As a stand-alone space heating solution, underfloor heating (UFH) has much to offer; it’s an installer-friendly system that is reasonably simple to fit, it can help to secure quicker sales cycles and achieve optimum selling prices, it enables better use of available space and it helps to reduce heating bills.
Back to basics
In simple terms, UFH works by pumping temperature controlled warm water from any heat source through jointless plastic tubing embedded in the floor. Unlike radiators that rely on convection and circulate heat in an inefficient way, UFH uses radiated heat for indoor climate control. Radiators heat the ceiling space first, but UFH provides warmth to a room from the floor up, creating an even heat without stuffiness, draughts or cold spots. As the emitting area is large, sufficient warmth is provided even on a cold day without the need for supplementary heating.
When used with a traditional boiler the standard operating temperature for UFH is 50˚C compared to 70˚C for radiators. However, if you substitute the boiler with a heat pump, the energy saving potential of underfloor heating is even more impressive. An independent report by Eu Ray (European Radiant Floor Heating Association)
When underfloor heating systems are specifically designed to be fed by a heat pump, additional tubing and more efficient floor constructions can be used to allow even lower flow temperatures, typically 35oC – 45oC, whilst still achieving the required air temperature inside the property.
Heat pump integration
Insulation is essential to the efficient operation of UFH as a general rule, but is even more important when a heat pump is integrated. Insulation levels should ideally ensure that less than 45 watts of heating are required per square metre of floor space. In general it is more cost effective to increase insulation levels than it is to install a larger heat pump. With adequate levels of floor insulation, heat pumps operate at a higher Coefficient of Performance (CoP). A ground source heat pump, for example, can attain a CoP of 4 – 5, providing 4 to 5 kilowatts of free energy for every 1 kilowatt of electricity used to power it.
The performance of underfloor heating when used with a heat pump is affected by three key variables; temperature of the heating water, quantity of tube in the floor and thermal resistance of the floor structure and covering. Complex heat loss calculations are needed to determine what tube spacing is required to achieve the necessary heat outputs.
There are three standard floor constructions available: floating floor, suspended timber and screed. Screed is better suited to new-builds, extensions and conservatories due to an average floor height build-up of 150mm and renovation projects where floors are being removed or sufficient height is available.
Most floor finishes can be used with UFH although some, including slate, stone and ceramic tile are better than others at transferring heat.
Interest in the feasibility of retrofitting UFH has steadily increased and we are seeing more and more installations into older properties. There is no doubt that retrofitting UFH can present major challenges, but as long as installers are aware of requirements and limitations there should be no problems.
Number one on the list is the need for insulation. The existing property should be brought broadly in line with the requirements of Part L of the Building Regulations;
Suspended timber floors have little impact on floor height build-up, although ceilings or floors will have to be removed in order to lay the floor heating tube. This is fine if they are being replaced anyway but if they have to remain in-situ a floating floor is a better solution. The floating floor construction is a popular option for retro-fitting UFH as it benefits from minimal floor height build-up and is straightforward to install, laying over the existing deck.
Finally, it is possible to install UFH on its own with view to changing to heat pump technology at a later date. Future-proofing UFH at installation stage will cause less impact than attempting to change everything when the heat pump is installed. Considerations include pipe spacing, floor coverings, insulation (again) and practical issues such as space to put the pump and house the cylinder, buffer tank and other equipment.
Underfloor heating definitely has a firm foothold as a product that helps to meet the demand for energy efficiency and low carbon targets, particularly when introduced to its ideal partner, the heat pump.
Adrian Troop is Sales & Marketing Director for Nu-Heat Underfloor & Renewables
Contact: www.nu-heat.co.uk or 0800 731 1976