The Real Deal New York

Will Cornell’s energy-efficient dorm change how we make buildings?

A look at the world's tallest and largest passive-house building

July 12, 2015 11:00AM
By Business Insider

aerial-view-of-residential-building---credit-handel-architects(credit: Handel Architects)

Cornell Tech, an applied sciences program out of Cornell University, is building a giant futuristic campus on New York City’s Roosevelt Island. But the most exciting part of the campus isn’t in the academic buildings or green spaces — it’s the dorms.

The campus’s 250-foot tall residential high-rise will be so energy efficient that it could change the way buildings are constructed in New York City, if not the rest of the country.

The high-rise, which will house 520 people when it’s completed in 2017, will be the world’s tallest and largest passive-house building, meeting strict energy efficiency standards set by Germany’s Passive House Institute.

When all is said and done, it will save 882 tons of CO2 each year compared to a normal building.

That’s not much compared to the average yearly emissions of a coal power plant (3.5 million tons of CO2), but start thinking about a future where passive house buildings are the norm, and the emissions savings become significant.

cornells-passive-house-building-1(credit: Handel Architects)

Passive House buildings use little in the way of energy, heating, and cooling. In order to meet the standards, “You need to have every crack sealed,” according to Blake Middleton, a partner at Handel Architects, which designed the building. Essentially, the Cornell building has to be completely airtight to pass muster.

Overall, the $115 million residential building will use 60% to 70% less energy than other similarly sized buildings. It will also cost up to 5% more to develop — but that money will come back many times over in energy savings.

Making the building airtight was a vexing problem, both from a structural and a design point of view. When architects design urban buildings — especially condos — they usually highlight sweeping views with floor to ceiling windows.

In order to make that work from an energy efficiency perspective, a passive house high-rise would need a double envelope, basically creating a building within a building. That’s prohibitively expensive, so Cornell opted instead for slightly smaller windows.

“There will be well-sized windows that take advantage of views, but they’re not as big as they might be if they were catering to that [condo] market,” says Arianna Sacks Rosenberg, a senior project manager at Hudson, the developer behind the high-rise.

The airtight design, combined with a unique ventilator system that brings in fresh air from outside, means that the building doesn’t need much in the way of a heating and cooling system.

But that ventilator system went outside of New York City’s building code, so the developers had to get special permission to install it.

aerial-view-from-manhattan---credit-kilograph,-weiss-manfredi,-and-handel-architects(credit: Kilograph, Weiss Manfredi, and Handel Architects)

Another challenge: getting builders to seal up the prefab high-rise to passive house standards. “It requires a much higher degree of care than is traditionally found in sealing up the envelope of a building for more conventional construction,” says Middleton.

In Europe, the passive house standard is used for low-rise buildings, offices, and schools (the Cornell building will beat out a 20-story office building in Vienna, Austria, as the tallest passive house structure in the world). Not so in the U.S, where the standard is generally used only for single-family homes.

Cornell’s high-rise could change that.

As Middleton points out, the environmentally-minded LEED building standards raised eyebrows when they were first introduced two decades ago. Now LEED has been adopted into building codes. In New York City, for example, new buildings on city property have to be LEED Silver certified.

“In a way, it’s like we’re beta testing a new model of a car that everybody already knows pretty well, but there are certain tweaks going on, and components in that car that have to be machined better, to fit more exactly,” says Middleton.

If all of those tweaks add up to a functional high-rise, then Cornell may have paved the way to a more energy-efficient urban future.