Label A while retaining wooden window frames

1e Binnenvestgracht / Kort Galgewater Leiden

The Netherlands must be 100% circular by 2050, and even 50% by 2030. Circular construction and renovation is about closing loops by repairing and reusing raw materials and materials, among other things. For renovation, maintenance and neighborhood transformation specialist Elk® Group, circularity starts with awareness. What that looks like explains project leader Demi Roelofzen, responsible for the renovation of 25 homes owned by housing foundation Portaal in downtown Leiden. Owner Portaal wants to improve the building, which dates from 1983, with a quality improvement in design and performance and make it future-proof. One way of doing this is by aiming for Energy Label A, which means most economical and most sustainable, including insulation measures such as filling the cavity, roof insulation and tackling the frames, windows and doors.

Elk® project manager Demi Roelofzen says, "For us, installing insulating glass is a fairly standard renovation procedure in buildings from the 1980s. Many of those homes struggle with heat buildup in the summer and high energy use for heating in the winter. Draughts and cold complaints at doors and windows are also common for us."

Life Extension

Client Portaal wanted to equip the facade with HR++ glass. Elk® has a standard methodology for this. The procedure starts with an inspection. Demi Roelofzen: "In this project, we were dealing with forty-year-old wooden window frames. With plastic or aluminum window frames of that age, in most cases it is not possible to reuse the old window frames. This is different with wood. We encourage clients to first have research done on the current state of the wooden facade carpentry. With partial replacement, repair and a new coat of paint, a wooden window frame can, in most cases, be restored to almost new condition. That saves time and money, and extends the life of existing components. And life extension also has an environmental benefit on the circular R-ladder because you save raw materials."

Suitable

Elk® has its own inspection and repair teams for the facade. Inspection of the window frames reveals that they are far from being at the end of their useful life in Leiden. Demi Roelofzen: "At the time of the new construction forty years ago, pine window frames were chosen. Because of the systematic maintenance that Portaal has done over four decades, all the window frames were still in tiptop order. We therefore did not have to do any major repair or partial replacement of deteriorated parts." 

Accordingly, research showed that the current window frames were suitable for installation of the new HR++ glass without many problems. "This did prove to be a problem with the windows," says Roelofzen. "They were corroded here and there and were not suitable in terms of size to support the new HR++ glass." It was decided to equip all 62 hinged parts with new frames (meranti stiles and sills 54 x 90 mm) directly from the factory with insulating glass HR++ and painted to achieve glass and window replacement within one day. 

Weekamp Deuren in Dedemsvaart, manufacturer of the 36 wooden balcony and terrace doors, four Tricomfort front doors and the six access doors for the storeroom also signed for the windows. The member carpentry manufacturers of SGT/HOUT100% make every effort to ensure that the quality of their products for delivery is as high as possible through the use of modern production techniques and a certified manufacturing process. Factory checks, construction site checks, delivery checks and maintenance checks accompany the wooden window frame during production, installation and service life.

Extending service life and dealing smartly with construction and material costs, in short circular building, will become increasingly important towards 2030 and 2050. Demi Roelofzen: "Our experience is that in the case of wooden window frames, this can be done very well in most cases." The wish is therefore that more clients follow the good example set by Portaal and Elk®. Elk® began the project Oct. 7, 2024, and completed it in the second week of March 2025. End result is a fresh and new-looking energy label A building with a high quality of living and a comfortable living environment and reused window frames. And that for at least the next forty years.