INDUSTRY VIEWFINDER 35


WWHR plus modulating electric showers could see an increase in specifi cation in coming months.


Challenges


What were the greatest design challenges when delivering FHS projects, for our cohort? And, which building elements or systems were most diffi cult to specify? Capital cost increase was the main concern, and the second most prominent answer was client resistance based on those cost uplifts – a concerningly high 42% of respondents picking this. The other barriers were predictable, with skills shortages in third, followed by design time and resources, and ‘contractor competency’ not far behind, at 32%. A lack of clarity of Government guidance was an issue for 22% of our respondents, but somewhat reassuringly, space requirements for plant such as MVHR and other services only presented a challenge for 16%. Also, overheating mitigation might have been assumed to be higher up the list, but was only 12%; planning restrictions were chosen by 11%. Somewhat of a cautionary fi nding for suppliers, reinforced by later questions, was that ‘lack of reliable performance data’ [on products] was chosen by 9% of our respondents. The most diffi cult building elements and systems to specify for compliant homes at this point, said our respondents, were ventilation systems (53%), followed by renewable technologies such as PVs (50%). Heat pumps were signifi cantly challenging too (46%), but other elements such as airtightness products, building fabric and insulation, and moisture management were less of a concern (30%, 17% and 13% respectively). Glazing manufacturers will be pleased to hear that only 1% said that specifi cation for FHS compliance was a challenge, despite the more onerous per-unit performance calculation methods being introduced for windows.


Performance data


While data on product performance was clearly important for specifi ers, how critical was the factor of that data being verifi ed by third-parties? Despite not being offi cially mandated, a conclusive 72% said it was ‘very important,’ and the remaining 28% said it was ‘moderately important.’ Bearing in mind the above fi nding, how confi dent were our respondents in the accuracy and transparency of manufacturers’ own environmental and performance information? This was less conclusive than the fi gure on the importance of third party testing, with most respondents being in the ‘middle ground’ – 42% saying they were ‘not very confi dent,’ and only 20% saying they were ‘very confi dent.’ Manufacturers either need to improve their accuracy and transparency of data, or consult better with suppliers to help them understand the veracity of what they are offering. Despite this challenging fi nding for manufacturers, what types of technical information were more critical for architects? Due to the focus of this survey, the somewhat generic factor of ‘compliance guidance’ was most popular, at 62%, with Declaration of Performance (including ‘verifi ed thermal performance’) just behind at 61%. A key issue in terms of overall thermal performance, junction detailing info was only picked by 23%,


perhaps pointing to the diffi culty in obtaining such info from single manufacturers.


Performance Gap Most respondents (64%) were ‘very concerned’ about the risk of a persistent gap between design and built performance post-FHS, while 33% said they were ‘moderately’ concerned. Unfortunately, yet predictably, a resounding 74% said that ‘poor installation quality’ was the culprit, no doubt aligning with a contingent of 51% saying ‘insuffi cient contractor knowledge.’ Also, supporting manufacturer concerns in the sector, ‘product substitution or value engineering’ was a substantial factor, with 44% choosing it. Coordination problems in design processes, occupant behaviour,


and ‘airtightness failures’ were all further down the list, but not insignifi cant numbers (29%, 21% and 15%). Echoing the responses around heat pumps in the subsequent question, ‘commissioning’ of systems post-install was higher up the list, at 38%. A glaring lack of post-occupancy evaluation in residential projects was not seen as a major reason for the performance gap, suggesting that such data would not be the necessary ‘stick’ to drive more onsite rigour.


Heat pumps


Heat pumps’ effectiveness, particularly if not correctly sized and commissioned, may be a moot point for many specifi ers. We devoted a question to the specifi c design challenges that architects were seeing in FHS compliance using ‘heat pump-led’ designs currently. The results confi rmed expectations, although perhaps many would have expected ‘upfront cost’ to be above ‘plant space requirements’ as the top challenge picked. This shows just how diffi cult the spatial issues around including heat pumps in residential designs may prove to be at scale – 56% said it was a challenge. At the other end of the spectrum, noise was a negligible concern, with only 3% choosing it.


There were some other concerning issues around heat pumps, according to our survey, with ‘installer competency,’ and the related issue of commissioning new systems coming in at 46% and 33%. Commissioning systems correctly for optimising their performance in each domestic setting has been pinpointed as an acute issue currently, with attendant risks for a performance gap between design and in-use. Increasing the knowledge level of installers across the board remains a work in progress. Other critical issues around heat pumps were hot water storage, and the associated demand on the electricity grid, both having a signifi cant 31% vote from our respondents. And the more latent issue of having adequate building fabric to ensure as-designed heat pump performance was picked by 20%, so was clearly a real issue.


Overheating


Mitigating overheating, and thereby balancing Part O requirements with Part L, was not perhaps as large a concern for the overall shape of schemes as may have been expected, from our sample. While 21% said that their glazing specifi cation strategy had been affected ‘signifi cantly,’ suggesting that they had reduced window


ADF OCTOBER/NOVEMBER 2026


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