SERIES 23 / Module 10 Underfloor Heating


In practical terms, this represents


a move away from gas boilers in new homes and toward systems designed specifically to operate with heat pumps. These systems are not simply retrofitted alternatives but are expected to be designed from the outset to operate at lower temperatures. For designers, this places greater


emphasis on emitter performance. Heating systems must be capable of delivering required outputs at lower temperatures, which in turn requires careful coordination between building fabric, emitter design, and controls. Regulatory guidance also places


increasing importance on controls. Systems are expected to include zoning, temperature control and strategies to manage thermal response. For higher thermal mass systems such as UFH, this typically requires continuous operation or setback strategies rather than simple on/off control.


System types Underfloor heating systems can be divided into wet (hydronic) systems and direct electric systems. Wet systems circulate warm water


through pipes embedded within the floor and are typically used for whole- building heating. They are well suited to integration with heat pumps and form the majority of UFH installations in new build projects. Electric UFH systems use resistive


heating elements and are generally easier to install. They are commonly used in smaller areas, such as bathrooms, or in retrofit applications where installation constraints limit the use of wet systems. Electric systems, however, are


typically less suitable for whole-house heating due to higher running costs associated with direct electric heating. For this reason, they are generally used selectively rather than as a primary heat source. In some cases, hybrid approaches


are adopted, combining wet systems for main spaces with electric systems in targeted areas where rapid response or installation simplicity is beneficial.


Flow temperature A key development since 2021 is the increased focus on emitter design and flow temperature. While UFH is often described as a low-temperature system, achieving low flow temperatures depends on careful design. The design process begins with heat loss calculations, which determine the


Produced in Association with Regulatory guidance places increasing importance on controls


required heat output for each space. This output, typically expressed in W/m², dictates pipe spacing, layout and flow temperature. Underfloor heating systems


typically provide outputs in the range of approximately 50–100 W/m² depending on design, floor construction and floor finish. This creates a direct relationship between building performance and system capability. In simple terms:


● Higher heat loss → higher required output → higher flow temperature. ● Lower heat loss → lower required output → lower flow temperature and improved efficiency. Lower flow temperatures are


desirable because they improve heat pump efficiency and reduce energy consumption. However, if heat losses are too high or heat transfer is restricted, the system may require higher flow temperatures, reducing overall efficiency. Floor finishes play a significant role


in this process. Materials such as tile and stone allow efficient heat transfer, while higher resistance finishes such as carpet can limit output and may require design adjustments. UFH therefore provides the potential


for low-temperature heating, but this potential must be achieved through coordinated design rather than assumed.


Produced in Association with


Controls and system operation Controls are now recognised as one of the most important aspects of UFH system performance. Modern systems typically incorporate


zoning, allowing individual rooms or areas to be controlled independently. This enables better alignment between heat delivery and occupancy patterns. Weather compensation or internal


temperature control is used to adjust system operation dynamically in response to external conditions. This helps maintain stable internal temperatures while minimising energy consumption. Due to the thermal mass associated


with many UFH systems, particularly screeded floors, response times are slower than those of radiator systems. Heat-up times can extend to several hours. As a result, UFH systems are generally


best operated continuously with a setback approach rather than being switched on and off. A typical strategy is to maintain a steady background temperature and reduce it slightly during periods of reduced occupancy. User behaviour and control setup play


a significant role in system performance. Systems that are incorrectly configured or frequently switched on and off can experience long delays in achieving comfort conditions and may operate inefficiently. There is also a strong link between


commissioning and controls. Incorrect flow balancing or poor control setup can lead to uneven heat distribution and reduced performance, even where the physical installation is sound.


Floors and finishes Floor construction plays a key role in UFH performance. The floor acts as both a heat emitter and a thermal store, and its characteristics directly affect system behaviour. Adequate insulation beneath the


system is essential to prevent downward heat loss. Perimeter insulation is also required to reduce edge losses. The thermal resistance of the floor


finish influences how effectively heat is transferred into the space. Hard finishes such as tile and stone provide the most efficient heat transfer, while timber and laminate can perform well if correctly specified. Carpeted finishes require careful


UFH systems typically provide outputs in the range of approximately 50–100 W/m²


LOW CARBON HEATING SOLUTIONS.


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consideration, as excessive thermal resistance can significantly reduce heat output. These factors should be considered


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EIBI | MAY 2026


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