City Hall Gets an Overhaul
Integrating Lighting and HVAC Retrofits: Case Study
Benjamin J. Biada, PE, LEED AP, & Scott Gray, LC, LEED AP, AE Consultants
Constructed in the late 1920s, Columbus City Hall represents the art deco style that was very prominent throughout that era. While the building still has the original charm and character that it did when it was first built, the HVAC and lighting systems have aged significantly and are in need of an upgrade. The existing HVAC system is a hodgepodge of different systems that have been added and modified over the years.
The existing HVAC equipment will be removed and replaced with a new four-pipe fan coil system supplemented with dedicated outdoor air units (DOAU) to provide proper ventilation. The four-pipe fan coil system can prove to be 10% to 15% more efficient than a traditional variable air volume (VAV) system because the need for reheat has been eliminated and the DOAU can provide the minimum amount of outdoor air required. With a traditional VAV system, there is a tendency to over-ventilate a space because of the need to calculate outdoor air requirements based on the critical space method.
The majority of existing lighting at city hall consists of T12 fluorescent and incandescent lamps in a variety of fixture types that appear very dated. There are several historic pendants in many of the main hallways that use screw-in incandescent candelabras. Many of these historic luminaires have been retrofitted with replacement screw-in fluorescents, which have taken away from the historic look. These fixtures are being removed, shipped to a custom luminaire manufacturer, refurbished and cleaned, and then fit-out with LED light sources consistent to the original incandescent look. This will reduce the luminaires’ energy consumption by nearly 80% from their original incandescent versions and by more than 30% of their retrofit compact fluorescents.
The T12 parabolic and lensed troffers will be replaced with T5 volumetric type luminaires and T8 lensed troffers in the majority of spaces. It is anticipated that the new luminaires will be able to produce the same light levels that currently exist while reducing consumption by up to 30%. Changing from T12 to T5 luminaires will result in approximately a $1/sq-ft savings annually. There is more than 90,000 sq-ft of space being renovated at city hall, resulting in a $90,000 savings. This number does not take into account additional savings that will be witnessed by occupancy sensor and time of day control automatic lighting control.
A major culprit of energy consumption at city hall is the exterior floor lights, 400 and 1000 W metal halide drum-style flood lights that consume 460 and 1080 W, respectively. The total exterior consumption is 36,960 W. These are being replaced by LED wall washers and flood lights that consume a mere 30 W each. The total wattage of the new LED system that is capable of producing any color in the spectrum as called for by the city of Columbus for special events is 4160 W. This is a reduction of 89% and can yield a payback of less than seven years, even with the significant investment for color-changing LEDs upfront. It currently costs the city approximately $26/night to run the metal halides; this number will be reduced to $3/night, based on an 8-hour night at $0.09 per kWh.
With these lighting and HVAC changes, the city hall renovation is in the process of pursuing U.S. Green Building Council LEED Certification.
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