Queens, New York—The Corona Senior Residence of the Hellenic American Neighborhood Action Committee (HANAC) will be the first affordable housing facility built for seniors in New York City’s Corona, Queens neighborhood in more than 30 years. It will also be the first affordable senior housing development in the US to meet the Passive House Institute design standard for energy efficiency and ecological footprint reduction.
HANAC Corona is meeting the standard by building its senior residence with passive solar design, high-impact underslab insulation, triple-glazed windows, balanced ventilation, efficient heating and cooling systems, a thermally broken (by clips) rain-screen system, energy recovery ventilation systems, and a continuous super-insulated building envelope. In preserving the integrity of that envelope, HANAC is installing structural thermal breaks where steel elements penetrate the insulated envelope to support rooftop ventilation equipment and two steel canopies.
“We’ve done LEED projects for years,” explains Jack Esterson, design partner with project architect, Think! Architecture and Design, “but Passive House is a much more specific and robust system. Passive House certification makes perfect sense as HANAC holds onto and operates its buildings for a long time and wants to keep energy and maintenance costs low. Being able to save between 60%-80% on your energy bills is a real benefit.
“Also, the Passive House standard looks to maximize occupant comfort, which was important to HANAC as its user population, seniors, are more sensitive to temperature,” Esterson says.
Completed in 2018, Corona is a $27 million, eight-story, 57,675 sq ft (5358 sq m), facility for low-income seniors. Floors two through eight will comprise 68 rental units, while the ground floor will house a 5,000 sq ft (465 sq m) early childhood education facility. The back of the building will include a yard with a vegetable garden, tables and seating for residents, and a children’s natural play area. A fifth-floor terrace will provide additional open space for residents.
Passive House measures influence every aspect of Corona’s design. For one, structural elements should not penetrate the continuous insulated building envelope, as it would cause thermal bridging. That’s where structural thermal breaks play a strategic role in meeting the Passive House standard. Schöck Isokorb® steel-to-steel connections mitigate thermal bridging where rooftop energy recovery ventilation units connect to the building, and at the building’s two 8 x 10 ft (244 x 305 cm) canopies.
Thermal bridging typically occurs where steel or concrete balconies, canopies, slab edges, parapets, rooftop supports and other structures penetrate the insulated building envelope. These penetrations draw heat from interior concrete or structural steel through the envelope, dissipating it into the exterior environment. In addition to wasting energy, chilling of support structures can cause condensation and mold to form in interior cavities adjacent to the penetration, particularly in today's air-tight, higher-humidity buildings, exposing the developer to remediation and liability risk.
Gahl Spanier, a Passive House consultant with the Association for Energy Affordability (AEA), adds, “Every multifamily building has a lot of equipment on the roof and typically at least one canopy extending from other floors. These are structural elements that must connect to the building. Except for Schöck’s Isokorb® thermal breaks, the only other way to connect them is with continuous steel beams, which is very thermally conductive. Without them, thermal bridges would impact the thermal performance of the building and might cause moisture accumulation and other problems. Passive House has no tolerance for that, and therefore in the places where we have thermal bridging we have to use structural thermal breaks.”
AEA serves as the general sustainability consultant, helping the project team meet Passive House, NYSERDA, and Enterprise Green Community certifications both during the design phase and construction.
The Isokorb® assembly is a load-bearing thermal insulation element for steel structures that accommodates axial and shear forces. It consists of an 80 mm (3.125 in.) thick block of Neopor® insulation foam held held under compression with high-strength bolted stainless steel rods between two end plates.
Schöck North America reports that thermal breaks reduce heat loss at connection points by about 50%, as compared to heat transfer through a continuous steel beam. Spanier says, “It’s hard to say exactly how much energy Isokorb® thermal breaks will save, but they’re definitely an effective way to address thermal bridging.”
Think! Architectural Designer Brian Dobrolsky explains, “This is a concrete, cast-in-place building. For the two 8’ x 10’ canopies we have steel that is anchor-bolted back to the beam. One canopy shields the entrance of the early childhood education facility and one the residential portion. One is clad in a metal panel rainscreen system and the other in high performance phenolic panel material. Inside the canopies is steel tubing. So, for the structural connections we need to add thermal breaks at those points.
“We also have thermal breaks at the steel dunnage on the roof at the feet where the two large energy recovery ventilation units sit. The units are a requirement for Passive House projects.”
Bernie Colletti, executive project manager with Bruno Frustaci Contracting, says “I’ve never used them before, but installing the Isokorb® structural thermal breaks has been easy. It just adds an extra step to the building process, but I took Passive House training and can see that over time they are a better deal than solar. There’s no maintenance, and those modules perform for the life of the building.”
While Corona is one of the first Passive House senior residences in the U.S., it is among dozens of recent projects in the New York area to employ structural thermal breaks.
“We’re going to see more use of structural thermal breaks in the area because both energy codes and voluntary codes are paying more attention to what affects thermal performance and general building performance,” Spanier adds. “Even code officials in the New York City area are starting to ask about them. They are a great solution and they’re off the shelf. Other solutions are not as well documented or well received. For horizontal connections like balconies and canopies, it’s almost the only solution.”
Dobrolsky concurs. “When we were designing and drawing the project, I knew we would need thermal breaking. I did some research and found the Isokorb unit. That was two years ago. Now, thermal breaks are definitely a valuable element for future use.”
thermal breaks for rooftop
connections and canopies
Think! Architecture and Design
Association for Energy Affordability
Bruno Frustaci Contracting