Class: SetNISTInfiltrationCorrelations

Inherits:

OpenStudio::Measure::ModelMeasure

• Object
• OpenStudio::Measure::ModelMeasure
• SetNISTInfiltrationCorrelations

Defined in:

lib/measures/set_nist_infiltration_correlations/measure.rb

Overview

start the measure

Instance Method Summary

• #arguments(model) ⇒ Object

  define the arguments that the user will input.

• #description ⇒ Object

  human readable description.

• #infer_nist_building_type(model) ⇒ Object
• #invert_schedule_day(old_schedule_day, new_schedule_day, new_schedule_name) ⇒ Object

  method to invert a schedule day.

• #invert_schedule_ruleset(schedule_ruleset, new_schedule_name) ⇒ Object

  method to invert a schedule ruleset.

• #modeler_description ⇒ Object

  human readable description of modeling approach.

• #name ⇒ Object

  human readable name.

• #nist_building_types ⇒ Object

  DOE prototype buildings for which there are NIST infiltration coefficients.

• #run(model, runner, user_arguments) ⇒ Object

  define what happens when the measure is run.

Instance Method Details

#arguments(model) ⇒ Object

define the arguments that the user will input

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 176

def arguments(model)
  args = OpenStudio::Measure::OSArgumentVector.new

  # airtightness value
  airtightness_value = OpenStudio::Measure::OSArgument::makeDoubleArgument('airtightness_value', false)
  airtightness_value.setDefaultValue(13.8)
  airtightness_value.setDisplayName('Airtightness design value (m^3/h-m^2)')
  airtightness_value.setDescription('The airtightness design value from a building pressurization test. Use 5.0 (m^3/h-m^2) as a default for buildings with air barriers. Convert (cfm/ft^2) to (m^3/h-m^2) by multiplying by 18.288 (m-min/ft-hr). (0.3048 m/ft)*(60 min/hr) = 18.288 (m-min/ft-hr).')
  args << airtightness_value

  # airtightness pressure
  airtightness_pressure = OpenStudio::Measure::OSArgument::makeDoubleArgument('airtightness_pressure', false)
  airtightness_pressure.setDefaultValue(75.0)
  airtightness_pressure.setDisplayName('Airtightness design pressure (Pa)')
  airtightness_pressure.setDescription('The corresponding pressure for the airtightness design value, typically 75 Pa for commercial buildings and 50 Pa for residential buildings.')
  args << airtightness_pressure

  # choices for air-tightness scope
  airtightness_choices = OpenStudio::StringVector.new
  airtightness_choices << '4-sided'
  airtightness_choices << '5-sided'
  airtightness_choices << '6-sided'

  # airtightness area
  airtightness_area = OpenStudio::Measure::OSArgument.makeChoiceArgument('airtightness_area', airtightness_choices, false)
  airtightness_area.setDefaultValue('5-sided')
  airtightness_area.setDisplayName('Airtightness exterior surface area scope')
  airtightness_area.setDescription('Airtightness measurements are weighted by exterior surface area. 4-sided values divide infiltration by exterior wall area.  5-sided values additionally include roof area. 6-sided values additionally include floor and ground area.')
  args << airtightness_area

  # air barrier
  air_barrier = OpenStudio::Measure::OSArgument::makeBoolArgument('air_barrier', false)
  air_barrier.setDefaultValue(false)
  air_barrier.setDisplayName('Does the building have an air barrier?')
  air_barrier.setDescription('Buildings with air barriers use a different set of coefficients.')
  args << air_barrier

  # populate choice argument for schedules in the model
  sch_handles = OpenStudio::StringVector.new
  sch_display_names = OpenStudio::StringVector.new

  # populate choice argument for schedules that are applied to surfaces in the model
  schedule_handles = OpenStudio::StringVector.new
  schedule_display_names = OpenStudio::StringVector.new

  # putting space types and names into hash
  schedule_names = []
  schedule_names << 'Lookup From Model'
  model.getScheduleRulesets.each { |sch| schedule_names << sch.name.to_s }
  model.getScheduleConstants.each { |sch| schedule_names << sch.name.to_s }

  # hvac operation schedule
  hvac_schedule = OpenStudio::Measure::OSArgument::makeChoiceArgument('hvac_schedule', schedule_names, false, true)
  hvac_schedule.setDefaultValue('Lookup From Model')
  hvac_schedule.setDisplayName('HVAC Operating Schedule')
  hvac_schedule.setDescription('Choose the HVAC Operating Schedule for the building. The schedule must be a Schedule Constant or Schedule Ruleset object. Lookup From Model will use the operating schedule from the largest airloop by floor area served. If the largest airloop serves less than 5% of the building, the measure will attempt to use the Building Hours of Operation schedule instead.')
  args << hvac_schedule

  # climate zone options
  cz_choices = OpenStudio::StringVector.new
  cz_choices << '1A'
  cz_choices << '1B'
  cz_choices << '2A'
  cz_choices << '2B'
  cz_choices << '3A'
  cz_choices << '3B'
  cz_choices << '3C'
  cz_choices << '4A'
  cz_choices << '4B'
  cz_choices << '4C'
  cz_choices << '5A'
  cz_choices << '5B'
  cz_choices << '5C'
  cz_choices << '6A'
  cz_choices << '6B'
  cz_choices << '7A'
  cz_choices << '8A'
  cz_choices << 'Lookup From Model'

  # climate zone
  climate_zone = OpenStudio::Measure::OSArgument.makeChoiceArgument('climate_zone', cz_choices, false)
  climate_zone.setDefaultValue('Lookup From Model')
  climate_zone.setDisplayName('Climate Zone')
  climate_zone.setDescription('Specify the ASHRAE climate zone. CEC climate zones are not supported.')
  args << climate_zone

  # building type options
  building_types = nist_building_types
  building_types << 'Lookup From Model'

  # building type
  building_type = OpenStudio::Measure::OSArgument.makeChoiceArgument('building_type', building_types, false)
  building_type.setDefaultValue('Lookup From Model')
  building_type.setDisplayName('Building Type')
  building_type.setDescription('If the building type is not available, pick the one with the most similar geometry and exhaust fan flow rates.')
  args << building_type

  return args
end

#description ⇒ Object

human readable description

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 17

def description
  return "This measure incorporates infiltration that varies with weather and HVAC operation, and takes into account building geometry (height, above-ground exterior surface area, and volume). It is based on work published by Ng et al. (2018) <a href='https://doi.org/10.1016/j.buildenv.2017.10.029'>'Weather correlations to calculate infiltration rates for U.S. commercial building energy models'</a> and Ng et al. (2021) <a href='https://doi.org/10.1016/j.buildenv.2021.107783'>'Evaluating potential benefits of air barriers in commercial buildings using NIST infiltration correlations in EnergyPlus'</a>. This method of calculating infiltration was developed using eleven of the DOE commercial prototype building models (<a href='https://www.energycodes.gov/development/commercial/prototype_models'>Goel et al. 2014</a>) and TMY3 weather files for eight climate zones (CZ). Guidance on implementing the infiltration correlations are explained in the NIST technical report <a href='https://doi.org/10.6028/NIST.TN.2221'>'Implementing NIST Infiltration Correlations'</a>. Ng et al. (2018) shows that when analyzing the benefits of building envelope airtightening, greater HVAC energy savings were predicted using the infiltration inputs included in this Measure compared with using the default inputs that are included in the prototype building models. Brian Polidoro (NIST) first developed this Measure in 2015 and updated it in 2018 and 2019. Matthew Dahlhausen (NREL) updated the 2019 Measure and published this current version in 2023. To provide feedback on the NIST infiltration correlations, please email infiltration@list.nist.gov or lisa.ng@nist.gov. For measure implementation questions or issues, contact matthew.dahlhausen@nrel.gov."
end

#infer_nist_building_type(model) ⇒ Object

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 44

def infer_nist_building_type(model)
  if model.getBuilding.standardsBuildingType.is_initialized
    model_building_type = model.getBuilding.standardsBuildingType.get
  else
    model_building_type = ''
  end

  case model_building_type
  when 'Office'
    # map office building type to small medium or large
    floor_area = model.getBuilding.floorArea
    if floor_area < 2750.0
      nist_building_type = 'SmallOffice'
    else
      nist_building_type = 'MediumOffice'
    end
  when 'LargeOffice'
    nist_building_type = 'MediumOffice'
  when 'Retail'
    # map retal building type to RetailStripmall or RetailStandalone based on building name
    building_name = model.getBuilding.name.get
    if building_name.include? 'RetailStandalone'
      nist_building_type = 'RetailStandalone'
    else
      nist_building_type = 'RetailStripmall'
    end
  when 'StripMall'
    nist_building_type = 'RetailStripmall'
  when 'Warehouse'
    nist_building_type = 'RetailStripmall'
  when 'QuickServiceRestaurant'
    nist_building_type = 'RetailStripmall'
  when 'FullServiceRestaurant'
    nist_building_type = 'RetailStripmall'
  when 'Outpatient'
    nist_building_type = 'MediumOffice'
  when 'SuperMarket'
    nist_building_type = 'RetailStandalone'
  when 'EPr'
    nist_building_type = 'PrimarySchool'
  when 'ESe'
    nist_building_type = 'SecondarySchool'
  when 'RtL'
    nist_building_type = 'RetailStandalone'
  when 'RtS'
    nist_building_type = 'RetailStripmall'
  when 'RSD'
    nist_building_type = 'RetailStripmall'
  when 'RFF'
    nist_building_type = 'RetailStripmall'
  when 'Mtl'
    nist_building_type = 'SmallHotel'
  when 'Htl'
    nist_building_type = 'LargeHotel'
  when 'Hsp'
    nist_building_type = 'Hospital'
  when 'OfS'
    nist_building_type = 'SmallOffice'
  when 'OfL'
    nist_building_type = 'MediumOffice'
  when 'SCn'
    nist_building_type = 'RetailStripmall'
  else
    nist_building_type = model_building_type
  end

  results = {}
  results['model_building_type'] = model_building_type
  results['nist_building_type'] = nist_building_type

  return results
end

#invert_schedule_day(old_schedule_day, new_schedule_day, new_schedule_name) ⇒ Object

method to invert a schedule day

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 118

def invert_schedule_day(old_schedule_day, new_schedule_day, new_schedule_name)
  new_schedule_day.setName("#{new_schedule_name}")
  for index in 0..old_schedule_day.times.size-1
    old_value = old_schedule_day.values[index]
    if old_value == 0
      new_value = 1
    else
      new_value = 0
    end
    new_schedule_day.addValue(old_schedule_day.times[index], new_value)
  end

  return new_schedule_day
end

#invert_schedule_ruleset(schedule_ruleset, new_schedule_name) ⇒ Object

method to invert a schedule ruleset

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 134

def invert_schedule_ruleset(schedule_ruleset, new_schedule_name)
  model = schedule_ruleset.model
  new_schedule = OpenStudio::Model::ScheduleRuleset.new(model, 0.0)
  new_schedule.setName(new_schedule_name)

  # change summer design day
  summer_design_day_schedule = schedule_ruleset.summerDesignDaySchedule
  new_summer_design_day_schedule = OpenStudio::Model::ScheduleDay.new(model)
  invert_schedule_day(summer_design_day_schedule, new_summer_design_day_schedule, "#{new_schedule_name} Summer Design Day Schedule")
  new_schedule.setSummerDesignDaySchedule(new_summer_design_day_schedule)

  # change winter design day
  winter_design_day_schedule = schedule_ruleset.winterDesignDaySchedule
  new_winter_design_day_schedule = OpenStudio::Model::ScheduleDay.new(model)
  invert_schedule_day(winter_design_day_schedule, new_winter_design_day_schedule, "#{new_schedule_name} Winter Design Day Schedule")
  new_schedule.setWinterDesignDaySchedule(new_winter_design_day_schedule)

  # change the default day values
  default_day_schedule = schedule_ruleset.defaultDaySchedule
  new_default_day_schedule = new_schedule.defaultDaySchedule
  invert_schedule_day(default_day_schedule, new_default_day_schedule, "#{new_schedule_name} Default Day Schedule")

  # change for schedule rules
  schedule_ruleset.scheduleRules.each_with_index do |rule, i|
    old_schedule_day = rule.daySchedule
    new_schedule_day = OpenStudio::Model::ScheduleDay.new(model)
    invert_schedule_day(old_schedule_day, new_schedule_day, "#{new_schedule_name} Schedule Day #{i}")

    new_rule = OpenStudio::Model::ScheduleRule.new(new_schedule, new_schedule_day)
    new_rule.setName("#{new_schedule_day.name} Rule")
    new_rule.setApplySunday(rule.applySunday)
    new_rule.setApplyMonday(rule.applyMonday)
    new_rule.setApplyTuesday(rule.applyTuesday)
    new_rule.setApplyWednesday(rule.applyWednesday)
    new_rule.setApplyThursday(rule.applyThursday)
    new_rule.setApplyFriday(rule.applyFriday)
    new_rule.setApplySaturday(rule.applySaturday)
  end
  return new_schedule
end

#modeler_description ⇒ Object

human readable description of modeling approach

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 22

def modeler_description
  return "This measure will remove any existing infiltration objects (OS:SpaceInfiltration:DesignFlowRate and OS:SpaceInfiltration:EffectiveLeakageArea). Every zone will then get two OS:SpaceInfiltration:DesignFlowRate objects that add infiltration using the 'Flow per Exterior Surface Area' input option, one infiltration object when the HVAC system is on and one object when the HVAC system is off. The method assumes that HVAC operation is set by a schedule, though it may not reflect actual simulation/operation when fan operation may depend on internal loads and temperature setpoints. By default, interior zones will receive no infiltration. The user may enter a design building envelope airtightness at a specific design pressure, and whether the design value represents a 4-sided, 5-sided, or 6-sided normalization.  By default, the measure assumes an airtightness design value of 13.8 (m^3/h-m^2) at 75 Pa. The measure assumes that infiltration is evenly distributed across the entire building envelope, including the roof. The user may select the HVAC system operating schedule in the model, or infer it based on the availability schedule of the air loop that serves the largest amount of floor area. The measure will make a copy of the HVAC operating schedule, 'Infiltration HVAC On Schedule', which is used with the HVAC on infiltration correlations.  The measure will also make an 'Infiltration HVAC Off Schedule' with inverse operation, used with the HVAC off infiltration correlations. OS:SpaceInfiltration:DesignFlowRate object coefficients (A, B, C, and D) come from Ng et al. (2018). The user may select the Building Type and Climate Zone, or the measure will infer them from the model."
end

#name ⇒ Object

human readable name

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 11

def name
  # Measure name should be the title case of the class name.
  return 'SetNISTInfiltrationCorrelations'
end

#nist_building_types ⇒ Object

DOE prototype buildings for which there are NIST infiltration coefficients

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 27

def nist_building_types
  building_types = OpenStudio::StringVector.new
  building_types << 'SecondarySchool'
  building_types << 'PrimarySchool'
  building_types << 'SmallOffice'
  building_types << 'MediumOffice'
  building_types << 'SmallHotel'
  building_types << 'LargeHotel'
  building_types << 'RetailStandalone'
  building_types << 'RetailStripmall'
  building_types << 'Hospital'
  building_types << 'MidriseApartment'
  building_types << 'HighriseApartment'

  return building_types
end

#run(model, runner, user_arguments) ⇒ Object

define what happens when the measure is run

# File 'lib/measures/set_nist_infiltration_correlations/measure.rb', line 277

def run(model, runner, user_arguments)
  super(model, runner, user_arguments)

  # use the built-in error checking
  if !runner.validateUserArguments(arguments(model), user_arguments)
    return false
  end

  # assign the user inputs to variables
  airtightness_value = runner.getDoubleArgumentValue('airtightness_value', user_arguments)
  airtightness_pressure = runner.getDoubleArgumentValue('airtightness_pressure', user_arguments)
  airtightness_area = runner.getStringArgumentValue('airtightness_area', user_arguments)
  air_barrier = runner.getBoolArgumentValue('air_barrier', user_arguments)
  hvac_schedule = runner.getStringArgumentValue('hvac_schedule', user_arguments)
  climate_zone = runner.getStringArgumentValue('climate_zone', user_arguments)
  building_type = runner.getStringArgumentValue('building_type', user_arguments)

  # validate airtightness value and pressure
  if airtightness_value < 0.0
    runner.registerError('Airtightness value must be postive.')
    return false
  end

  if airtightness_pressure < 0.0
    runner.registerError('Airtightness pressure must be postive.')
    return false
  end

  # calculate infiltration design value at 4 Pa
  airtightness_value_4pa_per_hr = airtightness_value * ((4.0 / airtightness_pressure)**0.65)
  runner.registerInfo("User-inputed airtightness design value #{airtightness_value} (m^3/h-m^2) at #{airtightness_pressure} Pa converts to #{airtightness_value_4pa_per_hr.round(7)} (m^3/h-m^2) at 4 Pa")

  # convert to m^3/s-m^2
  airtightness_value_4pa_per_s = airtightness_value_4pa_per_hr / 3600.0

  # get 4-sided, 5-sided, and 6-sided areas
  exterior_wall_area = 0.0
  exterior_roof_area = 0.0
  exterior_floor_area = 0.0
  ground_wall_area = 0.0
  ground_roof_area = 0.0
  ground_floor_area = 0.0
  model.getSurfaces.each do |surface|
    bc = surface.outsideBoundaryCondition
    type = surface.surfaceType
    area = surface.grossArea
    exterior_wall_area += area if bc == 'Outdoors' && type == 'Wall'
    exterior_roof_area += area if bc == 'Outdoors' && type == 'RoofCeiling'
    exterior_floor_area += area if bc == 'Outdoors' && type == 'Floor'
    ground_wall_area += area if bc == 'Ground' && type == 'Wall'
    ground_roof_area += area if bc == 'Ground' && type == 'RoofCeiling'
    ground_floor_area += area if bc == 'Ground' && type == 'Floor'
  end
  four_sided_area = exterior_wall_area + ground_wall_area
  five_sided_area = exterior_wall_area + ground_wall_area + exterior_roof_area + ground_roof_area
  six_sided_area = exterior_wall_area + ground_wall_area + exterior_roof_area + ground_roof_area + exterior_floor_area + ground_floor_area
  energy_plus_area = exterior_wall_area + exterior_roof_area
  runner.registerInfo("4-sided area = #{four_sided_area.round(2)} m^2, 5-sided area = #{five_sided_area.round(2)} m^2, 6-sided area = #{six_sided_area.round(2)} m^2.")

  # The SpaceInfiltrationDesignFlowRate object FlowperExteriorSurfaceArea method only counts surfaces with the 'Outdoors' boundary conditions towards exterior surface area, not surfaces with the 'Ground' boundary conditions.  That means all values need to be normalized to exterior wall and roof area.
  case airtightness_area
  when '4-sided'
    design_infiltration_4pa = airtightness_value_4pa_per_s * (four_sided_area / energy_plus_area)
    runner.registerInfo("#{airtightness_area} infiltration design value #{airtightness_value_4pa_per_s.round(7)} (m^3/s-m^2) converted to #{design_infiltration_4pa.round(7)} (m^3/s-m^2) based on 4-sided area #{four_sided_area.round(2)} m^2 and 5-sided area #{energy_plus_area.round(2)} m^2 excluding ground boundary surfaces for energyplus.")
  when '5-sided'
    design_infiltration_4pa = airtightness_value_4pa_per_s * (five_sided_area / energy_plus_area)
    runner.registerInfo("#{airtightness_area} infiltration design value #{airtightness_value_4pa_per_s.round(7)} (m^3/s-m^2) converted to #{design_infiltration_4pa.round(7)} (m^3/s-m^2) based on 5-sided area #{five_sided_area.round(2)} m^2 and 5-sided area #{energy_plus_area.round(2)} m^2 excluding ground boundary surfaces for energyplus.")
  when '6-sided'
    design_infiltration_4pa = airtightness_value_4pa_per_s * (six_sided_area / energy_plus_area)
    runner.registerInfo("#{airtightness_area} infiltration design value #{airtightness_value_4pa_per_s.round(7)} (m^3/s-m^2) converted to #{design_infiltration_4pa.round(7)} (m^3/s-m^2) based on 6-sided area #{six_sided_area.round(2)} m^2 and 5-sided area #{energy_plus_area.round(2)} m^2 excluding ground boundary surfaces for energyplus.")
  end
  runner.registerValue('design_infiltration_4pa', design_infiltration_4pa, 'm/s')

  # validate hvac schedule
  if hvac_schedule == 'Lookup From Model'
    # lookup from model, using largest air loop
    # check multiple kinds of systems, including unitary systems
    hvac_schedule = nil
    largest_area = 0.0

    model.getAirLoopHVACs.each do |air_loop|
      air_loop_area = 0.0
      air_loop.thermalZones.each { |tz| air_loop_area += tz.floorArea }
      if air_loop_area > largest_area
        hvac_schedule = air_loop.availabilitySchedule
        largest_area = air_loop_area
      end
    end

    model.getAirLoopHVACUnitarySystems.each do |unitary|
      next unless unitary.thermalZone.is_initialized
      air_loop_area = unitary.thermalZone.get.floorArea
      if air_loop_area > largest_area
        if unitary.availabilitySchedule.is_initialized
          hvac_schedule = unitary.availabilitySchedule.get
        else  
          hvac_schedule = model.alwaysOnDiscreteSchedule
        end
        largest_area = air_loop_area
      end
    end

    model.getAirLoopHVACUnitaryHeatPumpAirToAirs.each do |unitary|
      next unless unitary.controllingZone.is_initialized
      air_loop_area = unitary.controllingZone.get.floorArea
      if air_loop_area > largest_area
        hvac_schedule = unitary.availabilitySchedule.get
        largest_area = air_loop_area
      end
    end

    model.getAirLoopHVACUnitaryHeatPumpAirToAirMultiSpeeds.each do |unitary|
      next unless unitary.controllingZoneorThermostatLocation.is_initialized
      air_loop_area = unitary.controllingZoneorThermostatLocation.get.floorArea
      if air_loop_area > largest_area
        if unitary.availabilitySchedule.is_initialized
          hvac_schedule = unitary.availabilitySchedule.get
        else  
          hvac_schedule = model.alwaysOnDiscreteSchedule
        end
        largest_area = air_loop_area
      end
    end

    model.getFanZoneExhausts.each do |fan|
      next unless fan.thermalZone.is_initialized
      air_loop_area = fan.thermalZone.get.floorArea
      if air_loop_area > largest_area
        if fan.availabilitySchedule.is_initialized
          hvac_schedule = fan.availabilitySchedule.get
        else  
          hvac_schedule = model.alwaysOnDiscreteSchedule
        end
        largest_area = air_loop_area
      end
    end

    building_area = model.getBuilding.floorArea
    if largest_area < 0.05*building_area
      runner.registerWarning("The largest airloop or HVAC system serves #{largest_area.round(1)} m^2, which is less than 5% of the building area #{building_area.round(1)} m^2. Attempting to use building hours of operation schedule instead.")
      default_schedule_set = model.getBuilding.defaultScheduleSet
      if default_schedule_set.is_initialized
        default_schedule_set = default_schedule_set.get
        hoo = default_schedule_set.hoursofOperationSchedule
        if hoo.is_initialized
          hvac_schedule = hoo.get
          largest_area = building_area
        else
          runner.registerWarning("Unable to determine building hours of operation schedule. Treating the building as if there is no HVAC system schedule.")
          hvac_schedule = nil
        end
      else
        runner.registerWarning("Unable to determine building hours of operation schedule. Treating the building as if there is no HVAC system schedule.")
        hvac_schedule = nil
      end
    end

    unless hvac_schedule.nil?
      area_fraction = 100.0 * largest_area / building_area
      runner.registerInfo("Using schedule #{hvac_schedule.name} serving area #{largest_area.round(1)} m^2, #{area_fraction.round(0)}% of building area #{building_area.round(1)} m^2 to determine infiltration on/off schedule.")
    end
  else
    hvac_schedule = model.getScheduleByName(hvac_schedule)
    unless schedule_object.is_initialized
      runner.registerError("HVAC schedule argument #{hvac_schedule} not found in the model. IT may have been removed by another measure.")
      return false
    end
    hvac_schedule = hvac_schedule.get
    if hvac_schedule.get.to_ScheduleRuleset.is_initialized
      hvac_schedule = hvac_schedule.get.to_ScheduleRuleset.get
    elsif hvac_schedule.get.to_ScheduleConstant.is_initialized
      hvac_schedule = hvac_schedule.get.to_ScheduleConstant.get
    else
      runner.registerError("HVAC schedule argument #{hvac_schedule} is not a Schedule Constant or Schedule Ruleset object.")
      return false
    end

    runner.registerInfo("Using HVAC schedule #{hvac_schedule.name} from user arguments to determine infiltration on/off schedule.")
  end

  # creating infiltration schedules based on hvac schedule
  if hvac_schedule.nil?
    runner.registerWarning('Unable to determine the HVAC schedule. Treating the building as if there is no HVAC system with outdoor air.  If this is not the case, input a schedule argument, or assign one to an air loop in the model.')
    on_schedule = OpenStudio::Model::ScheduleConstant.new(model)
    on_schedule.setName("Infiltration HVAC On Schedule")
    on_schedule.setValue(0.0)
    off_schedule = OpenStudio::Model::ScheduleConstant.new(model)
    off_schedule.setName("Infiltration HVAC Off Schedule")
    off_schedule.setValue(1.0)
  elsif hvac_schedule.to_ScheduleConstant.is_initialized
    hvac_schedule = hvac_schedule.to_ScheduleConstant.get
    on_schedule = OpenStudio::Model::ScheduleConstant.new(model)
    on_schedule.setName("Infiltration HVAC On Schedule")
    on_schedule.setValue(hvac_schedule.value)
    off_schedule = OpenStudio::Model::ScheduleConstant.new(model)
    off_schedule.setName("Infiltration HVAC Off Schedule")
    if hvac_schedule.value > 0
      off_schedule.setValue(0.0)
    else
      off_schedule.setValue(1.0)
    end
  elsif hvac_schedule.to_ScheduleRuleset.is_initialized
    hvac_schedule = hvac_schedule.to_ScheduleRuleset.get
    on_schedule = hvac_schedule.clone.to_ScheduleRuleset.get
    on_schedule.setName("Infiltration HVAC On Schedule")
    off_schedule = invert_schedule_ruleset(hvac_schedule, 'Infiltration HVAC Off Schedule')
  end

  # validate climate zone
  if climate_zone == 'Lookup From Model'
    climate_zone = ''
    model.getClimateZones.climateZones.each do |cz|
      next if cz.value == ''
      cz_institution = cz.institution
      if cz_institution == 'ASHRAE'
        climate_zone = cz.value
        climate_zone = climate_zone.gsub('ASHRAE 169-2006-','')
        climate_zone = climate_zone.gsub('ASHRAE 169-2013-','')
        climate_zone = climate_zone.gsub('ASHRAE 169-2020-','')
        climate_zone = climate_zone.gsub('ASHRAE 169-2021-','')
      elsif cz_institution == 'CEC'
        california_cz = cz.value.gsub('CEC','')
        case california_cz
        when '1'
          climate_zone = '4B'
        when '2','3','4','5','6'
          climate_zone = '3C'
        when '7','8','9','10','11','12','13','14'
          climate_zone = '3B'
        when '15'
          climate_zone = '2B'
        when '16'
          climate_zone = '5B'
        end
        runner.registerWarning("Using ASHRAE climate zone #{climate_zone} for California climate zone #{california_cz}.")
      end
    end

    if climate_zone == ''
      runner.registerError('Unable to determine an ASHRAE climate zone for the model.  An ASHRAE climate zone value is necessary to lookup the coefficients.')
      return false
    end

    runner.registerInfo("Using climate zone #{climate_zone} from model.")
  else
    runner.registerInfo("Using climate zone #{climate_zone} from user arguments.")
  end

  # get climate zone number
  climate_zone_number = climate_zone.delete('^0-9').to_i

  # validate building type
  if building_type == 'Lookup From Model'

    # get building type from the model
    building_type_data = infer_nist_building_type(model)
    model_building_type = building_type_data['model_building_type']
    nist_building_type = building_type_data['nist_building_type']
    building_type = nist_building_type

    # check that model building type is supported
    unless nist_building_types.include? nist_building_type
      runner.registerError("NIST coefficients are not available for model building type #{nist_building_type}.")
      return false
    end

    # warn the user if the model building type is different from support nist building types
    unless model_building_type == nist_building_type
      runner.registerWarning("Using building type #{building_type} for model building type #{model_building_type}.")
    else
      runner.registerInfo("Using building type #{building_type} from model.")
    end
  else
    runner.registerInfo("Using building type #{building_type} from user arguments.")
  end

  # remove existing infiltration objects
  runner.registerInitialCondition("The modeled started with #{model.getSpaceInfiltrationDesignFlowRates.size} infiltration objects and #{model.getSpaceInfiltrationEffectiveLeakageAreas.size} effective leakage area objects.")
  model.getSpaceInfiltrationDesignFlowRates.each(&:remove)
  model.getSpaceInfiltrationEffectiveLeakageAreas.each(&:remove)

  # load NIST infiltration correlations file and convert to hash table
  nist_infiltration_correlations_csv = "#{File.dirname(__FILE__)}/resources/Data-NISTInfiltrationCorrelations.csv"
  if not File.file?(nist_infiltration_correlations_csv)
    runner.registerError("Unable to find file: #{nist_infiltration_correlations_csv}")
    return nil
  end
  coefficients_tbl = CSV.table(nist_infiltration_correlations_csv)
  coefficients_hsh = coefficients_tbl.map { |row| row.to_hash }

  # select down to building type and climate zone
  coefficients = coefficients_hsh.select { |r| (r[:building_type] == building_type) && (r[:climate_zone] == climate_zone_number) }

  # filter by air barrier
  if air_barrier
    coefficients = coefficients.select { |r| r[:air_barrier] == 'yes'}
  else
    coefficients = coefficients.select { |r| r[:air_barrier] == 'no'}
  end

  # determine coefficients
  # if no off coefficients are defined, use 0 for a and the on coefficients for b and d
  on_coefficients = coefficients.select { |r| r[:hvac_status] == 'on'}
  off_coefficients = coefficients.select { |r| r[:hvac_status] == 'off'}
  a_on = on_coefficients[0][:a]
  b_on = on_coefficients[0][:b]
  d_on = on_coefficients[0][:d]
  a_off = off_coefficients[0][:a].nil? ? on_coefficients[0][:a] : off_coefficients[0][:a]
  b_off = off_coefficients[0][:b].nil? ? on_coefficients[0][:b] : off_coefficients[0][:b]
  d_off = off_coefficients[0][:d].nil? ? on_coefficients[0][:d] : off_coefficients[0][:d]

  # add new infiltration objects
  # define infiltration as flow per exterior area
  model.getSpaces.each do |space|
    next unless space.exteriorArea > 0.0

    hvac_on_infiltration = OpenStudio::Model::SpaceInfiltrationDesignFlowRate.new(model)
    hvac_on_infiltration.setName("#{space.name.get} HVAC On Infiltration")
    hvac_on_infiltration.setFlowperExteriorSurfaceArea(design_infiltration_4pa)
    hvac_on_infiltration.setConstantTermCoefficient(a_on)
    hvac_on_infiltration.setTemperatureTermCoefficient(b_on)
    hvac_on_infiltration.setVelocityTermCoefficient(0.0)
    hvac_on_infiltration.setVelocitySquaredTermCoefficient(d_on)
    hvac_on_infiltration.setSpace(space)
    hvac_on_infiltration.setSchedule(on_schedule)

    hvac_off_infiltration = OpenStudio::Model::SpaceInfiltrationDesignFlowRate.new(model)
    hvac_off_infiltration.setName("#{space.name.get} HVAC Off Infiltration")
    hvac_off_infiltration.setFlowperExteriorSurfaceArea(design_infiltration_4pa)
    hvac_off_infiltration.setConstantTermCoefficient(a_off)
    hvac_off_infiltration.setTemperatureTermCoefficient(b_off)
    hvac_off_infiltration.setVelocityTermCoefficient(0.0)
    hvac_off_infiltration.setVelocitySquaredTermCoefficient(d_off)
    hvac_off_infiltration.setSpace(space)
    hvac_off_infiltration.setSchedule(off_schedule)

  end

  runner.registerFinalCondition("The modeled finished with #{model.getSpaceInfiltrationDesignFlowRates.size} infiltration objects.")

  return true
end