The new Part L Building Regulations will be in force from 2025. While Part L focuses on new buildings, it will affect the EPC methodology. Why? It will affect EPCs as the National Calculation Methodology (NCM) is updated with new carbon factors for grid electricity.

Part L Building Regulations, what is the significant change?

When we transitioned from Part L 2013 to Part L 2021, there was a significant decrease of 400% in the carbon factor for grid electricity. The effect of this was generally to:

• Improve the EPC ratings of VRF buildings
• Decrease the EPC ratings of gas buildings

All this without doing any work. With the change to Part L 2025, the carbon factor is reducing from its monthly factor of circa 0.163kgCO₂/kWh to 0.086kgCO₂/kWh, a 90% decrease.

Part L Building Regulations, how will this affect EPCs?

We have carried out an analysis using the new carbon factor on some three buildings we have previously lodged EPCs for:

Our analysis has found that there is not much movement in gas boiler/FCU buildings; it could be that anything built after the 2010 Building Regulations serviced with gas could still achieve an EPC ‘B’.

The VRF building continues to improve under the new regulations, mainly due to less carbon emitted from the heating system.

The quirk of the Part L Building Regulations is that the building serviced via VAV improved by 22 points.  This is because of the high pumping energy required for a VAV building under the EPC modelling, where the carbon is reduced under the new regulations.

Part L Building Regulations – Conclusion

As ever with EPCs,  there will be significant nuances regarding whether an EPC should improve or worsen. However, the general trend points to further improvements in VRF buildings and substantial improvements in systems that have traditionally been considered inefficient, such as VAV.

Read more about the NCM modelling guide here