Rehau has worked in partnership with Roseview Windows to develop an energy efficient solution for heritage style sash windows that can achieve U values of 1.2 W/m²K without triple or vacuum glazing – reportedly the first sash window to do so.

The ThermoVFlex system has been designed to improve the energy efficiency of a sash window by improving the performance of the frame, rather than relying on high performance glazing.

Keane Grantham, marketing manager at Roseview Windows, commented: “Energy efficiency is becoming an increasingly important factor for customers in the self-build market, but they still want a variety of design options for their windows.

“Currently, we recommend that new build projects aim for a U-value of 1.2 W/m²K to futureproof and stay ahead of any potential updates to the Future Homes Standard or any further environmental legislation.

“However, current methods of achieving this performance level in sash windows can be expensive for self-builders while also restricting the design and aesthetic options available, such as astragal bars, safety glass, and other traditional patterns. This is why the ThermoVFlex system is so crucial; it enhances the frame’s overall energy efficiency without compromising the appearance of the finished window.”

The ThermoVFlex system is currently used by Roseview to manufacture its Heritage Rose and Ultimate Rose sash windows.

Russell Hand, head of windows at Rehau UK, said: “It is commonly known that the UK’s housing stock is among the draughtiest in Europe.

“As the Committee on Climate Change has previously made clear, decarbonising new and existing homes will be vital to achieving net zero decarbonisation goals.

“We pride ourselves on being a whole systems provider and hope we can make a major impact in this ongoing journey to greener homes. Providing innovations such as the ThermoVFlex system to the self-build market and beyond will be key to this.”