[Paju (Gyeonggi) = E-Daily Reporter Kim Se-yeon ] At a mixed-use residential and commercial building construction site in Paju, Gyeonggi Province, pre-move-in inspections are in full swing. Upon taking the elevator to the top floor—the fourth floor—my gaze was immediately drawn to the floor-to-ceiling windows that filled the walls and the minimalist window frames that did not obstruct the view.

The large windows on the exterior of the building I visited gave the impression that the structure was supported entirely by glass. This was achieved by using “Cleance,” the top-tier window brand from the building materials company KCC Corporation(002380). Notably, at the building’s corners, the glass panels were joined at right angles without the concrete columns or rebar typically found in conventional buildings.

This construction method is considered a highly challenging technique. Generally, concrete columns or separate structural elements are installed at building corners to finish the window installation. This is because any minor deviations can be compensated for by the structural elements. Interlocking glass panels, however, requires minimizing the margin of error and executing the work with extreme precision. To this end, KCC Corporation maintains a separate program called the “Cleance E-Max Club,” comprising dealers nationwide with exceptional fabrication and installation capabilities. Among them, KN—a top-tier member—was entrusted with this residential project, ensuring a high level of construction precision.

The Clence windows observed on-site demonstrated competitiveness in various aspects, including design and functionality. While window frames that encase the glass are typically over 9 cm thick, the frames here were less than 3 cm thick. Viewed from inside, obstructions to the view are minimized, creating a sense of wide-open space. The “soft-closing” feature, which automatically slows the closing speed during the final stage, ensures the window closes gently. This not only enhances user convenience but also reduces the risk of fingers getting pinched while closing the window.

A four-sided compression structure minimizes drafts seeping through the window gaps when the window is closed. It also reduces the inflow of outside air when ventilation is needed. Turning the handle 180 degrees upward opens the window slightly, allowing fresh air to enter without fully opening it.

These features combine to deliver superior thermal insulation performance compared to standard windows. According to KCC Corporation, Cleance offers thermal insulation performance that is approximately 30–40% higher than that of standard windows. The company explains that this reduces energy loss from heating and cooling, thereby simultaneously improving energy efficiency and residential comfort.

As demand for high-performance windows has recently grown, particularly in the high-end housing and premium remodeling markets, the number of consumers seeking Clenche is rapidly increasing. According to KN, Clenche’s share of total sales has been gradually expanding; currently, the sales ratio between standard windows and Clenche, based on value, stands at approximately 50:50. Sales of Clenche installed by KN have also continued to grow at a steep rate, increasing by about 200% annually over the past three years.

Kim Dae-wook, a director at KN, a KCC Corporation dealership, said, “In this case, the homeowner initially requested foreign-made windows but switched to Cleance after visiting a Cleance exhibition.” He added, “Cleance has strengths over foreign-made windows in terms of after-sales service and adherence to delivery deadlines. Furthermore, thanks to its clean finish, it has a clear design advantage at first glance.”