A collaborative venture of Charlotte Mecklenburg Library and Children's Theatre of Charlotte, the 113,000-sq-ft ImaginOn: The Joe & Joan Martin Center in Charlotte, N.C., features a library, a theater, a museum, a science center, a multimedia production studio, and more—all with the intent to bring "stories to life through extraordinary experiences that challenge, inspire, and excite young minds."

Hoffman Building Technologies installed a BACnet-based energy-management system (EMS) from Alerton that enables energy-efficient operation, including occupancy-based HVAC control, carbon-dioxide (CO2) demand ventilation, and lighting control. The ImaginOn project included global controllers, water-cooled chillers, water towers, boilers, chilled- and hot-water pumps, air-handling units, and variable-air-volume (VAV) boxes. Alerton's Envision for BACtalk software serves as the front end of Imagin-On’s building controls, managing all of the functions and seamlessly integrating third-party devices and systems.

Hoffman established sophisticated control strategies to manage the varying heating and cooling needs of the library and the theater. These strategies include supply-air reset control, static-pressure reset control, and fan-speed modulation based on airflow measuring. In addition to motion-based space sensors, precision controls are used to reduce ImaginOn's energy use and increase savings by ensuring no space is over- or underventilated.

ImaginOn features electronically commutated motors (ECMs). An analog output on an Alerton unitary controller uses an ECM speed card to control VAV-box fan speed.

Hoffman established interfaces with a packaged Bell & Gossett pumping system for secondary chilled- and hot-water systems. Piping is classic constant-volume primary and variable-volume secondary with differential-pressure control. ONICON BTU meters are utilized in the hot- and chilled-water systems for energy measurement and verification. The meters are connected to the EMS, with energy consumption trended for review and analysis.

Hoffman tied in York chillers using a master-slave/token-passing trunk off of an Alerton BACtalk Integrator. The chillers pick up between 40 and 50 points, which enables the trunk to generate a great deal of building data.

An integrated lighting-control panel energizes lighting in a zone once it picks up an occupancy-sensor contact. For additional control, an Alerton Microtouch unit offers a push-button override option.

Hoffman also tied in CO2 demand-controlled ventilation (DCV). DCV controls the outdoor-air intake, enabling the EMS to reduce the potential for overventilation during periods of low occupancy.

The project required the controls contractor to provide power to fire/smoke dampers. The fire-alarm contractor provided a contact and P-tap station for each damper. A great deal of work was involved in placing and concealing the transformers that power the fire/smoke dampers.

To maintain the whimsical look and feel of spaces, Hoffman concealed as much equipment as possible. Tasks included hiding conduit during the construction phase, integrating wireless sensors, and using perforated ceiling "clouds"—painted metal laths suspended in a T-grid. As a result, VAV boxes in the basement distribute air to spaces on the second floor.

Over the course of three months, Hoffman worked with Engineering Economics to commission the installation. The process included point-to-point testing of all control components. The graphics package also was commissioned to ensure it displayed real-time data and was user-friendly.

In 2006, ImaginOn was awarded LEED Silver certification, largely because of the energy-efficient operation of its building-automation system.

Information and photograph courtesy of Public Library of Charlotte & Mecklenburg County, Children's Theatre of Charlotte, and Hoffman Building Technologies.