Air Source Heat Pumps

Air Source Heat Pumps are probably the most common type of heat pump. Many of the roof-top air-conditioners that you see on offices and homes are reversible, and can operate in heating mode as well as cooling, but these are usually optimised for cooling mode. Non-reversible air source types for heating-only are usually much more energy-efficient, but the build quality and efficiency will vary greatly.

The air source heat pump system however will be less effective for heating in winter since the air temperature fluctuates and can become very cold. Furthermore, at low air temperatures, ice will form on the heat-exchanger requiring a mechanism of reverse-heating to melt the ice. This process is not as wasteful as maybe first thought, but it still contributes to a reduction in efficiency.

Air Source Heat Pumps are being improved all the time, and are a simpler and cheaper option to install. But there is no way getting around the fact that the air is coldest when you need most heat for the house.

A back-up heater in the form of a conventional electric heater is usually included within the heat pump package. This is far more necessary for air source systems, and usually controlled automatically, if an existing back up heat source is available for the colder months of the year then air source heat pumps can work well if tied in correctly.

Exhaust air heat-recovery heat pumps take their heat from within a building. Such systems can help in buildings with damp problems. However, the electricity consumption of such heat pumps can be considerable. Such systems are common in countries like Sweden where electrical heating is more common, in-part due to their cleaner electricity generating network which has a large hydro-power input.

In new-build houses, such systems can work well if designed well, but there is always a danger that badly installed systems increase the demand on the houses heating system. i.e. ventilation is in excess of requirements, and the boiler load goes up.