Assessing the minimum instrumentation to well tune existing medium sized office building energy models

Dynamic whole building energy models (BEMs) are created for various reasons: to evaluate alternative design strategies; compliance checks with energy codes; apply certifications at the design stage of a new building; continuously improve building performance through its life cycle; assist decision making on implementation of energy conservation measures (ECMs). Before it can be used to evaluate proposed ECMs with reasonable certainly, BEM must be constructed and calibrated to a predetermined level of fidelity with the measured energy use for existing building's actual operation conditions. Given that even a simplified model would normally comprise hundreds of inputs, reconciling a specific BEM to a particular building system's measured energy use is tedious, time-consuming, labor-intensive and without a guiding protocol methodology. This study demonstrates an entire workflow of establishing the minimum instrumentation to capture the essential building operation features and using them to build and well tune BEMs for existing medium sized office buildings. Sensitivity analysis is first conducted to generate a concise list of parameters that have the greatest potential to impact the performance of critical building subsystems using prototyped, "newly constructed" medium office building EnergyPlus models, developed by U.S. Department of Energy (DOE), known as the DOE commercial reference buildings, with representative characteristics of numerous building types in U.S. market to generate. By relating the reference buildings to the variety of existing building types in the U.S. building stock, these reference buildings serve as baseline models to establish a guiding parametric list. Guided by this prioritized key parameter list, building information is then collected and used to build and tune "as-operated" BEMs for three case study buildings in Climate Zone 4A. The models can be claimed as "calibrated" if the calculated errors are within a pre-determined threshold. Finally, the minimum instrumentation required to well tune existing medium-size office buildings are assessed accordingly.