diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 0546ab6a9c..6a2901287e 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -1378,6 +1378,11 @@ SUBROUTINE HVAC_CALC(T,DT,FIRST_PASS)
 
 TNOW = CURRENT_TIME()
 
+IF (N_ZONE > 0) THEN
+   IF (.NOT. ALLOCATED(DPSTAR)) ALLOCATE(DPSTAR(0:N_ZONE))
+   DPSTAR = 0._EB
+ENDIF
+
 IF (.NOT. ALLOCATED(LHS)) ALLOCATE(LHS(N_DUCTS+N_DUCTNODES,N_DUCTS+N_DUCTNODES))
 IF (.NOT. ALLOCATED(RHS)) ALLOCATE(RHS(N_DUCTS+N_DUCTNODES))
 
@@ -1451,11 +1456,7 @@ SUBROUTINE HVAC_CALC(T,DT,FIRST_PASS)
 
 ITER = 0
 
-IF (N_ZONE>0) THEN
-   ALLOCATE(DPSTAR(1:N_ZONE))
-   DPSTAR = 0._EB
-   CALL DPSTARCALC
-ENDIF
+IF (N_ZONE>0) CALL DPSTARCALC
 
 DUCTNODE%P = DUCTNODE%P - P_INF
 
@@ -1517,10 +1518,6 @@ SUBROUTINE HVAC_CALC(T,DT,FIRST_PASS)
 
 DUCTNODE%P = DUCTNODE%P + P_INF
 
-!CALL UPDATE_NODE_BC
-
-IF (ALLOCATED(DPSTAR)) DEALLOCATE(DPSTAR)
-
 T_USED(13)=T_USED(13)+CURRENT_TIME()-TNOW
 
 END SUBROUTINE HVAC_CALC
@@ -2638,8 +2635,7 @@ END SUBROUTINE DETERMINE_FIXED_ELEMENTS
 
 SUBROUTINE FIND_NETWORKS(CHANGE,T)
 INTEGER:: NZ,NN,ND,DUCT_COUNTER(N_DUCTS),NODE_COUNTER(N_DUCTNODES),COUNTER,COUNTER2,ZONE_COUNTER(N_ZONE),&
-          CONNECTED_ZONES2(0:N_ZONE,0:N_ZONE)
-INTEGER, DIMENSION(:), ALLOCATABLE :: NETWORK_DCOUNTER,NETWORK_NCOUNTER,RENUMBER
+          CONNECTED_ZONES2(0:N_ZONE,0:N_ZONE),NETWORK_DCOUNTER(N_DUCTS),NETWORK_NCOUNTER(N_DUCTS),RENUMBER(N_DUCTNODES)
 LOGICAL, INTENT(OUT) :: CHANGE
 LOGICAL :: CHANGE2
 REAL(EB), INTENT(IN):: T
@@ -2723,7 +2719,6 @@ SUBROUTINE FIND_NETWORKS(CHANGE,T)
    ENDIF
 END DO
 
-ALLOCATE(RENUMBER(MAXVAL(NODE_COUNTER)))
 RENUMBER = 0
 N_NETWORKS = 0
 DO NN = 1,N_DUCTNODES
@@ -2738,14 +2733,11 @@ SUBROUTINE FIND_NETWORKS(CHANGE,T)
 DO ND = 1,N_DUCTS
    DUCT_COUNTER(ND) = RENUMBER(DUCT_COUNTER(ND))
 ENDDO
-DEALLOCATE(RENUMBER)
 
 ALLOCATE(NETWORK(N_NETWORKS))
 NETWORK%N_DUCTS=0
 NETWORK%N_DUCTNODES=0
-ALLOCATE(NETWORK_DCOUNTER(N_NETWORKS))
 NETWORK_DCOUNTER=0
-ALLOCATE(NETWORK_NCOUNTER(N_NETWORKS))
 NETWORK_NCOUNTER=0
 COUNTER = 0
 DO ND = 1, N_DUCTS
@@ -2771,8 +2763,6 @@ SUBROUTINE FIND_NETWORKS(CHANGE,T)
    DUCTNODE_NE(NN) = NETWORK_NCOUNTER(NODE_COUNTER(NN))
 ENDDO
 
-DEALLOCATE(NETWORK_DCOUNTER)
-DEALLOCATE(NETWORK_NCOUNTER)
 CALL SETUP_SOLUTION_POINTERS
 
 END SUBROUTINE FIND_NETWORKS
@@ -3626,12 +3616,20 @@ SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
 USE PHYSICAL_FUNCTIONS,ONLY: GET_TEMPERATURE, GET_ENTHALPY
 REAL(EB), INTENT(IN) :: DT
 INTEGER, INTENT(IN) :: NR
-INTEGER :: N_SUBSTEPS,ND,NS,NC
+INTEGER :: N_SUBSTEPS,ND,NS,NC,MAX_CELLS
 TYPE(DUCT_TYPE),POINTER :: DU
 REAL(EB) :: DT_CFL,DT_DUCT,MASS_FLUX,ZZ_GET(N_TRACKED_SPECIES),HGAS
 REAL(EB), ALLOCATABLE, DIMENSION(:) :: CPT_C,CPT_F,RHOCPT_C
 REAL(EB), ALLOCATABLE, DIMENSION(:,:) :: RHOZZ_C,ZZ_F
 
+MAX_CELLS = MAXVAL(DUCT(:)%N_CELLS)
+
+ALLOCATE(ZZ_F(0:MAX_CELLS,N_TRACKED_SPECIES))
+ALLOCATE(CPT_F(0:MAX_CELLS))
+ALLOCATE(CPT_C(MAX_CELLS))
+ALLOCATE(RHOCPT_C(MAX_CELLS))
+ALLOCATE(RHOZZ_C(MAX_CELLS,N_TRACKED_SPECIES))
+
 DUCT_LOOP: DO ND = 1,DUCTRUN(NR)%N_DUCTS
    DU => DUCT(DUCTRUN(NR)%DUCT_INDEX(ND))
    IF (DU%N_CELLS == 0 ) CYCLE DUCT_LOOP
@@ -3646,11 +3644,6 @@ SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
    DT_DUCT = DT/REAL(N_SUBSTEPS,EB)
 
    ! Set upwind face indices and allocate flux arrays
-   ALLOCATE(ZZ_F(0:DU%N_CELLS,N_TRACKED_SPECIES))
-   ALLOCATE(CPT_F(0:DU%N_CELLS))
-   ALLOCATE(CPT_C(DU%N_CELLS))
-   ALLOCATE(RHOCPT_C(DU%N_CELLS))
-   ALLOCATE(RHOZZ_C(DU%N_CELLS,N_TRACKED_SPECIES))
 
    SUBSTEP_LOOP: DO NS = 1,N_SUBSTEPS
 
@@ -3690,14 +3683,13 @@ SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT(DT,NR)
 
    ENDDO SUBSTEP_LOOP
 
-   DEALLOCATE(RHOZZ_C)
-   DEALLOCATE(ZZ_F)
-   DEALLOCATE(CPT_F)
-   DEALLOCATE(CPT_C)
-   DEALLOCATE(RHOCPT_C)
-
 ENDDO DUCT_LOOP
 
+DEALLOCATE(RHOZZ_C)
+DEALLOCATE(ZZ_F)
+DEALLOCATE(CPT_F)
+DEALLOCATE(CPT_C)
+DEALLOCATE(RHOCPT_C)
 
 END SUBROUTINE UPDATE_HVAC_MASS_TRANSPORT