Proposed changes and consultations around the Future Homes Standard continue to leave the New Dwelling housebuilding sector in a state of uncertainty, with potential ramifications for professionals in all areas of the supply chain. However, by focussing solely on u-values, the industry risks losing sight of the wider benefits of the proposed introduction of the Home Energy Model. Head of Technical Services and Certification Manager at REHAU Mark Gajda, discusses this pressing issue further.
The announcement of the Future Homes Standard (FHS) in 2019 has caused major upheaval across the housebuilding sector. Changing the requirements around property ventilation and energy efficiency detailed in Part F and Part L of the Building Regulations would undoubtedly have a knock-on effect on component specification and housing design. Further, significant regulatory adjustments in 2022 and the publication of a new consultation document in December 2023 has kept many stakeholders in a state of flux as the housebuilding industry looks to reach net zero emissions by 2050.
Though uncertainty continues over what level of thermal performance is required for New Dwellings, an unchanging fact remains – change is coming. More updates are expected ahead of the FHS’s implementation in January 2025, and these changes will affect all aspects of a build, from the structure’s fabric to components including window frames. Indeed, the shifting and non-shifting requirements around window thermal performance provides an excellent example of this unpredictability in action.
Changing Compliance
In the run-up to the latest consultation on the FHS being published last December, it was widely expected that the required u-value for frames would drop from 1.2 W/m²K to 1.0 W/m²K or even 0.8 W/m², improving a home’s thermal performance. However, the update said no tightening of restrictions would be forthcoming, surprising many in the fenestration sector.
Considering the expected impact of the FHS, this sort of upheaval is to be expected as January draws closer, but this specific event emphasises something particularly important. Namely, that when it comes to window specification at this moment, these metrics may be a red herring. Other updates within the consultation demonstrate a need to look beyond the numbers and take a holistic view of each individual property when specifying components.
Simply put, there are so many permutations that make each home different, and this will affect what frames housebuilders require. What is right for a home in London city centre may not be for a house on the Cornish coast, as both properties will be subject to different stresses and environmental strains.
There may also be additional changes to the FHS ahead of 2025, further emphasising that overly focusing on current u-value figures during specification is not advised. By concentrating only on unchanging thermal performance metrics of certain components, project stakeholders may not select the most efficient and carbon-friendly solutions that suit a specific home’s overall footprint and geographic location.
SAP vs. the Home Energy Model
The fact this issue has been recognised is to the consultation’s credit and can be seen in the introduction of the new Home Energy Model (HEM). Used to calculate a building’s overall energy efficiency under the FHS, the HEM replaces the old SAP10 assessment method. Under SAP10, energy use for Part F of the Building Regulations was calculated with fixed, component-by-component targets, based on a UK property’s average monthly energy use. Similarly, ventilation requirements for Part L took a similarly wide-reaching view, being informed by national weather patterns.
While this approach provided guideline figures for thermal performance and air movement, they were arguably not specific enough. By contrast, the HEM assesses a property’s peak energy use in half-hour segments to discern between peaks and troughs in consumption, while local weather patterns are considered instead of a country-wide average. Though this assessment methodology will undoubtedly need to be refined ahead of the FHS’s 2025 introduction, the HEM’s more nuanced approach also allows for greater latitude over individual, structural components of the property.
After all, windows make up part of a larger whole within the house’s fabric and should be treated as such during specification. This once again goes back to each home being unique, whether by design or location. Where a frame cannot meet a specific u-value due to where and how it is situated within the property or the home’s location, the HEM’s methodology allows housebuilders to compensate for through the specification of other components, including insulation and flooring.
Direction of travel
More clarity should be expected for housebuilders in the coming months, but these changes to the assessment methodology are nonetheless encouraging. Removing the emphasis from unchanging performance metrics such as window u-values means more suitable solutions can be selected on a house-by-house basis. However, this approach necessitates even closer cooperation throughout housebuilder supply chains if they are to adapt to the FHS’s demands.
The sector’s preparedness for this upcoming change remains a concern, regardless of changes to how property performance is assessed. According to REHAU’s latest market readiness report, Future Homes Standard: Preparing UK Housing for 2025, two thirds of the industry are not ready for the FHS’s mandatory regulations. The report’s findings, taken from a survey of 200 decision-makers across the various housing sectors, also present other challenges.
For example, a worrying 79% of respondents also expressed that meeting the current FHS timeline would be ‘somewhat challenging’ or ‘very challenging’. Though the room for interpretation set out within the HEM assessment method is clearly a good thing overall, housebuilders would undoubtedly appreciate greater, more immediate certainty during the specification process. Given the importance of components such as windows to a home’s overall energy efficiency, this is understandable.
Working Together
An ongoing, collaborative effort across supply chains is therefore crucial to identifying best practices and solutions for developers. Component suppliers and manufacturers have a large role to play in bridging the gap between current practice and FHS compliance, especially as the situation surrounding the FHS continues to shift and January 2025 draws nearer.
With this in mind, it is advised housebuilders leverage the expertise of these organisations. Where windows are concerned, system houses such as REHAU are continuing to engage with all stakeholders in the FHS consultation process to better support housebuilders before and after its introduction. Addressing potential uncertainty within the housebuilding sector is essential to these efforts, and advice will undoubtedly continue to evolve as the FHS’s requirements are clarified further.
Yet as the deadline looms, it is imperative all parties look to proactively navigate any challenges that may arise ahead of 2025. For housebuilders, this should include consulting with component providers over the specifics of the HEM assessment model and its impact on individual parts of a building’s fabric. Going beyond the numbers and performance metrics alone will be key to constructing thermally efficient homes fit for the future, and this approach should be integrated into specification processes at the earliest opportunity.