The Most Energy-Efficient Skyscraper Ever?
New York City scored a major coup when it successfully lured Cornell University to build a campus for Cornell Tech, its applied sciences program, on Roosevelt Island, smack in the middle of the East River. (Check it out in this video.) What better place to demonstrate how cutting-edge energy efficiency techniques can blend with architectural advances to yield beautiful buildings that run like finely tuned machines?
The tallest building on the compact 2.5-acre campus will be a 250-foot-tall dorm for 520 residents scheduled for completion in 2017, and its specs could make it the most efficient skyscraper ever built. Rather than focusing on the well-known LEED certification, which is widely accepted worldwide, Cornell asked the designers at Handel Architects to aim much higher and embrace the Passive House standard, an extremely strict international building standard designed to cut energy consumption drastically as it creates a healthier living environment.
Invented by Germany's Passive House Institute, the standard is usually applied to small-scale construction and has been met with approval across Europe, especially in Germany and Scandinavia, where about 25,000 certified structures have been built. To date, the tallest Passive House building is a 20-story tower in Vienna.
Passive house rules focus on performance, with some very specific parameters. For example:
- The Space Heating Energy Demand can’t exceed 15 kWh per square meter of net living space (treated floor area) per year. In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements.
- The Primary Energy Demand, the total energy to be used for all domestic applications (heating, hot water, and domestic electricity) can’t exceed 120 kWh per square meter of treated floor area per year.
- In terms of Air Tightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure is allowed. In other words, the building must not leak more air than 0.6 times its total volume per hour.
- Thermal Comfort must be met for all living areas during winter as well as in summer, with not more than 10 percent of the hours in a given year over 25 degrees Celsius (77 degrees Fahrenheit).
Architects achieve these goals with a mix of innovative windows, ventilation, heat recovery, insulation, and airtight construction. At Cornell Tech, that will include a façade constructed of a prefabricated metal panel system that acts as a thermally insulated blanket wrapping the building structure.
On the façade facing Manhattan, the exterior will include a louver system that extends the entire height of the building. It will act as the “gills” of the building, providing an enclosed, louvered exterior space where the heating and cooling equipment will live, allowing the building system to breathe. Handel Architects says that compared to conventional construction, the building is projected to save 882 tons of CO2 per year, equal to planting 5,300 new trees. While that may not amount to much in the grand scale of things, the building will be closely watched as a test case and as a template for future large-scale Passive House construction, a place where architects on this side of the Atlantic can see the possibilities and spread the trend.
XPRIZE contributor Don Willmott is a New York-based journalist who writes about technology, travel, and the environment for a wide variety of publications and websites.