The Future Homes and Buildings Standards (FHS/FBS) are finally here. For non-higher-risk buildings (non-HRBs), they will come into force in March 2027, with a one-year transition period; HRBs follow six months later. For at least two years, SAP 10.3 and the new Home Energy Model will be available as approved methodologies for homes.
On the whole, the FHS/FBS are in line with consultation proposals, and continue to use primary energy and carbon emissions as metrics. However, we believe total energy use would better represent building performance independently from the system.
In homes, the standards continue to use the Fabric Energy Efficiency Standard (FEES), which is theoretical and cannot be checked against actual performance. (In the recent HEM:EPC consultation, CIBSE expressed opposition to the use of FEES. It proposed that if FEES is used, it must at least incorporate fabric test results within the calculation or as a factor in the confidence rating.) Overall fabric and efficiency services proposals are largely in line with consultation proposals.
As expected, they effectively prevent onsite fossil fuel heating (although there are exemptions, such as backup in hospitals). For buildings connected to heat networks, the implications will be covered in future columns, as they rely on a number of factors, including: the Heat Network Technical Assurance Scheme; the approach to sleeving (how new network capacity is accounted for); carbon factors for technologies such as combined heat and power, and energy from waste; and carbon content of heat limits in heat zones.
An important change is the approach to renewable energy. A new Part L3 introduces a functional requirement for renewable electricity generation for homes; it becomes an objective in itself and cannot be traded against fabric or services efficiency.
The requirement is for an annual output (kWh) and peak power (kWp) at least equal to that of a PV array with an efficiency of 0.22kWp m-2 installed over an area equivalent to 40% of the home’s ground-floor area, orientated south-east to south-west at 45° and not overshaded. Constraints such as roof design or access can reduce this requirement. Buildings are exempt if constraints cut the generation to less than 720kWh per home, or for HRBs.
CIBSE supports these principles to contribute to Grid decarbonisation and benefit consumers, but the detail will depend on how systems are modelled and how constraints are interpreted. We welcome feedback on whether the requirement is meaningful and has reasonable flexibility. In non-residential buildings, renewables are encouraged through the notional building, with a PV area equivalent to 40% of the foundation area (reduced from 75% on top-lit buildings following consultation).
Other important items are a disappointment for consumer protection and building performance:
Despite strong support (more than 90% of respondents), homes will be modelled using average, rather than regional, weather. This means the same home could comply in the north and south, putting customers in the north at risk of higher energy bills. It is also problematic with heat pumps becoming the norm, as they are more impacted by the weather than boilers.
The government is not yet taking forward proposals encouraging performance testing, even though 90% of respondents supported it. It intends to call for evidence on the performance gap and building performance evaluation, alongside research by the Building Safety Regulator.
In spite of strong backing (nearly 85% of respondents), homes created by material change of use will not yet be subject to whole-building standards – there will be consultations on this.
Looking forward
In 2026, the government intends to review the National Calculation Methodology (NCM). CIBSE has been advocating this for years (see our 2022 evidence submission), as the NCM has serious limitations in modelling energy use and driving the right design choices.
There will also be a review of Approved Document O, to examine concerns including overlaps with other Parts. CIBSE recommends further reviewing of fabric and services needs to truly deliver net zero-ready buildings, alongside ventilation systems to address air quality and energy use.
Incorporating embodied carbon needs should also be reviewed, as per the Part Z proposal. This was (again) recommended by the Environmental Audit Committee, to which government responded that it ‘rejects the committee’s recommendation to introduce mandatory whole life carbon assessments’, but ‘continues to assess the evidence to consider the best way forward for reducing embodied carbon emissions in new buildings’.
ABOUT THE AUTHOR
Julie Godefroy is the CIBSE head of net zero