Reynaers Aluminium UK is urging developers to act now as the Future Homes Standard ushers in a fundamental calculation shift that will reshape the specification of windows and doors to meet energy targets.
Reynaers’ technical experts believe the most critical implication of the Future Homes Standard is how energy performance must now be calculated, arguing that for newbuild homes under Approved Document L, the impact will prove to be far more significant than a series of regulatory revisions.
Under previous Part L regulations, the U-value of a window or door could be assessed using its actual size and configuration, a standard reference configuration, or the hot-box method. That standard configuration route has now been removed, meaning every window, door and patio door must be assessed using its actual size, or verified through hot-box testing. The design implications are expected to be far-reaching, with any change to a single U-value significantly impacting the build.
The Government has confirmed that compliance will initially be assessed using SAP 10.3, while the long-term intention is a transition toward the Home Energy Model (HEM). Once implemented, the HEM will introduce a fundamentally different approach to energy assessment.
Projects specified for completion in 2027 are already in the design stages, with key specifications – such as fenestration systems – being fixed now. With the implementation of Approved Document L fixed for March 2027 – or September of that year for high-risk buildings – Reynaers believes the window for the market to respond is deceptively short when factoring in the time to assemble data sets, invest in simulation capability, complete training and build supplier relationships.
John McComb, Technical Director at Reynaers Aluminium UK, said: “This transition marks a significant change in both the process and methodology used to demonstrate compliance in the newbuild residential setting, requiring considerably greater levels of design accuracy, coordination and performance forecasting from the earliest stages of a project.
“Given the long lead times associated with specification, procurement and construction within the newbuild sector, the implications of this new calculation methodology must be considered well in advance of formal implementation.”