KJ Tait

Part L Changes

24 June 2022

The long awaited Part L 2021 is here, so what are the main changes to the methodology that new buildings need to achieve? The changes are being termed an ‘uplift’; it is acknowledged that the changes are an interim step to more fundamental changes come 2025. To reflect the continued adoption of heat pumps for heating, the new Part L will move to a Primary Energy metric as the main mechanism to assessing whether a building has passed the Building Regulations. The current carbon dioxide stipulation will remain, but as a secondary metric to assess against. By using a Primary Energy metric, the need to worry about the ever-decreasing carbon factor for grid electricity is removed.

PV will be specified on the Notional Building making it harder to achieve compliance with the Building Regulations for heating systems such direct electric or gas fired boilers. For buildings supplied via heat pumps, this stipulation is removed. If a percentage of the building is supplied via heat pumps, then the PV on the Notional Building will be pro-rated in line with the percentage of the heating system that is heat pumps.


More generally, the systems and fabric specified for the Notional Building are significantly better than Part L 2013. For example, lighting within the Notional Building is now 95lm/W and the external wall 0.18W/m2K. Whilst our Design Teams have been specifying lighting and external wall U-values better than this, it still may present challenges when the whole building is assessed.


The changes may not lead to a revolution in sustainability standards, that will still be reserved for local planning and industry schemes such as Design for Performance, but the changes will make it make it harder to comply with Building Regulations for those buildings not being heated via a heat pump, which is what the industry wants.