Underfloor Heating – System Controls

Heating system controls contribute greatly to the energy efficiency of a building. Such controls are focused on adjusting the delivery of heat / cooling at the right temperature at the right time and at the right place for an occupant / owner of that building. At an initial level, on/off controls provide a baseline to control but can lead to long response times. Proportional controls, such as mixing valves, provide more sensitive and quick acting responses where the control effort is pro rata to temperature differences. Zoning, based on variables such as function, occupancy, solar gain and building structure can be very effective in improving energy efficiency. With the manifold approach to UFH, each pipe run can be selected as its own zone. Timing controls, such as night setbacks, time of day / week (e.g. to provide for occupancy levels) are also important controls. Weather compensation controls are also a useful set of controls available to the designer. More recently, intelligent pumps provide designers with even more tools to ensure optimum design of heating system controls. In any case, UFH enables the best and most efficient and effective approach to heating distribution system controls.

In physical terms heating system distribution controls refers to items such as thermostats, timers, programmers, actuators, building management systems (BMS) and the like. Actuators can be mounted on the return manifold and act on an on/off basis within a given zone when connected to the appropriate thermostat. Other more traditional components include mixing valves, isolation valves, fill / drain valve, valves in general, pumps, couplings etc. These all have their own role to play in Underfloor Heating. The most interesting of these controls are programmable thermostats and BMS which incorporate IT and networking capabilities. Such networking devices / systems now allow one to control one’s heating & hot water from anywhere in the world from one’s SmartPhone.

As regards bathrooms – some people prefer room temperatures to be around 24 degree C, whereas in living rooms the room temperature tends to be set around 20 degrees C (DIN En 12831) and bedrooms around 18 degrees C. In this context, a bathroom, especially an en-suite may require its own zonal control as the neighbouring master bedroom may be set at 18 degrees C (difference of 6 degrees). Due to this sometimes small floor areas in a bathroom for UFH, the floor heating area can be supplemented by wall heating.

Since underfloor heating provides a comfortable temperature at floor level,  the building height has less effect on the heating system design and little to no allowance is needed for a stack effect in buildings that, for example, incorporate the full height of two stories in the entrance hall of a house. This would not be the case with convective / radiator systems and increases the potential savings in energy costs over that approach. (Illustrations provided by MULTIBETON UK)

Air Tightness

The energy efficiency of a building is dependent on the interaction between a complex set of factors, including the overall design, type of building, building elements / materials, insulation, heating system and ventilation / air tightness. Modern buildings tend to be air tight. However, air tightness can vary between 1 air change/hr (for passive house) to 2 (more often for general low energy housing) to even 5 to 7  and more for older housing. This is quite a variation and can have a significant impact on the heat demand for a building and consequentially on the sizing of the heating system and consequentially on the sizing of any UFH system to address such a heat demand. It is always advisable to include air tightness values in any design parameters set for heating calculations, including that for UFH and is, in any case, part of modern building requirements.