INSULATION
READY FOR THE FUTURE
Jonathan Ducker, Head of Regulatory Affairs at Kingspan Insulation tells BMJ about insulation implications of the Future Homes Standard.
W
ith the Future Homes Standard due to come into force next year, new homes will need to be fully “net zero ready”. These
new regulations will bring a number of changes for customers, requiring most new homes to be fitted with heat pumps and solar PV panels. The changes may also affect some existing developments as transitional arrangements, which have allowed developers to build to older energy standards, are set to close. As ever, delivering a good level of fabric performance will be key to achieving compliance and ensuring homes are affordable to heat. To achieve this, customers will be looking to merchants for guidance on how changes may impact their projects and what insulation options and thicknesses may work best for their budget and requirements.
What’s in the Standard? At the moment, the Government is yet to publish the final version of the FHS. However, the consultation on the standard and further announcements in May give a good steer on what is likely to be included.
Two different options were proposed for the Notional Dwelling specification in the consultation. One proposed option is largely unchanged from the existing requirements in Approved Document L 2021 (ADL 2021), other than switching to low carbon heating. The second option limits air loss to 4 m3/m2.h@50Pa with ventilation provided via a mechanical ventilation heat recovery system, and includes both roof PV and wastewater heat recovery. In May, the Government indicated that it was leaning towards an approach where PV would
England ADL 2021 – Notional Dwelling & Proposed FHS
External wall (W/m2K) Floor (W/m2K) Roof (W/m2K)
0.18 0.13 0.11
be installed in “the vast majority of new build homes”.
Surprisingly, neither of the specifications require the roofs, walls and floors to be upgraded beyond the current values. With low carbon heating appliances performing most efficiently at lower flow temperatures than conventional boilers, ensuring homes retain heat well will be vital to enabling them to be heated affordably. This means it is worth customers considering improving on the notional specification U-values and looking to the values in Wales and Scotland (shown below). Importantly, the consultation on the standard also suggested that “transitional arrangements” from the 2010 and 2013 versions of ADL will come to an end. These arrangements have allowed some developers to continue to build new homes to these outdated standards where initial work on the developments began before the “transitional” deadline. This change may require some customers to substantially improve the fabric performance on new units. Getting the insulation choice right will therefore be key.
Finding the right insulation With the wide range of insulation products now stocked by merchants, it is important to be clear how these products differ and where they may be most suitable to meet a customers’ needs. A fundamental consideration is the thermal conductivity of the insulation. The lower this value is, the more effective it will be at preventing heat loss. This can allow a specific U-value to be reached with a slimmer thickness of insulation than might be possible with worse performing alternatives.
Phenolic insulation boards achieve some of the Wales Part L 2025
Consultation Notional Dwelling
0.15 0.11 0.11
Table 1: Selected fabric performance requirements from Notional Dwelling/Building specifications November 2025
www.buildersmerchantsjournal.net Scotland –
Section 6 (Energy) – Notional Building
0.15 0.12 0.09
Above: Kingspan Kooltherm K106 Cavity Board is a full fill phenolic insulation cavity solution with a thermal conductivity of 0.019 W/mK. The boards can be fitted with a 10 mm residual cavity in suitable applications
lowest thermal conductivities of commonly used insulation — as low as 0.019 W/mK. This can be beneficial in a number of applications such as cavity walls, where they can allow low U-values to be reached with 100 mm or 125 mm cavities – allowing internal floor space to be maximised. Similarly, in room-in-the-roof constructions, this performance can reduce the depth of insulation needed below or above rafters to achieve a given U-value. This can raise the floor-to-ceiling height internally whilst also meeting any ridge height restrictions externally.
Polyisocyanurate (PIR) insulation can offer another versatile option which is suitable for a wide range of applications. These boards typically have a higher thermal conductivity than phenolic boards, which can result in somewhat thicker constructions, but can provide a solution where budgets are limited. PIR boards also provide a practical solution for flat roof areas where phenolic solutions are unavailable. There are also specific areas of a property where the use of specialist insulation materials may be beneficial. Extruded polystyrene (XPS) boards provide a practical solution in these areas, providing effective insulation and resistance to ground moisture penetration.
Addressing all areas
The introduction of the FHS is a key step for the whole industry and will mean some upheaval in the approaches builders adopt. However, getting the fabric right will remain a fundamental requirement.
With the wide range of insulation options currently available, and dedicated training and support, merchants have the tools to support customers in reaching compliance with the regulations and delivering “net zero ready” homes. BMJ
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