Air Source Heat Pumps: A Guide

How Do Heat Pumps Work?
Is My Home Suitable?

What if you could take the cold air from outdoors, push it through a whirring metal box, and have the air come out at a high enough temperature to heat your home? It sounds like a crazy idea, but that's exactly what an air source heat pump does.

By Josephine Smit, editor of Building4change.com

Air source heat pumps have been used in countries around the world for years and now they're becoming increasingly popular in the UK as the cost of fuel, particularly oil and liquefied petroleum gas (LPG) rises. The technology is tried and tested, but choosing the right heat pump for an existing home can be complex, so it's essential to do your homework before buying.

What Is A Heat Pump?

A heat pump comes as a box-like unit, either around the size of a washing machine and sited adjacent to the house in the garden, or smaller and generally mounted on an external wall. Heating experts say it is often difficult to explain to customers how the technology works, simply because the idea of getting heat from the air, particularly during the winter, sounds implausible. However, it does absorb heat from the air, which is then used to warm air inside your home or to warm the water flowing through your heating system.

How Do They Work?

Heat pumps work in exactly the same way as a refrigerator, but in reverse. While a fridge extracts heat from the air inside it to make the space colder, a heat pump extracts heat from the air around it to warm your home. There are two types of heat pump: air-to-air which produces hot air, and air-to-water which produces water to a temperature of around 35-45 degrees centigrade.

What If The Weather's Cold?

The principle of extracting heat from the outside air works, even when it is freezing cold outside. Manufacturers say heat pumps can work in temperatures as low as -15 degrees centigrade. The heat pumps are equipped with an automatic 'defrost mode' which removes any ice inside the unit during very cold weather.

Pros & Cons

If your home is right for them, and particularly if you are currently using costly oil or LPG for heating, then air source heat pumps can help you save money and carbon emissions.

The units do make some noise when they are running, but this should not be excessive and makers and installers recommend siting the unit away from noise-sensitive areas.

If you do opt for a heat pump, then it is important to learn how to use it so that you get the best out of the technology.