Underfloor heating is fast becoming the heating solution of choice for domestic and non-domestic buildings in the UK. When choosing underfloor heating, there are two options, Hydronic (wet) or Electric. By Antony White, technical director, Warmup Plc.
There are many different heat emitters available, currently the most common choice is the radiator. Although radiators have been the default method of installing central heating for many years, underfloor heating has been consistently growing and taking market share from radiators year after year. Radiator systems are typically designed to operate with a flow water temperature of 75°C and a return water temperature of 65°C, therefore running at 87 per cent efficiency. Underfloor heating by comparison is largely radiant with very little heat dispersed through convection. This immediately eliminates the excessive heat loss through windows and the ceiling that is attributable to radiators. With underfloor heating, the return water temperature is likely to be lower than 40°C by design. This allows the boiler to condense and boosts its efficiency to 94 per cent, an 8 per cent increase in comparison to the conventional systems.
The government’s Standard Assessment Procedure (SAP) for energy rating buildings and the Microgeneration Certification Scheme both award improved efficiency ratings through reduced design water temperatures. While the ability to reduce the design water temperature is not unique to hydronic underfloor heating, it is a much more natural fit. Underfloor heating is often designed to operate at 40°C with zero impact on the room layout, but a radiator designed to operate with 40°C return water temperature instead of 65°C would need to be approximately four times the size of its predecessor – this would be impractical in many situations, as it would remove so much usable space within a room.
Hydronic underfloor heating can be used with a variety of heating sources from boilers to heat pumps. The benefits with renewable technologies such as air source heat pumps are even more significant as their total efficiencies typically increase by 2.5 per cent for every 1°C reduction in design water temperature. Therefore, moving from a renewables optimised radiator system fitted with oversized radiators, to an optimised hydronic underfloor heating system with pipes fitted closer together within the floor, can substantially improve the efficiency of an air source heat pump by allowing it to operate at a 10°C lower water temperature.
Most hydronic systems are fitted onto the structural subfloor of a building, which often means that they are best suited to new-builds where the floor heights have not yet been established. For renovations, or those projects where the source of heating is selected upon completion of other works – a low build hydronic insulation system will offer a complete solution, and because it is not embedded within screed, the heat up time is faster.
The minimal circulation of air allows advanced smart thermostats to accurately control the air temperature in individual rooms. Therefore heating each room only when it is needed, rather than wasting energy by heating unoccupied rooms within the house. It provides comfortable, radiant heat, while reducing the amount of energy wasted by inefficient heating systems.
Finally, hydronic underfloor heating requires very little maintenance. Any potential damage to a system normally occurs only during installation, where the underfloor heating pipe gets cut accidentally or becomes otherwise damaged. For those rare occasions some companies offer installation guarantees with free replacement of the damaged product.
When you add up all of the above, hydronic underfloor heating is more efficient to run, has lower maintenance requirements, and allows you to make full use of your heated rooms. With underfloor heating we are not unnecessarily wasting energy and it just feels right. The air does not feel stuffy, and unlike with radiators, everyone in the room experiences the same comfortable temperature. It is everything a modern heating system should be.