Glossary

Acronyms and terms used in InverseAudit and its reports.

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Acronyms

  • AHU: Air Handling Unit
  • ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers
  • BEMS: Building Energy Management System
  • CFM: Cubic Feet per Minute
  • CHW: Chilled Water
  • COP: Coefficient of Performance
  • CV(RMSE): Coefficient of Variation of the Root Mean Squared Error
  • DHW: Domestic Hot Water
  • DOAS: Dedicated Outdoor Air System
  • DX: Direct Expansion
  • ECM: Energy Conservation Measure
  • EER: Energy Efficiency Ratio
  • EUI: Energy Use Intensity
  • FEMP: Federal Energy Management Program
  • GHG: Greenhouse Gas
  • GSF: Gross Square Feet
  • HVAC: Heating, Ventilation and Air Conditioning
  • IPMVP: International Performance Measurement and Verification Protocol
  • kBtu: Thousand British Thermal Units
  • kW: Kilowatt, a unit of power (demand)
  • kWh: Kilowatt-hour, a unit of energy
  • MBtu: Million British Thermal Units, as reported by the DOE-2 energy model
  • NMBE: Normalized Mean Bias Error
  • O&P: Overhead and Profit
  • PSZ-AC: Packaged Single-Zone Air Conditioner
  • PTAC / PTHP: Packaged Terminal Air Conditioner / Heat Pump
  • PVAV: Packaged Variable Air Volume
  • SC: Shading Coefficient
  • SHGC: Solar Heat Gain Coefficient
  • SIR: Savings-to-Investment Ratio
  • TMY3: Typical Meteorological Year 3
  • VAV: Variable Air Volume
  • VRF: Variable Refrigerant Flow
  • WSHP: Water-Source Heat Pump
  • WWR: Window-to-Wall Ratio

Terms

  • Analyzer: The person who enters the baseline’s data, runs the calibration and performs the energy audit. Other people the baseline is shared with see it in view-only mode. See Roles and the analyzer.
  • ASHRAE Guideline 14: A guideline for measuring energy savings. Its CV(RMSE) and NMBE limits are used to judge whether a calibrated model fits the meter data.
  • ASHRAE Level 2 audit: An energy survey and analysis that identifies energy conservation measures with their savings and cost estimates.
  • Asset gap: The energy a building uses above the code-compliant scenario because of its design, envelope and equipment (B - C).
  • Asset score: A rating of a building’s as-built physical characteristics and energy systems, independent of occupancy and operation. It compares the calibrated model with the same building built to the selected energy code: 100 - 50 × A / C.
  • Audit report: The report produced on the Energy Audit page, with the Summary, Analysis, Recommendations and Utility analysis tabs. It can be downloaded as PDF.
  • Average rate: A single rate per unit of energy, used when your utility’s rate structure isn’t selected. With an average rate, demand cost savings and utility incentives aren’t calculated. Also called a blended rate.
  • Baseline: Your building in InverseAudit: its information, meter data, geometry, systems and rates, and the energy model calibrated from them.
  • Calibration: The process that tunes the building’s energy model until it matches the meter data. See Check inputs and run calibration.
  • Calibration length: How long the calibration searches for the best fit: Quick (about 3 minutes), Standard (about 20 minutes, recommended) or Thorough (about 40 minutes).
  • Client: A company you share audits with. Its contacts sign in with I’m reviewing an audit report and see the posted audits of baselines assigned to the company.
  • Climate zone: A geographic region defined by ASHRAE standards, characterized by similar weather patterns, used to determine the energy code requirements.
  • Compared scenarios (A, B, C): The three versions of the building used on the Benchmark page, all derived from the calibrated model. A is the building as it operates today, B is the same building with typical schedules and setpoints, and C is the same building built to the selected energy code.
  • CV(RMSE): A statistical measure of how much the model’s results vary from the measured data: the root mean squared error divided by the mean of the measured data. A lower value means a better fit. ASHRAE Guideline 14 accepts up to 30% for hourly data and 15% for monthly data.
  • End-use analysis: A breakdown of energy use by category within a building, such as lighting, heating, cooling or plug loads.
  • Energy conservation measure (ECM): A specific action or upgrade that reduces a building’s energy use or improves its efficiency.
  • Energy use gap: How much more energy the building uses than the code-compliant scenario (A - C), split into the asset gap and the operational gap. See Scenarios and the energy use gap.
  • Energy use intensity (EUI): A building’s annual energy use divided by its floor area, usually in kBtu/ft².
  • ENERGY STAR score: A 1-100 rating of a building’s energy efficiency compared with similar buildings nationwide. Higher is better, and 50 is the median.
  • Green Button: A standardized XML format for downloading energy use data from a utility.
  • Interval data: Meter data recorded every 15, 30 or 60 minutes, usually by a smart meter or a BEMS.
  • Lighting power density: Installed lighting power per floor area, in W/ft².
  • Net payback period: The cost of the measures minus incentives, divided by the annual cost savings.
  • NMBE: A statistical measure of the model’s overall bias: the mean difference between measured and simulated data, divided by the mean of the measured data. A value closer to zero is better. ASHRAE Guideline 14 accepts within ±10% for hourly data and ±5% for monthly data.
  • Operational gap: The energy a building uses above the typical operation scenario because of its schedules, setpoints and operating practice (A - B).
  • Operational score: A rating of how the building is operated. It compares the calibrated model with the same building run on typical (ASHRAE) schedules: 100 - 50 × A / B.
  • Payback period: The time it takes for a measure’s savings to equal its cost.
  • Performance-based incentive: A utility incentive paid per kWh and per kW saved.
  • Post / Unpost: Posting shares the audit report with the baseline’s client and adds the building to the Dashboard. Unposting hides the report again so you can make changes.
  • R-value: A material’s thermal resistance, in ft²·h·°F/Btu. Higher is better insulated.
  • Savings-to-investment ratio (SIR): A measure’s savings over its lifetime divided by its net cost (retrofit cost minus incentives). InverseAudit doesn’t discount future savings.
  • Setback temperature: A less strict temperature setting used during unoccupied periods to save energy while keeping minimal comfort.
  • Setpoint temperature: The temperature the HVAC system maintains during occupied periods.
  • Site EUI: The energy used on site per floor area, in kBtu/ft² per year.
  • Source EUI: Site energy plus the losses from producing and delivering it, per floor area. ENERGY STAR uses source energy.
  • Subscriber: The baseline’s owner: the person who created it, or the new owner after a transfer. The subscriber subscribes and cancels, and assigns the analyzer.
  • U-value: The rate of heat transfer through a building element, in Btu/h·ft²·°F. Lower is better insulated.
  • Weather normalization: Adjusting energy use for weather, so different periods or locations can be compared fairly.
  • Whole-building energy model: A simulation of the building’s energy performance as one system, including climate, envelope and mechanical systems.