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Development of Maximum Technically Achievable Energy Targets for Commercial Buildings

How energy efficient can commercial and multifamily buildings become in the near future if first cost is not considered? This ASHRAE sponsored project (1651-RP) used building energy simulation modeling to try to answer this question. The first step was to assemble a list of energy efficiency measures that can be included in the design of commercial and multifamily residential buildings. The list needed to include both commonly used and cutting edge energy efficiency measures with the goal of being comprehensive, at least for measures that can be modeled. Input was sought from many people to ensure that the list of measures did not exclude any important one. From the resulting list of almost 400 measures, some were recommended and ultimately thirty were chosen.  Sixteen EnergyPlus prototype buildings that were consistent with ASHRAE Standard 90.1-2013 across seventeen climate zones were used as baseline models. The thirty measures were individually modeled using an open source Python based library called Eppy, created for the study. Each of the thirty measures, often with many options, were applied to each building and climate combination. In general, the measures were applied in the following order:

  • Reduce internal loads
  • Reduce building envelope loads
  • Reduce HVAC distribution system losses
  • Decrease HVAC equipment energy consumption
  • Major HVAC reconfigurations.

After each measure was applied to each of the 272 building and climate combinations, if the energy consumption was reduced it remained in the model. After all thirty measures were applied, the projected U.S. national weighted energy consumption for new buildings was nearly cut in half compared to ASHRAE Standard 90.1-2013.

EnergyPlus 8.3 was used to perform the final building energy simulation modeling used in this analysis. It had the capability of modeling almost every measure found in the project. The seventeen cities and their respective climate zones used were:

  • Miami (1A)
  • Riyadh (1B)
  • Houston (2A)
  • Phoenix (2B)
  • Memphis (3A)
  • El_Paso (3B)
  • San_Francisco (3C)
  • Baltimore (4A)
  • Albuquerque (4B)
  • Salem (4C)
  • Chicago (5A)
  • Boise (5B)
  • Vancouver (5C)
  • Burlington (6A)
  • Helena (6B)
  • Duluth (7)
  • Fairbanks (8)

The PNNL commercial prototype building models used for the final simulations in this analysis were based on ASHRAE Standard 90.1-2013 and include:

  • ApartmentHighRise
  • ApartmentMidRise
  • Hospital
  • HotelLarge
  • HotelSmall
  • OfficeLarge
  • OfficeMedium
  • OfficeSmall
  • OutPatientHealthCare
  • RestaurantFastFood
  • RestaurantSitDown
  • RetailStandalone
  • RetailStripmall
  • SchoolPrimary
  • SchoolSecondary
  • Warehouse.

The thirty energy efficiency measures modeled in EnergyPlus were:

  • LED Exterior Lighting
  • Highest Efficiency Office Equipment
  • High Performance Lighting (LED)
  • Shift from General to Task Illumination
  • Optimal Daylighting Control
  • Optimal Roof Insulation Level
  • Optimal Choice of Vertical Fenestration
  • External Light Shelves
  • Daylighting Control by Fixture
  • High Performance Fans
  • High Performance Ducts to Reduce Static Pressure
  • Demand Controlled Ventilation/CO2 Controls
  • Multiple-zone VAV System Ventilation Optimization
  • Optimal Water/Air Cooling Coils
  • Occupant Sensors for Air Handling Equipment
  • Energy Recovery Ventilators
  • Indirect Evaporative Cooling
  • High Eff./Var. Speed Packaged DX Cooling
  • High Efficiency Heat Pumps
  • Ground Source Heat Pump
  • High Efficiency and Variable Speed Chillers
  • Heat Recovery from Chillers
  • High Efficiency Boilers
  • High Efficiency Building Transformers
  • Chilled/Cooled Beam
  • Dedicated Outside Air System with Heat Recovery
  • Underfloor Air Distribution
  • Hybrid/Mixed Mode Ventilation
  • Radiant Heating and Cooling and DOAS
  • Variable Refrigerant Flow Air Conditioning.

The national weighted  reduction was 47.8% based on site energy and 47.8% based on source energy.