Passive House senior high-rise uses structural thermal breaks to insulate steel penetrations

Built to International Passive House standards, the Corona Senior Residence in Queens, N.Y., prevents thermal bridging between interior and exterior steel structures by insulating canopies and rooftop supports where they penetrate the building envelope.

November 06, 2019 |
Flange-mounted Isokorb Type S22 structural thermal breaks

Flange-mounted Isokorb Type S22 structural thermal breaks prevent equipment support structures from conducting heat through the heavily insulated rooftop, while providing load-bearing support equivalent to that of conventional monolithic penetrations. (NOTE: Photo taken prior to installation of the roof insulation layer.)

Queens, N.Y.The Corona Senior Residence of the Hellenic American Neighborhood Action Committee (HANAC) is 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 U.S. 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) rainscreen system, energy-recovery ventilation systems, and a continuous superinsulated building envelope. To preserve the integrity of the envelope, HANAC is installing structural thermal breaks (STBs) where steel elements penetrate the insulated envelope to support rooftop ventilation equipment and two steel canopies.

“We’ve done LEED projects for years, but Passive House is a much more specific and robust system," said Jack Esterson, design partner with Think! Architecture and Design. "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."

 

HANAC Corona Passive House senior living. Photo: Alex Severin

 

“The Passive House standard also looks to maximize occupant comfort, which was important to HANAC as its user population, seniors, are more sensitive to temperature,” Esterson said.

Opened in May 2019, Corona is a $27 million, eight-story, 57,675 sf facility for low-income seniors. Floors two through eight comprise 67 rental units, while the ground floor houses a 5,000-sf early childhood education facility. The back of the building has a yard with a vegetable garden, tables, and seating for residents, and a children’s natural play area. A fifth-floor terrace provids additional open space for residents.

 

Structural thermal breaks mitigate thermal bridging in Passive House

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 Type S22 structural thermal breaks for steel construction mitigate thermal bridging where rooftop energy recovery ventilation units connect to the building, and at the building’s two 8x10-foot 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 airtight, higher-humidity buildings, exposing the developer to remediation and liability risk.

Gahl Spanier, a Passive House consultant with the Association for Energy Affordability (AEA), said, “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 break, the only other way to connect them is with continuous steel beams, which is very thermally conductive. Without the STBs, 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 Type S22 STB is a load-bearing thermal insulation element for steel structures that accommodates axial and shear forces. It consists of an 80-mm-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 STBs 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® STBs will save, but they’re definitely an effective way to address thermal bridging.”

 

Structural thermal breaks insulate roof and canopies

“This is a concrete, cast-in-place building," said Think! Architectural Designer Brian Dobrolsky." For the two 8x10 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 STBs at those points.

“We also have STBs 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® STBs 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 STBs are a better deal than solar. There’s no maintenance, and those modules perform for the life of the building.” 

Corona is among dozens of recent projects in the New York area to employ structural thermal breaks. “We’re going to see more use of STBs in the area because both energy codes and voluntary codes are paying more attention to what affects thermal performance and general building performance,” said Spanier. “Even code officials in the New York City area are starting to ask about them. These STBs 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.”

Contact Information:

Schöck North America

(855) 572 4625

www.schock-na.com

info@schock-na.com

                                   

THINK! Architecture and Design, PLC

(646) 688 5898

www.think-arc.com

 

Association for Energy Affordability, Inc.

(718) 292 6733

Aea.us.org

yli@aea.us.org

 

Bruno Frustaci Contracting

(718) 567 0229

www.bfrustaci.com

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