The BREEAM system for measuring the environmental sustainability of a building is now considered to be the world’s leading building assessment programme.
Under this system, air-source heat pumps should score highly, as they use renewable heat and are more energy and carbon-efficient than systems that use conventional fossil fuels.
Indeed, by using the latest heat pump technology with integrated heat recovery equipment, the number of credits received will be increased.
But there is a contradiction in the way heat pumps are assessed. Under BREEAM’s pollution section, credits are awarded for systems that use less than 5 kg of refrigerant - refrigerant with <5 GWP - and provide a detection and pump down facility should a leak occur, reflecting concern over the possible release of gases with high global warming potentials.
However, most commercial buildings with air conditioning are ruled out of the first credit, as they will use more than 5 kg of refrigerant.
Specifying <5 GWP presupposes that any system using a high global warming property (GWP) refrigerant will produce greater greenhouse gas emissions than one using a low-GWP one.
It completely ignores the TEWI equation (BS, EN 378-1), which looks at the whole-life approach and takes electrical
generation emissions into consideration.
There are many systems using gasses such as R410A whose lifetime emissions can be shown to be far lower than less efficient but lower-GWP refrigerants. This is true even where a high average leakage rate is used for the HFC in question.
There is also a problem with the use of low-GWP refrigerants, such as hydrocarbons and ammonia, (alternatives suggested by BREEAM), which are either explosive or highly toxic.
Direct expansion refrigerant systems, such as those used by heat pumps and which require the use of HFCs, are highly energy efficient and contribute enormously to the reduction of carbon emissions.
Understandably, the credits given for leak prevention and detection monitoring do not apply to direct expansion systems, which have coils in the open air, as any leak will be diluted before it can be measured by a gas sampling analyser.
This precludes air-source heat pump systems from qualifying for the credit unless they can show a practical, permanent and automatic method of detecting a leak by other means. It is up to manufacturers to develop these.
Overall, heat pumps have an important role to play in gaining BREEAM credits and can contribute significantly to creating buildings that are environmentally sustainable.
However, because there are unintended conflicts between the different sections within the credit rating system, heat pumps are, in my view, unfairly penalised.
Simon Keel is product executive at Daikin UK