Deep Energy-Reducing Retrofits of the Empire State Building
By Ewen Coxworth, SES Volunteer Researcher
Improving the energy efficiency of commercial buildings is an important part of a strategy to reduce greenhouse gas (GHG) emissions from towns, cities and countries around the world. In Canada, 13% of end-use GHG emissions from the whole economy come from commercial and institutional buildings (OEE, NRCan, 2011) compared to 15% for residential buildings. Since 1990 GHG emissions from commercial buildings have been rising faster than emissions from residential buildings. One of the fastest increasing sources of GHG emissions has been building contents, such as computers and other office equipment.
In the U.S., the majority (86%) of current building construction costs comes from renovations of existing buildings (Zhal et al., 2011). 30% of existing U.S. commercial buildings are estimated to be due for major repairs and renovations. A similar figure probably holds for Canadian buildings. There is thus an opportunity to include improvements in energy efficiency as part of these renovations to commercial buildings. Can we use this opportunity to make major improvements (deep retrofits) to energy efficiency, rather than just small ones? What would be the cost and payback time of major energy-efficiency improvements?
The Rocky Mountain Institute (RMI) in the USAhas been working with building owners and construction companies to demonstrate that: Deep energy retrofits improve the economics of efficiency and achieve bigger energy savings at equal or lower cost, driving much larger savings (more than 50 percent) than conventional, shallow retrofits. The following example of is taken from RMI’s retrofits web site (http://retrofitdepot.org.)
The Empire State Building, New York City
This is one of the best-know skyscrapers in the world. It was built before the Second World War, so it is quite old, as skyscrapers go. It is a very large office building (2,700,000 square feet or 823,000 square meters). The annual utility bill for heating, cooling, air conditioning and electrical needs, before the deep retrofit, was $11 million. This is about $4.00 per square foot. After the deep retrofit is completed the total utility bill is expected to be about $2.50 per square foot, a 37.5% reduction. The reoccurring annual savings are thus $4.4 million. Many of the major retrofit changes have been completed; the remaining changes are ongoing and dependent on tenant turnover and refinishing schedules.
The overall incremental simple payback for the energy retrofit is three years. While the total cost of the major items in the energy portion of the retrofit was $23.76 million, a number of the changes reduce the energy demand so much that it was possible to do a chiller plant retrofit, rather than replacing it with an expensive new chiller. Retrofitting the old chiller plant was much less expensive than buying and installing a new one, so $17.3 million was saved. A number of the retrofit changes had individual simple payback times greater than ten years; but when they were all put together they reduced energy demand so much that the huge cost saving achieved by retrofitting the chiller plant, rather than buying a new one, was possible. This is a great example of ‘tunneling through the cost barrier’ since the overall integrated changes payback time is now three years.
Projects completed to date include:
Increasing the energy efficiency of the windows.
The 6,500 existing insulted windows were remanufactured on site to include a suspended coated film and gas fill. This more than tripled the insulating value of the windows.
Radiative barriers.
Radiative barriers were placed behind all the radiator units. Before the barriers were installed it was estimated that half the heat expended by the radiators was escaping the building and heating New York City but not the Empire State Building!
Tenant daylighting, lighting from fixtures and plug loads (computers, etc.)
The lighting power density was reduced in tenant spaces, dimmable ballasts were installed, photosensors were added to perimeter spaces and occupants were provided with plug load occupancy sensors for individual work stations.
Other changes.
These include improvements to the chiller plant during its retrofit, replacing constant air flow units with variable flow units, upgrading the direct digital control systems to many parts of the heating, cooling and air handling systems, providing a demand control ventilation system involving installing carbon dioxide sensors to control the amount of outside air needed by the air handling units, and implementing tenant energy management to provide live energy use feedback on energy use by office equipment and other energy using features under tenant control.
Could more energy savings have been done?
A life cycle cost analysis (LCCA) program was used to calculate what combination of energy-saving changes had the best payback times. The analysis showed that further energy savings changes over the package chosen made only small increases in energy savings, but had high costs. The owners of the building chose a package of savings which would save about 110,000 tonnes of carbon dioxide over 15 years at a net present value in the 15-year period of about $20,000.
The result.
The Empire State Buildingis on target to receive LEED for Existing Buildings: Operations & Maintenance. Some tenants are pursuing LEED status for Commercial Interiors. The building has received an Energy Star score of 90 out of a possible 100. This would place the building in the top 10 percent of all buildings for energy efficiency. Not bad for a pre-war building.
Tony Malkin, president of Malkin Securities and owner of the EmpireStateBuildingstated that “The Empire State Building [retrofit] project, with its 40 percent energy savings, had a three-year payback period. It would be bad business not to do this.”
