The Gledhill Thermal Store has immersion heaters to boost the hot water and even the heating where necessary but for most of the time the heat pump should be able to meet the heating demands without backup. The control system is commissioned with the aid of a laptop to make sure that the output and demand are matched. If the house cools down the fan will speed up and the pump will extract more heat from the air. With a well insulated house the idea is to just keep pace with the heat loss rather than push masses of heat into the building to make it uncomfortable.

Scott Rawling from Ankers and Rawling told us "In our houses nobody ever complains that they are cold. If there is one complaint we get it is that they are often too hot. People come in and turn the thermostats and boiler up full blast then forget about it until they are overheating then of course the house won't lose the heat quickly enough. It is a matter of getting used to the idea of maintaining a steady heat. The heat pump and under floor heating will do this without them even thinking about it because the comfort levels are controlled to a constant temperature".

The stored water has two high efficiency coils passing through it. One contains the water for the taps and the other lower down has the central heating water which in this case feeds under floor heating on both floors.

TRENCH METHOD

Ground source heat pumps work in the same way as air source but the heat is extracted from the ground which tends to give a more consistent heat source with very little fluctuation throughout the heating season. The draw back is that you need to bury a long pipe in the ground. If you don't happen to have a spare plot of land or a river or lake (it can extract from water as well as ground) then a bore hole is another alternative. Bore holes are expensive so the payback period on a ground source can be longer even though it is more efficient than an air source pump.

Worcester Bosch (known primarily for boilers) is a leading company in ground source heat pumps. They have working examples installed in UK homes that can be viewed or monitored on line. The company provides training courses for installers.