Page 127 - Zero Net Energy Case Study Buildings-Volume 1

CLASSROOM & OFFICE BUILDING
CASE STUDY NO. 6
Post-Occupancy Adjustments to Lower Energy Use: HVAC Systems
As discussed in the previous case study section, the value of recording and reviewing the energy use patterns of the building systems is obviously to identify locations of higher consumption than expected and opportunities to improve the overall efficiency by changing components or opera- tions. UC Merced has been continuously engaged in this monitoring and evaluation activity since 2006, when the two case study buildings opened, and has steadily made system changes that have resulted in improvements in the energy performance.
The charts on the facing page reflect the improved performance: the principal measure of build- ing annual energy use, the building’s EUI (site energy), has been reduced to 38 kBtu/gsf-year. The following subsections describe the principal issues and adjustments made to the building systems based on observed data over the past six years.
Correction of Basic Control System Issues
The same control system issues experienced with the Science & Engineering Building I created difficulties with the system operations of the Classroom & Office Building during the first year of occupancy, and for the same reasons. The building’s local control system was incompatible with the campus BMS.
To recap this issue:
Buildings on the UC Merced campus are controlled using a central BMS so that all buildings can be scheduled from one center. Based on the instructions from the BMS, the individual building’s control systems are supposed to operate the various system components according to those instructions.
Metered data revealed that schedule changes made with the BMS were not resulting in any effect on the local building control systems. The communication “protocols” of the two systems were different: the campus BMS uses “BACnet protocols” while the local laboratory ventilation control system uses “LonTalk protocols”. A great deal of time was required for the staff at UC Merced, working with the engineers of the control system manufacturers, to recommission the controls and solve the compatibility problem. The solution ultimately was to set up a separate computer specifically to coordinate the control systems.
The importance of this problem solution was that many energy efficiency measures of the build- ing design could not be implemented nor could the building be placed into a setback mode as allowed by the building schedule.
For UC Merced, this problem was the most significant one encountered because it affected the low-energy operation of the building as intended in the design and because it required so much time to solve. It was at least two years in the observation, solution and implementation to bring about the basic system operation as intended.
The principal outcome of this experience is that UC Merced has enacted the future requirement that any control system specification for new UC Merced buildings in subsequent phases must be entirely BACnet protocol to ensure compatibility with the central campus system.
Post-Commissioning Work: HVAC System Coordination with Room Scheduling
Just as in the case of the Science & Engineering Building I, the UC Merced staff have been work- ing during the post-commissioning period to coordinate the detailed building schedule with the HVAC temperature and ventilation requirements for the Classroom & Office Building.
Certain rooms such as classrooms, auditoriums and conference rooms are scheduled through an online reservation system known as Astra. The campus BMS system, with the solution of the coordination problem with the local building HVAC control system, now can adjust the tempera- ture setpoints and/or vents according to the Astra scheduler. This linkage of the space schedul- ing software with the campus BMS by the UC Merced staff is providing energy saving dividends. Classrooms can be put into a non-occupancy mode, for example, where there is minimal ventila- tion air and the space temperature is allowed to float.
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