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Vision Zero Consult are doing a series of ‘Facts on….’ articles to highlight current technologies and key elements of a sustainable approach to developing, retrofitting and powering the UK’s building stock.

As much as 80% of the buildings that will be standing in 2050 have already been built. Therefore the biggest challenge in achieving net zero for UK plc is developing a practical decarbonisation strategy for both existing domestic and commercial property.

In this context there are multiple variables in achieving net zero, but what role can Air source Heat Pumps play?

Air Source Heat Pumps are highly efficient at generating heat, but generally have output temperatures about 20o lower than gas or oil boilers.

That means they are best specified on new developments or in wider retrofits along with fabric improvements such as insulation and double glazing.

Less common are high temperature heat pumps which generally use an additional heat source to provide the boost to typical heating system temperatures.

The efficiency of ASHPs means they deliver more heat energy than the electrical energy they consume. So a heat-pump system can cost less to run than a traditional fossil fuel heating system.

Air source heat pumps are a key part of the government funded public sector decarbonisation fund, which has provided over £2 billion to a wide range of public sector bodies for the decarbonisation of their estates. ASHPs are replacing gas boilers.

Air source heat pumps are very efficient, with an outstanding SCOP (seasonal coefficient of performance). A typical air source heat pump runs at a COP 3.2 when the outside temperature is above 7°C. This means that the heat pump is 320% efficient: for each kWh of electricity used by the fans and the compressor, 3.2 kWh of heat is generated. The higher the COP, the better.

Although air source heat pumps can work at temperatures as low as -20°C, they do lose efficiency below 0°C. This is because they exclusively depend on outside air and as the temperature drops, so does the overall heat output that the pump can produce. Ground source heat pumps on the other hand have pipes buried deep under the ground and have a more stable temperature and are little affected by cold climate

Current challenges include both lead times and increasing costs, in common with many other items of equipment.