the floors to be pulled up.
  3. Thinner Profiles:
    • Retrofit UFH systems are specifically designed to be thin, often adding only 10-30mm to the floor height, which minimizes the impact on room dimensions and avoids the need for significant modifications to doors and skirting boards.
  4. Improved Comfort and Efficiency:
    • Like traditional UFH, retrofit systems offer even heat distribution and improved comfort, with radiant heat rising from the floor. They are still more efficient than radiators as they can operate at lower temperatures, particularly in well-insulated homes.
  5. Quicker Installation (Compared to Traditional UFH):
    • These systems are easier and faster to install than standard underfloor heating, making them a more convenient option for reworks. Some systems can even be laid over existing tiles or concrete floors, depending on the surface.
  6. Can Be Combined with Renewable Energy Sources:
    • Retrofit UFH systems, particularly water-based ones, can still be paired with low-temperature heating sources like heat pumps, which makes them a good fit for homes aiming to reduce energy consumption and environmental impact.

Cons:

  1. Increased Floor Height:
    • While the increase in floor height is less than traditional UFH systems, even a 10-30mm rise could require adjustments to doors, skirting boards, and thresholds, which may add to installation costs.
  2. Slightly Less Efficient Than Fully Embedded UFH:
    • Because they aren’t embedded in the subfloor, retrofit UFH systems might not be quite as efficient as traditional UFH systems, particularly when installed over less conductive surfaces. They may take longer to heat up and may not retain heat as effectively.
  3. Limited Heat Output (Compared to Full UFH):
    • Retrofitted UFH systems typically have a lower heat output than traditional underfloor heating systems that are fully integrated into the screed. This could make them less suitable for poorly insulated homes or very large spaces unless they are well-insulated.
  4. Suitability of Existing Floors:
    • The type of existing flooring can impact the effectiveness of retrofit UFH. Some surfaces (like thick carpets or wood) can act as an insulator and reduce the efficiency of the heat transfer. In these cases, changing the top layer (e.g., switching to thinner carpet or tiles) might be necessary to optimize performance.
  5. Higher Operating Costs (for Electric Systems):
    • If you opt for an electric retrofit system, it’s generally less energy-efficient and could be more expensive to run than water-based systems, particularly in larger areas. Electric UFH is typically more suitable for smaller rooms like bathrooms.

Comparing Retrofitted UFH to Radiators and Traditional UFH:

In a Rework:

  • Radiators: The most straightforward and cost-effective solution if you want minimal disruption.
  • Traditional UFH (embedded in the floor): Involves significant disruption and higher costs due to floor excavation but offers the best long-term efficiency and comfort.
  • Retrofit UFH (on top of the floor): Offers a middle ground, combining some of the benefits of UFH (even heat, comfort) with a less disruptive installation process. It's more costly than radiators but may be more feasible in existing homes than traditional UFH.

In a New Build:

  • Radiators: Easier and cheaper to install but less efficient in well-insulated modern homes.
  • Traditional UFH: The preferred choice, as it can be fully integrated into the building’s design from the outset and paired with energy-efficient systems like heat pumps.
  • Retrofit UFH: May be less relevant in new builds unless retrofitting is part of a phased build, but it could still be an option if there's a specific need for a lower-profile system.

Conclusion:

 

Retrofitting UFH systems that lay on top of existing flooring offers a practical compromise for homeowners who want the benefits of underfloor heating without the extensive work and disruption of fully embedding it in the floor. While it comes with some trade-offs, especially in terms of slightly higher floor height and reduced efficiency compared to traditional UFH, it can still be a comfortable, energy-efficient alternative to radiators, particularly for smaller spaces or targeted reworks.

 

By Kevin Knox