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INDUSTRY VIEWFINDER
Which of these building elements or systems are you fi nding most challenging to specify for Future Homes Standard compliance? Survey fi ndings
The key design change under the new Part L, brought in with the FHS, is the airtightness target used in the ‘notional building.’ Most new build homes achieve air-tightness in the 4-6 m3/(h·m2) range, but achieving the new notional target of 4 m3/(h·m2), but as well as better detailing such as at junctions and penetrations, it demands a better level of site discipline, and independent verifi cation. Higher insulation and airtightness levels can mean a need for complex mechanical ventilation and wastewater heat recovery systems to prevent indoor air quality as well as overheating issues. On-site renewable integration in the form of PVs on the roof (to 40% of ground fl oor area), and EV charging complicate roof design, procurement, and site logistics. The ongoing skills shortages in the industry compound these challenges, including a lack of expertise in planning and SAP assessment, for example. While windows’ U-values (1.2 W/m2K) are staying ‘as per’ Part L under the FHS, the method of calculation being far more rigorous, calculated based on the specifi c size and confi guration of each individual opening rather than a standard model of window. This could be one area where cost is added to the entire build, because a non-standard window may be required.
Design strategies Given the overall targets, what design and specifi cation strategies were currently being pursued for residential projects in order to comply, based on what respondents currently knew of the FHS? Given the somewhat lower profi le of ‘fabric fi rst’ in recent months as the focus has shifted towards heating and renewables, the top answer was ‘a fabric fi rst approach, with increased air-tightness.’ This could also refl ect the key change in
terms of building envelope design being the increased air-tightness requirement from Part L 2021. However, air source heat pumps were only one percentage point
behind, showing just how far the industry has moved towards seeing their inclusion as a ‘fait accompli’ for FHS compliance. In third place, refl ecting the 40% of ground fl oor area requirement in the standard, was solar PV (plus battery storage). Showing the impact of air-tight constructions, MVHR was included by 28% of our survey cohort, and mixed mode and/or natural ventilation was also in the mix (27% picked it). Of our surveyed architects, 10% said they were making ‘no signifi cant changes to their current design approach,’ and only 8% were pursuing offsite/MMC construction solutions. This meant the onus was on improving onsite approaches to bring a lot more rigour in construction to achieve desired performance levels. Which specifi c building technologies and approaches did architects expect to specify most frequently as the standard comes into force? Solar PV was ahead of heat pumps (67% and 52% respectively), with air-tightness measures, mixed mode/natural ventilation, and thermally broken windows/lintels all sitting in joint third, just ahead of air to water heat pumps, at 56%. A reasonable number (22%) said they would be specifying battery storage – to maximise solar PV installations’ effectiveness. District heating, ground source, and water-only heat pumps were only forecasts as likely options by a shockingly low 1% of our sample. Smart controls for ventilation and overall energy management fared better, with 23% and 18% respectively, but only 11% picked waste water heat recovery and only 10% underfl oor heating as likely to be specifi ed by them. Now included in the still in force Appendix Q of SAP however, as a compliant measure,
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ADF OCTOBER/NOVEMBER 2026
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