NatLabRockies · joseph-robertson · Jul 1, 2026 · Jul 2, 2026 · Jul 2, 2026 · Jul 2, 2026
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -195,18 +195,18 @@ if(hasParent)
 endif()
 
 # EnergyPlus Idd version
-set(ENERGYPLUS_VERSION_MAJOR 25)
-set(ENERGYPLUS_VERSION_MINOR 2)
+set(ENERGYPLUS_VERSION_MAJOR 26)
+set(ENERGYPLUS_VERSION_MINOR 1)
 set(ENERGYPLUS_VERSION_PATCH 0)
 set(ENERGYPLUS_VERSION "${ENERGYPLUS_VERSION_MAJOR}.${ENERGYPLUS_VERSION_MINOR}.${ENERGYPLUS_VERSION_PATCH}")
 # Build SHA is not required to have a value, but if it does OpenStudio will require this build.
-set(ENERGYPLUS_BUILD_SHA "cf7368216c")
+set(ENERGYPLUS_BUILD_SHA "6f2e40d102")
 
 # ENERGYPLUS_RELEASE_NAME is used to locate the E+ download
 # from the github releases
-set(ENERGYPLUS_RELEASE_NAME "v25.2.0")
+set(ENERGYPLUS_RELEASE_NAME "v26.1.0")
 
-set(ENERGYPLUS_REPO "NREL")
+set(ENERGYPLUS_REPO "NatLabRockies")
 
 # Radiance
 set(RADIANCE_VERSION "5.0.a.12")
@@ -668,10 +668,10 @@ endif()
 if(UNIX)
   if(APPLE)
     if (ARCH MATCHES "arm64")
-      set(ENERGYPLUS_EXPECTED_HASH 4a6bece818e89eb88b50249c823b97d9)
+      set(ENERGYPLUS_EXPECTED_HASH 00046c474efe5fbf69ffcae504175d18)
       set(ENERGYPLUS_PLATFORM "Darwin-macOS13-arm64")
     else()
-      set(ENERGYPLUS_EXPECTED_HASH 6b10baada08857a9284c2583e01e735a)
+      set(ENERGYPLUS_EXPECTED_HASH 6f0dfef6c4a6529dbe5998c9c9505bf5)
       set(ENERGYPLUS_PLATFORM "Darwin-macOS12.1-x86_64")
     endif()
   elseif(LSB_RELEASE_ID_SHORT MATCHES "CentOS")
@@ -683,9 +683,9 @@ if(UNIX)
   else()
     if(LSB_RELEASE_VERSION_SHORT MATCHES "24.04")
       if (ARCH MATCHES "arm64")
-        set(ENERGYPLUS_EXPECTED_HASH 304fddba0082d833263a0128ee96a0ff)
+        set(ENERGYPLUS_EXPECTED_HASH 1f3d39f84a45eefdacca66f905bc4fba)
       else()
-        set(ENERGYPLUS_EXPECTED_HASH 3c03a2eaac845ac2e9d8b5601e7abbde)
+        set(ENERGYPLUS_EXPECTED_HASH 8b8cd4e21c1bcec778c4c7b17f84908d)
       endif()
     elseif(LSB_RELEASE_VERSION_SHORT MATCHES "22.04")
       if (ARCH MATCHES "arm64")
@@ -728,7 +728,7 @@ elseif(WIN32)
   if(CMAKE_SIZEOF_VOID_P EQUAL 8) # 64 bit
     set(ENERGYPLUS_PATH "EnergyPlus-${ENERGYPLUS_VERSION}-${ENERGYPLUS_BUILD_SHA}-Windows-x86_64")
     set(ENERGYPLUS_ARCH 64)
-    set(ENERGYPLUS_EXPECTED_HASH 22a1d7e594fe8fb0f8e4d2cc0604f05d)
+    set(ENERGYPLUS_EXPECTED_HASH f5c3822fd27700757827c85403c44f20)
   else()
     set(ENERGYPLUS_PATH "EnergyPlus-${ENERGYPLUS_VERSION}-${ENERGYPLUS_BUILD_SHA}-Windows-i386")
     set(ENERGYPLUS_ARCH 32)

diff --git a/resources/CMakeLists.txt b/resources/CMakeLists.txt
@@ -133,6 +133,7 @@ set(utilities_resources_src
   utilities/SqlFile/1ZoneEvapCooler-V24-2-0.sql
   utilities/SqlFile/1ZoneEvapCooler-V25-1-0.sql
   utilities/SqlFile/1ZoneEvapCooler-V25-2-0.sql
+  utilities/SqlFile/1ZoneEvapCooler-V26-1-0.sql
   utilities/xml/base.xml
   utilities/xml/hpxml_with_error.xml
   utilities/xml/schema/HPXML.xsd

diff --git a/resources/energyplus/5ZoneAirCooled/in.idf b/resources/energyplus/5ZoneAirCooled/in.idf
@@ -100,7 +100,7 @@
 ! Environmental Emissions:        None
 ! Utility Tariffs:                None
 
-  Version,25.2;
+  Version,26.1;
 
   Building,
     Building,                !- Name

diff --git a/resources/energyplus/AllFuelTypes/in.idf b/resources/energyplus/AllFuelTypes/in.idf
@@ -1,4 +1,4 @@
-  Version,25.2;
+  Version,26.1;
 
   Timestep,6;
 

diff --git a/resources/energyplus/BestestEx/in.idf b/resources/energyplus/BestestEx/in.idf
@@ -5,7 +5,7 @@
 !BESTEST-EX Case L200EX-PH BASE-CASE, developed by NREL
 !Use EnergyPlus IDFEditor to view inputs in IP units
 
-  Version,25.2;
+  Version,26.1;
 
   SimulationControl,
     No,                      !- Do Zone Sizing Calculation

diff --git a/resources/energyplus/Daylighting_School/in.idf b/resources/energyplus/Daylighting_School/in.idf
@@ -33,7 +33,7 @@
 ! WeatherFileName=USA_CO_Boulder_TMY2.epw
 ! End SimMetaData
 
-  Version,25.2;
+  Version,26.1;
 
   Timestep,6;
 

diff --git a/resources/energyplus/FrameAndDivider/in.idf b/resources/energyplus/FrameAndDivider/in.idf
@@ -1,4 +1,4 @@
-  Version,25.2;
+  Version,26.1;
 
   Timestep,4;
 

diff --git a/resources/energyplus/HospitalBaseline/in.idf b/resources/energyplus/HospitalBaseline/in.idf
@@ -100,7 +100,7 @@
 ! End SimMetaData
 ! Number of Zones: 130
 
-  Version,25.2;
+  Version,26.1;
 
   Timestep,6;
 

diff --git a/resources/energyplus/NewFileTemplate.idf b/resources/energyplus/NewFileTemplate.idf
@@ -1,6 +1,6 @@
 !-   ===========  ALL OBJECTS IN CLASS: VERSION ===========
 
-  Version,25.2;
+  Version,26.1;
 
 !-   ===========  ALL OBJECTS IN CLASS: BUILDING ===========
 

diff --git a/resources/energyplus/Office_With_Many_HVAC_Types/in.idf b/resources/energyplus/Office_With_Many_HVAC_Types/in.idf
@@ -1,4 +1,4 @@
-  Version,25.2;
+  Version,26.1;
 
   Building,
     Building 1,              !- Name
@@ -2692,7 +2692,6 @@
     Node 94,                 !- Supply Air Inlet Node Name
     Node 96,                 !- Secondary Air Inlet Node Name
     Node 88,                 !- Outlet Node Name
-    Air Terminal Single Duct Parallel PIU Reheat 1 Mixer Outlet,  !- Reheat Coil Air Inlet Node Name
     Air Terminal Single Duct Parallel PIU Reheat 1 Mixer,  !- Zone Mixer Name
     Fan Constant Volume 4,   !- Fan Name
     Coil:Heating:Electric,   !- Reheat Coil Object Type
@@ -2978,7 +2977,6 @@
     Node 99,                 !- Supply Air Inlet Node Name
     Node 100,                !- Secondary Air Inlet Node Name
     Node 97,                 !- Outlet Node Name
-    Air Terminal Single Duct Parallel PIU Reheat 2 Mixer Outlet,  !- Reheat Coil Air Inlet Node Name
     Air Terminal Single Duct Parallel PIU Reheat 2 Mixer,  !- Zone Mixer Name
     Fan Constant Volume 5,   !- Fan Name
     Coil:Heating:Electric,   !- Reheat Coil Object Type
@@ -4049,7 +4047,6 @@
     Node 195,                !- Supply Air Inlet Node Name
     Node 197,                !- Secondary Air Inlet Node Name
     Node 177,                !- Outlet Node Name
-    Air Terminal Single Duct Parallel PIU Reheat 3 Mixer Outlet,  !- Reheat Coil Air Inlet Node Name
     Air Terminal Single Duct Parallel PIU Reheat 3 Mixer,  !- Zone Mixer Name
     Fan Constant Volume 6,   !- Fan Name
     Coil:Heating:Electric,   !- Reheat Coil Object Type
@@ -4335,7 +4332,6 @@
     Node 200,                !- Supply Air Inlet Node Name
     Node 201,                !- Secondary Air Inlet Node Name
     Node 198,                !- Outlet Node Name
-    Air Terminal Single Duct Parallel PIU Reheat 4 Mixer Outlet,  !- Reheat Coil Air Inlet Node Name
     Air Terminal Single Duct Parallel PIU Reheat 4 Mixer,  !- Zone Mixer Name
     Fan Constant Volume 7,   !- Fan Name
     Coil:Heating:Electric,   !- Reheat Coil Object Type

diff --git a/resources/energyplus/ProposedEnergy+.idd b/resources/energyplus/ProposedEnergy+.idd
@@ -1,4 +1,4 @@
-!IDD_Version 25.2.0
+!IDD_Version 26.1.0
 !IDD_BUILD TBD
 ! **************************************************************************
 ! This file is the Input Data Dictionary (IDD) for EnergyPlus.
@@ -405,7 +405,7 @@ Version,
       \format singleLine
       \min-fields 1
   A1 ; \field Version Identifier
-      \default 25.2
+      \default 26.1
 
 SimulationControl,
       \unique-object
@@ -28304,24 +28304,22 @@ AirTerminal:SingleDuct:SeriesPIU:Reheat,
        \type node
   A5,  \field Outlet Node Name
        \type node
-  A6,  \field Reheat Coil Air Inlet Node Name
-       \type node
-  A7,  \field Zone Mixer Name
+  A6,  \field Zone Mixer Name
        \type object-list
        \object-list ZoneMixers
-  A8,  \field Fan Name
+  A7,  \field Fan Name
        \note Fan type must be Fan:SystemModel or Fan:ConstantVolume
        \type object-list
        \object-list FansCV
        \object-list FansSystemModel
-  A9,  \field Reheat Coil Object Type
+  A8,  \field Reheat Coil Object Type
        \required-field
        \type choice
        \key Coil:Heating:Water
        \key Coil:Heating:Electric
        \key Coil:Heating:Fuel
        \key Coil:Heating:Steam
-  A10, \field Reheat Coil Name
+  A9,  \field Reheat Coil Name
        \required-field
        \type object-list
        \object-list HeatingCoilName
@@ -28342,7 +28340,7 @@ AirTerminal:SingleDuct:SeriesPIU:Reheat,
        \type real
        \minimum> 0.0
        \default 0.001
-  A11, \field Fan Control Type
+  A10, \field Fan Control Type
        \note If VariableSpeed, then the fan object type must be Fan:SystemModel
        \type choice
        \key VariableSpeed
@@ -28355,7 +28353,7 @@ AirTerminal:SingleDuct:SeriesPIU:Reheat,
        \minimum 0.0
        \maximum 1.0
        \default 0.3
-  A12, \field Heating Control Type
+  A11, \field Heating Control Type
        \type choice
        \key Staged
        \key Modulated
@@ -28416,25 +28414,22 @@ AirTerminal:SingleDuct:ParallelPIU:Reheat,
        \type node
   A5,  \field Outlet Node Name
        \type node
-  A6,  \field Reheat Coil Air Inlet Node Name
-       \type node
-       \note mixer outlet node
-  A7,  \field Zone Mixer Name
+  A6,  \field Zone Mixer Name
        \type object-list
        \object-list ZoneMixers
-  A8,  \field Fan Name
+  A7,  \field Fan Name
        \note Fan type must be Fan:SystemModel or Fan:ConstantVolume
        \type object-list
        \object-list FansCV
        \object-list FansSystemModel
-  A9,  \field Reheat Coil Object Type
+  A8,  \field Reheat Coil Object Type
        \required-field
        \type choice
        \key Coil:Heating:Water
        \key Coil:Heating:Electric
        \key Coil:Heating:Fuel
        \key Coil:Heating:Steam
-  A10, \field Reheat Coil Name
+  A9,  \field Reheat Coil Name
        \required-field
        \type object-list
        \object-list HeatingCoilName
@@ -28455,7 +28450,7 @@ AirTerminal:SingleDuct:ParallelPIU:Reheat,
        \type real
        \minimum> 0.0
        \default 0.001
-  A11, \field Fan Control Type
+  A10, \field Fan Control Type
        \note If VariableSpeed, then the fan object type must be Fan:SystemModel
        \type choice
        \key VariableSpeed
@@ -28468,7 +28463,7 @@ AirTerminal:SingleDuct:ParallelPIU:Reheat,
        \minimum 0.0
        \maximum 1.0
        \default 0.3
-  A12, \field Heating Control Type
+  A11, \field Heating Control Type
        \type choice
        \key Staged
        \key Modulated
@@ -28478,12 +28473,22 @@ AirTerminal:SingleDuct:ParallelPIU:Reheat,
        \default 32.1
        \note Only used if Heating Control Type is Modulated
        \note Used to control second stage heating, typically zone heat setpoint plus 20F
-  N10; \field High Limit Heating Discharge Air Temperature
+  N10, \field High Limit Heating Discharge Air Temperature
        \type real
        \units C
        \default 37.7
        \note Only used if Heating Control Type is Modulated
        \note Used to determine end of third stage heating
+  A12, \field Backdraft Damper Leakage Fraction Curve Name
+       \type object-list
+       \object-list UnivariateFunctions
+       \note Backdraft damper leakage fraction is the ratio of mass leakage flow rate to primary air flow rate
+       \note at a constant static pressure setpoint. This curve should describe the ratio as a function primary
+       \note air flow fraction (ratio of primary flow fraction to maximum nominal primary air flow rate).
+  A13; \field Backdraft Damper Leakage Zone Name
+       \note Name of a zone that will be impacted by the backdraft damper leakage.
+       \type object-list
+       \object-list ZoneNames
 
 AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction,
        \memo Central air system terminal unit, single duct, variable volume, induction unit with
@@ -50289,7 +50294,6 @@ HeatExchanger:FluidToFluid,
         \note This field controls end use reporting for heat transfer meters
         \type choice
         \key FreeCooling
-        \key HeatRecovery
         \key HeatRejection
         \key HeatRecoveryForCooling
         \key HeatRecoveryForHeating
@@ -53293,11 +53297,11 @@ PlantEquipmentOperationSchemes,
        \min-fields 4
        \max-fields 25
   A1 , \field Name
-        \required-field
+       \required-field
        \reference PlantOperationSchemes
   A2 , \field Control Scheme 1 Object Type
-        \required-field
-        \begin-extensible
+       \required-field
+       \begin-extensible
        \type choice
        \key PlantEquipmentOperation:CoolingLoad
        \key PlantEquipmentOperation:HeatingLoad
@@ -58385,6 +58389,7 @@ PhotovoltaicPerformance:Simple,
         \memo which surfaces convert incident solar radiation to electricity and need not specify
         \memo arrays of specific modules.
    A1 , \field Name
+        \required-field
         \reference PVModules
    N1 , \field Fraction of Surface Area with Active Solar Cells
         \required-field
@@ -58410,6 +58415,7 @@ PhotovoltaicPerformance:EquivalentOne-Diode,
         \memo using an equivalent one-diode circuit. This model is also known as
         \memo the 4- or 5-parameter TRNSYS model for photovoltaics.
    A1 , \field Name
+        \required-field
         \reference PVModules
    A2 , \field Cell type
         \type choice
@@ -58520,6 +58526,7 @@ PhotovoltaicPerformance:Sandia,
         \memo Describes performance input data needed for specific makes and models of production
         \memo PV panels using the empirical coefficients assembled by Sandia National Laboratory.
    A1 , \field Name
+        \required-field
         \reference PVModules
    N1 , \field Active Area
         \note (m2, single module)

diff --git a/resources/energyplus/RefLargeOffice/RefBldgLargeOfficeNew2004_Chicago.idf b/resources/energyplus/RefLargeOffice/RefBldgLargeOfficeNew2004_Chicago.idf
@@ -68,7 +68,7 @@
 ! ***GENERAL SIMULATION PARAMETERS***
 ! Number of Zones: 19
 
-  Version,25.2;
+  Version,26.1;
 
   SimulationControl,
     YES,                     !- Do Zone Sizing Calculation

diff --git a/resources/energyplus/ScheduleFile/in.idf b/resources/energyplus/ScheduleFile/in.idf
@@ -1,4 +1,4 @@
-  Version,25.2;
+  Version,26.1;
 
   Timestep,4;
 

diff --git a/resources/energyplus/SimpleSurfaces/4ZoneWithShading_Simple_2.idf b/resources/energyplus/SimpleSurfaces/4ZoneWithShading_Simple_2.idf
@@ -81,7 +81,7 @@
 ! Environmental Emissions:        None
 ! Utility Tariffs:                None
 
-  Version,25.2;
+  Version,26.1;
 
   Timestep,4;
 

diff --git a/resources/energyplus/SimpleSurfaces/SimpleSurfaces_Reference.idf b/resources/energyplus/SimpleSurfaces/SimpleSurfaces_Reference.idf
@@ -1,7 +1,7 @@
 ! Basecase reference for SimpleSurfaces_Test
 !-   ===========  ALL OBJECTS IN CLASS: VERSION ===========
 
-  Version,25.2;
+  Version,26.1;
 
 !-   ===========  ALL OBJECTS IN CLASS: BUILDING ===========
 

diff --git a/resources/energyplus/SimpleSurfaces/SimpleSurfaces_Relative.idf b/resources/energyplus/SimpleSurfaces/SimpleSurfaces_Relative.idf
@@ -1,7 +1,7 @@
 ! File to test the import of simple surfaces
 !-   ===========  ALL OBJECTS IN CLASS: VERSION ===========
 
-  Version,25.2;
+  Version,26.1;
 
 !-   ===========  ALL OBJECTS IN CLASS: BUILDING ===========
 

diff --git a/resources/energyplus/SmallOffice/SmallOffice.idf b/resources/energyplus/SmallOffice/SmallOffice.idf
@@ -67,7 +67,7 @@
 ! ExtWallConstruction=Mass
 ! End SimMetaData
 
-  Version,25.2;
+  Version,26.1;
 
   Timestep,6;
 

diff --git a/resources/energyplus/ZoneBoundaryCondition/Bug_486_zone_bdr_test.idf b/resources/energyplus/ZoneBoundaryCondition/Bug_486_zone_bdr_test.idf
@@ -1,6 +1,6 @@
 !-   ===========  ALL OBJECTS IN CLASS: VERSION ===========
 
-  Version,25.2;
+  Version,26.1;
 
 !-   ===========  ALL OBJECTS IN CLASS: BUILDING ===========