What is the Part L 2021 uplift for the Building Regulations in England?

October 28, 2021

What is the Part L 2021 uplift for the Building Regulations in England?

The energy efficiency requirements of the Building Regulations in England are being updated. Part L 2021 is due to come into effect in June 2022 and will act as an ‘uplift’ to help the construction industry adapt to changing regulations and low carbon heating.

The government refers to Part L 2021 interchangeably as the ‘interim Part L’ or the ‘2021 Part L uplift’, because it is a stepping stone to the introduction of the Future Homes and Future Buildings Standards in 2025. It is important to be clear that Part L 2021 is not the Future Homes Standard or the Future Buildings Standard.

What is the timeline for updates to Part L of the Building Regulations?

The government has made the Future Homes Standard a central part of how domestic buildings will help the country to achieve its net zero carbon goals. The Future Buildings Standard is proposed to do the same for non-domestic buildings.

To give industry time to adapt, and to give supply chains time to mature, Part L 2021 proposes an interim reduction in carbon emissions, paving the way for greater reductions, the banning of gas boilers and wider adoption of heat pumps in 2025.

As of July 2021, the government has consulted on, and responded to the feedback for, the proposed Part L 2021 as it relates to new dwellings. This blog post therefore focuses on new-build homes, as that is the detail we have so far. The general principles, however, are relevant to all building types.

A separate consultation dealing with existing dwellings, non-domestic buildings and regulations for overheating is currently in progress. When the government has published its response to that consultation, a ‘full’ Part L 2021 is expected at the end of 2021, alongside a new Part F and Overheating Regulations, with an expected implementation date in June 2022.

By that point, technical work to develop the Future Homes Standard and Future Buildings Standard will be underway. The intention is to publish consultations for these standards in 2023, ready to make the regulations in 2024 and see them come into effect in 2025. That’s a rapid series of change – more rapid than is normally the case for building regulations.

As part of thinking about the long term goal of net zero, it’s important to also remember that planning authorities can still set their own targets to align with their local carbon reduction pledges.

What are the key regulation changes in Part L 2021?

If a building notice or full plans have been submitted by June 2022, the proposed transitional arrangements mean that work will have to start by June 2023. A significant change to transitional arrangements is that they will apply on a dwelling-by-dwelling basis, rather than to the site as a whole.

For larger sites, that could mean the design and construction of properties that span three different sets of regulations.

One of the aims of Part L 2021 is to build the knowledge and expertise to deliver net zero carbon homes. To do that, the uplift will deliver a 31% reduction in carbon emissions without the need for additional carbon offsetting measures and include a number of metrics that will underpin building performance in the years and decades to come.

Building fabric standards are ambitious but, in terms of U-values, are not a significant leap compared to Part L 2013. The airtightness and ventilation of the notional dwelling are not as ambitious as the fabric performance. Ventilation continues to depend on unreliable and uncontrollable natural ventilation, which has disappointed some in the industry.

To deliver the 31% reduction, new homes will be assessed against the following four performance metrics.

  • Primary energy.
  • Carbon dioxide emissions.
  • The fabric energy efficiency standard (FEES).
  • Minimum standards for fabric and fixed building services.

With increasing amounts of renewable energy generation, fuel factors are no longer required to offset ‘dirty’ electricity generation. This will adversely impact any property using oil, LPG or solid mineral fuel, and therefore stands to make the most difference to homes that are off-grid. More widely, it will help to drive the uptake of heat pumps that is a crucial part of the government’s long-term strategy.

How is the compliance calculation methodology changing with Part L 2021?

An updated version of SAP 10 will be introduced with Part L 2021 to produce the necessary compliance calculations for dwellings. SAP 10 represents something of an overhaul of the calculation methodology, introducing new inputs that have a significant impact on the calculation results, and therefore the approach to design and specification.

Among these new inputs are specific details regarding lighting, including the number of lights and their lumens per watt. And for anyone thinking about on site energy storage, photovoltaic diverters and batteries are now included.

Reducing space heating demand therefore remains an essential part of compliance. After space heating, however, hot water is responsible for the biggest proportion of energy demand and carbon emissions in domestic properties. Another significant change in SAP is that its calculation of hot water consumption has been adjusted to take account of shower flow rates. SAP 10 also accounts for electric showers for the first time.

Waste water heat recovery is an excellent way to reduce water heating demand, and is prominent in the calculation methodology. Despite this, it’s a technology that many designers and specifiers seem relatively unfamiliar with. It reduces water heating by 8 to 10% and the savings remain ‘locked in’ with the dwelling - but is not always high on the agenda.

What is the role of Accredited Construction Details (ACDs) in Part L 2021?

As part of the focus on building fabric performance, Part L 2021 removes Accredited Construction Details. They have been around for fifteen years, and the industry has moved on in that time. ACDs are, essentially, no longer useful.

Junction details and psi values will have to come from other detail libraries or be calculated for the specific project. This will give greater certainty that the calculated junction heat losses are being accurately represented in SAP and will reflect how the finished building performs.

It’s still possible to use default psi values in SAP, but the penalty to performance will cause a dwelling to fail to meet the FEES metric - meaning it is not a feasible option.  A key part of dwelling performance for Part L 2021 and beyond is the junction details, highlighting the importance of getting the building fabric right.

How does Part L 2021 aim to address the performance gap?

A new Building Regulations England Part L - or BREL - report will be required as part of the dwelling completion. It will be signed by the SAP assessor and developer and provided to the Building Control Officer and homeowner. To give greater transparency, Energy Performance Certificates will now include the version of the Building Regulations that the property complies with.

Reducing space heating demand and meeting net zero carbon targets can’t happen without addressing the performance gap, and Part L 2021 proposes some quality control measures to try and address it. A photographic record must be kept for each dwelling to confirm that the products named in the BREL report have been used, and that workmanship is of sufficient quality to support the values entered into the SAP calculation.

The scope of airtightness testing is also being expanded. Rather than a sample of dwellings, all dwellings on a development must now be individually airtightness tested. This includes small sites, which were previously exempt.

Planning for Part L 2021 and beyond with Darren Evans

Approaching Part L 2021, while also thinking about the rapid introduction of the Future Homes/Buildings Standard shortly after, requires a holistic approach. Design and specification needs to be based on sensible risk management, focusing on the timeline of regulation changes and long-term climate goals.

The introduction of Part L 2021 provides the impetus to act now – and Darren Evans can help with that. Taking advantage of our services as early as possible means we can have the most impact on your projects.

By taking a more coordinated approach to compliance, we can help you to avoid the over-specification that typically occurs when the focus is on fabric U-values alone.[1]  For example, we can provide friendly, knowledgeable and professional advice about bespoke thermal bridge detailing and psi value calculations, to help save you time and money.

We have produced a CPD presentation that delves into Part L 2021 in greater detail, looking at the risk management aspects of the changes that are being introduced. We also have a range of resources on achieving net zero carbon in construction, including a white paper, CPD and case studies. To find out more and to arrange a CPD session, contact us.

The government website has the consultation-stage draft approved documents to support the new Part L, Part F and overheating regulations. This is subject to change as government moves further through the consultation process.


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