For many years, determining which version of Part L applied to a development was relatively straightforward. Today, however, the regulatory landscape is far more complex. The introduction of interim uplift standards, transitional arrangements and the forthcoming Future Homes Standard (FHS) has created an environment where compliance can influence project viability, programme risk, procurement decisions and long-term asset performance.
The uplift to Part L came into force in June 2022. These requirements were designed as an interim step towards the FHS and Future Buildings Standard, introducing more stringent energy performance targets and reducing operational carbon emissions from new buildings in England. While Wales is pursuing a broadly similar trajectory it does not formally use the FHS terminology, and Scotland operates under a separate regulatory system.
While the 2021 uplift remains the current regulatory benchmark in England, transitional provisions mean that not every project is necessarily required to comply with the same version of Part L.
A project’s planning status, Building Regulations application date and construction programme can all have a direct influence on which standards apply. Developments that secured Building Regulations approval before key regulatory deadlines may still be eligible to proceed under earlier requirements, provided certain conditions are met. However, failure to satisfy those conditions can result in a project being required to adopt a more demanding regulatory framework than originally anticipated.
These transitional arrangements exist to provide certainty for projects already progressing through the development pipeline. Without them, schemes that have invested heavily in design and approvals could face significant redesign costs every time regulations changed. However, these provisions are often misunderstood. Many stakeholders assume that obtaining Building Regulations approval automatically secures the right to build under earlier standards indefinitely. In reality, transitional protections are typically linked to commencement requirements and specific project timelines. Delays in mobilisation, design changes or failure to meet commencement criteria can all affect eligibility for transitional provisions.
Under the FHS’s transitional arrangements, compliance is assessed at the individual building level rather than at site or phase level. This means different plots within the same development may be subject to different requirements depending on when construction commenced. Early consideration of compliance strategy is therefore critical, particularly for developments with extended construction programmes.
TIMESCALES
Developers can continue to build to the current Part L standards provided their site is submitted to and accepted by the relevant Building Authority before 24 March, 2027. Sites that miss this deadline will be required to comply with the FHS across all plots. Where the submission deadline is met, work must commence on every building on the site before 24 March 2028; any buildings not started by this date will need to be redesigned to meet the new standard. For complex or high-rise developments of 18 metres or more, the submission deadline is extended by six months to 24 September 2027.
THE FUTURE HOMES STANDARD
The next major regulatory change will be the introduction of the FHS, to deliver homes that produce significantly lower operational carbon emissions while supporting the UK’s wider net-zero ambitions. This is expected to accelerate the move away from traditional fossil fuel heating systems and increase the importance of low-carbon technologies and fabric-first designs. Projects with long development horizons must consider whether designing solely to current minimum standards remains the most economical approach. In some cases, delivering enhanced energy performance now may reduce future redesigns and protect developments from regulatory uncertainty.
A STRATEGIC RISK
As energy standards tighten, compliance requirements are influencing building form, fabric specifications, heating strategies, renewable technologies and MEP design from much earlier stages. Decisions made during concept design can have significant consequences for regulatory compliance years later. The financial impact can also be substantial. Unexpected regulatory changes can affect procurement strategies, generate redesign costs and influence programme delivery. Where compliance considerations are not identified early enough, projects may find themselves balancing increased capital expenditure against planning and delivery pressures.
The key question is no longer simply, “Which Part L applies today?” Instead, project teams should be asking, “Which regulatory environment will this development operate within throughout its lifecycle?”
A future-focused compliance strategy can help reduce risk, improve programme certainty and create more resilient developments. This means understanding not only the current regulatory position, but also how upcoming changes could affect schemes already underway.
Early-stage assessments, robust compliance reviews and proactive energy strategies are becoming increasingly important tools in supporting informed decision-making. By considering regulatory requirements alongside commercial and programme objectives, developers can avoid costly surprises and position projects for long-term success. aessc.co.uk