Harry T. Nance Apartments | Brooklyn, NY

Windows make the difference in achieving multiple environmental goals

In achieving goals such as Passive House level energy efficiency and significant noise reduction, window technology is a major factor in the planners’ arsenal, with well-engineered and installed windows highly effective at keeping conditioned air in, keeping summer heat and winter cold out, and keeping loud city noise from audibly entering the living space. Through a prior project, RiseBoro and other members of the Nance team knew of the proven proficiency of window manufacturer Alpen High Performance Products at finding the right mix of technologies to meet the toughest challenges, and brought them on board.

Alpen quickly realized that they had their work cut out for them. According to Ali Ray, Alpen’s commercial sales manager, developing windows that deliver both ultra-high levels of energy efficiency and ultra-high levels of sound dampening presents an enormous challenge for window designers and manufacturers, since the technologies used to accomplish each goal are often at odds.

“Through laboratory testing, we identified that adding mass to the glass assembly is the most effective way to increase our windows’ OITC (Outdoor/Indoor Transmission Class) rating. To add mass, the most common solution is to use laminated glass—two pieces of glass held together by a PVB interlayer. In the US, however, it is economically challenging to source laminated glass with the exposed, high-performance, soft-coat Low-Emissivity coatings that we need to reduce thermal conductivity and control solar heat gain. So we needed to incorporate a different way to knock down the sound and retain thermal properties.

“What we came up with is a combination of a very thick, heavy monolithic low-e coated outer pane, a 1/2 in. thick laminated interior pane, and, to replace the “lost” low-e coating normally where the laminated glass is located, a middle “pane” of low-e coated suspended film. The resulting insulated glass unit weighed 10.9 lbs/ft²—more than twice the maximum carrying capacity of most window frames,” Ray explained.

Alpen then determined that the REHAU Geneo window framing system, composed of RAU-FIPRO^® glass-fiber reinforced PVC, was capable of supporting this unique glass configuration. With its 2 3/32 in (53 mm) glazing capacity and designation of Certified Passive House Component by the Passive House Institute (PHI), the system allowed Alpen to achieve the project’s targeted acoustic rating of STC-45/OITC-35 while maintaining a 0.13 U-value.

“The RAU-FIPRO core of the Geneo system provides the strength to support such heavy glass without requiring in-frame steel reinforcements that would have compromised our passive house frame performance,” said Ray.

“REHAU Geneo tilt-turn windows are incredibly air tight—they seal like a vault door—and the RAU-FIPRO frame delivers a passive house level U-value,” she said. “Frankly, without the Geneo product, I don’t think that these specs could have been met.”

A back and forth collaboration and partnership

In order to meet stringent goals like these, Ray noted, constant communication between Alpen and REHAU was vital. Demands were constantly shifting and there was a lot of detailed technical and logistical information needed.

“This was far from an ‘off the shelf’ situation. We would often ask very tough questions that needed far more than ‘yes’ or ‘no’ answers. For example, at one point in development we found that wind loads would be much higher than what we were expecting, so we needed some real-world information that would enable us to optimize the structural design. These types of questions kept us in close dialog with the REHAU engineering team on a frequent basis,” she explained.

“With some suppliers, when you get in a cutting edge, ‘pushing the technology envelope’ situation like this, all you hear is ‘we don’t know, take your best guess’ or ‘check the manual’ or some other unhelpful answer. Not with REHAU. We would ask a question and they would go test and research it in their lab and get back to us with precise, practical data on how to achieve what we needed to achieve. It is absolutely invaluable for us to have this level of support behind us,” Ray continued.

A big success for all involved

With the Nance building completed and the lease up well underway, New York is delighted to have a new hyper-efficient and ultra-quiet affordable housing option available for residents—especially one that is expected to use 75% less overall energy than conventional buildings. It is a testament to the outstanding efforts of RiseBoro and their entire team—REHAU, Alpen, installer John Mokas and his team at Eco Remodeling, project manager Galaxy General Contractors, Heritage Architecture and other top construction professionals. The project was certified to Passive House PHIUS+ 2015 in March 2023.

“The demand for improved energy efficiency standards like Passive House is an important trend in the industry—and it’s one that is getting more and more rigorous and challenging all the time. You can’t come close to achieving those goals without really great windows,” said Ryan Cassidy, RiseBoro’s director of sustainability and construction. “At RiseBoro, sustainability and energy performance are the basis of every design, and the Alpen/REHAU product was absolutely essential to meeting a highly challenging mix of goals and delivering high quality for our residents.”