Window systems made of post-consumed aluminum for circular repurposing project

National monument De Meelfabriek in Leiden is undergoing a true metamorphosis, with existing buildings being thoroughly renovated and new volumes added. Alwiti BV of Dordrecht was commissioned by main contractor Van der Wiel Bouw to manufacture and integrate the window frames and curtain wall systems for the Singeltoren. Meanwhile, the Meelpakhuis and Silotoren were also awarded to the facade builder. Systems from SAPA are chosen for these projects: Avantis window frames, Confort 160 sliding doors and Elegance 52 ST curtain wall systems. All profiles consist of Hydro CIRCAL 75R post-consumed aluminum, which fits perfectly within the story of this circular reuse project. 

In early 2015, Studio Akkerhuis was commissioned to revitalize the site of the former Flour Factory. Some existing buildings retain their unique historical character, while others are renewed with the help of architectural interventions. In addition, several new volumes with their own identity will be integrated. On a floor space of no less than 55,000 m² there will be lofts, apartments, student housing, a hotel, a restaurant, sports and wellness facilities, stores, a space for art and culture and offices. 

Van der Wiel Bouw was commissioned to co-execute this redevelopment project as the general contractor. Thus, in 2018, construction began on the Singel Tower, a slender new residential tower 45 m high, good for 30 apartments and 2 penthouses. This new construction volume was recently completed. Meanwhile, a number of other subprojects were also started, such as the redevelopment of the Meelpakhuis with 12 lofts, 8 penthouses and a commercial and cultural concept on the first floor (completion in 2023) and the new Silotoren with 33 apartments and 2 penthouses spread over 12 residential floors (completion in 2024).

Many large windows

The general contractor commissioned facade builder Alwiti BV to manufacture and install the window frames, sliding doors and curtain wall systems. These run from floor to high ceiling in most residential units, resulting in plenty of natural light and a grandiose view of the surroundings. "We were involved in the various projects at a fairly early stage by the facade contractor. After all, since these are high-rise buildings, the systems have to meet strict requirements. Moreover, it is important to plan everything well and deliver the windows just-in-time to the construction site," explains Roger Cremer, country manager Benelux for the SAPA brand. "For the Singel Tower and the Silotoren, window frames type Avantis 75 and curtain wall systems type Elegance 52 ST were chosen, while in the Flour Warehouse Avantis Smartline window frames, Confort 160 sliding doors and Elegance 52 ST curtain wall systems were provided. All window systems are characterized by their slim aluminum profiles and score highly in terms of thermal and acoustic insulation, wind and water tightness and burglar resistance."

Post-consumed aluminum

The most important feature, however, is that the frames, sliding doors and curtain walls are realized with profiles made of post-consumer aluminum. From 2022, only Hydro CIRCAL 75R will be used for the production of the SAPA windows and doors, sliding windows and curtain wall systems; aluminum that consists of at least 75% of post-consumer scrap and has a footprint of only 2.3 kg CO2 per kg aluminum. "During discussions with the architect, the plan was raised to effectively implement the theme of circularity and produce the systems entirely in CIRCAL 75R. Aluminum is ideal as a circular material. After all, it can be used endlessly, without loss of quality and properties," Cremer points out. "Our parent company is one of the largest producers of primary and recycled aluminum and an important European supplier of extruded products, including to customers in the construction industry. Today, more than 200,000,000 tons of aluminum is stockpiled in buildings around the world and this is a true source of recycling opportunities. We want to give old windows and doors a new life ... as a window or door system. And so this project fits our story perfectly. It does bring the necessary challenges in terms of production, but a project like this shakes you up because then you really have to organize everything perfectly. In the future, more and more projects will be realized, where old industrial and semi-industrial buildings will be transformed and that using circular material."