FGHRS & WWHRS

At the time of writing the methodology for EPC assessments of existing dwellings is RDSAP 9.94. The much anticipated RDSAP 10 update is due in Q1 2025 and a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026.

This is a device that essentially uses remaining heat in the exhaust gases passing out of the flue of a boiler to heat up incoming mains cold water before it goes into the boiler.

Some boilers can have this built in, but its 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 specific 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.

WWHRS is essentially a heat exchanger that uses the heat of used waste water exiting a bath or shower, to slightly heat up the incoming cold water feed before it reaches the shower.

There are at least three ways this device can be configured in a property, particularly in new-builds, but for my existing 1950s house the easiest way for me to retrofit this would be the type that sits directly under the bath and is self contained. This type is suitable for me because I have a mixer shower over my bath, and fitting other types would require a more costly installation.

This type of device can only be recognised in the EPC assessment when fitted to mixer showers.

If I was happy spending the money, I would look first at the Recoup Easyfit+ device. This costs around £600 for the device plus fitting. The cost per SAP points increase is relatively high but it's another option that could be useful if you are on the threshold of moving up a rating band.

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.

Example picture of the Recoup Easyfit+:

To be included in the EPC assessment, any WWHRS device you install must be listed in the Product Characteristics Database (PCDB), which is maintained by the Building Research Establishment (BRE).

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.

The PCDB is available to search here:

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

Click on the section for Waste 'Water Heat Recovery Systems' and view the list of devices.

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