Page 131 - Zero Net Energy Case Study Buildings-Volume 1

OBSERVATIONS ZERO NET ENERGY CASE STUDY BUILDINGS, VOL. 1
daylight and occupancy controls: sophisticated lighting design software in the hands of a skilled modeler can yield excellent results, but energy modeling software does not include this level of sophistication. Engineers are now starting to factor such experiences into the modeling of these types of loads in their current projects.
At present, the ability to show during the design phase that the building will meet targeted energy budgets has limitations, especially with complex buildings: design professionals cannot guaran- tee a certain level of performance as measured during the post occupancy period.
Establishing the practice of comparing the results of a whole building en- ergy model of the pre-constructed design with the measured energy use data from the occupied building will improve the industry’s energy model- ing capabilities. As design professionals gain experience and the design analysis tools improve, the basis for setting realistic future energy perfor- mance targets will also generally improve. This is an important area for continued research and software product development.
Building to the Design: Building Metering Issues
ZNE buildings do not assume that internal environmental conditions will be maintained, if neces- sary, by an expenditure of extra energy to overcome deviant factors from the exterior environ- ment that affect comfort and functionality. Rather, the building features and systems are specifi- cally designed to be in efficient and economical balance with the exterior environment so that energy demand is minimized. ZNE buildings therefore usually employ new approaches (from the standard industry perspective) to the design of these features and systems, which may or may not have a cost premium (a subject of much current discussion).
“Building to the Design” is therefore a major current concern as the industry shifts and adopts the new design approaches as they are tested and prove out over time. Part of this process involves the recognized need for post-occupancy building commissioning as well as the need to avoid the use of “value engineering” (unless it is true value engineering considering life cycle cost and not just blunt cost reduction) to remove high-performance features. It is also important that a build- ing metering sub-system be included in the design and specification so that it can be verified that the performance objective was in fact achieved or, perhaps more importantly, to help identify measures that need to be taken to “get to zero”. By reviewing several years of this metered data it is possible to sort out problem issues, to confirm the effectiveness of selected design strategies and to help the building manager make good decisions about the building operation.
In relation to the last point, the experience with the case study buildings discussed in this mono- graph has led to the interesting conclusion that the building metering sub-system itself must be commissioned and validated. In all six buildings studied, the monitoring systems needed post-occupancy adjustments to function properly. We need to have as much accurate data as possible about the energy use of each building subsystem, component and electric circuit once these low-energy buildings are occupied. In several cases, faulty data recording or outright failure was discovered during the measurement and verification process some time after initial occupancy.
The clients and A/E teams for the ZNE case study buildings described in this monograph rec- ognized the importance of post-occupancy monitoring of the building performance and installed meters on each electric panel and, in the case of the UC Merced buildings, on the hot and chilled water from the campus central plant as well. It is most useful if the circuits are segregated by end-use so that metering can be done at the breaker level on the main distribution board, which is relatively inexpensive since breakers can have metering at little additional cost. This is now standard practice for new buildings at UC Merced2.
In the case of the Science & Engineering Building I at UC Merced, the early problem was with the metering system itself. There was an initial period of troubleshooting, including even some assistance from Lawrence Berkeley National Laboratory, before the data stream was deemed to be representative of actual energy use.
The normal commissioning process does not include the metering system—whether the meters are working correctly and whether the data is accurate. John Elliott, former Director of Sustain-
2 Private communication, John Elliott, Former Director of Sustainability at UC Merced, Mar. 2014.
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