John Miles, technical manager and business development manager at Assent Building Control, explains how architects must balance creativity with compliance to implement the changes to Part L building regulations

From 15 June 2022, changes to Part L of the Building Regulations will set ambitious efficiency standards for UK housing. The changes pave the way for the 2025 Future Homes Standard (FHS), which calls for the average house to produce at least 75% fewer carbon emissions than current rules allow.

The Plan L uplifts provide a run-up to 2025’s more rigorous measures – and a chance for industry and suppliers to find their feet before the FHS comes into force. Under interim guidance, new houses must reduce carbon emissions by 31%. Glazing must mitigate overheating risks. And building materials, heating and power systems must meet tougher energy performance metrics.

The updates are a vital step in the evolution of green construction, making bold strides towards the government’s net-zero goals. But to succeed, the end-to-end process must evolve too. More than ever, architects must balance creativity with compliance – and collaborate at every step of design and build.

Building as a balancing act

The revised Plan L speeds the move to low-carbon technology in place of gas boilers. However, the overarching aim is to replace reliance on heating systems with fabric-first heat retention. In the home of the future, materials must do the heavy lifting.

With that in mind, the Plan L updates tighten minimum efficiency standards for new and replacement thermal elements, windows and doors. U-values have been reduced to limit heat loss and tackle the performance gap:

  • Walls – 0.28 to 0.18
  • Roof lights – 1.6 to 1.4
  • Windows – 1.8 to 1.4

While the U-value decreases are minimal, they signal a critical shift to materials-led design. For example, updated U-values for windows could mean the difference between double and triple glazing – with all associated cost, labour and approval implications. Products are likely to become more expensive, lead times longer and the planning process more complex.

Similarly, new rules that limit glazing in any dwelling to 25% will challenge customer demand for light-filled homes and extensions. But with the right materials, creative workarounds are possible. Solar control glass on south-facing rooms and low emissivity glazing in north-facing spaces can achieve a compliant middle ground.

This give and take is a key Plan L takeaway. Shortfalls in one area can be boosted in others – but it pays to build in compliance from the very beginning. Under current regulations, it’s feasible to construct homes using only basic information. Builders can deviate from plans based on product availability or preference. However, updated standards call for significant efficiencies in building services.

Off-the-peg boilers and go-to glazing schemes are no longer viable options. Instead, designs must examine the function of individual building fabrics and their contribution to a coordinated, compliant whole.

Architects need to consider sustainability from the first sketch, engage early with building control and approved inspectors – and ensure best practice carries through to construction.

SAP assessment and building control – the importance of early engagement

Working with an accredited SAP assessor before plans are submitted is crucial. Their experience of build techniques, heating systems and energy performance does more than encourage sign-off from building control. They shape a holistic view of every home.

Compliance questions are simple to solve at design stage, but costly and disruptive once the build has begun. Initial drawings should include details of construction methods, airtightness, insulation and lighting, heating and ventilation systems. They also need enough flex to weave in assessor feedback and recommendations of greener products and processes.

Flexibility also futureproofs designs from unpredictable legislative changes. Reviewing new-build plans now will clarify which version of Part L you need to adhere to.

  • The transitional Plan L arrangement runs until June 2023.
  • Beyond that date, existing projects must comply with the updated requirements.
  • New projects submitted after 15 June 2022 must comply with the new standards.
  • If regulations alter again in the future, unbuilt plots must reflect the latest guidelines.

Ideally, architects, SAP assessors and building control professionals should collaborate from the outset of any project – and throughout construction – to model the energy footprint of each new house and lock in compliance from start to finish.

Your four-step path to new Plan L compliance

With updated Plan L requirements launching in June, teamwork between every member of the build effort has never been more essential. The changes require a rethink of working practices and architects can take practical steps to prepare:

  • Take an early lead – Engaging early with construction crews, developers and building control brings clarity to any project. It allows compliance to be ‘designed in’ from day one and ensures a shared understanding of materials and methods.
  • Adopt a team approach – Establish clear communication lines with every project player. Regular check-ins and solid working relationships mean concerns are quickly raised and resolved, cutting the odds of costly performance gap problems.
  • Consider the big picture – Your project team can’t work in isolation – and neither can your materials. Use SAP calculations and the expertise of assessors and approved building inspectors to adjust efficiency levers and create a successful, symbiotic system.
  • Plan ahead – Review upcoming projects against key Plan L dates to make sure you remain With the pandemic still affecting supply chains, you may also need to allow for stock shortages and sourcing issues. Plan L changes could also see building professionals taking time out to upskill.

Architects will play a pivotal role in implementing Plan L revisions – and the more stringent standards to come. As we draw closer to decarbonisation, practical measures such as U-value reductions and air source heat pumps will cut emissions. But collaborative working practices will create comfortable, compliant homes.

As project leaders and pioneers, architects will set the tone for communication and commitment across every build team. The change in approach will bring us nearer to our net-zero objectives – and the sooner the benefits begin, the better.


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