What’s the plan?

There is insufficient ambition for new buildings in 2025, says CIBSE’s Julie Godefroy, who also questions the plan for the existing stock

In late January, the government published a long-awaited consultation package on Building Regulations, covering: new and existing dwellings and non-domestic buildings; 2021 Approved Documents L and F; a new overheating standard for new homes; and outlines of the 2025 Future Homes Standard (FHS) and Future Buildings Standard (FBS). There are some positive changes in the proposals, compared with the 2019-20 FHS consultation:

  • Retaining the right of local authorities to set energy and carbon standards beyond regulatory minima, allowing more carbon savings earlier, and developing the rest of the market
  • Accelerated development of the FHS, with a draft now due in 2023. This will allow early adoption by market leaders and local authorities, and support the development of supply chains.
  • Retaining fabric energy efficiency standards (FEES), the removal of which created serious risks of fuel poverty and poor fabric performance
  • For non-domestic buildings, clear statements acknowledging the performance gap, with a strengthening of commissioning requirements, changes to the NCM to ‘better account for energy uses and incentivise appropriate design solutions’, and energy performance modelling (for example, CIBSE TM54) for buildings of more than 1,000m2
  • For non-domestic buildings, clear statements about the importance of heat decarbonisation, anticipating a central role for heat pumps and no role for hydrogen in the timescale considered.

However, there are many concerning measures and omissions, which could be addressed by the following key asks (with implementation date in brackets):

1. Target setting: the consultation retains the approach based on a notional building. All opportunities need to be captured towards the net-zero carbon target. The notional building prevents like-for-like comparisons and does not drive optimisation of building form and orientation. New buildings of the same type should be compared with the same target level of performance. (2025)

For non-domestic buildings, the 2021 uplift proposes to vary the heating fuel in the notional building – for example, district heating or gas if this is in the actual building. This gives artificial support factors for particular systems, rather than a like-for-like evaluation of low carbon options. (2025)

2. Metrics: the consultation proposes a dual-metric system – primary energy and carbon – alongside a fabric performance requirement. Neither metric means much to consumers, especially primary energy. They rely on conversion factors, which change over time, and this does not facilitate tracking of progress, comparing buildings, or creating a closer link with actual performance. Also, primary energy favours gas over electricity, so goes against heat decarbonisation. Energy use and carbon would better address energy efficiency, carbon reduction, and consumer engagement. (2021)

3. A commitment to actual performance, starting with disclosure: actual in-use performance beyond practical completion must be addressed – for example, as part of the regulatory regime created in response to the Hackitt Review. This should start with disclosure of energy use (broken down into fuels where applicable). (2021) The data could inform future revisions of Building Regulations and the setting of absolute, not relative, targets (see point 1). (2025)

4. Commissioning: there should be stronger incentives for commissioning and performance testing, such as a penalty in as-built Part L calculations unless satisfactory results are given to Building Control. This will benefit energy efficiency and, for ventilation, air quality. (2021)

5. Airtightness and ventilation: the draft FHS specification proposes an airtightness of 5m3.h-1.m-2 at 50Pa, and natural ventilation. This is far from the ‘world class’ levels of energy efficiency intended for the FHS, and is a remaining important opportunity for energy savings. The FHS specification should show best-practice airtightness and MVHR (even if other systems remain allowed). This would encourage the development of supply chains so that MVHR is well designed and installed, and delivers energy savings and good indoor air quality. (2025)

6. A trajectory for existing stock: for existing domestic and non-domestic buildings, the consultation package only includes a 2021 revision, and it is a relatively modest one. Government must commit to a 2025 upgrade and set out a programme of works to introduce upgraded requirements informed by evidence, and supported by clear guidance on complex technical issues. This should incorporate lessons from recent exemplar retrofit projects, past programmes, such as Retrofit for the Future, and additional research if required – for example, on dealing with thermal bridges and moisture. (2021)

7. A plan and a whole-building approach for the existing stock: the current requirements for existing buildings do not provide an end goal compatible with net zero, and they rely heavily on an elemental approach. This doesn’t sufficiently make the links between energy, overheating, air quality and fabric, and it doesn’t prevent carbon lock-ins and unintended consequences. All works covered by Building Regulations must contribute to putting buildings on track to net zero, while being healthy and comfortable. The Part F requirement that ventilation should be ‘no worse’ than before the works is highly inadequate, as many homes are not well ventilated. The works should be ‘net zero ready’, and a longer-term plan should be produced for the building, to reduce operational, embodied and financial expenditure. It is the approach promoted in PAS 2035, which regulations should build on. (2021)

8. Calculation methodologies that are fit for net zero: there is little evidence that NCM drives improvements on non-domestic buildings. Space heating is routinely underestimated, clearly an issue for heat decarbonisation and the appraisal of options. BEIS recently commissioned a study on how to turn SAP/RdSAP 111 into a tool for net zero. MHCLG should commission a similar exercise on the NCM. (2025)

More detailed points are available at CIBSE’s pages on Building Regulations Part L & F, overheating, Future Homes and Future Buildings Standards

Get involved

The consultation deadline is 13 April 2021. CIBSE is working with LETI and others on our response. Please get in touch at JGodefroy@cibse.org to get involved. We are very interested in contributions on the following:

  • Testing of the new simplified overheating method
  • Improvements to NCM – for example, changes to the method; comparisons between Part L calculations and performance modelling, Passivhaus, or actual energy use
  • Fabric/thermal performance metric: views and evidence on the best approach – for example, for homes: space-heating demand, heat transfer coefficient, a combination, or both? For non-domestic: a combined space-heating and cooling demand metric, or separate ones?
  • Heat pumps: comments on the proposals for heat pump applications, their efficiency and applicability depending on space heating and hot-water usage profiles, and implementation timescales
  • Performance modelling against TM54: comments on the draft requirement and making it as effective as possible
  • Comments on TM39 and TM23, which are referred to in the draft Approved Documents, and which CIBSE is planning to revise alongside.2


1 Led by Etude, with CIBSE, Elementa, Levitt Bernstein, WDP, Clarion Housing Group and UCL.

2 TM23 Revision, and TM39 Consultation,