VIEWPOINT
POST- PART L SUPPORT FOR HOUSEBUILDERS
Matt Neary, Knauf Insulation T
he changes to Approved Document L (Part L) of the building regulations in England brought in the most significant change in energy efficiency standards for over a decade. The transition period ended in June 2023, so all new homes must now be built to the new standard. This means they must achieve a 31% reduction in CO2 emissions through fabric efficiency and low-carbon technologies.
However, the sands are still shifting. The Future Homes Standard looms large on the horizon. Set to come into force in 2025 – just two years away – it will bring even stricter energy efficiency standards. To prepare, there’s a simple change that housebuilders can consider making now – increasing cavity widths.
Which leaves them with a dilemma. Do they simply address the short-term regulatory requirements? Or do they take the leap now and widen cavity widths to ensure their designs are futureproofed?
Large housebuilders will of course have whole departments looking at this very topic, but smaller housebuilders will need support. So, it’s important that merchants understand the pros and cons so they can help guide them to the right solution.
The immediate need of Part L The current standards required under Part L give housebuilders flexibility in their approach to compliance. For example, insulation can be increased in one part of the building fabric to offset a lower level of insulation in another. Installing 500mm of our Loft Roll 44 in the loft will increase the thermal performance of the roof, meaning that 100mm of DriTherm® Cavity Slab 32 can be installed in the cavity walls, allowing the housebuilder to retain traditional 100mm cavity widths. This approach is ideal for plots or developments where it’s not possible to increase cavity widths due to other project requirements . But as previously mentioned, Part L is due to be replaced by the Future
Homes Standard which will introduce a massive 75% reduction in CO2 emissions. So, it’s worth merchants flagging this to their housebuilder customers now so they can prepare, because building with 100mm cavities may not be viable for much longer.
Preparing for the future So, how can you advise your housebuilder customers to prepare for the future? With The Future Homes Standard, building with 150mm cavities is likely to become the norm – indeed, it’s something that many of the large housebuilders are already doing. Taking steps to adapt their design specifications now means that small housebuilders have plenty of time to get it right – and they won’t have to adapt a scheme midway through the build or undertake retrofit work later.
More importantly, increasing cavity widths by 50mm has a minimal impact on floor space or plot sizes, but will provide optimal fabric performance in low and mid-rise homes. It will also give housebuilders more flexibility to choose the best insulation for the job. For example, 150mm of DriTherm® Cavity Slab 32 not only provides reliable thermal and
August 2023
www.buildersmerchantsjournal.net
acoustic performance, it also offers greater peace of mind because it’s non-combustible. That’s important because regulations are only going in one direction – towards stricter standards. This is evidenced by last year’s update to Approved Document B. Non- combustible materials must now be used in certain external wall system build-ups, such as rainscreen façades and timber frames, on all residential buildings between 11m and 18m, unless a full-scale fire test to BS 8414-1 or BS 8414-2 has been conducted.
There’s another factor too. We’re operating in a time of supply chain disruption – which can have a huge impact on build schedules. The good news is that increasing cavity widths opens up the choice of products, meaning that if a chosen solution isn’t available, merchants will have a greater range of options to help them achieve compliance.
It’s clear that where energy efficiency standards are concerned, the status quo is not an option. And while building to 150mm cavities may seem like a step that’s easier to delay for as long as possible, it’s clear there are plenty of benefits for small housebuilders who make the change now. So, it makes sense to start highlighting them to your customers. BMJ
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