Analysis of the Potential Energy Savings for 14 Office Buildings with VAV Systems

Abstract

At the beginning of an existing building commissioning (EBCx)/energy retrofit project, some form of screening is usually applied to determine whether there is sufficient potential for savings to justify a formal EBCx assessment/energy audit. In this study, an improved methodology for potential energy savings estimation from EBCx/retrofit measures, based on Baltazar's methodology (2006), is proposed to perform this type of screening. The improvements are included on optimization parameters, space load calculation, simulation of buildings with multiple types of HVAC systems, AHU shutdown simulation, among others. The improved methodology was used to estimate annual potential energy cost savings for 14 office buildings in Austin, TX with either single duct VAV (SDVAV) systems or dual duct VAV (DDVAV) systems. The estimates are based on very limited information about the buildings and the built-in HVAC systems as well as one year of utility bills. From this analysis, the methodology has predicted an average total potential savings of 36% for SDVAV systems with electric terminal reheat, 22% for SDVAV systems with hot water reheat, and 25% for DDVAV systems. To validate these results, the estimated potential savings are compared with savings proposed in respective EBCx assessment reports. Based on the comparison of the report estimates and the potential savings with the improved methodology, it was found that 'generalized' factors of assessment predicted energy cost savings to estimated potential energy cost savings could be found. The factors identified in these cases were 0.68, 0.66, and 0.61 for each type of system - SDVAV w/electric reheat, SDVAV w/hot water reheat, and DDVAV, respectively.