MATERIALS IN ARCHITECTURE SUPPLEMENT 43
Calculating the impact of the new window calcs
John McComb at Reynaers Aluminium UK discusses how the new, more rigorous method of calculating window performance is reshaping the fenestration industry.
S
ince the latest Future Homes Standard was published outlining the changes to Part L and Part F of the Building
Regulations, much of the early industry commentary has understandably focused on what those changes will bring. However, now that the standard has fi nally arrived, perhaps the more important discussion should be about how energy performance must now be calculated. Following a lengthy delay, the Future Homes Standard was fi nally published in March 2026, with much of the industry response to date focused on the detail of the extensive consultation. However, for new- build homes under Approved Document L1 (ADL1), the impact will prove to be far more signifi cant than a series of regulatory revisions, representing instead a fundamental shift in how compliance is demonstrated.
In commercial fenestration projects this kind of detail oriented, project specifi c calculation has been considered best practice and commonplace for many years. The Future Homes Standard now requires the residential sector – particularly new-build housing – to adopt the same approach. Where compliance had previously relied on standard sizes and blanket energy ratings, every window, door and patio door must now be calculated on its specifi c dimensions and composition. In addition, hardware such as couplers must now be accounted for and distinguished between load-bearing and non-load bearing. Why do these design implications matter? As each element must now be calculated individually, any change to a single U-value, even a small one, can signifi cantly impact the entire build. For instance, if a door is widened by even a few millimetres to achieve compliance under the new standard this could reduce the square footage of an adjacent room. This is the sort of design
ADF OCTOBER/NOVEMBER 2026
decision that Tier 1 developers should be considering now.
The Government has confi rmed that compliance will initially be assessed using SAP 10.3, while the longer-term intention is a transition toward the Home Energy Model (HEM). Once implemented, HEM will introduce a fundamentally different approach to energy assessment. This transition represents far more than a software update. It marks a signifi cant change in both the process and methodology used to demonstrate
Each element must now be calculated individually – any change to a single U-value can signifi cantly impact the entire build
WWW.ARCHITECTSDATAFILE.CO.UK
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108
