Personalising Part L: Find the right path to compliance for your project

Matthew Prowse, Specification and Housing Director for Knauf Insulation, discusses how to find your best route to compliance with the Part L Building Regulations. 

Part L (Conservation of fuel and power) of England’s Building Regulations has been a hot topic within the construction industry for the last couple of years. Updates to the regulations came into full force this June, including a 31% reduction in operational carbon for new build homes and tighter fabric efficiency standards. Housebuilders are also required to complete a new Building Regulations England Part L (BREL) report, providing photo evidence of thermal continuity and quality of insulation. 

Standards are rising fast and new homes are under greater scrutiny than ever before. Housebuilders must deliver homes that comply with increasingly complex regulations, without compromising on other priorities, such as quality and cost.

Part L offers some generic guidance in the form of its ‘notional dwelling’, an example recipe for fabric and heating that shows a possible route to compliance for a typical home. However, this is purely illustrative and copying it is unlikely to be the most cost-effective option for housebuilders. A better approach is to find the solution that works for each individual project. 

Whilst a ‘fabric first’ approach will always be key to achieving energy efficiency, factors like the size and type of development, will determine the right combination of fabric, heat source and renewable technologies. 

Let’s look at some examples…

Volume housebuilding

Large-scale developments often benefit from continuity of design. Volume housebuilders may prefer to keep their fabric specification more or less the same as with the previous regulations and use low and zero carbon (LZC) heat sources or photovoltaic (PV) panels to reduce the carbon emissions of each home. 

Alternatively, design continuity could be maintained across most UK sites by increasing wall cavity widths to 150mm. Updates to National House Building Council guidance now allow 150mm of full fill insulation to be used in masonry applications across all exposure zones in England and Wales, including severe and very severe. This not only negates the need for separate designs per location, it also futureproofs builds beyond the requirements of Part L and prepares them for the tighter requirements of the 2025 Future Homes Standard.

Another consideration is the shape of the building. Thermal bridging is more likely to occur in geometrically complex builds, which can reduce energy efficiency. Housebuilders can ‘design out’ some of that energy loss by creating homes with a simpler footprint.

Smaller housebuilding

Housebuilders working on smaller or medium-sized developments may be concerned about availability when specifying larger quantities of LZC technologies. In these cases, prioritising a higher-efficiency fabric could be a more reliable way to meet Part L’s carbon reduction requirements. This reduces risk whilst still allowing flexibility to specify LZC technologies on a project-by-project basis. 

High-rise housebuilding

A high-rise development’s limited roof space leaves little room for technologies such as PV panels to reduce carbon emissions. At the same time, the height of the building means large-scale boilers are required to heat it. And generating that same heat from a LZC technology, like a heat pump, is unlikely to be cost-effective. With that in mind, high-rise housebuilders might opt for smaller LZC heating, alongside ultra-efficient fabric, to achieve Part L compliance. 

Beyond Part L 

Although Part L is understandably front-of-mind for housebuilders right now, it’s important to remember that energy efficiency is just one area of regulatory change. These requirements sit alongside a whole alphabet of evolving regulations, which often interconnect. For example, insulation plays a key role in complying with both Part L and Part B (Fire safety). Last December, Part B banned the use of combustible materials in certain external wall system build-ups, such as rainscreen façades and timber frames, of residential buildings between 11m and 18m, unless a full-scale fire test to BS 8414-1 or BS 8414-2 has been successfully conducted. The Building Safety Act is also introducing ‘Gateways’ before and after construction, when compliance with Building Regulations must be demonstrated in order for the development to progress further.

It’s clear that regulations will continue to tighten across the board, so it makes sense for housebuilders to choose products which meet multiple needs. Mineral wool insulation is a good example because it’s naturally non-combustible* (with Euroclass A1 or A2-s1,d0 reaction to fire classification), so it offers peace of mind, as well as supporting Part L compliance.

Housebuilding isn’t a ‘one size fits all’ industry and complying with Building Regulations is no different. Yes, it’s important to meet requirements but how this is achieved will differ from project to project. The best route to Part L compliance is one that takes all the factors of a development into account. Insulation choice will be key to any approach and housebuilders can streamline the specification process by choosing products like mineral wool, which offer thermal, fire safety, and acoustic benefits.

For more information on Part L and the wider housebuilding sector, visit Knauf Insulation’s Housebuilders Hub.

*As set out in changes to the building regulations 2010 which bans the use of combustible materials, limiting use of materials to
those achieving A1 or A2-s1,d0 on buildings in scope of the ban (as defined in regulation 7(4)).