Merge pull request #717 from NREL/mf_aext_infiltration

MF Aext infiltration

Changelog.md

@@ -4,6 +4,7 @@ __New Features__
 - **Breaking change**: Each `VentilationFan` must have one (and only one) `UsedFor...` element set to true.
 
 __Bugfixes__
+- Fixes incorrect Reference Home mechanical ventilation flowrate for attached units (when Aext is not 1).
 - Fixes possible 301ruleset.rb error due to floating point arithmetic.
 
 ## OpenStudio-ERI v1.7.0

rulesets/resources/301ruleset.rb

@@ -73,7 +73,7 @@ def self.apply_reference_home_ruleset(orig_hpxml, iecc_version: nil, is_all_elec
     set_enclosure_windows_reference(orig_bldg, new_bldg)
     set_enclosure_skylights_reference(orig_bldg, new_bldg)
     set_enclosure_doors_reference(orig_bldg, new_bldg)
-    set_enclosure_air_infiltration_reference(new_bldg)
+    set_enclosure_air_infiltration_reference(orig_bldg, new_bldg)
 
     # Systems
     set_systems_hvac_reference(orig_bldg, new_bldg, is_all_electric: is_all_electric)
@@ -276,7 +276,6 @@ def self.set_summary_reference(orig_bldg, new_bldg)
     @nbeds = orig_bldg.building_construction.number_of_bedrooms
     @ncfl = orig_bldg.building_construction.number_of_conditioned_floors
     @ncfl_ag = orig_bldg.building_construction.number_of_conditioned_floors_above_grade
-    _sla, _ach50, _nach, @infil_volume, @infil_height = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
 
     new_bldg.site.fuels = orig_bldg.site.fuels
     new_bldg.site.site_type = HPXML::SiteTypeSuburban
@@ -296,7 +295,6 @@ def self.set_summary_rated(orig_bldg, new_bldg)
     @nbeds = orig_bldg.building_construction.number_of_bedrooms
     @ncfl = orig_bldg.building_construction.number_of_conditioned_floors
     @ncfl_ag = orig_bldg.building_construction.number_of_conditioned_floors_above_grade
-    _sla, _ach50, _nach, @infil_volume, @infil_height = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
 
     new_bldg.site.fuels = orig_bldg.site.fuels
     new_bldg.site.site_type = HPXML::SiteTypeSuburban
@@ -316,7 +314,6 @@ def self.set_summary_iad(orig_bldg, new_bldg)
     @nbeds = 3
     @ncfl = 2.0
     @ncfl_ag = 2.0
-    @infil_volume = 20400.0
 
     new_bldg.site.fuels = orig_bldg.site.fuels
     new_bldg.site.site_type = HPXML::SiteTypeSuburban
@@ -341,38 +338,38 @@ def self.set_climate(orig_bldg, new_bldg)
     @is_southern_hemisphere = (@weather.header.Latitude < 0)
   end
 
-  def self.set_enclosure_air_infiltration_reference(new_bldg)
-    @infil_a_ext = calc_mech_vent_Aext_ratio(new_bldg)
+  def self.set_enclosure_air_infiltration_reference(orig_bldg, new_bldg)
+    _, _, _, infil_volume, infil_height, _ = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
 
     sla = 0.00036
-    ach50 = Airflow.get_infiltration_ACH50_from_SLA(sla, 0.65, @cfa, @infil_volume)
+    ach50 = Airflow.get_infiltration_ACH50_from_SLA(sla, 0.65, @cfa, infil_volume)
     new_bldg.air_infiltration_measurements.add(id: 'Infiltration_ACH50',
                                                house_pressure: 50,
                                                unit_of_measure: HPXML::UnitsACH,
                                                air_leakage: ach50.round(2),
-                                               infiltration_volume: @infil_volume,
-                                               infiltration_height: @infil_height,
+                                               infiltration_volume: infil_volume,
+                                               infiltration_height: infil_height,
                                                infiltration_type: HPXML::InfiltrationTypeUnitExterior,
-                                               a_ext: @infil_a_ext.round(3))
+                                               a_ext: 1.0)
   end
 
   def self.set_enclosure_air_infiltration_rated(orig_bldg, new_bldg)
-    @infil_a_ext = calc_mech_vent_Aext_ratio(new_bldg)
+    _, _, _, infil_volume, infil_height, _ = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
+    ach50, a_ext = calc_rated_home_infiltration_ach50(orig_bldg)
 
-    ach50 = calc_rated_home_infiltration_ach50(orig_bldg)
     new_bldg.air_infiltration_measurements.add(id: 'AirInfiltrationMeasurement',
                                                house_pressure: 50,
                                                unit_of_measure: HPXML::UnitsACH,
                                                air_leakage: ach50.round(2),
-                                               infiltration_volume: @infil_volume,
-                                               infiltration_height: @infil_height,
+                                               infiltration_volume: infil_volume,
+                                               infiltration_height: infil_height,
                                                infiltration_type: HPXML::InfiltrationTypeUnitExterior,
-                                               a_ext: @infil_a_ext.round(3))
+                                               a_ext: a_ext.round(3))
   end
 
   def self.set_enclosure_air_infiltration_iad(new_bldg)
-    @infil_height = new_bldg.inferred_infiltration_height(@infil_volume)
-    @infil_a_ext = calc_mech_vent_Aext_ratio(new_bldg)
+    infil_volume = 20400
+    infil_height = new_bldg.inferred_infiltration_height(infil_volume)
 
     if ['1A', '1B', '1C', '2A', '2B', '2C'].include? @iecc_zone
       ach50 = 5.0
@@ -383,10 +380,10 @@ def self.set_enclosure_air_infiltration_iad(new_bldg)
                                                house_pressure: 50,
                                                unit_of_measure: HPXML::UnitsACH,
                                                air_leakage: ach50,
-                                               infiltration_volume: @infil_volume,
-                                               infiltration_height: @infil_height,
+                                               infiltration_volume: infil_volume,
+                                               infiltration_height: infil_height,
                                                infiltration_type: HPXML::InfiltrationTypeUnitExterior,
-                                               a_ext: @infil_a_ext.round(3))
+                                               a_ext: 1.0)
   end
 
   def self.set_enclosure_attics_reference(orig_bldg, new_bldg)
@@ -1460,7 +1457,8 @@ def self.set_systems_mechanical_ventilation_reference(orig_bldg, new_bldg, iecc_
       q_fan_airflow = (0.01 * @cfa) + (7.5 * (@nbeds + 1))
     else
       q_tot = Airflow.get_mech_vent_qtot_cfm(@nbeds, @cfa)
-      q_fan_airflow = calc_mech_vent_q_fan(q_tot, ref_sla, 0.0) # cfm for airflow
+      infil_height = new_bldg.air_infiltration_measurements[0].infiltration_height
+      q_fan_airflow = calc_mech_vent_qfan(q_tot, ref_sla, true, infil_height) # cfm for airflow
     end
 
     mech_vent_fans = orig_bldg.ventilation_fans.select { |f| f.used_for_whole_building_ventilation }
@@ -1627,15 +1625,9 @@ def self.set_systems_mechanical_ventilation_iad(new_bldg)
     q_tot = Airflow.get_mech_vent_qtot_cfm(@nbeds, @cfa)
 
     # Calculate fan cfm
-    sla = nil
-    new_bldg.air_infiltration_measurements.each do |new_infil_measurement|
-      next unless (new_infil_measurement.unit_of_measure == HPXML::UnitsACH) && (new_infil_measurement.house_pressure == 50)
-
-      ach50 = new_infil_measurement.air_leakage
-      sla = Airflow.get_infiltration_SLA_from_ACH50(ach50, 0.65, @cfa, @infil_volume)
-      break
-    end
-    q_fan = calc_mech_vent_q_fan(q_tot, sla, 0.0)
+    _, ach50, _, infil_volume, infil_height, _ = Airflow.get_values_from_air_infiltration_measurements(new_bldg, @cfa, @weather)
+    sla = Airflow.get_infiltration_SLA_from_ACH50(ach50, 0.65, @cfa, infil_volume)
+    q_fan = calc_mech_vent_qfan(q_tot, sla, true, infil_height)
     fan_power_w = 0.70 * q_fan
 
     new_bldg.ventilation_fans.add(id: 'MechanicalVentilation',
@@ -2443,18 +2435,31 @@ def self.calc_rated_home_q_fans_by_system(orig_bldg, all_mech_vent_fans)
   end
 
   def self.calc_rated_home_infiltration_ach50(orig_bldg)
-    _sla, ach50, _nach, _volume, _height = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
+    # Note: The infiltration rate returned will *include* the Aext term.
+    # We separately report out the Aext in the HPXML file for inspection, but the
+    # AirInfiltrationMeasurement element will use infiltration_type: 'unit exterior'
+    # so as not to double-count the Aext term.
+    _, ach50, _, infil_volume, infil_height, _ = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
 
-    if [HPXML::ResidentialTypeApartment, HPXML::ResidentialTypeSFA].include? @bldg_type
-      if (Constants.ERIVersions.index(@eri_version) >= Constants.ERIVersions.index('2019'))
-        cfm50 = ach50 * @infil_volume / 60.0
-        tot_cb_area, _ext_cb_area = orig_bldg.compartmentalization_boundary_areas()
-        if cfm50 / tot_cb_area <= 0.30
-          ach50 *= @infil_a_ext
+    if @bldg_type == HPXML::ResidentialTypeSFD
+      a_ext = 1.0
+    else
+      tot_cb_area, ext_cb_area = orig_bldg.compartmentalization_boundary_areas()
+      a_ext = ext_cb_area / tot_cb_area
+
+      if Constants.ERIVersions.index(@eri_version) >= Constants.ERIVersions.index('2019')
+        if [HPXML::ResidentialTypeApartment, HPXML::ResidentialTypeSFA].include? @bldg_type
+          cfm50 = ach50 * infil_volume / 60.0
+          tot_cb_area, _ext_cb_area = orig_bldg.compartmentalization_boundary_areas()
+          if cfm50 / tot_cb_area > 0.30
+            a_ext = 1.0
+          end
         end
       end
     end
 
+    ach50 *= a_ext
+
     # Apply min Natural ACH?
     min_nach = nil
     mech_vent_fans = orig_bldg.ventilation_fans.select { |f| f.used_for_whole_building_ventilation }
@@ -2463,21 +2468,21 @@ def self.calc_rated_home_infiltration_ach50(orig_bldg)
     elsif Constants.ERIVersions.index(@eri_version) >= Constants.ERIVersions.index('2019')
       has_non_exhaust_systems = (mech_vent_fans.select { |f| f.fan_type != HPXML::MechVentTypeExhaust }.size > 0)
       mech_vent_fans.each do |orig_vent_fan|
-        if orig_vent_fan.flow_rate_not_tested || ((@infil_a_ext < 0.5) && !has_non_exhaust_systems)
+        if orig_vent_fan.flow_rate_not_tested || ((a_ext < 0.5) && !has_non_exhaust_systems)
           min_nach = 0.30
         end
       end
     end
 
     if not min_nach.nil?
-      min_sla = Airflow.get_infiltration_SLA_from_ACH(min_nach, @infil_height, @weather)
-      min_ach50 = Airflow.get_infiltration_ACH50_from_SLA(min_sla, 0.65, @cfa, @infil_volume)
+      min_sla = Airflow.get_infiltration_SLA_from_ACH(min_nach, infil_height, @weather)
+      min_ach50 = Airflow.get_infiltration_ACH50_from_SLA(min_sla, 0.65, @cfa, infil_volume)
       if ach50 < min_ach50
         ach50 = min_ach50
       end
     end
 
-    return ach50
+    return ach50, a_ext
   end
 
   def self.calc_mech_vent_supply_exhaust_cfms(ventilation_fans, total_or_oa)
@@ -2524,23 +2529,25 @@ def self.calc_mech_vent_is_balanced(ventilation_fans)
   end
 
   def self.calc_rated_home_qfan(orig_bldg, is_balanced)
-    ach50 = calc_rated_home_infiltration_ach50(orig_bldg)
-    sla = Airflow.get_infiltration_SLA_from_ACH50(ach50, 0.65, @cfa, @infil_volume)
+    _, _, _, infil_volume, infil_height, _ = Airflow.get_values_from_air_infiltration_measurements(orig_bldg, @cfa, @weather)
+    ach50, _ = calc_rated_home_infiltration_ach50(orig_bldg)
+    sla = Airflow.get_infiltration_SLA_from_ACH50(ach50, 0.65, @cfa, infil_volume)
     q_tot = Airflow.get_mech_vent_qtot_cfm(@nbeds, @cfa)
-    q_fan_power = calc_mech_vent_q_fan(q_tot, sla, is_balanced)
-    return q_fan_power
+    q_fan = calc_mech_vent_qfan(q_tot, sla, is_balanced, infil_height)
+    return q_fan
   end
 
-  def self.calc_mech_vent_q_fan(q_tot, sla, is_balanced)
-    nl = Airflow.get_infiltration_NL_from_SLA(sla, @infil_height)
+  def self.calc_mech_vent_qfan(q_tot, sla, is_balanced, infil_height)
+    nl = Airflow.get_infiltration_NL_from_SLA(sla, infil_height)
     q_inf = nl * @weather.data.WSF * @cfa / 7.3 # Effective annual average infiltration rate, cfm, eq. 4.5a
+    a_ext = 1.0 # Use Aext=1.0 because sla reflects 'unit exterior' infiltration so it already incorporates Aext
     if Constants.ERIVersions.index(@eri_version) >= Constants.ERIVersions.index('2019')
       if is_balanced
         phi = 1.0
       else
         phi = q_inf / q_tot
       end
-      q_fan = q_tot - phi * (q_inf * @infil_a_ext)
+      q_fan = q_tot - phi * (q_inf * a_ext)
     else
       if [HPXML::ResidentialTypeApartment, HPXML::ResidentialTypeSFA].include? @bldg_type
         # No infiltration credit for attached/multifamily
@@ -2557,15 +2564,6 @@ def self.calc_mech_vent_q_fan(q_tot, sla, is_balanced)
     return [q_fan, 0].max
   end
 
-  def self.calc_mech_vent_Aext_ratio(hpxml)
-    tot_cb_area, ext_cb_area = hpxml.compartmentalization_boundary_areas()
-    if @bldg_type == HPXML::ResidentialTypeSFD
-      return 1.0
-    end
-
-    return ext_cb_area / tot_cb_area
-  end
-
   def self.get_new_distribution_id(orig_bldg, new_bldg)
     i = 0
     while true

rulesets/tests/test_ventilation.rb

@@ -59,13 +59,13 @@ def test_mech_vent_attached_or_multifamily
     _all_calc_types.each do |calc_type|
       _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
       if [Constants.CalcTypeERIReferenceHome, Constants.CalcTypeCO2eReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 50.6, hours: 24, power: 0.0 }]) # Should have airflow but not fan energy
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 31.1, hours: 24, power: 0.0 }]) # Should have airflow but not fan energy
       elsif [Constants.CalcTypeERIRatedHome].include? calc_type
         _check_mech_vent(hpxml_bldg)
       elsif [Constants.CalcTypeERIIndexAdjustmentDesign].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 70.6, hours: 24, power: 49.4 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 60.0, hours: 24, power: 42.0 }])
       elsif [Constants.CalcTypeERIIndexAdjustmentReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 32.1, hours: 24, power: 55.0 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 8.5, hours: 24, power: 49.4 }])
       end
     end
 
@@ -885,14 +885,14 @@ def test_mech_vent_shared
     _all_calc_types.each do |calc_type|
       _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
       if [Constants.CalcTypeERIReferenceHome, Constants.CalcTypeCO2eReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 50.6, hours: 24, power: 19.7 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 31.1, hours: 24, power: 19.0 }])
       elsif [Constants.CalcTypeERIRatedHome].include? calc_type
         _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeSupply, flowrate: 800.0, hours: 24, power: 240.0, in_unit_flowrate: 80.0, frac_recirc: 0.5, has_preheat: true, has_precool: true },
                                       { fantype: HPXML::MechVentTypeExhaust, flowrate: 72.0, hours: 24, power: 26.0 }])
       elsif [Constants.CalcTypeERIIndexAdjustmentDesign].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 70.6, hours: 24, power: 49.4 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 60.0, hours: 24, power: 42.0 }])
       elsif [Constants.CalcTypeERIIndexAdjustmentReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 32.1, hours: 24, power: 54.9 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 8.5, hours: 24, power: 49.4 }])
       end
     end
   end
@@ -914,7 +914,7 @@ def test_mech_vent_shared_defaulted_fan_power
     calc_types.each do |calc_type|
       _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
       if [Constants.CalcTypeERIReferenceHome, Constants.CalcTypeCO2eReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 50.6, hours: 24, power: 19.7 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 31.1, hours: 24, power: 19.0 }])
       elsif [Constants.CalcTypeERIRatedHome].include? calc_type
         _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeSupply, flowrate: 800.0, hours: 24, power: 800.0, in_unit_flowrate: 80.0, frac_recirc: 0.5, has_preheat: true, has_precool: true },
                                       { fantype: HPXML::MechVentTypeExhaust, flowrate: 72.0, hours: 24, power: 26.0 }])
@@ -939,7 +939,7 @@ def test_mech_vent_shared_unmeasured_airflow_rate
     calc_types.each do |calc_type|
       _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
       if [Constants.CalcTypeERIReferenceHome, Constants.CalcTypeCO2eReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 50.6, hours: 24, power: 17.9 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 31.1, hours: 24, power: 11.6 }])
       elsif [Constants.CalcTypeERIRatedHome].include? calc_type
         _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeSupply, flowrate: 800.0, hours: 24, power: 240.0, in_unit_flowrate: 30.0, frac_recirc: 0.5, has_preheat: true, has_precool: true },
                                       { fantype: HPXML::MechVentTypeExhaust, flowrate: 72.0, hours: 24, power: 26.0 }])
@@ -966,7 +966,7 @@ def test_mech_vent_shared_unmeasured_airflow_rate_and_defaulted_fan_power
     calc_types.each do |calc_type|
       _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
       if [Constants.CalcTypeERIReferenceHome, Constants.CalcTypeCO2eReferenceHome].include? calc_type
-        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 50.6, hours: 24, power: 17.9 }])
+        _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeBalanced, flowrate: 31.1, hours: 24, power: 11.6 }])
       elsif [Constants.CalcTypeERIRatedHome].include? calc_type
         _check_mech_vent(hpxml_bldg, [{ fantype: HPXML::MechVentTypeSupply, flowrate: 800.0, hours: 24, power: 800.0, in_unit_flowrate: 30.0, frac_recirc: 0.5, has_preheat: true, has_precool: true },
                                       { fantype: HPXML::MechVentTypeExhaust, flowrate: 72.0, hours: 24, power: 26.0 }])

workflow/tests/base_results/EPA_Tests.csv

@@ -1,13 +1,13 @@
 [Version] XML,Reference Home ERI,Rated Home ERI
-[MF_National_1.0] MFNCv1_CZ2_FL_gas_ground_corner_slab.xml,66.62,66.62
-[MF_National_1.0] MFNCv1_CZ4_MO_gas_top_corner.xml,72.15,72.15
-[MF_National_1.0] MFNCv1_CZ6_VT_elec_middle_interior.xml,67.71,67.71
-[MF_National_1.1] MFNCv11_CZ2_FL_elec_top_corner.xml,61.71,61.71
-[MF_National_1.1] MFNCv11_CZ4_MO_elec_ground_corner_vented_crawl.xml,61.97,61.97
-[MF_National_1.1] MFNCv11_CZ6_VT_gas_ground_corner_cond_bsmt.xml,58.53,58.53
-[MF_National_1.2] MFNCv12_CZ2_FL_gas_ground_corner_slab.xml,51.12,51.12
-[MF_National_1.2] MFNCv12_CZ4_MO_gas_top_corner.xml,47.78,47.78
-[MF_National_1.2] MFNCv12_CZ6_VT_elec_middle_interior.xml,55.72,55.72
+[MF_National_1.0] MFNCv1_CZ2_FL_gas_ground_corner_slab.xml,66.99,66.99
+[MF_National_1.0] MFNCv1_CZ4_MO_gas_top_corner.xml,74.15,74.15
+[MF_National_1.0] MFNCv1_CZ6_VT_elec_middle_interior.xml,73.52,73.52
+[MF_National_1.1] MFNCv11_CZ2_FL_elec_top_corner.xml,62.2,62.2
+[MF_National_1.1] MFNCv11_CZ4_MO_elec_ground_corner_vented_crawl.xml,63.87,63.87
+[MF_National_1.1] MFNCv11_CZ6_VT_gas_ground_corner_cond_bsmt.xml,62.19,62.19
+[MF_National_1.2] MFNCv12_CZ2_FL_gas_ground_corner_slab.xml,51.4,51.4
+[MF_National_1.2] MFNCv12_CZ4_MO_gas_top_corner.xml,49.03,49.03
+[MF_National_1.2] MFNCv12_CZ6_VT_elec_middle_interior.xml,59.95,59.95
 [SF_National_3.0] SFNHv3_CZ2_FL_gas_slab.xml,72.77,72.77
 [SF_National_3.0] SFNHv3_CZ4_MO_gas_vented_crawl.xml,80.3,80.3
 [SF_National_3.0] SFNHv3_CZ6_VT_elec_cond_bsmt.xml,70.0,70.0