Design for energy efficiency facilitates construction of New York’s tallest residential building heated and cooled with a geothermal system.
The building located at 1 Java Street, in the Greenpoint neighborhood of Brooklyn, New York, is a mixed-use new construction with 800 residential units, 13,000 square feet of retail space and below-grade parking. Within the building, 30% of apartments are designated as affordable housing, with the remainder at market rate.
Energy efficiency measures in the design of the building envelope include high-performance windows and specialized insulation techniques to reduce thermal bridging. On the equipment side, energy recovery ventilators (ERVs) are included to reduce heating and cooling energy lost in ventilation air. These energy efficiency measures were designed to meet the standards for U.S. Green Building Council’s LEED v4 BD+C Gold.
The building’s HVAC system is entirely electric, with water-source heat pumps serving all residential spaces and common areas. Condenser water for the water-source heat pumps is connected to a ground heat exchanger consisting of closed loop piping in 320 boreholes, each 500 feet deep. Air‑source heat pumps are used for garage spaces and some mechanical areas. According to the New York State Energy Research and Development Authority, 1 Java will be the largest residential building in New York State to be heated and cooled via a geothermal system.
Energy modeling was performed by GEOptimize and the model was used by CDM Smith and ZBF Geothermal to design the geothermal heat exchanger. 1 Java is located in Brooklyn, New York, which International Energy Conservation Code classifies as Climate Zone 4A.
Buildings in New York are typically heating dominant owing to the lengthy and cold winter season; however, because of the height and overall large size of this building, it is cooling dominant at baseline. The energy efficient design of the building, particularly the effectiveness of the ERVs, pushed the building to be even more cooling dominant as insulation and heat recovery significantly reduced heating loads (see Table 2).
Table 2: 1 Java Street annual cooling and heating loads
| ASHRAE 90.1 minimum baseline | Projected loads after efficiency measures | Percent reduction | |
| Peak cooling load (kBtu/hour) | 12,800 | 8,500 | 34% |
| Total annual cooling load (MMBtu) | 24,900 | 13,300 | 47% |
| Peak heating load (kBtu/hpur) | 7,300 | 3,800 | 48% |
| Total annual heating load (MMBtu) | 12,500 | 4,300 | 66% |
Table 2: Comparison of peak and annual heating and cooling loads between baseline and designed building; 1 Java in Brooklyn, New York. Courtesy: CDM Smith
To counteract this imbalance and prevent overheating of the ground heat exchanger, domestic hot water heat pumps were added to the system, allowing for a beneficial use of the excess heat pulled out of the building spaces. A dry cooler was installed on the roof of the building to improve system resiliency and further protect against overheating of the ground heat exchanger. The dry cooler contained a controls package to run at optimal water and air temperatures, thus rejecting the net imbalance of heating and cooling energy.
Comparison of peak and total energy use between an initial baseline model of the building built to minimum ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings requirements and an energy model of the final building design shows a substantial decrease in heating, ventilation and air conditioning loads. This reduction in load allowed for a geothermal heat pump system to be designed that meets the entire building demand using boreholes located entirely under building foundations.
