Unique airtight connection for prefab plastic window frames

The combination of the company's expertise and drive for innovation recently resulted in a unique solution for airtight sealing of the seams between plastic window frames and wooden frame frames. A clever, efficient and time-saving invention that gives Wijnsma Kozijnen a significant lead in the market....

In addition to industrialization and prefabrication, airtightness is playing an increasingly important role in the construction industry. Also at Wijnsma Kozijnen from Drachten. The company manufactures some 400 prefabricated plastic window frames every week from a state-of-the-art production facility. Quality products that feature a high-quality, durable and above all airtight seal on the border between plastic and wood. It is a many-benefit feature that is the direct result of the cooperation between Wijnsma and Celdex. "The connection between plastic window frames and wooden set frames is a critical seam that can lead to air loss," says Jos ten Brincke, Account Manager Airtight Building on behalf of Celdex. 

"In practice, this seam is usually sealed with PU foam. But the question is whether you then achieve a completely tight connection. This is because the success of the operation depends very much on the person doing the work. And precisely because of this, it is difficult to check whether the seam is full, sat and therefore airtight." 

New application

The search for a better quality, durable, controllable and dry sealing of the connection brought Wijnsma Kozijnen to Celdex. This gave the close relationship between both specialists a nice continuation. "Director Arnold Wijnsma knows that we are open to coming up with new applications for our sealing products," says Ten Brincke. 

"It was therefore a logical step to take on this challenge together." The solution eventually found was Pre-Seal LF ZK, a product with a very fine semi-closed-cell polyurethane foam. However, the application of this air seal did have consequences for the way in which Wijnsma mounts the wooden frames around the plastic window frame. 

"The foam tape is glued to the side of the plastic frame," Ten Brincke explains. "Then the wooden structural frame is pushed around the plastic frame, so to speak. This had to be taken into account in terms of applying the foam tape. The solution to this is a low-friction top layer. This ensures that the tape is strong enough and does not get damaged during installation."

After Pre-Seal LF ZK was selected as the solution, the filler blocks also had to be considered. "These shims, which act as spacers between the plastic window frame and the wooden structural frame, were causing an air leak because they went through the airtight line of the Pre-Seal," Ten Brincke says. "To prevent this, Wijnsma is now using a partially rounded spacer over which the Pre-Seal runs."    

A true class product
The cooperation between Celdex and Wijnsma Kozijnen has literally resulted in a class product. "To check the system for airtightness, it was extensively tested at test and consultancy firm SHR in Wageningen," Ten Brincke said. "This yielded the highest possible result, namely a class 4 according to NEN-EN 12207, the airtightness class for windows and doors."