diff --git a/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.C b/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.C
index 652a9a6d71..7dabf10a89 100644
--- a/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.C
+++ b/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2018 OpenCFD Ltd.
+    Copyright (C) 2015-2018, 2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -56,8 +56,8 @@ Foam::radiation::constantAbsorption::constantAbsorption
 :
     wallAbsorptionEmissionModel(dict, pp),
     coeffsDict_(dict),
-    a_(coeffsDict_.get<scalar>("absorptivity")),
-    e_(coeffsDict_.get<scalar>("emissivity"))
+    a_(Function1<scalar>::New("absorptivity", coeffsDict_)),
+    e_(Function1<scalar>::New("emissivity", coeffsDict_))
 {}
 
 
@@ -70,7 +70,23 @@ Foam::tmp<Foam::scalarField> Foam::radiation::constantAbsorption::a
     const scalarField* T
 ) const
 {
-    return tmp<scalarField>::New(pp_.size(), a_);
+    if (a_->constant())
+    {
+        // Use arbitrary argument for a_
+        return tmp<scalarField>::New(pp_.size(), a_->value(0));
+    }
+
+    if (T)
+    {
+        return a_->value(*T);
+    }
+
+    FatalErrorInFunction
+        << "Attempted to set 'a' using a non-uniform function of Temperature, "
+        << "but temperature field is unavailable"
+        << abort(FatalError);
+
+    return nullptr;
 }
 
 
@@ -82,7 +98,7 @@ Foam::scalar Foam::radiation::constantAbsorption::a
     const scalar T
 ) const
 {
-    return a_;
+    return a_->value(T);
 }
 
 
@@ -93,7 +109,23 @@ Foam::tmp<Foam::scalarField> Foam::radiation::constantAbsorption::e
     const scalarField* T
 ) const
 {
-    return tmp<scalarField>::New(pp_.size(), e_);
+    if (e_->constant())
+    {
+        // Use arbitrary argument for e_
+        return tmp<scalarField>::New(pp_.size(), e_->value(0));
+    }
+
+    if (T)
+    {
+        return e_->value(*T);
+    }
+
+    FatalErrorInFunction
+        << "Attempted to set 'e' using a non-uniform function of Temperature, "
+        << "but temperature field is unavailable"
+        << abort(FatalError);
+
+    return nullptr;
 }
 
 
@@ -105,7 +137,7 @@ Foam::scalar Foam::radiation::constantAbsorption::e
     const scalar T
 ) const
 {
-    return e_;
+    return e_->value(T);
 }
 
 
diff --git a/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.H b/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.H
index a3e3b64618..c7669eabe7 100644
--- a/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.H
+++ b/src/thermophysicalModels/radiation/submodels/wallAbsorptionEmissionModel/constantAbsorption/constantAbsorption.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018, 2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -41,6 +41,7 @@ SourceFiles
 #define Foam_radiation_constantAbsorption_H
 
 #include "wallAbsorptionEmissionModel.H"
+#include "Function1.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -64,10 +65,10 @@ class constantAbsorption
         dictionary coeffsDict_;
 
         //- Absorptivity coefficient
-        scalar a_;
+        autoPtr<Function1<scalar>> a_;
 
         //- Emissivity coefficient
-        scalar e_;
+        autoPtr<Function1<scalar>> e_;
 
 
 public:
diff --git a/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.C b/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.C
index b5f7fbb7cc..eac1e6c949 100644
--- a/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.C
+++ b/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2018 OpenCFD Ltd.
+    Copyright (C) 2015-2018, 2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -56,21 +56,36 @@ Foam::radiation::constantTransmissivity::constantTransmissivity
 :
     wallTransmissivityModel(dict, pp),
     coeffsDict_(dict),
-    tau_(coeffsDict_.get<scalar>("transmissivity"))
+    tau_(Function1<scalar>::New("transmissivity", coeffsDict_))
 {}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-Foam::tmp<Foam::scalarField>
-Foam::radiation::constantTransmissivity::t
+Foam::tmp<Foam::scalarField> Foam::radiation::constantTransmissivity::t
 (
     const label bandI,
     const vectorField* incomingDirection,
     const scalarField* T
 ) const
 {
-    return tmp<scalarField>::New(pp_.size(), tau_);
+    if (tau_->constant())
+    {
+        // Use arbitrary argument for a_
+        return tmp<scalarField>::New(pp_.size(), tau_->value(0));
+    }
+
+    if (T)
+    {
+        return tau_->value(*T);
+    }
+
+    FatalErrorInFunction
+        << "Attempted to set 't' using a non-uniform function of Temperature, "
+        << "but temperature field is unavailable"
+        << abort(FatalError);
+
+    return nullptr;
 }
 
 
@@ -82,7 +97,7 @@ Foam::scalar Foam::radiation::constantTransmissivity::t
     const scalar T
 ) const
 {
-    return tau_;
+    return tau_->value(T);
 }
 
 
diff --git a/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.H b/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.H
index 5c68c58d2f..1aa513bb67 100644
--- a/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.H
+++ b/src/thermophysicalModels/radiation/submodels/wallTransmissivityModel/constantTransmissivity/constantTransmissivity.H
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2018 OpenCFD Ltd.
+    Copyright (C) 2015-2018, 2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -41,6 +41,7 @@ SourceFiles
 #define Foam_radiation_constantTransmissivity_H
 
 #include "wallTransmissivityModel.H"
+#include "Function1.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -64,7 +65,7 @@ class constantTransmissivity
         dictionary coeffsDict_;
 
         //- Transmissivity coefficient
-        scalar tau_;
+        autoPtr<Function1<scalar>> tau_;
 
 
 public: