diff --git a/src/thermophysicalModels/radiation/radiationModels/P1/P1.C b/src/thermophysicalModels/radiation/radiationModels/P1/P1.C
index 1e4de417bf2dc3bf9ec75dde4b859ab4d69b463e..d4336dd3c7640bed79203fe3b267a6c009b01d5f 100644
--- a/src/thermophysicalModels/radiation/radiationModels/P1/P1.C
+++ b/src/thermophysicalModels/radiation/radiationModels/P1/P1.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -142,7 +142,7 @@ Foam::radiation::P1::P1(const dictionary& dict, const volScalarField& T)
             "qr",
             mesh_.time().timeName(),
             mesh_,
-            IOobject::NO_READ,
+            IOobject::READ_IF_PRESENT,
             IOobject::AUTO_WRITE
         ),
         mesh_,
@@ -190,12 +190,6 @@ Foam::radiation::P1::P1(const dictionary& dict, const volScalarField& T)
 {}
 
 
-// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
-
-Foam::radiation::P1::~P1()
-{}
-
-
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 bool Foam::radiation::P1::read()
@@ -240,19 +234,19 @@ void Foam::radiation::P1::calculate()
         fvm::laplacian(gamma, G_)
       - fvm::Sp(a_, G_)
      ==
-      - 4.0*(e_*physicoChemical::sigma*pow4(T_) ) - E_
+      - 4.0*(e_*physicoChemical::sigma*pow4(T_)) - E_
     );
 
+    // Calculate radiative heat flux on boundaries.
     volScalarField::Boundary& qrBf = qr_.boundaryFieldRef();
+    const volScalarField::Boundary& GBf = G_.boundaryField();
+    const volScalarField::Boundary& gammaBf = gamma.boundaryField();
 
-    // Calculate radiative heat flux on boundaries.
     forAll(mesh_.boundaryMesh(), patchi)
     {
-        if (!G_.boundaryField()[patchi].coupled())
+        if (!GBf[patchi].coupled())
         {
-            qrBf[patchi] =
-                -gamma.boundaryField()[patchi]
-                *G_.boundaryField()[patchi].snGrad();
+            qrBf[patchi] = -gammaBf[patchi]*GBf[patchi].snGrad();
         }
     }
 }
@@ -282,12 +276,9 @@ Foam::tmp<Foam::volScalarField> Foam::radiation::P1::Rp() const
 Foam::tmp<Foam::DimensionedField<Foam::scalar, Foam::volMesh>>
 Foam::radiation::P1::Ru() const
 {
-    const volScalarField::Internal& G =
-        G_();
-    const volScalarField::Internal E =
-        absorptionEmission_->ECont()()();
-    const volScalarField::Internal a =
-        absorptionEmission_->aCont()()();
+    const volScalarField::Internal& G = G_();
+    const volScalarField::Internal E = absorptionEmission_->ECont()()();
+    const volScalarField::Internal a = absorptionEmission_->aCont()()();
 
     return a*G - E;
 }
@@ -298,4 +289,5 @@ Foam::label Foam::radiation::P1::nBands() const
     return absorptionEmission_->nBands();
 }
 
+
 // ************************************************************************* //
diff --git a/src/thermophysicalModels/radiation/radiationModels/P1/P1.H b/src/thermophysicalModels/radiation/radiationModels/P1/P1.H
index 4b8a724434ba769c6895363a54321d5f2639c03d..b1daa691663412f89963653a56f43f353cdf2214 100644
--- a/src/thermophysicalModels/radiation/radiationModels/P1/P1.H
+++ b/src/thermophysicalModels/radiation/radiationModels/P1/P1.H
@@ -107,7 +107,7 @@ public:
 
 
     //- Destructor
-    virtual ~P1();
+    virtual ~P1() = default;
 
 
     // Member functions