Heat Pump Basics

What this is

A heat pump moves heat from outside air or from the ground into the house rather than producing heat by burning something. Because it works by moving heat, it delivers water at a lower temperature than a conventional boiler, and that single fact changes almost everything else about how the system has to be designed.

Telling whether your home is ready

Lower water temperature means each radiator gives out less, so emitters usually need to be larger, and the shell of the house needs to be losing less heat in the first place. That is why the envelope entries in this catalogue come first. A house with thin loft insulation, leaking draughts and radiators sized for a hot boiler is not yet in a position to make this decision.

What the job involves

The work begins with a room-by-room heat loss calculation rather than a product choice. That calculation sets the flow temperature, which sets the emitter sizes, which sets whether pipework needs changing. There is also an outdoor unit or a ground loop to site, a hot water cylinder to place, and controls that suit steady low-output running rather than short bursts.

Things to watch

The habit of turning the heating on and off through the day suits a boiler and does not suit a heat pump, which works best running gently for long periods. Outdoor units need clear air around them and a position where noise and defrost water are not a problem. This is design-led work: the calculation is the deliverable that matters, and it should exist before any equipment is chosen.