Window Cladding: Historical Accuracy that Performs

For some homeowners, maintaining historical accuracy is more than a priority – it’s a code requirement where they live. So Pella designed a new cladding spring for the Architect Series® Reserve™ product line. The cladding spring delivers the classic look of butt-jointed windows, while delivering on homeowners’ and contractors’ needs for historical accuracy. Plus, it meets modern performance standards.

“We wanted to make sure we had the construction method that replicated the look of historical craftsmanship, while still hitting the performance mark,” explained Product Manager Melissa Berger.

While today’s standard mitered joints effectively withstand swelling and can help resist rot, aluminum butt-jointed cladding snaps and seals over the wood frame. Pella’s innovative cladding spring sets these windows apart from the competition. Using stainless steel leaf springs, the cladding “floats” above the wood frame, while keeping the corners tight. This system allows the cladding to expand and retract with the frame to adjust to seasonal changes.

“Keeping the joints together without creating gaps has always been the challenge. With an overlapped corner, the product can move around in the summer and winter, which really addresses that challenge,” engineer Scot Miller noted.

inserted into the sash frame, steel springs expand and contract to keep the cladding pressed together in the joints

Inserted into the sash frame, steel springs expand and contract to keep the cladding pressed together in the joints.

In fact, Pella put the butt-jointed clad frames through extensive hot-cold testing to ensure its ability to protect wood frames. By alternating between -40°F and 160°F for several weeks at a time while simultaneously conducting frequent water tests, Pella’s butt-jointed clad frames were proven for long-term durability.

Historically, many window sashes were made with butt joints. Pella’s new cladding spring helps maintain both the look and performance standards of Architect Series® Reserve™ products

Historically, many window sashes were made with butt joints. Pella’s new cladding spring helps maintain both the look and performance standards of Architect Series® Reserve™ products.

While other manufacturers may use corner-locking joints on their butt-jointed clad frames, Pella believed a simple engineering solution could prevent gapping. “The spring works very well without adding cost or intricacy to manufacturing the Architect Series Reserve line,” explained Miller.

Springs are inserted into the sash frame in a way that applies constant pressure, helping eliminate gaps and supporting the cladding by staying tight to the sash. This simple solution allows for easy installation and a smarter option to the more complex corner-lock designs. “Less complexity in the design always leaves a smaller chance for issues,” Miller continued.

Window with mitered joints, commonly used for its ability to manage water and resist gapping

Left: Window with mitered joints, commonly used for its ability to manage water and resist gapping. Right: Window with butt joints known for historical accuracy of its traditional detail.

And while performance is important, so is style – it’s one of many reasons Pella launched the Architect Series® Reserve™ line. The Reserve line takes style a step further with optional anodized coloring, which allows for an expanded color offering that goes beyond our standard 27.

“Homeowners want historical styling, but they want it with modern conveniences. Whether it’s corner joints, the profile of the window or the locks, we spent a lot of time on every little detail to get it right to meet those historical needs,” Miller emphasized.