diff --git a/idd/Energy+.idd.in b/idd/Energy+.idd.in
index fa0cf2f26d9..da81362f9e2 100644
--- a/idd/Energy+.idd.in
+++ b/idd/Energy+.idd.in
@@ -977,6 +977,17 @@ HVACSystemRootFindingAlgorithm,
        \type integer
        \default 5
 
+HeatIndexAlgorithm,
+       \memo Specify whether the simplified or the extended method should be used
+       \memo Simplified: based on regression analysis carried out by Lans P. Rothfusz
+       \memo Extended: Based on paper by Lu & Romps
+       \unique-object
+  A1 ; \field Algorithm
+       \type choice
+       \key Simplified
+       \key Extended
+       \default Simplified
+
 \group Compliance Objects
 
 Compliance:Building,
diff --git a/src/EnergyPlus/DataHeatBalance.hh b/src/EnergyPlus/DataHeatBalance.hh
index d0c04f26035..7de88a379c4 100644
--- a/src/EnergyPlus/DataHeatBalance.hh
+++ b/src/EnergyPlus/DataHeatBalance.hh
@@ -547,6 +547,19 @@ namespace DataHeatBalance {
         {
         }
     };
+
+    enum class HeatIndexMethod : int
+    {
+        Invalid = -1,
+        Simplified,
+        Extended,
+        Num
+    };
+    static constexpr std::array<std::string_view, static_cast<int>(HeatIndexMethod::Num)> HeatIndexMethodUC = {
+        "SIMPLIFIED",
+        "EXTENDED",
+    };
+
     struct ZoneData : ZoneSpaceData
     {
         // Members
@@ -1847,6 +1860,7 @@ struct HeatBalanceData : BaseGlobalStruct
     bool NoRegularMaterialsUsed = true;
     bool DoLatentSizing = false; // true when latent sizing is performed during zone sizing
     bool isAnyLatentLoad = false;
+    DataHeatBalance::HeatIndexMethod heatIndexMethod = DataHeatBalance::HeatIndexMethod::Simplified;
 
     Array1D<Real64> ZoneListSNLoadHeatEnergy;
     Array1D<Real64> ZoneListSNLoadCoolEnergy;
diff --git a/src/EnergyPlus/HeatBalanceManager.cc b/src/EnergyPlus/HeatBalanceManager.cc
index a4c2d6ceed3..2c2b3f14cd6 100644
--- a/src/EnergyPlus/HeatBalanceManager.cc
+++ b/src/EnergyPlus/HeatBalanceManager.cc
@@ -277,6 +277,8 @@ namespace HeatBalanceManager {
 
         GetIncidentSolarMultiplier(state, ErrorsFound);
 
+        GetHeatIndexMethod(state, ErrorsFound);
+
         // Added SV 6/26/2013 to load scheduled surface gains
         GetScheduledSurfaceGains(state, ErrorsFound);
 
@@ -2165,6 +2167,38 @@ namespace HeatBalanceManager {
         }
     }
 
+    void GetHeatIndexMethod(EnergyPlusData &state, bool &ErrorsFound)
+    {
+        static constexpr std::string_view RoutineName("GetHeatIndexMethod: ");
+
+        Array1D_string Alphas(1);
+        Array1D<Real64> Numbers(1);
+        int NumAlpha;
+        int NumNumber;
+        int IOStat;
+
+        state.dataHeatBalMgr->CurrentModuleObject = "HeatIndexAlgorithm";
+        int NumObjects = state.dataInputProcessing->inputProcessor->getNumObjectsFound(state, state.dataHeatBalMgr->CurrentModuleObject);
+        if (NumObjects > 0) {
+            state.dataInputProcessing->inputProcessor->getObjectItem(state,
+                                                                     state.dataHeatBalMgr->CurrentModuleObject,
+                                                                     1,
+                                                                     Alphas,
+                                                                     NumAlpha,
+                                                                     Numbers,
+                                                                     NumNumber,
+                                                                     IOStat,
+                                                                     state.dataIPShortCut->lNumericFieldBlanks,
+                                                                     state.dataIPShortCut->lAlphaFieldBlanks,
+                                                                     state.dataIPShortCut->cAlphaFieldNames,
+                                                                     state.dataIPShortCut->cNumericFieldNames);
+            if (NumAlpha > 0) {
+                state.dataHeatBal->heatIndexMethod =
+                    static_cast<DataHeatBalance::HeatIndexMethod>(getEnumValue(DataHeatBalance::HeatIndexMethodUC, Util::makeUPPER(Alphas(1))));
+            }
+        }
+    }
+
     void GetZoneLocalEnvData(EnergyPlusData &state, bool &ErrorsFound) // Error flag indicator (true if errors found)
     {
         // SUBROUTINE INFORMATION:
diff --git a/src/EnergyPlus/HeatBalanceManager.hh b/src/EnergyPlus/HeatBalanceManager.hh
index 7b415723c7b..e688bdd0f98 100644
--- a/src/EnergyPlus/HeatBalanceManager.hh
+++ b/src/EnergyPlus/HeatBalanceManager.hh
@@ -167,6 +167,8 @@ namespace HeatBalanceManager {
 
     void GetIncidentSolarMultiplier(EnergyPlusData &state, bool &ErrorsFound);
 
+    void GetHeatIndexMethod(EnergyPlusData &state, bool &ErrorsFound);
+
     void GetScheduledSurfaceGains(EnergyPlusData &state, bool &ErrorsFound); // If errors found in input
 
     void CheckScheduledSurfaceGains(EnergyPlusData &state, int const ZoneNum); // Zone number for which error check will be performed
diff --git a/src/EnergyPlus/HeatBalanceSurfaceManager.cc b/src/EnergyPlus/HeatBalanceSurfaceManager.cc
index 1875ef883d0..f283b9f64b4 100644
--- a/src/EnergyPlus/HeatBalanceSurfaceManager.cc
+++ b/src/EnergyPlus/HeatBalanceSurfaceManager.cc
@@ -5522,7 +5522,7 @@ void CalcThermalResilience(EnergyPlusData &state)
             Real64 const ZoneW = state.dataZoneTempPredictorCorrector->zoneHeatBalance(ZoneNum).airHumRatAvg;
             Real64 const ZoneRH = Psychrometrics::PsyRhFnTdbWPb(state, ZoneT, ZoneW, state.dataEnvrn->OutBaroPress) * 100.0;
             Real64 const ZoneTF = ZoneT * (9.0 / 5.0) + 32.0;
-            if (ZoneTF * 3.0 + ZoneRH * 100.0 - 340.0 < 0.0) {
+            if (state.dataHeatBal->heatIndexMethod == DataHeatBalance::HeatIndexMethod::Simplified) {
                 Real64 constexpr c1 = -42.379;
                 Real64 constexpr c2 = 2.04901523;
                 Real64 constexpr c3 = 10.14333127;
diff --git a/testfiles/1ZoneUncontrolled_Win_ASH55_Thermal_Comfort.idf b/testfiles/1ZoneUncontrolled_Win_ASH55_Thermal_Comfort.idf
index f357a9ebc52..e0a12c4c1b3 100644
--- a/testfiles/1ZoneUncontrolled_Win_ASH55_Thermal_Comfort.idf
+++ b/testfiles/1ZoneUncontrolled_Win_ASH55_Thermal_Comfort.idf
@@ -653,6 +653,9 @@
     7.5,                     !- Y-Coordinate of Reference Point {m}
     0.7;                     !- Z-Coordinate of Reference Point {m}
 
+  HeatIndexAlgorithm,
+    Simplified;
+
   Output:Variable,*,Site Outdoor Air Barometric Pressure,hourly;
 
   Output:Variable,*,Site Outdoor Air Drybulb Temperature,hourly;