UFH vs Wet Radiators – Which to to choose?


A conventional radiator system uses one or more heat surfaces within a room. These heat the air in their immediate vicinity by radiation and convection, air currents around the room then distribute this air. Doorways and windows, which create their own airflows, will also affect the heat distribution. This results in the colder air being at the floor level and much warmer air at ceiling level. Some products advertised as ‘saving wasted heat’ or even ‘using free heat’ use this effect. These consist of a de-stratification fan that takes the warmer air at ceiling level and discharges it at floor level. Even with extra air circulation the room will have hot and cold spots within it. A further disadvantage of air circulation is that it will distribute dust as well as the heat.

A modern underfloor heating system works almost completely by radiating heat. Furniture will reflect and absorb this radiated heat. By absorbing heat, they also become secondary heat emitters. This results in a much more even heat distribution, and the air at floor level being warmer than that near the ceiling. This type of heat distribution is also more comfortable for the people using the room. People often say that if their feet are comfortable then they are more likely to be comfortable in themselves. However, it is important that one’s feet do not get too hot.


If an underfloor heating system is run so that the floor surface temperature goes above 29°C it will feel uncomfortably hot. With wet radiator systems the radiator surface temperature is the same as the circulating heated water. This can be as high as 80-85°C, but lower surface temperature radiators are available which protect the room users from contact with high temperature surfaces. The fact that there is much less air movement with underfloor heating systems has already been mentioned, as well as the resultant effect on dust distribution. This can be very important for people who have some of the more common dust allergies.

Underfloor heating also has the major advantage of depriving the common house dust mite of the one thing it needs to survive and reproduce: moisture. Without moisture the house dust mite will simply die. Underfloor heating maintains a much higher relative temperature in carpets and consequently reduces the amount of moisture available.


All underfloor heating systems work on a lower temperature than a radiator system. Normally a radiator system will have 82°C hot water for the flow, the underfloor heating will run at much lower temperatures in the region of 35 to 60°C, depending on the floor construction and the building. The tempering or blending valve is the heart of an underfloor heating system. It blends colder water from the underfloor heating system return with hot water from the heat source to supply the correct temperature of water to the underfloor pipework. The required temperature will vary depending on the type of flooring and the sub-floor structure but as these valves are adjustable the correct temperature can be easily obtained. RWC has been supplying a variety of high quality UFH Blending Valves for use in underfloor heating systems for many years. As the floor area served in domestic applications has increased so the required flow rate has also increased.

Reliance UK has an active interest in the fitting dimensions of these valves as they are now supplied in pre-plumbed kits. We currently supply the underfloor heating industry with several different underfloor heating packs, details of which can be found in our Underfloor Heating Brochure. In addition, Reliance UK has developed for many years a range of bespoke valves for specific OEM customers to sell on as part of their own product range.