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Cornell Tech Campus ... Passive House

BREAKING NEW GROUND: NYC TAKES THE LEAD IN PASSIVE HOUSE ... Cornell Tech’s 26-story, 352-unit residential tower will redefine the city’s skyline

Burgess COMMENTARY

Peter Burgess

BREAKING NEW GROUND: NYC TAKES THE LEAD IN PASSIVE HOUSE

Construction is underway on what will be the tallest Passive House building in the world. Cornell Tech’s 26-story, 352-unit residential tower will redefine the city’s skyline in more ways than one, potentially impacting future construction methods and even occupant behavior. Our Cornell Tech: Passive House Reaches New Heights panel earlier this month featured the major players and ideas bringing this revolutionary vision into reality. Arianna Sacks Rosenberg (Hudson Companies) and Luke Falk (Related Companies)––representing the joint venture developing the tower––joined design consultants Deborah Moelis (Handel Architects) and Lois Arena (Steven Winter Associates) for the discussion.

Born out of a partnership between Cornell University and Technion, Cornell Tech won the city’s 2011 RFP for a new engineering or applied sciences school, envisioning a state-of-the-art, sustainable campus on Roosevelt Island; the new tower will house over 500 of the campus’s graduate students, faculty and staff. “While Passive House is well-established,” said Rosenberg, “its systems haven’t been applied at this scale before.”

Falk called scaling up Passive House an exercise in how to reduce load. The main strategies include breaking thermal bridges, eliminating leaks, and installing energy recovery ventilators (ERVs) to provide airflow while minimizing heat loss. However, with 26 stories, ERV configuration gets complicated. Two approaches were considered in this project: an ERV in every apartment or connecting vents vertically. Opting for the latter required relief from NYC code since vertical trunk lines are not allowed. A second variance was related to airflow. Building code stresses ventilation, but since every cubic foot of air moved is a “huge penalty” in terms of PH heat requirements, hitting the code minimum of 45 CFM for 352 residential apartments would significantly undermine the goal of minimizing heat transfer. In this case, the DOB allowed the tower to meet a lower ventilation requirement more in line with Passive House standards.

Cornell Tech ERV System

The next challenge was to limit any air transfer not handled by the ERVs. Moelis explained that the slim eastern and western facades reduced solar exposure and heat gain––but siting is the easy part. More complicated is to combine the many components of the wall into an integrated whole. With over 3,000 anchors holding up the exterior assembly, each one had to be individually taped and insulated. With no established protocol for this process, the building crews had to be trained on an entirely novel method. The result, accounting for all the penetrations, is a wall with an average R20 rating.

Arena then drilled into the details of the wall’s individual components. While the tower got relief from code for the ERVs and airflow, NYC buildings over eight stories can’t use vinyl windows. And the aluminum alternative must meet the European standards for low U-values across both the frame and the center of the glass. With those minimums in mind, the team had to make sure that the continuous air and vapor barriers held wherever there was a change in material. This meant everyone needed to be involved in the process: the construction manager marked up the drawings; methods worked out for the various trades were integrated into the specs; even the different tapes used to seal the joints had their own schedules keyed into the drawings.

Once completed, Cornell Tech will need to maintain the low operational load it was designed to support. Ideally, this will be accompanied by a low plug load with the help of sub-metered data for each apartment, all highlighted in a kiosk on the ground floor.

Cornell Tech: Passive House Reaches New Heights

VIDEO: CORNELL TECH, THE WORLD'S LARGEST PASSIVE HOUSE

July 6, 2016 | Urban Green Council

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Slated for completion in 2017, the apartment tower on Cornell Tech's Roosevelt Island campus will be the largest Passive House completed so far. This is important not only for the energy it will save, but for the inspiration it will provide: at over 270,000 square feet and housing over 500 graduate students, the simple proof that a Passive House of this size can be built is impressive. Last year, we invited project leaders and industry experts to speak at length about the challenges and opportunities of a Passive House project like Cornell Tech, in collaboration with AIA New York and New York Passive House. Below are eight video highlights from our panel.

About Cornell Tech

Ariana Sacks Rosenberg (Hudson Companies) and Luke Falk (Related Companies), who represent the joint venture developing the tower, joined design consultants Deborah Moelis (Handel Architects) and Lois Arena (Steven Winter Associates) for an overview of the Cornell Tech project.

What is a Passive House?

In this talk, Falk explains what the Passive House standard is and how it fits into New York City’s building landscape.

The Thermal Envelope

In this segment, Moelis describes the challenge of meeting Passive House criteria while maintaining the architectural vision. In order to create an appealing indoor-outdoor space, the team faced obstacles like bending the thermal envelope to incorporate outdoor balconies, constructing windows in a controlled environment, and navigating wall thickness and insulation values, while communicating with the contractor through it all.

Passive House Consultants, Windows, and Testing

Here, Arena highlights the goals of Passive House construction that go beyond energy efficiency such as comfort and durability. She relates these topics back to the challenges of window installation and the need to test air sealing throughout construction.

Energy Efficient Heating and Cooling

In this segment, Falk expounds on the team’s surprising strategy to regulate indoor temperature; because the building is so thoroughly insulated, the VRF system is not designed to provide heat at all! Falk explains how this system works and compares global trends in HVAC equipment and design.

Ventilation

In a well-sealed space, the only air movement is intentional air movement through mechanical ventilation: as a result, creating a ventilation plan is a crucial part of the Passive House design and construction process. Falk elaborates on this process and how to comply with (often conflicting) city codes and other green standards.

Duct Sealing

Here, Luke Falk describes the process of creating healthy ventilation without the side effect of unintended air movement. In order to achieve the right balance, he stresses the importance of well-sealed ductwork that ensures air is moving where and how it is intended.

Unregulated Loads & Sub-metering

Rosenberg and Falk speak on the innovative ways the team is using technology to engage tenants and encourage resource conservation. With real-time tracking and usage-based billing, utility transparency will encourage tenants to modify behavior.