GB Joinery, a manufacturer of premium timber windows and doors, has achieved U-Values as low as 1.2 W/(m²K) for its windows through ER Certification.

With growing demand for energy-efficient solutions, GB Joinery’s flush casement windows can now achieve a U-Value of 1.2, its Stormproof casement windows 1.3, and its sliding sash windows can deliver a U-Value of 1.4.

Lee Parrott, managing director of GB Joinery, said: “Achieving these U-values is a significant milestone for GB Joinery. We’re proud to offer our trade customers exceptionally crafted timber windows that not only meet but exceed the energy efficiency demands of today’s market.

“For installers, this translates into a product that can meet contemporary expectations while retaining the traditional beauty of genuine timber that discerning homeowners want.”

The improvements come as part of GB Joinery’s ongoing commitment to providing premium, energy-efficient products made from sustainable, high-performance Accoya timber, known for its superior strength and durability.

With lead times of just 4-6 weeks, GB Joinery says that it can ensure installers can rely on fast delivery while offering expert support and training – making them perfect for installers already working with timber and those looking to add it to their product offering.