Under Floor Heating with Hot Water Radiators

Under Floor Heating with Hot Water Radiators

The owner builders of this project approached us to design and install a heating system which would meet a number of requirements.

  1. Domestic hot water heating.
  2. Central heating system for the upstairs and downstairs areas.
  3. A single standalone heat source of excellent quality and efficiency.
  4. Simple but effective system control and operation
The design had to deal with 3 split levels and 3 different floor finishes.
  1. Ground floor with polished concrete.
  2. Entry and stairwell with polished concrete and timber.
  3. First floor with carpet and tiles
The design had to incorporate the domestic hot water heating and the house heating from the same heat source. The design required a control system to keep everything at its required temperature. It needed to operate independently, the upstairs area from the downstairs area to prevent uneven temperatures from solar gain and rising heat to the first floor.
Under Floor Heating with Hot Water Radiators

Downstairs area:

With polished concrete as the floor finish there was only ever one option for heating the ground floor area. Under floor heating for this area would provide an even radiant heat, while at the same time the exposed polished concrete floors are heated making walking around in bare feet during winter a pleasure. Polished concrete is a beautiful way to finish your floors but walking on freezing cold concrete in winter is nobody’s idea of fun.

Domestic Hot water:

We looked at a number of different options to satisfy the domestic hot water for this project and found that with a single heat source we would be unable to heat the domestic hot water all the way to 55 degrees without compromising the efficiency of the system which would defeat the whole purpose. A number of other factors helped to shape the design in the end, the major one being the requirement for a 180 litre buffer cylinder to cope with the upstairs heating design. We added 66 metres of 20mm water coil to the buffer tank. The incoming domestic cold water passes through this coil pre heating it from 16 degrees to 35 degrees before being topped up to 55 degrees in the domestic hot water cylinder by a standard electric element.

Upstairs area:

The upstairs floor is constructed from timber so under floor heating was not an option. As the whole system design is based on heated water and a single heat source we chose hot water radiators sized to accommodate the lower water temperature produce by the heat pump and a buffer storage tank to deal with the instant demand of the radiators reducing lag and increasing efficiency.


The buffer tank temperature is controlled by an electronic thermostat with an in tank probe. The thermostat talks directly to the 15kw heat pump. The radiators are feed through an 8 zone manifold and each Radiator has its own thermostatic head to control water flow and therefore the temperature in the room. The under floor heating is controlled by a digital electronic thermostat which calls in the hot water circulation pump when required. All the systems temperatures and run times can be changed simply at either of the two electronic thermostats.

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