Why ICP Does Not Use IPMVP Option D: Calibrated Simulation

Tracy Phillips
Currently the Investor Confidence Project (ICP) does not allow the use of an IPMVP Option D calibrated simulation for Measurement and Verification (See ICP Quick Reference). The Large Commercial/Multifamily protocol requires the use of an IPMVP Option C, Whole Facility measurement and verification (M&V) approach. While the Standard and Targeted protocols require Options A or B, Retrofit Isolation approaches.

The ICP Team has been asked on occasion "what happened to Option D, Calibrated Simulation?" We are using a calibrated simulation as the calculation method for Large (and sometimes Standard) projects after all. So why is this M&V approach excluded from the list of M&V options?

The fact is that Option D is primarily intended for new construction projects; essentially, projects in which there are no baseline data available (utility data). The energy model is used to estimate energy use for the proposed building, since none exists. The actual performance of the building, once it is built, is then compared to this estimate of energy use generated by the energy model.

Conversely, the ICP is designed to address the retrofit of existing buildings; buildings that have utility data - which can be used to develop an actual baseline for the building. So the Option D approach is unnecessary.

However, this does not mean that the calibrated simulation’s usefulness ends after the savings projections have been established. The model can and should still play a part in the M&V process. For most if not all M&V efforts, non-routine adjustments need to be made to the baseline, to reflect unanticipated changes in the building’s energy use after the retrofits have been completed. Adjustments such as increased occupancy, new internal loads, added square footage, etc. These items affect heating and cooling loads, and building energy use, and need to be calculated and essentially subtracted from or added to the baseline, so that it can be accurately compared to the post-retrofit energy use in an Option C approach.

Calculation of the effects of these adjustments on the building’s energy use can be challenging, especially adjustments that affect the loads in the building, and have potentially complicated interactive effects with the building’s HVAC systems. The calibrated energy model can subsequently be used to estimate these effects on energy use, in a more comprehensive and accurate manner than spreadsheet calculations or other methods.

If a modeling approach is used for a Standard project type, again, it can and in fact needs to be used in an Option A or B M&V approach. Options A and B assess the performance of energy conservation measures. If the measures are operating as expected, nothing else needs to be done. However, if the measures are not operating as expected, these variations in operation need to be quantified, so that “verified” energy savings can be calculated. Thus, if an energy model was used for the original savings calculations, this same model needs to be adjusted with the observed / measured variations in operation, so that the revised or verified energy savings can be calculated.

Does Option D have a place in existing building retrofit projects? The answer is yes, but it is mainly applied only when there is no baseline data available for the building. For example, a centrally-metered campus of buildings where no individual building meter exists. 

Energy modeling represents an important tool in energy efficiency project development. It is used to estimate energy savings, and can also be applied to determine the effects of non-routine adjustments or to calculate verified energy savings in the M&V effort. However, the ICP requires a baseline developed from actual historical utility data, a requirement that excludes the use of an Option D approach to M&V.

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