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Is there such a thing as ground-to-air heat pump and would you recommend one?

Posted by Tasha Kosviner on 27 January 2014 at 9:50 am

Q. Is it possible to have a ground source heat pump system linked to air vents rather than radiators and if so, would this be a less expensive option than installing radiators?

A. The system you describe is known as a ground-to-air heat pump, as opposed to a ground to water (or 'wet') heat pump system.

A ground source heat pump (GSHP) is usually considered to work best with underfloor heating, which is a 'wet' system as it heats water, rather than air. Underfloor heating is often expensive to install and may not be a viable option in a retrofit property (as opposed to a new build). 

After underfloor heating, installers tend to consider another 'wet' system, this time linked to radiators. Radiators circulating water warmed by a heat pump need to be larger than those in a traditional central heating system as water is heated to a lower temperature (this link is about radiator size and air source heat pumps but the same principle applies to GSHPs too).

Although the ground-to-air 'dry' system you mentioned is theoretically a third option, you may encounter a number of obstacles in your attempts to fit one.

The first is that they are not very common and you may struggle to find a manufacturer that makes them, or an installer who is reassuringly experienced enough at installing them. 

Even if you did - and where there's a will there's a way - you may find that because air contains less heat-to-volume compared to water, you will need to have very large ducts installed to transport sufficient heat. This may present constructional problems greater than installing the water pipes needed for a ‘wet’ system linked to radiators or underfloor heating. It may also be harder to control the delivery of heat into the house as heat in air is harder to adjust than heat in water. For all these reasons it is unlikely that you'll find a ground-to-air system is cheaper to installer than a 'wet' system linked to radiators or underfloor heating. 

Finally, and this may be the deciding factor if you're motivated by cost, a ground-to-air system is not currently eligible for the government's domestic renewable heat incentive scheme (RHI) when it comes into force this spring (2014).

If you’re concerned about the size of the radiators required for a ground source heat pump, you may consider fan-assisted radiators. These are radiators which have a small fan installed which pushes the warm air into the room meaning you can get more heat out of a smaller radiator. They come with a higher price tag than a standard radiator but are significantly smaller and come in a variety of designs which may better suit your project’s aesthetics.

Whichever system you go for, make sure that both the product and the installer are MCS-accredited to enable you to claim RHI, where eligible.

More information

YouGen guide to heat pumps

YouGen guide to renewable heat incentive

From the blog

Renewable heat incentive: your questions answered (Dec 2013)

How to install a heat pump in an existing property (Feb 2011)

Can heat pumps provide hot water? (May 2011)

Photo Credit: Pulpolux !!! via Compfight cc  

If you have a question about anything in the above blog, please ask it in the comments section below.

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