Empire State Building to use 40% less energy

In a move designed to spur energy efficiency efforts world-wide, it was announced this week that the Empire State Building will undergo an extensive retrofit designed to save 38% of its annual energy consumption. The aggressive retrofit was planned in partnership with the Rocky Mountain Institute, Johnson Controls, Jones Lang LaSalle, and the Clinton Climate Initiative, and targets several key areas.

Load Reduction

  1. Radiative barriers: more than six-thousand insulated reflective barriers will be installed behind radiator units on the perimeter of the building to prevent excess heat loss through the exterior wall.

  2. Building windows: a suspended coated film, and a gas fill will be added to the over six thousand existing double paned windows to improve the thermal resistance to R-6 from R-2.

  3. Tenant daylighting, lighting, plug loads: lighting power density will be reduced through the use of daylighting and task lighting, the installation of dimmable ballasts and photosensors in perimeter rooms, and plug load occupancy sensors for personal workstations will shut down equipment when it is not in use.

More Efficient Delivery

  1. Chiller plant retrofit: load reduction will allow for the existing chillers to be upgraded and retrofit for higher efficiency performance.

  2. Variable-air-volume air handling units: two floor-mounted units will replace four ceiling-mounted units per floor. Variable-air-volume units will allow for demand control ventilation, and floor-mounting will allow the HVAC system to be designed for a lower pressure drop, requiring less energy to run.

High Quality Controls

  1. Demand control ventilation: CO2 sensors will control the level of outside air introduced to the building. This will give better control over indoor air quality and prevent the wasteful addition of outdoor air when spaces are unoccupied.

  2. Direct digital controls: the existing controls, and building energy management system will be upgraded, and will include temperature sensors, and electrical service monitoring.

  3. Independent metering: tenants will have online access to their energy consumption along with sustainability tips. They will also be able to compare their performance to that of other tenants in the building.

The project is estimated to save $4.4 million annually, with a total incremental cost of $13.2 million over and above the cost of already planned upgrades. The building will be more comfortable to work in, with better insulated windows, improved indoor air quality, and well designed lighting. In order to bring tenants on board, 40% of whom will be turning over in the next four years, the Empire State Building has designed a space for the 42nd floor to market improvements to prospective tenants. They have also designed a 'green build' for tenants which will save $0.70-0.90 per square foot in operating costs annually for an additional first cost of $6 per square foot.

One of the key goals of the retrofit is to provide an example for the rest of the world to follow. To this end, a number of details and documents are available online, including decision making, rating and design tools and a "Lessons learned" document. Key among the lessons learned are:

  1. An integrated design process including engineers, property managers, energy models, efficiency experts, architects and building management is necessary to achieve deep cuts in energy consumption. Tenant involvement is also essential, as many of the measures rely on their direct involvement.

  2. It is very important for the retrofit to be aligned with planned replacements and upgrades of major building components for the project to be cost effective. If major upgrades are not planned, then retro-commissioning the building to optimize existing systems can save 5-15% of the energy used.

  3. Unless the price of carbon increases dramatically (on the order of 8% per year), it will not be profitable to make the steepest cuts to energy consumption. The Empire State Building project leaves almost 50% of the carbon dioxide reduction potential on the table.

  4. An easily repeated and streamlined process which allows for rapid categorization of buildings, and iteration between financial and energy modeling is needed.