230 Schilling Circle

The 230 Schilling Circle project involved construction of a 120,000 sq. ft. shell office structure which is now LEED®-certified Platinum Core and Shell. Mechanical Engineering & Construction Corporation (MEC²) was the design/build mechanical contractor responsible for the heating, ventilating, air conditioning, and control system installation. The project was a complete system removal and regeneration into a state of the art office facility with energy efficient mechanical systems, water reduction techniques, partial green roofing, and construction that reused building elements and materials to reduce waste products.

Construction was an intense coordination process with the Owner, Merritt Properties LLC, the commissioning agent, and the sub-contractors to build a state of the art office building that maintained site cleanliness, safety, and environmentally friendly impacts to the existing area.

The HVAC system serving 230 Schilling Circle provides year-round temperature and ventilation that meets or exceeds all applicable code and industry standards as defined by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE). The system utilizes high efficient rooftop units distributing air to fan powered variable air volume terminals, the rooftop units incorporate economizer cycles which constantly supply filtered air. Heating is supplied by high efficient hot water boilers housed in the boiler/pump room. The overall heating, ventilating and air conditioning system serving the building is monitored and controlled by a direct digital computer based control system. The control system automatically coordinates the function of all mechanical components to assure economical and reliable operation. The system may be monitored within the building and remotely for failures of equipment or operating criteria outside of pre-set levels.

The scope of the project consisted of providing heating, ventilating, and air conditioning for the new facility. The ventilation system and air conditioning system is provided by six (6) shell building variable air volume rooftop units provided with supply and relief fans, variable frequency drives, and refrigeration system consisting of high efficient compressors, condenser coils, and fans and high capacity evaporator cooling coils. As well as selecting high efficient cooling systems and energy saving variable frequency drives, the rooftop units are equipped with free cooling cycles and carbon dioxide monitoring to ensure acceptable indoor air quality levels. High efficient filtration is installed in the rooftop units to remove airborne contaminants. The supply air is distributed through insulated sheet metal ductwork to variable air volume terminal units consisting of single duct and fan powered units. The fan powered units were selected with high efficient ECM motors.

The heating system for the building is designed to provide heating water to the terminal units for the supply of warm air to the spaces. The terminal units are equipped with two (2) row heating coils so we can maximize the heat output of the units while minimizing the demand for heating water quantities. The heating water is generated by two high efficient condensing type boilers. The boiler system utilizes low water temperatures to increase the system's efficiency. The boilers can fully modulate the entire range of the heating demand spectrum and these boilers are coupled with inline pumps equipped with variable frequency drives that modulate the pump capacity based on heating demand from the building. The heating system will provide the required heating capacity with no excess energy wasted due to over-sizing of the system or inefficient system operation. The measurement and verification plan we incorporated called for an energy meter to regulate and record the energy used by the heating system. The monitor is tied into the building energy management system where data can be reviewed to increase the effective operation of this system.

The building automatic temperature control system monitors and controls every HVAC component in the building and also controls the building lighting system scheduling. The rooftop units and terminal units work in sequence to minimize energy usage while providing the required air conditioning capacity. The control system is married to the boiler control system to integrate the heating process efficiently and effectively. Innovative control strategies for static air pressure recalculation were implemented for the control of the variable frequency drives to minimize fan power usage and save energy use and costs.

Challenges to this $1.25 million mechanical undertaking included coordinating the design and construction effort to maximize the reuse of building components. The rooftop units were installed into the same building roof screen that existed prior to the existing system removal. The duct distribution and rooftop unit selection needed to be closely coordinated due the fact that the location of rooftop equipment needed to be consistent with the original plans but the interior shaft layouts were changed to create an open floor plan with increased glazing and plans for higher ceiling heights. Planning for the future is never an easy task in construction, certainly in a renovation project, but we implemented the core and shell to be flexible as a basis for many future designs and tenant layouts.

LEED® requirements added additional tasks to the construction process including storage of materials off of direct contact with the floor, temporary capping of duct work, and terminal units to minimize debris entrainment, providing required filtration over the return openings, specific leakage testing of our systems, and adding a two week building purge to the schedule. Close coordination with all trades was critical to minimize dust and debris in construction practices.

As future tenant improvements occur, special attention must be given to maintaining a clean environment inside the building. Building in an occupied building has its challenges, airtight partitions and filtration units which can pressurize specific sections of the building will be required. Advanced planning is currently underway.

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