PERFORMANCE MODELLING | CIBSE TM63 protocols can also be followed for other purposes such as establishing a baseline for performance in use, and monitoring and targeting strategies to improve performance. CIBSE TM63 provides a step-by-step guide to how such a baseline can be developed to evaluate energy performance in use. It complements CIBSE TM54, which is used at design stage to project operational energy use. The benefits of following a calibration-based approach to evaluate the actual performance of a building and derive a baseline for performance in use are twofold: 1) The calibration process provides a systematic approach to building diagnostics and identification of causes of any performance gap. 2) The calibration process can help improve the confidence in building performance models, and address potential modelling errors and uncertainties that are often inevitable at design stage. A baseline derived from a calibrated model can, therefore, be a more robust and practical operational target for a building. CJ E SFAND BURMAN, UCL Institute for Environmental Design and Engineering, and NISHESH JAIN, DesignBuilder Software. TM63 enables users to avoid the confusions that may arise when performance in use is compared against calculations that do not reflect actual operating conditions Table 1: Calibration criteria for energy performance, defined in ASHRAE Guideline 14-2014 Statistical Index Calibration method Calibration criteria NMBE Monthly 5% CVRMSE Monthly 15% CVRMSE Hourly 10% CVRMSE Hourly 30% NMBE: normalised mean bias error CVRMSE: coefficient of variation of the root mean square error USING THE PERFORMANCE MEASUREMENT AND VERIFICATION PROTOCOL The IPMVP is a framework created for measuring and ascertaining performance using best-practice techniques in verification of energy conservation measures (ECMs). The IPMVP provides guidance on measurement boundary, measurement period, and ways to calculate impact (savings) and undertake operational verification. Depending on the type of ECM and its relationship with other building performance input or output parameters, the IPMVP provides four options for calculating an ECMs impact: Option A: retrofit isolation, key parameter measurement Option B: retrofit isolation, all parameter measurement Option C: whole-facility Option D: calibrated simulation. While the first two options look at isolating the assessment and analysis to one or few building systems that are affected by the ECM, the other two are done at a whole-building level. For each of the options, the IPMVP explains the data required and monitoring and measurement protocols. It also suggests ways to undertake accurate calculations and validate results, linking to other relevant standards and protocols. IPMVP Option D, calibrated simulation, suggests using building performance modelling tools for energy consumption and demand simulation, calibrated with hourly or monthly energy data. The IPMVP framework provides a step-by-step method to fine-tune the model to reflect the building and its operating conditions accurately. It is underpinned by ASHRAE Guideline 14 (Measurement of Energy, Demand and Water Savings), which provides the criteria to check calibration accuracy either at hourly or monthly intervals. Detailed operational information should be collected during site surveys and by measurements to calibrate the model. Perfect balance Vital for our wellbeing With Swegons g Air Qualityy Control dynamic y pressure compensation p p functionality, y, GOLD will adapt p to changes g in the system, y taking control and balance to a new level. Fortunatelyy this onlyy requires q the push p of a button, not walking the tight rope! 34 March 2021 www.cibsejournal.com CIBSE March 21 pp32-34 TM63.indd 34 19/02/2021 15:13