He says for a building this complex, an off-the-shelf, cookie-cutter control sequence wouldn't work. Thus, Enovity is looking in depth at temperature trends and other details to see how the operable windows should function in order to achieve the temperatures needed for occupant comfort for each tenant on each floor. Soper stresses this sequence could not have been finalized before the building was occupied, as it depends on a number of site-specific criteria like occupant preference, changing weather patterns, and unknowns that computer models cannot analyze. It takes time, too, since the building has nearly 8,000 control points, with at least 2,000 of those points needing careful review by the commissioning agents. Enovity is particularly interested in a well-functioning building, since the firm also has been hired by the client to be its operations and maintenance contractor at the site.

Air-Flow Diagram Modeling helped engineers understand the natural ventilation system design, prior to writing a controls sequence.

Among other directives, Enovity will monitor energy use for the first 18 months after occupancy to verify the building exceeds California's stringent energy code-Title 24-by 15 percent. The data will be used to validate (or recalibrate) the models used to predict energy consumption. Arup's mechanical engineer, Erin McConahey, PE, talks of the engineer's role as the author of the sequence of operation. A properly working control system reacts to feedback from a device, such as a thermostat, in order to bring the system back into alignment with the desired conditions. It monitors and controls the automated environmental systems to ensure all the equipment performs as designed. In commissioning, the programming and control devices are tested, adjusted, and calibrated by a third party, such as Enovity, against the original intent of the written sequence of operations.

"There are two kinds of testing: pre-functional and functional," explains McConahey. "The goal of the pre-functional testing is to ensure there are no malfunctioning devices. In functional testing, the engineer may simulate a situation in which the control system must correct a malfunctioning device, such as a valve, sensor, or thermostat."

Each tower floor is a highly integrated system involving thermostats and daylight sensors to help guide the naturally ventilated building through a day. Photo © Roland Halbe