HOT TOPIC: 'The 2025 Future Homes Standard' consultation

Chris Cummings, Technical Director at chapmanbdsp, on Lower Carbon Factors and New Metrics: What does the new consultation tell us about the next chapter in residential design?

This time last year, we sat poring over the details of the GLA’s incoming guidance on production of energy strategies, which had taken a progressive step in getting ahead of Building Regulations by adopting the carbon factors for electricity as proposed in SAP 10.0, due to be enshrined in regulation this autumn.

This precipitated a fundamental shift in the feasibility discussion surrounding CHP and ASHP in London, requiring a re-think around several major projects to bring them in line with the re-positioned goalposts.

Now, 12 months on, we are reviewing the consultation on the 2025 Future Homes Standard, including the first glimpses of the incoming changes to Part L and Part F which we can now expect to come into force this time next year, with separate consultation on these starting in the next few months.

The headline consultation question appears to be whether to target a 20 per cent or 31 per cent reduction on the previous Part L for dwellings in 2020. As this is simply a transitional step towards an anticipated 75-80 per cent reduction just five years later, the real interest lies in the detail behind the targets.

The change of principal metric from carbon to primary energy was always going to become necessary at some point as the grid decarbonisation gathered pace.

The incoming Part L will be adopting even lower carbon factors for electricity than previously estimated, with SAP 10.1 electricity carbon factors significantly lower than gas for the first time (and with seasonal variation!) requiring that shift to come about earlier than expected.

The final regulations are to be based on SAP 10.2, but it would come as a surprise to most if the carbon factors were to change again, with the current proposals viewed as progressive in themselves.

As ever, the real interest can be found when exploring the gaps that are yet to be filled and how these filter through into the ‘real world’.

Arguably a bigger impact of the GLA’s updates to its Energy Assessment Guidance was the insistence on undertaking TM59 overheating analysis, with the pursuit of the twin goals of overheating mitigation and compliance with the Fabric Energy Efficiency (FEE) target resulting in a significant re-draw of many residential facades.

The new guidance proposes scrapping FEE, with improved U-values and thermal bridging as the primary passive backstops, whilst we await subsequent consultation on overheating, expected to form a new regulation in itself.

The introduction of an Affordability Standard is a welcome step towards safeguarding the occupant against higher running costs brought about by cheaper installations.

This would mean that a developer would potentially still be able to introduce cheaper direct electric heating but only with a very high quality of passive design to minimise running costs. Similarly, the push for more stringent transitional arrangements should help to ensure dwellings are not brought to the market based on obsolete performance targets.

Building Regulations in the UK have been responsible for a significant improvement in the energy efficiency of new dwellings over the past 20 years, but it is definitely time to take another big step forward. Hopefully these standards and regulations can help to bring that about.

We will be responding the consultation on the 2025 Future Homes Standard and upcoming consultations on Part L, Part F and overheating in the coming months. Labs, our R&D function here at chapmanbdsp, will be leading investigations into the impact of these and future changes on our projects to keep our clients informed on what lies ahead.

For more information email chris.cummings@chapmanbdsp.com