Dew-point temperature setpoint for zone humidity control by lymereJ · Pull Request #11500 · NatLabRockies/EnergyPlus

lymereJ · 2026-04-07T05:29:00Z

Pull request overview

Description of the purpose of this PR

This (small) feature proposal to allow users to specify a maximum/minimum dew-point temperature setpoint for zone humidity control.

Pull Request Author

Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
Label the PR with at least one of: Defect, Refactoring, NewFeature, Performance, and/or DoNoPublish
Pull requests that impact EnergyPlus code must also include unit tests to cover enhancement or defect repair
Author should provide a "walkthrough" of relevant code changes using a GitHub code review comment process
If any diffs are expected, author must demonstrate they are justified using plots and descriptions

Reviewer

… objects.

lymereJ · 2026-04-07T15:59:07Z

Here's a sample result of the new example file with dew-point temperature humidity control (dehumidifying setpoint set to 14.0 deg. C):

lymereJ

Code walkthrough:

lymereJ · 2026-04-07T16:00:42Z

idd/Energy+.idd.in

-  A3 , \field Humidifying Relative Humidity Setpoint Schedule Name
+  A3 , \field Humidifying Setpoint Schedule Name
       \required-field
-       \note hourly schedule values should be in Relative Humidity (percent)
       \type object-list
       \object-list ScheduleNames
-  A4 ; \field Dehumidifying Relative Humidity Setpoint Schedule Name
-       \note hourly schedule values should be in Relative Humidity (percent)
+  A4 , \field Dehumidifying Setpoint Schedule Name
       \type object-list
       \object-list ScheduleNames
+  A5 ; \field Control Variable
+       \note When using RelativeHumidity, the schedule values should be in percentages.
+       \type choice
+       \key RelativeHumidity
+       \key Dewpoint
+       \default RelativeHumidity


Make the existing schedule inputs non-variable specific and add a control variable to indicate what variable is described by the schedules.

lymereJ · 2026-04-07T16:02:44Z

src/EnergyPlus/ZoneTempPredictorCorrector.cc

+        if (humidityControlZone.humidityControlVariableType == DataZoneControls::HumidityCtrlVarType::RelativeHumidity) {
+            ZoneRHHumidifyingSetPoint = humidityControlZone.humidifyingSched->getCurrentVal();
+            ZoneRHDehumidifyingSetPoint = humidityControlZone.dehumidifyingSched->getCurrentVal();
+        } else if (humidityControlZone.humidityControlVariableType ==
+                   DataZoneControls::HumidityCtrlVarType::DewPoint) { // Recalculate RH setpoint from DP
+            ZoneRHHumidifyingSetPoint =
+                100 * Psychrometrics::PsyRhFnTdbWPb(
+                          state,
+                          this->ZT,
+                          Psychrometrics::PsyWFnTdpPb(state, humidityControlZone.humidifyingSched->getCurrentVal(), state.dataEnvrn->OutBaroPress),
+                          state.dataEnvrn->OutBaroPress);
+            ZoneRHDehumidifyingSetPoint =
+                100 * Psychrometrics::PsyRhFnTdbWPb(
+                          state,
+                          this->ZT,
+                          Psychrometrics::PsyWFnTdpPb(state, humidityControlZone.dehumidifyingSched->getCurrentVal(), state.dataEnvrn->OutBaroPress),
+                          state.dataEnvrn->OutBaroPress);
+        }


Use the less "invasive" approach; If a dew-point setpoint is used convert to RH since the existing approach uses RH.

lymereJ · 2026-04-07T16:03:21Z

tst/EnergyPlus/unit/ZoneTempPredictorCorrector.unit.cc

+    ASSERT_EQ(10.0, state->dataZoneCtrls->HumidityControlZone(CoolHeatZoneNum).humidifyingSched->getCurrentVal());
+    ASSERT_EQ(14.0, state->dataZoneCtrls->HumidityControlZone(CoolHeatZoneNum).dehumidifyingSched->getCurrentVal());
+    EXPECT_NEAR(-357.443,
+                state->dataZoneEnergyDemand->ZoneSysMoistureDemand(CoolHeatZoneNum).OutputRequiredToDehumidifyingSP,
+                0.001); // calculated based on 14 deg. C dew-point temperature


Check that the moisture demand is calculated based on the DP setpont.

rraustad · 2026-04-07T21:24:05Z

src/EnergyPlus/ZoneTempPredictorCorrector.cc

+        if (!s_ipsc->lAlphaFieldBlanks(5)) {
+            humidControlledZone.humidityControlVariableType =
+                static_cast<DataZoneControls::HumidityCtrlVarType>(getEnumValue(DataZoneControls::humidityCtrlVarTypeNamesUC, s_ipsc->cAlphaArgs(5)));
+        }


This field has a default so cannot be blank.

Ah, yes... Addressed.

rraustad · 2026-04-07T21:32:59Z

idd/Energy+.idd.in

-  A3 , \field Humidifying Relative Humidity Setpoint Schedule Name
+  A3 , \field Humidifying Setpoint Schedule Name
       \required-field
-       \note hourly schedule values should be in Relative Humidity (percent)


Maybe keep the notes and add "or Dew Point (C) based on the Control Variable field." That would also send home that both schedules need to have the same units.

mitchute · 2026-04-13T17:56:51Z

Thanks, @lymereJ. Your implementation looks correct to me. However, while reviewing I noticed this block:

EnergyPlus/src/EnergyPlus/SystemAvailabilityManager.cc

Lines 4824 to 4825 in e84d72a

    
           ZoneRHHumidifyingSetPoint = state.dataZoneCtrls->HumidityControlZone(HStatZoneNum).humidifyingSched->getCurrentVal(); 
        
           ZoneRHDehumidifyingSetPoint = state.dataZoneCtrls->HumidityControlZone(HStatZoneNum).dehumidifyingSched->getCurrentVal();

which reads the RH setpoints directly from the schedules, even though we're inside of a dew point control block. Am I reading this right? If so, that looks like a bug.

mitchute

This looks ready. We still need to investigate what I noted here, but we can take that as a separate issue.

lymereJ · 2026-04-13T21:51:57Z

@mitchute. Thanks for pointing this out. I looked at the code and I suspect that it might be correct.

This block that's located above determines if the ventilation control status is open or closed based on outdoor air dew-point temperature:

EnergyPlus/src/EnergyPlus/SystemAvailabilityManager.cc

Lines 4635 to 4643 in e84d72a

    
           case VentCtrlType::DewPoint: { 
        
               if (state.dataEnvrn->OutDewPointTemp >= hybridVentMgr.MinOutdoorDewPoint && 
        
                   state.dataEnvrn->OutDewPointTemp <= hybridVentMgr.MaxOutdoorDewPoint) { 
        
                   hybridVentMgr.ctrlStatus = VentCtrlStatus::Open; 
        
               } else { 
        
                   hybridVentMgr.ctrlStatus = VentCtrlStatus::Close; 
        
               } 
        
           } break;

Then, if it is open ...

EnergyPlus/src/EnergyPlus/SystemAvailabilityManager.cc

Line 4743 in e84d72a

if (hybridVentMgr.ctrlStatus == VentCtrlStatus::Open) {

... we get to the block that you shared. My understanding is that the intent is to ensure we don’t set the ventilation control status to “open” when the outdoor air has a humidity ratio above or below the level corresponding to the humidistat setpoint (which previously was evaluated only in terms of relative humidity). That makes sense to me. It also looks like I should add a check for the control variable I introduced to handle cases where the humidistat is controlled by dew point rather than RH. I’ll push those changes.

lymereJ · 2026-04-13T22:03:50Z

src/EnergyPlus/SystemAvailabilityManager.cc

                // Dew point control mode
                if (hybridVentMgr.ctrlType == VentCtrlType::DewPoint) {
                    ZoneAirRH = PsyRhFnTdbWPb(state, thisZoneHB.MAT, thisZoneHB.airHumRat, state.dataEnvrn->OutBaroPress) * 100.0;
-                    ZoneAirDewPoint = PsyTdpFnWPb(state, thisZoneHB.airHumRat, state.dataEnvrn->OutBaroPress);


I don't think that this was used.

lymereJ added 2 commits April 6, 2026 19:22

New test file.

3a0cb77

Add NFP document, code changes, unit test, and docs changes.

58ce6bb

lymereJ added NewFeature Includes code to add a new feature to EnergyPlus IDDChange Code changes impact the IDD file (cannot be merged after IO freeze) labels Apr 7, 2026

lymereJ added 3 commits April 6, 2026 22:44

Forgot to push two files...

4486df9

Add example file to test files list and update SizingPeriod:DesignDay…

59d14f5

… objects.

Change location to Miami. Fix trailing space.

0c3aad0

NatLabRockies deleted a comment from github-actions bot Apr 7, 2026

Correct typos and rename example file.

f777e26

lymereJ commented Apr 7, 2026

View reviewed changes

lymereJ marked this pull request as ready for review April 7, 2026 16:23

NatLabRockies deleted a comment from github-actions bot Apr 7, 2026

rraustad reviewed Apr 7, 2026

View reviewed changes

Address review comments.

b6ba220

rraustad approved these changes Apr 8, 2026

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rraustad assigned lymereJ Apr 8, 2026

Merge branch 'develop' into dewpoint_humidistat

20a42b6

minor doc touch-up

644d8df

mitchute approved these changes Apr 13, 2026

View reviewed changes

Add DP humidistat changes to system availability manager.

70f3328

lymereJ commented Apr 13, 2026

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Dew-point temperature setpoint for zone humidity control#11500

Dew-point temperature setpoint for zone humidity control#11500
lymereJ wants to merge 10 commits intodevelopfrom
dewpoint_humidistat

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Pull request overview

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