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INSULATION
‘Building ahead of the Future Homes Standard’ means getting the fabric right fi rst
Fabric fi rst is the key to LZC Solar PV, heat pumps and mechanical ventilation with heat recovery (MVHR) often dominate the conversation around future homes. While the exact requirements for these technologies are still being confi rmed, they are expected to play a central role in meeting future carbon targets. Their effectiveness, however, depends on a well-insulated building envelope, combined with controlled ventilation and suffi cient airtightness. Heat pumps, for example, must be correctly sized for the spaces they serve. If excessive heat is lost through the building fabric, the effective heating demand increases, reducing effi ciency and undermining performance even where the system has been correctly specifi ed. The lower the space heating demand, the smaller and more effi cient the low-carbon heating system can be, and the easier it becomes to avoid high peak loads and uncomfortable temperature swings. This makes an effi cient building fabric essential to the goal of reducing overall energy consumption that LZC technologies are designed to achieve.
Building ahead Taking a fabric fi rst approach to home design means considering how material choice affects as-built performance, and
where standard practices may need to change to ensure thermal effi ciency. Loft insulation is a good example. It is highly cost effective, relatively simple to install, and has a substantial impact on thermal performance. Many architects are already specifying insulation depths well beyond the current minimum of 270 mm, with some designs accommodating up to 500 mm. This maximises roof performance and provides fl exibility elsewhere in the overall energy strategy.
Change is also evident in cavity wall
design. Despite a modest increase in building footprint, 150 mm cavities make it easier to achieve lower U-values using full- fi ll insulation such as glass mineral wool. Wider cavities reduce thermal transmittance and allow the use of insulation that is more tolerant of site conditions and less prone to air gaps, helping to deliver consistent thermal performance in practice.
Making homes ready Honey, founded in 2022, is one example of a housebuilder deliberately working ahead of the incoming standard by focusing on buildability and measurable outcomes. At Thoresby Vale in Nottinghamshire, Honey has delivered homes designed to exceed the likely direction of FHS targets. The specifi cation includes fully fi lled 150 mm cavities, upgraded party wall insulation to prevent thermal bypass, and loft insulation installed to a depth of 500 mm, thereby achieving a reported roof U-value of 0.09 W/m2K.
One early completion achieved an EPC A rating with a score of 92, air permeability
of 3.9 m3/h.m2, and operational CO2 emissions of 1.4 tonnes per year, compared with a UK average of around six.
The future is stricter, but also more testable
Standards are tightening because outcomes matter: running costs, health, comfort and national carbon targets. With more detailed and nuanced assessments available through the Home Energy Model, understanding of how to close the performance gap should continue to improve.
Building ahead of the FHS means getting the fabric right fi rst, enabling low and zero carbon technologies and delivering real thermal effi ciency in new homes.
Bradley Hirst is technical services manager at Knauf Insulation
WWW.ARCHITECTSDATAFILE.CO.UK ADF FEBRUARY 2026
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