Riverhouse's innovative and sustainable window design

Todd Schliemann doesn’t shrink from a challenge. The design partner at the architecture firm Polshek Partnership, Schliemann has been designing buildings in Battery Park City since 1981, where he has had to navigate the strict design guidelines of the Battery Park City Authority (BPCA). “The BPCA regulates every building’s bulk, height, setbacks and massing”. Schliemann explains. The criteria are tough but well-intentioned. The BPCA looked to the prewar buildings along the Upper West Side’s Riverside Drive as in inspiration, so to replicate the stately look and familiar feel of that neighborhood, it pays close attention to a building’s shape, which should even include a nod to a traditional cornice.

Designing Riverhouse’s exterior would require more fancy footwork than usual. The real challenge lay specifically in the guidelines about windows. “Typically the BPCA requires that the facades have a 40/60 ratio of masonry to glass, which results in the traditional punched-window facade.” But, Schliemann continues, “Our building’s western facade offered tremendous views of the harbor, including Ellis Island and the Statue of Liberty. It made sense to maximize the amount of glass to take full advantage of that.”

Besides having to navigate the BPCA’s stringent aesthetic, there was also the matter of Riverhouse’s own LEED certification target. Traditional glass curtain walls can expose the building’s interior to solar heat gains, increasing the energy required to cool living spaces.

Schliemann and his team decided to design a high-performance glass wall for the western facade. Given the BPCA’s recently revised sustainability goals, which require that new buildings perform optimally, Schliemann figured that the environmental stewardship would be a top priority for the authority. As he puts it, “We went to the BPCA and demonstrated that a triple-glazed, double glass wall with increased exposure would perform environmentally equal to or better than the facade with the traditional 40/60 masonry-to-glass ratio. We asked if they would consider the substitution.” The authority agreed, thus inaugurating several firsts: not just one of the first buildings in New York City to achieve a LEED rating of Gold, but also the first residential use of double-glass wall technology in the United States.

So how does the double glass work? “The wall is made of two glass walls seperated by a 10-inch airspace, or cavity,” Schliemann explains. “Each window unit has a vent at the bottom and one at the top, which can be opened and closed manually. Within the cavity are blinds that can be raised and lowered, tilted open or closed. When the vents are open, air is allowed to enter at the bottom, and through natural convection, it rises and exits through the upper vent, effectively cooling the blinds. This reduces temperatures inside the cavity by a few degrees, reducing the amount of energy necessary to cool the interior of the apartment.”

And don’t forget “the blinds effectively remove solar heat gain from inside the apartment”—in other words, provide shade. Besides controlling temperature, residents can maneuver the blinds to change their homes’ ambiance. Schliemann paid close attention to this function, since he imagined sitting on the couch, perhaps with a glass of wine, watching a hot summer sun sink into the horizon over the water. All this without a drop of perspiration.

The Polshek team pulled off a deft maneuver. It took full advantage of waterfront views while respecting neighborhood aesthetic guidelines, and exceeding sustainability standards. “When you see Riverhouse from the outside, it has a lovely sense of depth, very soft shadows,” Schliemann says. “In the end, the glass wall becomes the building’s identity and makes a clear statement about its green intentions.”

-Jude Stewart