Flue Gas Heat Recovery Systems (FGHRS)

The current methodology for EPC assessments of existing dwellings in England and Wales is RdSAP 10. The Government plans to introduce reformed EPCs based on the Home Energy Model (HEM) in the second half of 2027.

Changes to EPC metrics will also affect how property energy performance is reported and how future Minimum Energy Efficiency Standards (MEES) are assessed. For privately rented homes in England and Wales, the Government has set 1 October 2030 as the compliance date for the new MEES standard.

These changes mean that the measures needed to improve a property's current EPC rating may not necessarily be the same as those required to meet future standards. The guidance on this page relates primarily to the current RdSAP methodology.

This uses remaining heat in the exhaust gases passing through a boiler flue to heat up the incoming mains cold water, for domestic hot water, before it enters the boiler.

This results in the boiler using slightly less energy to heat the incoming water  to the required  temperture. 

As EPC ratings for domestic properties are currently based entirely on cost, this results in a slightly better EPC rating.  

Some boilers can have FGHRS built in, but it's more often seen as an additional device fitted above the boiler, in-line with the flue.

The presence of FGHRS can only be recorded in an EPC assessment if the device in the property is listed in the Product Characteristics Database (PCDB), hosted by the Building Research Establishment (BRE):

https://www.ncm-pcdb.org.uk/sap/searchpod.jsp?id=17

On their page, click on the 'Flue gas heat recovery sytsems' button to see the range of systems listed.

Flue Gas Heat Recovery Systems in domestic properties are pretty rare. Most people aren't aware of this type of system and it provides quite a low EPC rating improvement considering the expense of having one fitted.

Example picture here of an Alpha Gas Saver FGHRS:

For my 1950s terraced house that we cover in Case Study 2, this could provide me with an increase of 1 SAP point from 68D to 69C.

This is a small increase in rating, but it's another option that could be useful if like me, you are on the threshold of moving up a rating band.

Check the PCDB before purchasing a device, and also check with a local Energy Assessor to make sure the device makes a difference to the rating for your property before proceeding.

Click here to return to our 'Improve Your EPC' main page, and see if there is another way you could improve your EPC rating.