ANSI 301-2022: Fraction Duct Area

Changelog.md

@@ -9,6 +9,7 @@ __New Features__
 - Ground source heat pump model enhancements.
 - Allows `Roof/RadiantBarrier` to be omitted; defaults to false.
 - Adds more error-checking for inappropriate inputs (e.g., HVAC SHR=0 or clothes washer IMEF=0).
+- Allows `FractionDuctArea` as alternative to `DuctSurfaceArea`
 
 __Bugfixes__
 - Fixes possible 301ruleset.rb error due to floating point arithmetic.

docs/source/workflow_inputs.rst

@@ -1532,16 +1532,16 @@ Additional information is entered in each ``DuctLeakageMeasurement``.
 
 Additional information is entered in each ``Ducts``.
 
-  =============================  =======  ============  ===========  ========  ==========  ===============================
-  Element                        Type     Units         Constraints  Required  Default     Notes
-  =============================  =======  ============  ===========  ========  ==========  ===============================
-  ``SystemIdentifier``           id                                  Yes                   Unique identifier
-  ``DuctType``                   string                 See [#]_     Yes                   Supply or return ducts
-  ``DuctInsulationRValue``       double   F-ft2-hr/Btu  >= 0         Yes                   R-value of duct insulation [#]_
-  ``DuctBuriedInsulationLevel``  string                 See [#]_     No        not buried  Duct buried insulation level [#]_
-  ``DuctLocation``               string                 See [#]_     Yes                   Duct location
-  ``DuctSurfaceArea``            double   ft2           >= 0         Yes                   Duct surface area
-  =============================  =======  ============  ===========  ========  ==========  ===============================
+  ===============================================  =======  ============  ================  ========  ==========  ======================================
+  Element                                          Type     Units         Constraints       Required  Default     Notes
+  ===============================================  =======  ============  ================  ========  ==========  ======================================
+  ``SystemIdentifier``                             id                                       Yes                   Unique identifier
+  ``DuctType``                                     string                 See [#]_          Yes                   Supply or return ducts
+  ``DuctInsulationRValue``                         double   F-ft2-hr/Btu  >= 0              Yes                   R-value of duct insulation [#]_
+  ``DuctBuriedInsulationLevel``                    string                 See [#]_          No        not buried  Duct buried insulation level [#]_
+  ``DuctLocation``                                 string                 See [#]_          Yes                   Duct location
+  ``FractionDuctArea`` and/or ``DuctSurfaceArea``  double   frac or ft2   0-1 or >= 0 [#]_  Yes [#]_  See [#]_    Duct fraction/surface area in location
+  ===============================================  =======  ============  ================  ========  ==========  ======================================
 
   .. [#] DuctType choices are "supply" or "return".
   .. [#] DuctInsulationRValue should not include the exterior air film (i.e., use 0 for an uninsulated duct).
@@ -1554,6 +1554,15 @@ Additional information is entered in each ``Ducts``.
          See the `Building America Solution Center <https://basc.pnnl.gov/resource-guides/ducts-buried-attic-insulation>`_ for more information.
   .. [#] DuctLocation choices are "conditioned space", "basement - conditioned", "basement - unconditioned", "crawlspace - unvented", "crawlspace - vented", "attic - unvented", "attic - vented", "garage", "outside", "exterior wall", "under slab", "roof deck", "other housing unit", "other heated space", "other multifamily buffer space", or "other non-freezing space".
          See :ref:`hpxmllocations` for descriptions.
+  .. [#] The sum of all FractionDuctArea must each equal to 1, both for the supply side and return side.
+  .. [#] If both are provided, DuctSurfaceArea will be used in the model.
+  .. [#] Duct surface areas will be calculated based on BSR/RESNET/ICC 301-2022 Table 4.2.2(1) footnote z. aa.:
+
+         \- **Supply duct area**: 0.27 * ConditionedFloorAreaServed
+
+         \- **Return duct area**: (if Number of Returns < 6, 0.05 * Number of Returns, 0.25 otherwise) * ConditionedFloorAreaServed
+
+         If FractionDuctArea is provided, each duct surface area will be FractionDuctArea times total duct area, which is calculated using the sum of primary and secondary duct areas from the equations above.
 
 .. _hvac_distribution_hydronic:
 

rulesets/resources/301ruleset.rb

@@ -1420,6 +1420,7 @@ def self.set_systems_hvac_rated(orig_bldg, new_bldg)
                                         duct_insulation_r_value: orig_duct.duct_insulation_r_value,
                                         duct_location: orig_duct.duct_location,
                                         duct_surface_area: orig_duct.duct_surface_area,
+                                        duct_fraction_area: orig_duct.duct_fraction_area,
                                         duct_buried_insulation_level: orig_duct.duct_buried_insulation_level)
       end
     end

rulesets/resources/301validator.xml

@@ -1100,9 +1100,12 @@
       <sch:assert role='ERROR' test='h:DuctBuriedInsulationLevel[text()="not buried" or text()="partially buried" or text()="fully buried" or text()="deeply buried"] or not(h:DuctBuriedInsulationLevel)'>Expected DuctBuriedInsulationLevel to be 'not buried' or 'partially buried' or 'fully buried' or 'deeply buried'</sch:assert>
       <sch:assert role='ERROR' test='count(h:DuctLocation) = 1'>Expected 1 element(s) for xpath: DuctLocation</sch:assert> <!-- See [HVACDuct=WithLocation] or [HVACDuct=WithoutLocation] -->
       <sch:assert role='ERROR' test='h:DuctLocation[text()="conditioned space" or text()="basement - conditioned" or text()="basement - unconditioned" or text()="crawlspace - vented" or text()="crawlspace - unvented" or text()="attic - vented" or text()="attic - unvented" or text()="garage" or text()="exterior wall" or text()="under slab" or text()="roof deck" or text()="outside" or text()="other housing unit" or text()="other heated space" or text()="other multifamily buffer space" or text()="other non-freezing space"] or not(h:DuctLocation)'>Expected DuctLocation to be 'conditioned space' or 'basement - conditioned' or 'basement - unconditioned' or 'crawlspace - vented' or 'crawlspace - unvented' or 'attic - vented' or 'attic - unvented' or 'garage' or 'exterior wall' or 'under slab' or 'roof deck' or 'outside' or 'other housing unit' or 'other heated space' or 'other multifamily buffer space' or 'other non-freezing space'</sch:assert>
-      <sch:assert role='ERROR' test='count(h:DuctSurfaceArea) = 1'>Expected 1 element(s) for xpath: DuctSurfaceArea</sch:assert>
+      <sch:assert role='ERROR' test='count(h:FractionDuctArea) + count(h:DuctSurfaceArea) &gt;= 1'>Expected 1 or more element(s) for xpath: FractionDuctArea | DuctSurfaceArea</sch:assert>
       <sch:assert role='ERROR' test='count(../h:NumberofReturnRegisters) = 1'>Expected 1 element(s) for xpath: ../NumberofReturnRegisters</sch:assert>
       <sch:assert role='ERROR' test='count(../../../h:ConditionedFloorAreaServed) = 1'>Expected 1 element(s) for xpath: ../../../ConditionedFloorAreaServed</sch:assert>
+      <!-- Sum Checks -->
+      <sch:assert role='ERROR' test='(sum(h:Ducts[h:DuctType="supply"]/h:FractionDuctArea) &gt;= 0.99 and sum(h:Ducts[h:DuctType="supply"]/h:FractionDuctArea) &lt;= 1.01) or count(h:Ducts[h:DuctType="supply"]/h:FractionDuctArea) = 0'>Expected sum(Ducts/FractionDuctArea) for DuctType="supply" to be 1</sch:assert>
+      <sch:assert role='ERROR' test='(sum(h:Ducts[h:DuctType="return"]/h:FractionDuctArea) &gt;= 0.99 and sum(h:Ducts[h:DuctType="return"]/h:FractionDuctArea) &lt;= 1.01) or count(h:Ducts[h:DuctType="return"]/h:FractionDuctArea) = 0'>Expected sum(Ducts/FractionDuctArea) for DuctType="return" to be 1</sch:assert>
     </sch:rule>
   </sch:pattern>
 

rulesets/resources/ES_ZERHruleset.rb

@@ -1173,7 +1173,8 @@ def self.get_radiant_barrier_bool(orig_bldg)
 
     ducts_in_uncond_attic = false
     all_ducts.each do |duct|
-      if [HPXML::LocationAtticVented, HPXML::LocationAtticUnvented].include?(duct.duct_location) && duct.duct_surface_area > 0
+      if [HPXML::LocationAtticVented, HPXML::LocationAtticUnvented].include?(duct.duct_location) &&
+         (!duct.duct_surface_area.to_f.zero? || !duct.duct_fraction_area.to_f.zero?)
         ducts_in_uncond_attic = true
       end
     end

rulesets/tests/test_hvac.rb

@@ -942,6 +942,39 @@ def test_ducts_buried
     end
   end
 
+  def test_duct_fraction_area
+    hpxml_name = 'base.xml'
+    hpxml = HPXML.new(hpxml_path: File.join(@root_path, 'workflow', 'sample_files', hpxml_name))
+    hpxml_bldg = hpxml.buildings[0]
+    hpxml_bldg.hvac_distributions.each do |hvac_distribution|
+      hvac_distribution.ducts.each do |duct|
+        duct.duct_surface_area = nil
+        duct.duct_fraction_area = 0.7
+      end
+    end
+    [HPXML::DuctTypeSupply, HPXML::DuctTypeReturn].each do |duct_type|
+      hpxml_bldg.hvac_distributions[-1].ducts.add(id: "Ducts#{hpxml_bldg.hvac_distributions[-1].ducts.size + 1}",
+                                                  duct_type: duct_type,
+                                                  duct_insulation_r_value: 0,
+                                                  duct_location: HPXML::LocationConditionedSpace,
+                                                  duct_fraction_area: 0.3)
+    end
+    hpxml_name = File.basename(@tmp_hpxml_path)
+    XMLHelper.write_file(hpxml.to_doc, @tmp_hpxml_path)
+
+    _all_calc_types.each do |calc_type|
+      _hpxml, hpxml_bldg = _test_ruleset(hpxml_name, calc_type)
+      if [Constants.CalcTypeERIRatedHome].include? calc_type
+        _check_ducts(hpxml_bldg, [{ duct_type: HPXML::DuctTypeSupply, duct_rvalue: 4.0, duct_area: 510.3, duct_location: HPXML::LocationAtticUnvented, duct_buried: HPXML::DuctBuriedInsulationNone },
+                                  { duct_type: HPXML::DuctTypeReturn, duct_rvalue: 0.0, duct_area: 189.0, duct_location: HPXML::LocationAtticUnvented, duct_buried: HPXML::DuctBuriedInsulationNone },
+                                  { duct_type: HPXML::DuctTypeSupply, duct_rvalue: 0.0, duct_area: 218.7, duct_location: HPXML::LocationConditionedSpace, duct_buried: HPXML::DuctBuriedInsulationNone },
+                                  { duct_type: HPXML::DuctTypeReturn, duct_rvalue: 0.0, duct_area: 81.0, duct_location: HPXML::LocationConditionedSpace, duct_buried: HPXML::DuctBuriedInsulationNone }])
+      else
+        _check_ducts(hpxml_bldg)
+      end
+    end
+  end
+
   def test_dse
     hpxml_name = 'base-hvac-dse.xml'
 

tasks.rb

@@ -2439,6 +2439,7 @@ def create_sample_hpxmls
                   'base-hvac-central-ac-only-var-speed.xml',
                   'base-hvac-central-ac-plus-air-to-air-heat-pump-heating.xml',
                   'base-hvac-dse.xml',
+                  'base-hvac-ducts-area-fractions.xml',
                   'base-hvac-ducts-leakage-cfm50.xml',
                   'base-hvac-ducts-buried.xml',
                   'base-hvac-dual-fuel-air-to-air-heat-pump-1-speed.xml',