Thermoseal Group is urging IGU manufacturers to reassess their component choices, as the Future Homes Standard (FHS) introduces a fundamental shift in how window performance is calculated.

Under the new Home Energy Model (HEM), calculations for new build homes move away from standardised assumptions, towards modelling each individual window based on its exact size, configuration and components.

This means that for new build glazing, every element within the window – including spacer bars, sealants and desiccants – will directly influence the overall thermal calculation of the installation.

“The Future Homes Standard represents a real change in how performance will be measured in new build housing,” said Mark Hickox, sales director at Thermoseal Group. “It’s no longer enough to rely on a notional window. Under HEM, every component within the IGU contributes to the final calculation – and that includes all ancillaries.”

According to Thermoseal, as window designs become more complex, with smaller apertures and added features such as Georgian bars and dummy sashes, achieving target U-values becomes increasingly difficult.

In this context, the performance of each component is critical – and even marginal gains can determine whether a window passes or fails.

Thermoseal Group says it has positioned itself at the forefront of this shift, offering IGU manufacturers a fully evidenced component supply chain backed by industry-leading testing and product performance.

Its Thermoflex warm edge spacer, independently tested and BFRC approved, delivers a thermal conductivity of 0.125 W/(mK) – reportedly making it the most thermally efficient flexible spacer system available.

“With HEM, higher-performing components like Thermoflex can make a real difference to whether a window achieves compliance in a new build project,” Mark explained. “When every decimal point counts, performance is no longer optional.”

Thermoseal supports this performance with robust in-house testing and validation. Operating one of the industry’s most advanced EN1279 laboratories, the company undertakes comprehensive analysis of materials, adhesion and long-term durability to ensure full traceability and real-world performance.

This level of evidence will be essential as the industry adapts to a regime where assumptions are replaced by measured data.

“As new build specifications tighten, IGU manufacturers need more than just components – they need evidence,” added Mark. “That’s where working with a supplier like Thermoseal Group, with a proven testing infrastructure, becomes critical.”