!> @file indoor_model_mod.f90
!--------------------------------------------------------------------------------!
! This file is part of the PALM model system.
!
! PALM is free software: you can redistribute it and/or modify it under the
! terms of the GNU General Public License as published by the Free Software
! Foundation, either version 3 of the License, or (at your option) any later
! version.
!
! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
! A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License along with
! PALM. If not, see <http://www.gnu.org/licenses/>.
!
! Copyright 2018-2019 Leibniz Universitaet Hannover
! Copyright 2018-2019 Hochschule Offenburg
!--------------------------------------------------------------------------------!
!
! Current revisions:
! -----------------
! 
! 
! Former revisions:
! -----------------
! $Id: indoor_model_mod.f90 3885 2019-04-11 11:29:34Z Giersch $
! Changes related to global restructuring of location messages and introduction 
! of additional debug messages
! 
! 3786 2019-03-06 16:58:03Z raasch
! unused variables removed
! 
! 3759 2019-02-21 15:53:45Z suehring
! - Calculation of total building volume
! - Several bugfixes
! - Calculation of building height revised
! 
! 3745 2019-02-15 18:57:56Z suehring
! - remove building_type from module
! - initialize parameters for each building individually instead of a bulk 
!   initializaion with  identical building type for all
! - output revised
! - add missing _wp
! - some restructuring of variables in building data structure
! 
! 3744 2019-02-15 18:38:58Z suehring
! Some interface calls moved to module_interface + cleanup
! 
! 3597 2018-12-04 08:40:18Z maronga
! Renamed t_surf_10cm to pt_10cm
! 
! 3593 2018-12-03 13:51:13Z kanani
! Replace degree symbol by degree_C
!
! 3524 2018-11-14 13:36:44Z raasch
! working precision added to make code Fortran 2008 conform
! 
! 3469 2018-10-30 20:05:07Z kanani
! Initial revision (tlang, suehring, kanani, srissman)
! 
! 
!
! Authors:
! --------
! @author Tobias Lang
! @author Jens Pfafferott
! @author Farah Kanani-Suehring
! @author Matthias Suehring
! @author Sascha Rißmann
!
!
! Description:
! ------------
!> <Description of the new module>
!> Module for Indoor Climate Model (ICM)
!> The module is based on the DIN EN ISO 13790 with simplified hour-based procedure.
!> This model is a equivalent circuit diagram of a three-point RC-model (5R1C).
!> This module differ between indoor-air temperature an average temperature of indoor surfaces which make it prossible to determine thermal comfort
!> the heat transfer between indoor and outdoor is simplified 

!> @todo Replace window_area_per_facade by %frac(1,m) for window
!> @todo emissivity change for window blinds if solar_protection_on=1 
!> @todo write datas in netcdf file as output data
!> @todo reduce the building volume with netto ground surface to take respect costruction areas like walls and ceilings. Have effect on factor_a, factor_c, airchange and lambda_at
!>
!> @note Do we allow use of integer flags, or only logical flags? (concerns e.g. cooling_on, heating_on)
!> @note How to write indoor temperature output to pt array?
!>
!> @bug  <Enter known bugs here>
!------------------------------------------------------------------------------!
 MODULE indoor_model_mod 

    USE control_parameters,                                                    &
        ONLY:  debug_output, initializing_actions

    USE kinds
    
    USE netcdf_data_input_mod,                                                 &
        ONLY:  building_id_f, building_type_f

    USE surface_mod,                                                           &
        ONLY:  surf_usm_h, surf_usm_v


    IMPLICIT NONE

!
!-- Define data structure for buidlings.
    TYPE build

       INTEGER(iwp) ::  id                                !< building ID
       INTEGER(iwp) ::  kb_min                            !< lowest vertical index of a building
       INTEGER(iwp) ::  kb_max                            !< highest vertical index of a building
       INTEGER(iwp) ::  num_facades_per_building_h = 0    !< total number of horizontal facades elements
       INTEGER(iwp) ::  num_facades_per_building_h_l = 0  !< number of horizontal facade elements on local subdomain
       INTEGER(iwp) ::  num_facades_per_building_v = 0    !< total number of vertical facades elements
       INTEGER(iwp) ::  num_facades_per_building_v_l = 0  !< number of vertical facade elements on local subdomain

       INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  l_v            !< index array linking surface-element orientation index
                                                                  !< for vertical surfaces with building 
       INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  m_h            !< index array linking surface-element index for
                                                                  !< horizontal surfaces with building
       INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  m_v            !< index array linking surface-element index for 
                                                                  !< vertical surfaces with building
       INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  num_facade_h   !< number of horizontal facade elements per buidling 
                                                                  !< and height level
       INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  num_facade_v   !< number of vertical facades elements per buidling
                                                                  !< and height level
                                                                  
       INTEGER(iwp) ::  ventilation_int_loads

       LOGICAL ::  on_pe = .FALSE.   !< flag indicating whether a building with certain ID is on local subdomain
       
       REAL(wp) ::  building_height   !< building height
       REAL(wp) ::  lambda_layer3     !< [W/(m*K)] Thermal conductivity of the inner layer  
       REAL(wp) ::  s_layer3          !< [m] half thickness of the inner layer (layer_3)
       REAL(wp) ::  f_c_win           !< [-] shading factor
       REAL(wp) ::  g_value_win       !< [-] SHGC factor
       REAL(wp) ::  u_value_win       !< [W/(m2*K)] transmittance
       REAL(wp) ::  air_change_low    !< [1/h] air changes per time_utc_hour
       REAL(wp) ::  air_change_high   !< [1/h] air changes per time_utc_hour
       REAL(wp) ::  eta_ve            !< [-] heat recovery efficiency
       REAL(wp) ::  factor_a          !< [-] Dynamic parameters specific effective surface according to Table 12; 2.5 
                                      !< (very light, light and medium), 3.0 (heavy), 3.5 (very heavy)
       REAL(wp) ::  factor_c          !< [J/(m2 K)] Dynamic parameters inner heatstorage according to Table 12; 80000 
                                      !< (very light), 110000 (light), 165000 (medium), 260000 (heavy), 370000 (very heavy)
       REAL(wp) ::  lambda_at         !< [-] ratio internal surface/floor area chap. 7.2.2.2.
       REAL(wp) ::  theta_int_h_set   !< [degree_C] Max. Setpoint temperature (winter)
       REAL(wp) ::  theta_int_c_set   !< [degree_C] Max. Setpoint temperature (summer)
       REAL(wp) ::  phi_h_max         !< [W] Max. Heating capacity (negative)
       REAL(wp) ::  phi_c_max         !< [W] Max. Cooling capacity (negative)
       REAL(wp) ::  qint_high         !< [W/m2] internal heat gains, option Database qint_0-23
       REAL(wp) ::  qint_low          !< [W/m2] internal heat gains, option Database qint_0-23
       REAL(wp) ::  height_storey     !< [m] storey heigth
       REAL(wp) ::  height_cei_con    !< [m] ceiling construction heigth
       REAL(wp) ::  vol_tot           !< total building volume

       REAL(wp), DIMENSION(:), ALLOCATABLE ::  t_in       !< mean building indoor temperature, height dependent
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  t_in_l     !< mean building indoor temperature on local subdomain, height dependent
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  volume     !< total building volume, height dependent
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  vol_frac   !< fraction of local on total building volume, height dependent
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  vpf        !< building volume volume per facade element, height dependent
       
    END TYPE build

    TYPE(build), DIMENSION(:), ALLOCATABLE ::  buildings   !< building array

    INTEGER(iwp) ::  num_build   !< total number of buildings in domain

!
!-- Declare all global variables within the module
    INTEGER(iwp) ::  cooling_on              !< Indoor cooling flag (0=off, 1=on)
    INTEGER(iwp) ::  heating_on              !< Indoor heating flag (0=off, 1=on)
    INTEGER(iwp) ::  solar_protection_off    !< Solar protection off
    INTEGER(iwp) ::  solar_protection_on     !< Solar protection on

    REAL(wp) ::  eff_mass_area               !< [m2] the effective mass-related area
    REAL(wp) ::  floor_area_per_facade       !< [m2] net floor area (Sum of all floors)
    REAL(wp) ::  total_area                  !<! [m2] area of all surfaces pointing to zone
    REAL(wp) ::  window_area_per_facade      !< [m2] window area per facade element
    REAL(wp) ::  air_change                  !< [1/h] Airflow
    REAL(wp) ::  facade_element_area         !< [m2_facade] building surface facade
    REAL(wp) ::  indoor_volume_per_facade    !< [m3] indoor air volume per facade element
    REAL(wp) ::  c_m                         !< [J/K] internal heat storage capacity
    REAL(wp) ::  dt_indoor = 3600.0_wp       !< [s] namelist parameter: time interval for indoor-model application
    REAL(wp) ::  h_tr_1                      !<! [W/K] Heat transfer coefficient auxiliary variable 1
    REAL(wp) ::  h_tr_2                      !<! [W/K] Heat transfer coefficient auxiliary variable 2
    REAL(wp) ::  h_tr_3                      !<! [W/K] Heat transfer coefficient auxiliary variable 3 
    REAL(wp) ::  h_tr_em                     !<! [W/K] Heat transfer coefficient of the emmision (got with h_tr_ms the thermal mass)
    REAL(wp) ::  h_tr_is                     !<! [W/K] thermal coupling conductance (Thermischer Kopplungsleitwert)
    REAL(wp) ::  h_tr_ms                     !<! [W/K] Heat transfer conductance term (got with h_tr_em the thermal mass)
    REAL(wp) ::  h_tr_op                     !<! [W/K] heat transfer coefficient of opaque components (assumption: got all thermal mass) contains of h_tr_em and h_tr_ms
    REAL(wp) ::  h_tr_w                      !<! [W/K] heat transfer coefficient of doors, windows, curtain walls and glazed walls (assumption: thermal mass=0)
    REAL(wp) ::  h_ve                        !<! [W/K] heat transfer of ventilation
    REAL(wp) ::  initial_indoor_temperature  !< namelist parameter
    REAL(wp) ::  net_sw_in                   !< net short-wave radiation (in - out; was i_global --> CORRECT?)
    REAL(wp) ::  phi_hc_nd                   !<! [W] heating demand and/or cooling demand
    REAL(wp) ::  phi_hc_nd_10                !<! [W] heating demand and/or cooling demand for heating or cooling 
    REAL(wp) ::  phi_hc_nd_ac                !<! [W] actual heating demand and/or cooling demand
    REAL(wp) ::  phi_hc_nd_un                !<! [W] unlimited heating demand and/or cooling demand which is necessary to reach the demanded required temperature (heating is positive, cooling is negative) 
    REAL(wp) ::  phi_ia                      !< [W] internal air load = internal loads * 0.5, Eq. (C.1)
    REAL(wp) ::  phi_m                       !<! [W] mass specific thermal load (internal and external)
    REAL(wp) ::  phi_mtot                    !<! [W] total mass specific thermal load (internal and external)
    REAL(wp) ::  phi_sol                     !< [W] solar loads
    REAL(wp) ::  phi_st                      !<! [W] mass specific thermal load implied non thermal mass 
!    REAL(wp) ::  q_emission                  !< emissions, in first version = 0, option for second part of the project
    REAL(wp) ::  q_wall_win                  !< heat flux from indoor into wall/window
    REAL(wp) ::  q_waste_heat                !< waste heat, sum of waste heat over the roof to Palm
!    REAL(wp) ::  q_waste_heat_bldg           !< [W/building] waste heat of the complete building, in Palm sum of all indoor_model-calculations
    REAL(wp) ::  schedule_d                  !< activation for internal loads (low or high + low)
    REAL(wp) ::  skip_time_do_indoor = 0.0_wp  !< [s] Indoor model is not called before this time
    REAL(wp) ::  theta_air                   !<! [degree_C] air temperature of the RC-node
    REAL(wp) ::  theta_air_0                 !<! [degree_C] air temperature of the RC-node in equilibrium
    REAL(wp) ::  theta_air_10                !<! [degree_C] air temperature of the RC-node from a heating capacity of 10 W/m2
    REAL(wp) ::  theta_air_ac                !< [degree_C] actual room temperature after heating/cooling
    REAL(wp) ::  theta_air_set               !< [degree_C] Setpoint_temperature for the room
    REAL(wp) ::  theta_m                     !<! [degree_C} inner temperature of the RC-node
    REAL(wp) ::  theta_m_t                   !<! [degree_C] (Fictive) component temperature timestep
    REAL(wp) ::  theta_m_t_prev              !< [degree_C] (Fictive) component temperature previous timestep (do not change)
    REAL(wp) ::  theta_op                    !< [degree_C] operative temperature
    REAL(wp) ::  theta_s                     !<! [degree_C] surface temperature of the RC-node
    REAL(wp) ::  time_indoor = 0.0_wp        !< [s] time since last call of indoor model
!    REAL(wp) ::  time_utc_hour               !< Time in hours per day (UTC)
    
    REAL(wp) ::  f_sr                        !< [-] factor surface reduction
    REAL(wp) ::  f_cei                       !< [-] ceiling reduction factor
    REAL(wp) ::  ngs                         !< [m2] netto ground surface
    
    REAL(wp), PARAMETER ::  params_f_f               = 0.3_wp      !< [-] frame ratio chap. 8.3.2.1.1 for buildings with mostly cooling 2.0_wp
    REAL(wp), PARAMETER ::  params_f_w               = 0.9_wp      !< [-] correction factor (fuer nicht senkrechten Stahlungseinfall DIN 4108-2 chap.8, (hier konstant, keine Winkelabhängigkeit) 
    REAL(wp), PARAMETER ::  params_f_win             = 0.5_wp      !< [-] proportion of window area, Database A_win aus Datenbank 27 window_area_per_facade_percent
    REAL(wp), PARAMETER ::  params_solar_protection  = 300.0_wp    !< [W/m2] chap. G.5.3.1 sun protection closed, if the radiation on facade exceeds this value
    REAL(wp), PARAMETER ::  params_waste_heat_c      = 4.0_wp      !< [-] anthropogenic heat outputs for cooling e.g. 4 for KKM with COP = 3
    REAL(wp), PARAMETER ::  params_waste_heat_h      = 1.111_wp    !< [-] anthropogenic heat outputs for heating e.g. 1 / 0.9 = 1.111111 for combustion with eta = 0.9 or -3 for WP with COP = 4
    REAL(wp), PARAMETER ::  h_is                     = 3.45_wp     !< [W/(m^2 K)]  h_is = 3.45 between surface and air (chap. 7.2.2.2)
    REAL(wp), PARAMETER ::  h_ms                     = 9.1_wp      !< [W/K] h_ms = 9.10 W / (m2 K) between component and surface (chap. 12.2.2)

    
    
    SAVE


    PRIVATE
    
!
!-- Add INTERFACES that must be available to other modules
    PUBLIC im_init, im_main_heatcool, im_parin, im_define_netcdf_grid,          &
           im_check_data_output, im_data_output_3d, im_check_parameters
    

!
!-- Add VARIABLES that must be available to other modules
    PUBLIC dt_indoor, skip_time_do_indoor, time_indoor

!
!-- PALM interfaces:
!-- Data output checks for 2D/3D data to be done in check_parameters
     INTERFACE im_check_data_output
        MODULE PROCEDURE im_check_data_output
     END INTERFACE im_check_data_output
!
!-- Input parameter checks to be done in check_parameters
     INTERFACE im_check_parameters
        MODULE PROCEDURE im_check_parameters
     END INTERFACE im_check_parameters
!
!-- Data output of 3D data
     INTERFACE im_data_output_3d
        MODULE PROCEDURE im_data_output_3d
     END INTERFACE im_data_output_3d

!
!-- Definition of data output quantities
     INTERFACE im_define_netcdf_grid
        MODULE PROCEDURE im_define_netcdf_grid
     END INTERFACE im_define_netcdf_grid
! 
! !
! !-- Output of information to the header file
!     INTERFACE im_header
!        MODULE PROCEDURE im_header
!     END INTERFACE im_header
!
!-- Calculations for indoor temperatures  
    INTERFACE im_calc_temperatures
       MODULE PROCEDURE im_calc_temperatures
    END INTERFACE im_calc_temperatures
!
!-- Initialization actions  
    INTERFACE im_init
       MODULE PROCEDURE im_init
    END INTERFACE im_init
!
!-- Main part of indoor model  
    INTERFACE im_main_heatcool
       MODULE PROCEDURE im_main_heatcool
    END INTERFACE im_main_heatcool
!
!-- Reading of NAMELIST parameters
    INTERFACE im_parin
       MODULE PROCEDURE im_parin
    END INTERFACE im_parin

 CONTAINS

!------------------------------------------------------------------------------!
! Description:
! ------------
!< Calculation of the air temperatures and mean radiation temperature
!< This is basis for the operative temperature
!< Based on a Crank-Nicholson scheme with a timestep of a hour
!------------------------------------------------------------------------------!
 SUBROUTINE im_calc_temperatures ( i, j, k, indoor_wall_window_temperature,    &
                                   near_facade_temperature, phi_hc_nd_dummy )
 
    USE arrays_3d,                                                             &
        ONLY:  pt
    
    
    IMPLICIT NONE
    
    
    INTEGER(iwp) ::  i
    INTEGER(iwp) ::  j
    INTEGER(iwp) ::  k
    
    REAL(wp) ::  indoor_wall_window_temperature  !< weighted temperature of innermost wall/window layer
    REAL(wp) ::  near_facade_temperature
    REAL(wp) ::  phi_hc_nd_dummy
   

    !< Calculation of total mass specific thermal load (internal and external)
    phi_mtot = ( phi_m + h_tr_em * indoor_wall_window_temperature              &
                       + h_tr_3  * ( phi_st + h_tr_w * pt(k,j,i)               &
                                            + h_tr_1 *                         &
                                               ( ( ( phi_ia + phi_hc_nd_dummy ) / h_ve )  &
                                                 + near_facade_temperature )   &
                                   ) / h_tr_2                                  &
               )                                                                !< [degree_C] Eq. (C.5)
    
    !< Calculation of component temperature at factual timestep
    theta_m_t = ( ( theta_m_t_prev                                               &
                    * ( ( c_m / 3600.0_wp ) - 0.5_wp * ( h_tr_3 + h_tr_em ) ) + phi_mtot &
                  )                                                              &
                  /   ( ( c_m / 3600.0_wp ) + 0.5_wp * ( h_tr_3 + h_tr_em ) )            &
                )                                                               !< [degree_C] Eq. (C.4)

    !< Calculation of mean inner temperature for the RC-node in actual timestep
    theta_m = ( theta_m_t + theta_m_t_prev ) * 0.5_wp                              !< [degree_C] Eq. (C.9)
    
    !< Calculation of mean surface temperature of the RC-node in actual timestep
    theta_s = ( (   h_tr_ms * theta_m + phi_st + h_tr_w * pt(k,j,i)                         &
                  + h_tr_1  * ( near_facade_temperature + ( phi_ia + phi_hc_nd_dummy ) / h_ve ) &
                )                                                                           &
                / ( h_tr_ms + h_tr_w + h_tr_1 )                                             &
              )                                                                 !< [degree_C] Eq. (C.10)
    
    !< Calculation of the air temperature of the RC-node
    theta_air = ( h_tr_is * theta_s + h_ve * near_facade_temperature         &
                                    + phi_ia + phi_hc_nd_dummy ) / ( h_tr_is + h_ve ) !< [degree_C] Eq. (C.11)

 END SUBROUTINE im_calc_temperatures

!------------------------------------------------------------------------------!
! Description:
! ------------
!> Initialization of the indoor model.
!> Static information are calculated here, e.g. building parameters and
!> geometrical information, everything that doesn't change in time.
!
!-- Input values
!-- Input datas from Palm, M4
!     i_global             -->  net_sw_in                         !global radiation [W/m2]
!     theta_e              -->  pt(k,j,i)                         !undisturbed outside temperature, 1. PALM volume, for windows
!     theta_sup = theta_f  -->  surf_usm_h%pt_10cm(m)
!                               surf_usm_v(l)%pt_10cm(m)   !Air temperature, facade near (10cm) air temperature from 1. Palm volume
!     theta_node           -->  t_wall_h(nzt_wall,m)
!                               t_wall_v(l)%t(nzt_wall,m)         !Temperature of innermost wall layer, for opaque wall
!------------------------------------------------------------------------------!
 SUBROUTINE im_init
  
    USE arrays_3d,                                                             &
        ONLY:  dzw

    USE control_parameters,                                                    &
        ONLY:  message_string

    USE indices,                                                               &
        ONLY:  nxl, nxr, nyn, nys, nzb, nzt, wall_flags_0

    USE grid_variables,                                                        &
        ONLY:  dx, dy

    USE pegrid

    USE surface_mod,                                                           &
        ONLY:  surf_usm_h, surf_usm_v
        
    USE urban_surface_mod,                                                     &
        ONLY:  building_pars, building_type

    IMPLICIT NONE

    INTEGER(iwp) ::  bt   !< local building type
    INTEGER(iwp) ::  i    !< running index along x-direction
    INTEGER(iwp) ::  j    !< running index along y-direction
    INTEGER(iwp) ::  k    !< running index along z-direction
    INTEGER(iwp) ::  l    !< running index for surface-element orientation
    INTEGER(iwp) ::  m    !< running index surface elements
    INTEGER(iwp) ::  n    !< building index
    INTEGER(iwp) ::  nb   !< building index

    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  build_ids           !< building IDs on entire model domain
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  build_ids_final     !< building IDs on entire model domain, 
                                                                    !< multiple occurences are sorted out 
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  build_ids_final_tmp !< temporary array used for resizing
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  build_ids_l         !< building IDs on local subdomain
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  build_ids_l_tmp     !< temporary array used to resize array of building IDs
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  displace_dum        !< displacements of start addresses, used for MPI_ALLGATHERV
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  k_max_l             !< highest vertical index of a building on subdomain
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  k_min_l             !< lowest vertical index of a building on subdomain
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  n_fa                !< counting array
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  num_facades_h       !< dummy array used for summing-up total number of 
                                                                    !< horizontal facade elements
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  num_facades_v       !< dummy array used for summing-up total number of 
                                                                    !< vertical facade elements
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  receive_dum_h       !< dummy array used for MPI_ALLREDUCE  
    INTEGER(iwp), DIMENSION(:), ALLOCATABLE ::  receive_dum_v       !< dummy array used for MPI_ALLREDUCE  

    INTEGER(iwp), DIMENSION(0:numprocs-1) ::  num_buildings         !< number of buildings with different ID on entire model domain
    INTEGER(iwp), DIMENSION(0:numprocs-1) ::  num_buildings_l       !< number of buildings with different ID on local subdomain
    
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  volume         !< total building volume at each discrete height level
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  volume_l       !< total building volume at each discrete height level,
                                                           !< on local subdomain

    IF ( debug_output )  CALL debug_message( 'im_init', 'start' )

!
!-- Initializing of indoor model is only possible if buildings can be 
!-- distinguished by their IDs.
    IF ( .NOT. building_id_f%from_file )  THEN
       message_string = 'Indoor model requires information about building_id'
       CALL message( 'im_init', 'PA0999', 1, 2, 0, 6, 0  )
    ENDIF
!
!-- Determine number of different building IDs on local subdomain.
    num_buildings_l = 0
    num_buildings   = 0
    ALLOCATE( build_ids_l(1) )
    DO  i = nxl, nxr
       DO  j = nys, nyn
          IF ( building_id_f%var(j,i) /= building_id_f%fill )  THEN
             IF ( num_buildings_l(myid) > 0 )  THEN
                IF ( ANY( building_id_f%var(j,i) .EQ.  build_ids_l ) )  THEN 
                   CYCLE
                ELSE
                   num_buildings_l(myid) = num_buildings_l(myid) + 1
!
!--                Resize array with different local building ids
                   ALLOCATE( build_ids_l_tmp(1:SIZE(build_ids_l)) )
                   build_ids_l_tmp = build_ids_l
                   DEALLOCATE( build_ids_l )
                   ALLOCATE( build_ids_l(1:num_buildings_l(myid)) )
                   build_ids_l(1:num_buildings_l(myid)-1) =                 &
                               build_ids_l_tmp(1:num_buildings_l(myid)-1)
                   build_ids_l(num_buildings_l(myid)) = building_id_f%var(j,i)
                   DEALLOCATE( build_ids_l_tmp )
                ENDIF
!
!--          First occuring building id on PE 
             ELSE 
                num_buildings_l(myid) = num_buildings_l(myid) + 1
                build_ids_l(1) = building_id_f%var(j,i)
             ENDIF
          ENDIF
       ENDDO
    ENDDO
!
!-- Determine number of building IDs for the entire domain. (Note, building IDs
!-- can appear multiple times as buildings might be distributed over several
!-- PEs.) 
#if defined( __parallel ) 
    CALL MPI_ALLREDUCE( num_buildings_l, num_buildings, numprocs,              &
                        MPI_INTEGER, MPI_SUM, comm2d, ierr ) 
#else
    num_buildings = num_buildings_l
#endif
    ALLOCATE( build_ids(1:SUM(num_buildings)) )
!
!-- Gather building IDs. Therefore, first, determine displacements used 
!-- required for MPI_GATHERV call.
    ALLOCATE( displace_dum(0:numprocs-1) )
    displace_dum(0) = 0
    DO i = 1, numprocs-1
       displace_dum(i) = displace_dum(i-1) + num_buildings(i-1)
    ENDDO

#if defined( __parallel ) 
    CALL MPI_ALLGATHERV( build_ids_l(1:num_buildings_l(myid)),                 &
                         num_buildings(myid),                                  &
                         MPI_INTEGER,                                          &
                         build_ids,                                            &
                         num_buildings,                                        &
                         displace_dum,                                         & 
                         MPI_INTEGER,                                          &
                         comm2d, ierr )   

    DEALLOCATE( displace_dum )

#else
    build_ids = build_ids_l
#endif
!
!-- Note: in parallel mode, building IDs can occur mutliple times, as 
!-- each PE has send its own ids. Therefore, sort out building IDs which 
!-- appear multiple times. 
    num_build = 0
    DO  n = 1, SIZE(build_ids)

       IF ( ALLOCATED(build_ids_final) )  THEN
          IF ( ANY( build_ids(n) .EQ. build_ids_final ) )  THEN    !FK: Warum ANY?, Warum .EQ.? --> s.o
             CYCLE
          ELSE
             num_build = num_build + 1
!
!--          Resize
             ALLOCATE( build_ids_final_tmp(1:num_build) )
             build_ids_final_tmp(1:num_build-1) = build_ids_final(1:num_build-1)
             DEALLOCATE( build_ids_final )
             ALLOCATE( build_ids_final(1:num_build) )
             build_ids_final(1:num_build-1) = build_ids_final_tmp(1:num_build-1)
             build_ids_final(num_build) = build_ids(n)
             DEALLOCATE( build_ids_final_tmp )
          ENDIF             
       ELSE
          num_build = num_build + 1
          ALLOCATE( build_ids_final(1:num_build) )
          build_ids_final(num_build) = build_ids(n)
       ENDIF
    ENDDO

!
!-- Allocate building-data structure array. Note, this is a global array
!-- and all building IDs on domain are known by each PE. Further attributes, 
!-- e.g. height-dependent arrays, however, are only allocated on PEs where 
!-- the respective building is present (in order to reduce memory demands).
    ALLOCATE( buildings(1:num_build) )

!
!-- Store building IDs and check if building with certain ID is present on
!-- subdomain. 
    DO  nb = 1, num_build
       buildings(nb)%id = build_ids_final(nb)

       IF ( ANY( building_id_f%var(nys:nyn,nxl:nxr) == buildings(nb)%id ) )    &
          buildings(nb)%on_pe = .TRUE.
    ENDDO 
!
!-- Determine the maximum vertical dimension occupied by each building. 
    ALLOCATE( k_min_l(1:num_build) )
    ALLOCATE( k_max_l(1:num_build) )
    k_min_l = nzt + 1
    k_max_l = 0    

    DO  i = nxl, nxr
       DO  j = nys, nyn
          IF ( building_id_f%var(j,i) /= building_id_f%fill )  THEN
             nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ),    &
                         DIM = 1 )
             DO  k = nzb+1, nzt+1
!
!--             Check if grid point belongs to a building. 
                IF ( BTEST( wall_flags_0(k,j,i), 6 ) )  THEN
                   k_min_l(nb) = MIN( k_min_l(nb), k )
                   k_max_l(nb) = MAX( k_max_l(nb), k )
                ENDIF

             ENDDO
          ENDIF
       ENDDO
    ENDDO

    DO nb = 1, num_build
#if defined( __parallel ) 
       CALL MPI_ALLREDUCE( k_min_l(nb), buildings(nb)%kb_min, 1, MPI_INTEGER,  &
                           MPI_MIN, comm2d, ierr )
       CALL MPI_ALLREDUCE( k_max_l(nb), buildings(nb)%kb_max, 1, MPI_INTEGER,  &
                           MPI_MAX, comm2d, ierr )
#else
       buildings(nb)%kb_min = k_min_l(nb)
       buildings(nb)%kb_max = k_max_l(nb)
#endif

    ENDDO 

    DEALLOCATE( k_min_l )
    DEALLOCATE( k_max_l )
!
!-- Calculate building height.
    DO  nb = 1, num_build
       buildings(nb)%building_height = 0.0_wp
       DO  k = buildings(nb)%kb_min, buildings(nb)%kb_max
          buildings(nb)%building_height = buildings(nb)%building_height        &
                                        + dzw(k)
       ENDDO
    ENDDO
!
!-- Calculate building volume
    DO  nb = 1, num_build
!
!--    Allocate temporary array for summing-up building volume
       ALLOCATE( volume(buildings(nb)%kb_min:buildings(nb)%kb_max)   )
       ALLOCATE( volume_l(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       volume   = 0.0_wp
       volume_l = 0.0_wp
!
!--    Calculate building volume per height level on each PE where 
!--    these building is present. 
       IF ( buildings(nb)%on_pe )  THEN
          ALLOCATE( buildings(nb)%volume(buildings(nb)%kb_min:buildings(nb)%kb_max)   )
          ALLOCATE( buildings(nb)%vol_frac(buildings(nb)%kb_min:buildings(nb)%kb_max) )
          buildings(nb)%volume   = 0.0_wp
          buildings(nb)%vol_frac = 0.0_wp
          
          IF ( ANY( building_id_f%var(nys:nyn,nxl:nxr) == buildings(nb)%id ) ) &
          THEN
             DO  i = nxl, nxr
                DO  j = nys, nyn
                   DO  k = buildings(nb)%kb_min, buildings(nb)%kb_max
                      IF ( building_id_f%var(j,i) /= building_id_f%fill )      &
                         volume_l(k) = volume_l(k) + dx * dy * dzw(k)
                   ENDDO
                ENDDO
             ENDDO
          ENDIF
       ENDIF
!
!--    Sum-up building volume from all subdomains
#if defined( __parallel ) 
       CALL MPI_ALLREDUCE( volume_l, volume, SIZE(volume), MPI_REAL, MPI_SUM,  &
                           comm2d, ierr )
#else
       volume = volume_l
#endif
!
!--    Save total building volume as well as local fraction on volume on 
!--    building data structure.
       IF ( ALLOCATED( buildings(nb)%volume ) )  buildings(nb)%volume = volume
!
!--    Determine fraction of local on total building volume
       IF ( buildings(nb)%on_pe )  buildings(nb)%vol_frac = volume_l / volume
!
!--    Calculate total building volume
       IF ( ALLOCATED( buildings(nb)%volume ) )                                &
          buildings(nb)%vol_tot = SUM( buildings(nb)%volume )
       
       DEALLOCATE( volume   )
       DEALLOCATE( volume_l )

    ENDDO

!
!-- Allocate arrays for indoor temperature.  
    DO  nb = 1, num_build
       IF ( buildings(nb)%on_pe )  THEN
          ALLOCATE( buildings(nb)%t_in(buildings(nb)%kb_min:buildings(nb)%kb_max)   )
          ALLOCATE( buildings(nb)%t_in_l(buildings(nb)%kb_min:buildings(nb)%kb_max) )
          buildings(nb)%t_in   = 0.0_wp
          buildings(nb)%t_in_l = 0.0_wp
       ENDIF
    ENDDO
!
!-- Allocate arrays for number of facades per height level. Distinguish between
!-- horizontal and vertical facades. 
    DO  nb = 1, num_build
       IF ( buildings(nb)%on_pe )  THEN
          ALLOCATE( buildings(nb)%num_facade_h(buildings(nb)%kb_min:buildings(nb)%kb_max) )
          ALLOCATE( buildings(nb)%num_facade_v(buildings(nb)%kb_min:buildings(nb)%kb_max) )

          buildings(nb)%num_facade_h = 0
          buildings(nb)%num_facade_v = 0
       ENDIF
    ENDDO
!
!-- Determine number of facade elements per building on local subdomain.
!-- Distinguish between horizontal and vertical facade elements.
!
!-- Horizontal facades
    buildings(:)%num_facades_per_building_h_l = 0
    DO  m = 1, surf_usm_h%ns
!
!--    For the current facade element determine corresponding building index.
!--    First, obtain j,j,k indices of the building. Please note the
!--    offset between facade/surface element and building location (for 
!--    horizontal surface elements the horizontal offsets are zero).
       i = surf_usm_h%i(m) + surf_usm_h%ioff
       j = surf_usm_h%j(m) + surf_usm_h%joff
       k = surf_usm_h%k(m) + surf_usm_h%koff
!
!--    Determine building index and check whether building is on PE
       nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ), DIM = 1 )
       IF ( buildings(nb)%on_pe )  THEN
!
!--       Count number of facade elements at each height level.
          buildings(nb)%num_facade_h(k) = buildings(nb)%num_facade_h(k) + 1 
!
!--       Moreover, sum up number of local facade elements per building.
          buildings(nb)%num_facades_per_building_h_l =                         &
                                buildings(nb)%num_facades_per_building_h_l + 1
       ENDIF
    ENDDO
!
!-- Vertical facades
    buildings(:)%num_facades_per_building_v_l = 0
    DO  l = 0, 3
       DO  m = 1, surf_usm_v(l)%ns
!
!--       For the current facade element determine corresponding building index.
!--       First, obtain j,j,k indices of the building. Please note the
!--       offset between facade/surface element and building location (for 
!--       vertical surface elements the vertical offsets are zero).
          i = surf_usm_v(l)%i(m) + surf_usm_v(l)%ioff
          j = surf_usm_v(l)%j(m) + surf_usm_v(l)%joff
          k = surf_usm_v(l)%k(m) + surf_usm_v(l)%koff

          nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ),        &
                       DIM = 1 )
          IF ( buildings(nb)%on_pe )  THEN
             buildings(nb)%num_facade_v(k) = buildings(nb)%num_facade_v(k) + 1 
             buildings(nb)%num_facades_per_building_v_l =                      &
                                buildings(nb)%num_facades_per_building_v_l + 1
          ENDIF
       ENDDO
    ENDDO

!
!-- Determine total number of facade elements per building and assign number to 
!-- building data type.
    DO  nb = 1, num_build
!
!--    Allocate dummy array used for summing-up facade elements. 
!--    Please note, dummy arguments are necessary as building-date type
!--    arrays are not necessarily allocated on all PEs.
       ALLOCATE( num_facades_h(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       ALLOCATE( num_facades_v(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       ALLOCATE( receive_dum_h(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       ALLOCATE( receive_dum_v(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       num_facades_h = 0
       num_facades_v = 0
       receive_dum_h = 0
       receive_dum_v = 0

       IF ( buildings(nb)%on_pe )  THEN
          num_facades_h = buildings(nb)%num_facade_h
          num_facades_v = buildings(nb)%num_facade_v
       ENDIF

#if defined( __parallel ) 
       CALL MPI_ALLREDUCE( num_facades_h,                                      &
                           receive_dum_h,                                      &
                           buildings(nb)%kb_max - buildings(nb)%kb_min + 1,    &
                           MPI_INTEGER,                                        &
                           MPI_SUM,                                            &
                           comm2d,                                             &
                           ierr )

       CALL MPI_ALLREDUCE( num_facades_v,                                      &
                           receive_dum_v,                                      &
                           buildings(nb)%kb_max - buildings(nb)%kb_min + 1,    &
                           MPI_INTEGER,                                        &
                           MPI_SUM,                                            &
                           comm2d,                                             &
                           ierr )
       IF ( ALLOCATED( buildings(nb)%num_facade_h ) )                          &  !FK: Was wenn not allocated? --> s.o.
           buildings(nb)%num_facade_h = receive_dum_h
       IF ( ALLOCATED( buildings(nb)%num_facade_v ) )                          &
           buildings(nb)%num_facade_v = receive_dum_v
#else
       buildings(nb)%num_facade_h = num_facades_h
       buildings(nb)%num_facade_v = num_facades_v
#endif
!
!--    Deallocate dummy arrays
       DEALLOCATE( num_facades_h )
       DEALLOCATE( num_facades_v )
       DEALLOCATE( receive_dum_h )
       DEALLOCATE( receive_dum_v )
!
!--    Allocate index arrays which link facade elements with surface-data type.
!--    Please note, no height levels are considered here (information is stored
!--    in surface-data type itself).
       IF ( buildings(nb)%on_pe )  THEN
!
!--       Determine number of facade elements per building.
          buildings(nb)%num_facades_per_building_h = SUM( buildings(nb)%num_facade_h )
          buildings(nb)%num_facades_per_building_v = SUM( buildings(nb)%num_facade_v )
!
!--       Allocate arrays which link the building with the horizontal and vertical
!--       urban-type surfaces. Please note, linking arrays are allocated over all
!--       facade elements, which is required in case a building is located at the
!--       subdomain boundaries, where the building and the corresponding surface
!--       elements are located on different subdomains. 
          ALLOCATE( buildings(nb)%m_h(1:buildings(nb)%num_facades_per_building_h_l) )

          ALLOCATE( buildings(nb)%l_v(1:buildings(nb)%num_facades_per_building_v_l) )
          ALLOCATE( buildings(nb)%m_v(1:buildings(nb)%num_facades_per_building_v_l) )
       ENDIF
!
!--    Determine volume per facade element (vpf)
       IF ( buildings(nb)%on_pe )  THEN
          ALLOCATE( buildings(nb)%vpf(buildings(nb)%kb_min:buildings(nb)%kb_max) )
          
          DO  k = buildings(nb)%kb_min, buildings(nb)%kb_max
             buildings(nb)%vpf(k) = buildings(nb)%volume(k) /                  &
                                    ( buildings(nb)%num_facade_h(k) +          &
                                      buildings(nb)%num_facade_v(k) )
          ENDDO
       ENDIF
    ENDDO
!
!-- Link facade elements with surface data type. 
!-- Allocate array for counting.
    ALLOCATE( n_fa(1:num_build) )
    n_fa = 1

    DO  m = 1, surf_usm_h%ns
       i = surf_usm_h%i(m) + surf_usm_h%ioff
       j = surf_usm_h%j(m) + surf_usm_h%joff

       nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ), DIM = 1 )

       IF ( buildings(nb)%on_pe )  THEN
          buildings(nb)%m_h(n_fa(nb)) = m
          n_fa(nb) = n_fa(nb) + 1  
       ENDIF
    ENDDO

    n_fa = 1
    DO  l = 0, 3
       DO  m = 1, surf_usm_v(l)%ns
          i = surf_usm_v(l)%i(m) + surf_usm_v(l)%ioff
          j = surf_usm_v(l)%j(m) + surf_usm_v(l)%joff

          nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ), DIM = 1 )

          IF ( buildings(nb)%on_pe )  THEN
             buildings(nb)%l_v(n_fa(nb)) = l
             buildings(nb)%m_v(n_fa(nb)) = m
             n_fa(nb) = n_fa(nb) + 1   
          ENDIF
       ENDDO
    ENDDO
    DEALLOCATE( n_fa )

!
!-- Initialize building parameters, first by mean building type. Note,
!-- in this case all buildings have the same type. 
!-- In a second step initialize with building tpyes from static input file, 
!-- where building types can be individual for each building.
    buildings(:)%lambda_layer3    = building_pars(63,building_type)
    buildings(:)%s_layer3         = building_pars(57,building_type)
    buildings(:)%f_c_win          = building_pars(119,building_type)
    buildings(:)%g_value_win      = building_pars(120,building_type)    
    buildings(:)%u_value_win      = building_pars(121,building_type)    
    buildings(:)%air_change_low   = building_pars(122,building_type)    
    buildings(:)%air_change_high  = building_pars(123,building_type)    
    buildings(:)%eta_ve           = building_pars(124,building_type)    
    buildings(:)%factor_a         = building_pars(125,building_type)    
    buildings(:)%factor_c         = building_pars(126,building_type)
    buildings(:)%lambda_at        = building_pars(127,building_type)    
    buildings(:)%theta_int_h_set  = building_pars(118,building_type)    
    buildings(:)%theta_int_c_set  = building_pars(117,building_type)
    buildings(:)%phi_h_max        = building_pars(128,building_type)    
    buildings(:)%phi_c_max        = building_pars(129,building_type)          
    buildings(:)%qint_high        = building_pars(130,building_type)
    buildings(:)%qint_low         = building_pars(131,building_type)
    buildings(:)%height_storey    = building_pars(132,building_type)
    buildings(:)%height_cei_con   = building_pars(133,building_type)
!
!-- Initialize ventilaation load. Please note, building types > 7 are actually
!-- not allowed (check already in urban_surface_mod and netcdf_data_input_mod. 
!-- However, the building data base may be later extended. 
    IF ( building_type ==  1  .OR.  building_type ==  2  .OR.                  &
         building_type ==  3  .OR.  building_type == 10  .OR.                  &
         building_type == 11  .OR.  building_type == 12 )  THEN
       buildings(nb)%ventilation_int_loads = 1
!
!-- Office, building with large windows
    ELSEIF ( building_type ==  4  .OR.  building_type ==  5  .OR.              &
             building_type ==  6  .OR.  building_type ==  7  .OR.              &
             building_type ==  8  .OR.  building_type ==  9)  THEN
       buildings(nb)%ventilation_int_loads = 2
!
!-- Industry, hospitals
    ELSEIF ( building_type == 13  .OR.  building_type == 14  .OR.              &
             building_type == 15  .OR.  building_type == 16  .OR.              &
             building_type == 17  .OR.  building_type == 18 )  THEN
       buildings(nb)%ventilation_int_loads = 3
    ENDIF
!
!-- Initialization of building parameters - level 2
    IF ( building_type_f%from_file )  THEN
       DO  i = nxl, nxr
          DO  j = nys, nyn
              IF ( building_id_f%var(j,i) /= building_id_f%fill )  THEN
                 nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ),    &
                              DIM = 1 )
                 bt = building_type_f%var(j,i)
                 
                 buildings(nb)%lambda_layer3    = building_pars(63,bt)
                 buildings(nb)%s_layer3         = building_pars(57,bt)
                 buildings(nb)%f_c_win          = building_pars(119,bt)
                 buildings(nb)%g_value_win      = building_pars(120,bt)    
                 buildings(nb)%u_value_win      = building_pars(121,bt)    
                 buildings(nb)%air_change_low   = building_pars(122,bt)    
                 buildings(nb)%air_change_high  = building_pars(123,bt)    
                 buildings(nb)%eta_ve           = building_pars(124,bt)    
                 buildings(nb)%factor_a         = building_pars(125,bt)    
                 buildings(nb)%factor_c         = building_pars(126,bt)
                 buildings(nb)%lambda_at        = building_pars(127,bt)    
                 buildings(nb)%theta_int_h_set  = building_pars(118,bt)    
                 buildings(nb)%theta_int_c_set  = building_pars(117,bt)
                 buildings(nb)%phi_h_max        = building_pars(128,bt)    
                 buildings(nb)%phi_c_max        = building_pars(129,bt)          
                 buildings(nb)%qint_high        = building_pars(130,bt)
                 buildings(nb)%qint_low         = building_pars(131,bt)
                 buildings(nb)%height_storey    = building_pars(132,bt)
                 buildings(nb)%height_cei_con   = building_pars(133,bt)                 
!
!--              Initialize ventilaation load. Please note, building types > 7 
!--              are actually not allowed (check already in urban_surface_mod  
!--              and netcdf_data_input_mod. However, the building data base may 
!--              be later extended. 
                 IF ( bt ==  1  .OR.  bt ==  2  .OR.                           &
                      bt ==  3  .OR.  bt == 10  .OR.                           &
                      bt == 11  .OR.  bt == 12 )  THEN
                    buildings(nb)%ventilation_int_loads = 1
!                    
!--              Office, building with large windows
                 ELSEIF ( bt ==  4  .OR.  bt ==  5  .OR.                       &
                          bt ==  6  .OR.  bt ==  7  .OR.                       &
                          bt ==  8  .OR.  bt ==  9)  THEN
                    buildings(nb)%ventilation_int_loads = 2
!
!--              Industry, hospitals
                 ELSEIF ( bt == 13  .OR.  bt == 14  .OR.                       &
                          bt == 15  .OR.  bt == 16  .OR.                       &
                          bt == 17  .OR.  bt == 18 )  THEN
                    buildings(nb)%ventilation_int_loads = 3
                 ENDIF
              ENDIF
           ENDDO
        ENDDO
    ENDIF
!
!-- Initial room temperature [K]
!-- (after first loop, use theta_m_t as theta_m_t_prev)
    theta_m_t_prev = initial_indoor_temperature
!
!-- Initialize indoor temperature. Actually only for output at initial state.
    DO  nb = 1, num_build
       buildings(nb)%t_in(:) = initial_indoor_temperature
    ENDDO

    IF ( debug_output )  CALL debug_message( 'im_init', 'end' )

 END SUBROUTINE im_init


!------------------------------------------------------------------------------!
! Description:
! ------------
!> Main part of the indoor model.
!> Calculation of .... (kanani: Please describe)
!------------------------------------------------------------------------------!
 SUBROUTINE im_main_heatcool

    USE arrays_3d,                                                             &
        ONLY:  ddzw, dzw

    USE date_and_time_mod,                                                     &
        ONLY:  time_utc

    USE grid_variables,                                                        &
        ONLY:  dx, dy

    USE pegrid
    
    USE surface_mod,                                                           &
        ONLY:  ind_veg_wall, ind_wat_win, surf_usm_h, surf_usm_v

    USE urban_surface_mod,                                                     &
        ONLY:  nzt_wall, t_wall_h, t_wall_v, t_window_h, t_window_v,           &
               building_type


    IMPLICIT NONE

    INTEGER(iwp) ::  i    !< index of facade-adjacent atmosphere grid point in x-direction
    INTEGER(iwp) ::  j    !< index of facade-adjacent atmosphere grid point in y-direction
    INTEGER(iwp) ::  k    !< index of facade-adjacent atmosphere grid point in z-direction
    INTEGER(iwp) ::  kk   !< vertical index of indoor grid point adjacent to facade
    INTEGER(iwp) ::  l    !< running index for surface-element orientation
    INTEGER(iwp) ::  m    !< running index surface elements
    INTEGER(iwp) ::  nb   !< running index for buildings
    INTEGER(iwp) ::  fa   !< running index for facade elements of each building

    REAL(wp) ::  indoor_wall_window_temperature   !< weighted temperature of innermost wall/window layer
    REAL(wp) ::  near_facade_temperature          !< outside air temperature 10cm away from facade
    REAL(wp) ::  time_utc_hour                    !< time of day (hour UTC)

    REAL(wp), DIMENSION(:), ALLOCATABLE ::  t_in_l_send   !< dummy send buffer used for summing-up indoor temperature per kk-level
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  t_in_recv     !< dummy recv buffer used for summing-up indoor temperature per kk-level
!
!-- Determine time of day in hours. 
    time_utc_hour = time_utc / 3600.0_wp
!
!-- Following calculations must be done for each facade element.
    DO  nb = 1, num_build
!
!--    First, check whether building is present on local subdomain. 
       IF ( buildings(nb)%on_pe )  THEN
!
!--       Determine daily schedule. 08:00-18:00 = 1, other hours = 0.
!--       Residental Building, panel WBS 70    
          IF ( buildings(nb)%ventilation_int_loads == 1 )  THEN
             IF ( time_utc_hour >= 6.0_wp  .AND.  time_utc_hour <= 8.0_wp )  THEN
                schedule_d = 1
             ELSEIF ( time_utc_hour >= 18.0_wp  .AND.  time_utc_hour <= 23.0_wp )  THEN
                schedule_d = 1
             ELSE
                schedule_d = 0
             ENDIF
          ENDIF
!
!--       Office, building with large windows
          IF ( buildings(nb)%ventilation_int_loads == 2 )  THEN
             IF ( time_utc_hour >= 8.0_wp  .AND.  time_utc_hour <= 18.0_wp )  THEN
                schedule_d = 1
             ELSE
                schedule_d = 0
             ENDIF
          ENDIF
!       
!--       Industry, hospitals
          IF ( buildings(nb)%ventilation_int_loads == 3 )  THEN
             IF ( time_utc_hour >= 6.0_wp  .AND.  time_utc_hour <= 22.0_wp )  THEN
                schedule_d = 1
             ELSE
                schedule_d = 0
             ENDIF
          ENDIF
!
!--       Initialize/reset indoor temperature
          buildings(nb)%t_in_l = 0.0_wp 
!
!--       Horizontal surfaces
          DO  fa = 1, buildings(nb)%num_facades_per_building_h_l
!
!--          Determine index where corresponding surface-type information 
!--          is stored. 
             m = buildings(nb)%m_h(fa)
!
!--          Determine building height level index. 
             kk = surf_usm_h%k(m) + surf_usm_h%koff
!            
!--          Building geometries --> not time-dependent
             facade_element_area      = dx * dy                             !< [m2] surface area per facade element    
             floor_area_per_facade    = buildings(nb)%vpf(kk) * ddzw(kk)    !< [m2] net floor area per facade element       
             indoor_volume_per_facade = buildings(nb)%vpf(kk)               !< [m3] indoor air volume per facade element           
             window_area_per_facade   = surf_usm_h%frac(ind_wat_win,m)  * facade_element_area  !< [m2] window area per facade element
             
! print*, "building_height", building_height
! print*, "num_facades_v_l", buildings(nb)%num_facades_per_building_v_l
! print*, "num_facades_v", buildings(nb)%num_facades_per_building_v
! print*, "kb_min_max", buildings(nb)%kb_min, buildings(nb)%kb_max
! print*, "dzw kk", dzw(kk), kk

             f_cei                    = buildings(nb)%building_height /        &
                                       (buildings(nb)%height_storey-buildings(nb)%height_cei_con) !< [-] factor for ceiling redcution
             ngs                      = buildings(nb)%vpf(kk)/f_cei                    !< [m2] calculation of netto ground surface
             f_sr                     = ngs/floor_area_per_facade                      !< [-] factor for surface reduction
             eff_mass_area            = buildings(nb)%factor_a * ngs    !< [m2] standard values according to Table 12 section 12.3.1.2  (calculate over Eq. (65) according to section 12.3.1.2)
             c_m                      = buildings(nb)%factor_c * ngs    !< [J/K] standard values according to table 12 section 12.3.1.2 (calculate over Eq. (66) according to section 12.3.1.2)
             total_area               = buildings(nb)%lambda_at * floor_area_per_facade   !< [m2] area of all surfaces pointing to zone  Eq. (9) according to section 7.2.2.2

!--          Calculation of heat transfer coefficient for transmission --> not time-dependent
             h_tr_w   = window_area_per_facade * buildings(nb)%u_value_win   !< [W/K] only for windows
             h_tr_is  = total_area * h_is                      !< [W/K] with h_is = 3.45 W / (m2 K) between surface and air, Eq. (9)
             h_tr_ms  = eff_mass_area * h_ms                    !< [W/K] with h_ms = 9.10 W / (m2 K) between component and surface, Eq. (64)
             h_tr_op  = 1.0_wp / ( 1.0_wp / ( ( facade_element_area - window_area_per_facade ) &
                                    * buildings(nb)%lambda_layer3 / buildings(nb)%s_layer3 * 0.5_wp ) + 1.0_wp / h_tr_ms )
             h_tr_em  = 1.0_wp / ( 1.0_wp / h_tr_op - 1.0_wp / h_tr_ms )      !< [W/K] Eq. (63), Section 12.2.2
!
!--          internal air loads dependent on the occupacy of the room
!--          basical internal heat gains (qint_low) with additional internal heat gains by occupancy (qint_high) (0,5*phi_int)
             phi_ia = 0.5_wp * ( ( buildings(nb)%qint_high * schedule_d + buildings(nb)%qint_low )            &
                              * ngs )         !< [W] Eq. (C.1)
!
!--          Airflow dependent on the occupacy of the room
!--          basical airflow (air_change_low) with additional airflow gains by occupancy (air_change_high)
             air_change = ( buildings(nb)%air_change_high * schedule_d + buildings(nb)%air_change_low )  !< [1/h]? 
!
!--          Heat transfer of ventilation 
!--          not less than 0.01 W/K to provide division by 0 in further calculations
!--          with heat capacity of air 0.33 Wh/m2K
             h_ve   = MAX( 0.01_wp , ( air_change * indoor_volume_per_facade *      &
                                    0.33_wp * (1.0_wp - buildings(nb)%eta_ve ) ) )    !< [W/K] from ISO 13789 Eq.(10)

!--          Heat transfer coefficient auxiliary variables
             h_tr_1 = 1.0_wp / ( ( 1.0_wp / h_ve )   + ( 1.0_wp / h_tr_is ) )  !< [W/K] Eq. (C.6)
             h_tr_2 = h_tr_1 + h_tr_w                           !< [W/K] Eq. (C.7)
             h_tr_3 = 1.0_wp / ( ( 1.0_wp / h_tr_2 ) + ( 1.0_wp / h_tr_ms ) )  !< [W/K] Eq. (C.8)
!
!--          Net short-wave radiation through window area (was i_global)
             net_sw_in = surf_usm_h%rad_sw_in(m) - surf_usm_h%rad_sw_out(m)
!
!--          Quantities needed for im_calc_temperatures
             i = surf_usm_h%i(m)
             j = surf_usm_h%j(m)
             k = surf_usm_h%k(m)
             near_facade_temperature = surf_usm_h%pt_10cm(m)
             indoor_wall_window_temperature =                                  &
                  surf_usm_h%frac(ind_veg_wall,m) * t_wall_h(nzt_wall,m)       &
                + surf_usm_h%frac(ind_wat_win,m)  * t_window_h(nzt_wall,m)
!
!--          Solar thermal gains. If net_sw_in larger than sun-protection 
!--          threshold parameter (params_solar_protection), sun protection will 
!--          be activated
             IF ( net_sw_in <= params_solar_protection )  THEN 
                solar_protection_off = 1
                solar_protection_on  = 0 
             ELSE 
                solar_protection_off = 0
                solar_protection_on  = 1 
             ENDIF
!
!--          Calculation of total heat gains from net_sw_in through windows [W] in respect on automatic sun protection 
!--          DIN 4108 - 2 chap.8
             phi_sol = (   window_area_per_facade * net_sw_in * solar_protection_off               &
                         + window_area_per_facade * net_sw_in * buildings(nb)%f_c_win * solar_protection_on )    &
                       * buildings(nb)%g_value_win * ( 1.0_wp - params_f_f ) * params_f_w              !< [W]
!
!--          Calculation of the mass specific thermal load for internal and external heatsources of the inner node
             phi_m   = (eff_mass_area / total_area) * ( phi_ia + phi_sol )          !< [W] Eq. (C.2) with phi_ia=0,5*phi_int
!
!--          Calculation mass specific thermal load implied non thermal mass 
             phi_st  =   ( 1.0_wp - ( eff_mass_area / total_area ) - ( h_tr_w / ( 9.1_wp * total_area ) ) ) &
                       * ( phi_ia + phi_sol )                                       !< [W] Eq. (C.3) with phi_ia=0,5*phi_int
!
!--          Calculations for deriving indoor temperature and heat flux into the wall
!--          Step 1: Indoor temperature without heating and cooling
!--          section C.4.1 Picture C.2 zone 3)
             phi_hc_nd = 0.0_wp
             
             CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                         near_facade_temperature, phi_hc_nd )
!
!--          If air temperature between border temperatures of heating and cooling, assign output variable, then ready   
             IF ( buildings(nb)%theta_int_h_set <= theta_air  .AND.  theta_air <= buildings(nb)%theta_int_c_set )  THEN
                phi_hc_nd_ac = 0.0_wp
                phi_hc_nd    = phi_hc_nd_ac
                theta_air_ac = theta_air
!
!--          Step 2: Else, apply 10 W/m2 heating/cooling power and calculate indoor temperature
!--          again.
             ELSE
!
!--             Temperature not correct, calculation method according to section C4.2
                theta_air_0 = theta_air !< Note temperature without heating/cooling

!--             Heating or cooling?
                IF ( theta_air > buildings(nb)%theta_int_c_set )  THEN
                   theta_air_set = buildings(nb)%theta_int_c_set
                ELSE 
                   theta_air_set = buildings(nb)%theta_int_h_set 
                ENDIF

!--             Calculate the temperature with phi_hc_nd_10 
                phi_hc_nd_10 = 10.0_wp * floor_area_per_facade
                phi_hc_nd    = phi_hc_nd_10
       
                CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                            near_facade_temperature, phi_hc_nd )

                theta_air_10 = theta_air !< Note the temperature with 10 W/m2 of heating
!
   
                phi_hc_nd_un = phi_hc_nd_10 * (theta_air_set - theta_air_0)                        &
                                            / (theta_air_10  - theta_air_0)            !< Eq. (C.13)
                                            
!--             Step 3: With temperature ratio to determine the heating or cooling capacity    
!--             If necessary, limit the power to maximum power
!--             section C.4.1 Picture C.2 zone 2) and 4)
                IF ( buildings(nb)%phi_c_max < phi_hc_nd_un  .AND.  phi_hc_nd_un < buildings(nb)%phi_h_max )  THEN
                   phi_hc_nd_ac = phi_hc_nd_un
                   phi_hc_nd = phi_hc_nd_un    
                ELSE
!--             Step 4: Inner temperature with maximum heating (phi_hc_nd_un positive) or cooling (phi_hc_nd_un negative)
!--             section C.4.1 Picture C.2 zone 1) and 5)
                   IF ( phi_hc_nd_un > 0.0_wp )  THEN
                      phi_hc_nd_ac = buildings(nb)%phi_h_max                                         !< Limit heating
                   ELSE 
                      phi_hc_nd_ac = buildings(nb)%phi_c_max                                         !< Limit cooling
                   ENDIF
                ENDIF
       
                phi_hc_nd = phi_hc_nd_ac   
!
!--             Calculate the temperature with phi_hc_nd_ac (new)
                CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                            near_facade_temperature, phi_hc_nd )

                theta_air_ac = theta_air
       
             ENDIF
!
!--          Update theta_m_t_prev
             theta_m_t_prev = theta_m_t
!
!--          Calculate the operating temperature with weighted mean temperature of air and mean solar temperature
!--          Will be used for thermal comfort calculations 
             theta_op     = 0.3_wp * theta_air_ac + 0.7_wp * theta_s          !< [degree_C] operative Temperature Eq. (C.12)
!
!--          Heat flux into the wall. Value needed in urban_surface_mod to 
!--          calculate heat transfer through wall layers towards the facade
!--          (use c_p * rho_surface to convert [W/m2] into [K m/s])
             q_wall_win = h_tr_ms * ( theta_s - theta_m )                    &
                                    / (   facade_element_area                  &
                                        - window_area_per_facade )
!
!--          Transfer q_wall_win back to USM (innermost wall/window layer)
             surf_usm_h%iwghf_eb(m)        = q_wall_win
             surf_usm_h%iwghf_eb_window(m) = q_wall_win
!
!--          Sum up operational indoor temperature per kk-level. Further below,
!--          this temperature is reduced by MPI to one temperature per kk-level
!--          and building (processor overlapping)
             buildings(nb)%t_in_l(kk) = buildings(nb)%t_in_l(kk) + theta_op
!
!--          Calculation of waste heat
!--          Anthropogenic heat output
             IF ( phi_hc_nd_ac > 0.0_wp )  THEN 
                heating_on = 1
                cooling_on = 0
             ELSE 
                heating_on = 0
                cooling_on = 1
             ENDIF

             q_waste_heat = (phi_hc_nd * (params_waste_heat_h * heating_on + params_waste_heat_c * cooling_on))!< [W/Gebäudemodell] , observe the directional convention in PALM!
             surf_usm_h%waste_heat(m) = q_waste_heat
             
          ENDDO !< Horizontal surfaces loop
!
!--       Vertical surfaces
          DO  fa = 1, buildings(nb)%num_facades_per_building_v_l
!
!--          Determine indices where corresponding surface-type information 
!--          is stored. 
             l = buildings(nb)%l_v(fa)
             m = buildings(nb)%m_v(fa)
!
!--          Determine building height level index. 
             kk = surf_usm_v(l)%k(m) + surf_usm_v(l)%koff
!
!--          (SOME OF THE FOLLOWING (not time-dependent COULD PROBABLY GO INTO A FUNCTION
!--          EXCEPT facade_element_area, EVERYTHING IS CALCULATED EQUALLY)
!--          Building geometries  --> not time-dependent
             IF ( l == 0  .OR. l == 1 ) facade_element_area = dx * dzw(kk)  !< [m2] surface area per facade element
             IF ( l == 2  .OR. l == 3 ) facade_element_area = dy * dzw(kk)  !< [m2] surface area per facade element
             floor_area_per_facade    = buildings(nb)%vpf(kk) * ddzw(kk)    !< [m2] net floor area per facade element       
             indoor_volume_per_facade = buildings(nb)%vpf(kk)               !< [m3] indoor air volume per facade element           
             window_area_per_facade   = surf_usm_v(l)%frac(ind_wat_win,m)  * facade_element_area  !< [m2] window area per facade element

             f_cei                    = buildings(nb)%building_height /        &
                                        (buildings(nb)%height_storey-buildings(nb)%height_cei_con) !< [-] factor for ceiling redcution
             ngs                      = buildings(nb)%vpf(kk)/f_cei                    !< [m2] calculation of netto ground surface
             f_sr                     = ngs/floor_area_per_facade                      !< [-] factor for surface reduction
             eff_mass_area            = buildings(nb)%factor_a * ngs    !< [m2] standard values according to Table 12 section 12.3.1.2  (calculate over Eq. (65) according to section 12.3.1.2)
             c_m                      = buildings(nb)%factor_c * ngs    !< [J/K] standard values according to table 12 section 12.3.1.2 (calculate over Eq. (66) according to section 12.3.1.2)
             total_area               = buildings(nb)%lambda_at * floor_area_per_facade   !< [m2] area of all surfaces pointing to zone  Eq. (9) according to section 7.2.2.2
!
!--          Calculation of heat transfer coefficient for transmission --> not time-dependent
             h_tr_w   = window_area_per_facade * buildings(nb)%u_value_win   !< [W/K] only for windows
             h_tr_is  = total_area * h_is                      !< [W/K] with h_is = 3.45 W / (m2 K) between surface and air, Eq. (9)
             h_tr_ms  = eff_mass_area * h_ms                   !< [W/K] with h_ms = 9.10 W / (m2 K) between component and surface, Eq. (64)
             h_tr_op  = 1.0_wp / ( 1.0_wp / ( ( facade_element_area - window_area_per_facade ) &
                                    * buildings(nb)%lambda_layer3 / buildings(nb)%s_layer3 * 0.5_wp ) + 1.0_wp / h_tr_ms )
             h_tr_em  = 1.0_wp / ( 1.0_wp / h_tr_op - 1.0_wp / h_tr_ms )      !< [W/K] Eq. (63), Section 12.2.2
!
!--          internal air loads dependent on the occupacy of the room
!--          basical internal heat gains (qint_low) with additional internal heat gains by occupancy (qint_high) (0,5*phi_int)
             phi_ia = 0.5_wp * ( ( buildings(nb)%qint_high * schedule_d + buildings(nb)%qint_low )            &
                              * ngs )                      !< [W] Eq. (C.1)
!
!--          Airflow dependent on the occupacy of the room
!--          basical airflow (air_change_low) with additional airflow gains by occupancy (air_change_high)
             air_change = ( buildings(nb)%air_change_high * schedule_d + buildings(nb)%air_change_low )  
!
!--          Heat transfer of ventilation 
!--          not less than 0.01 W/K to provide division by 0 in further calculations
!--          with heat capacity of air 0.33 Wh/m2K
             h_ve   = MAX( 0.01_wp , ( air_change * indoor_volume_per_facade *      &
                                    0.33_wp * (1 - buildings(nb)%eta_ve ) ) )                    !< [W/K] from ISO 13789 Eq.(10)
                                    
!--          Heat transfer coefficient auxiliary variables
             h_tr_1 = 1.0_wp / ( ( 1.0_wp / h_ve )   + ( 1.0_wp / h_tr_is ) )                  !< [W/K] Eq. (C.6)
             h_tr_2 = h_tr_1 + h_tr_w                                           !< [W/K] Eq. (C.7)
             h_tr_3 = 1.0_wp / ( ( 1.0_wp / h_tr_2 ) + ( 1.0_wp / h_tr_ms ) )                  !< [W/K] Eq. (C.8)
!
!--          Net short-wave radiation through window area (was i_global)
             net_sw_in = surf_usm_v(l)%rad_sw_in(m) - surf_usm_v(l)%rad_sw_out(m)
!
!--          Quantities needed for im_calc_temperatures
             i = surf_usm_v(l)%i(m)
             j = surf_usm_v(l)%j(m)
             k = surf_usm_v(l)%k(m)
             near_facade_temperature = surf_usm_v(l)%pt_10cm(m)
             indoor_wall_window_temperature =                                    &
                  surf_usm_v(l)%frac(ind_veg_wall,m) * t_wall_v(l)%t(nzt_wall,m) &
                + surf_usm_v(l)%frac(ind_wat_win,m)  * t_window_v(l)%t(nzt_wall,m)
!
!--          Solar thermal gains. If net_sw_in larger than sun-protection 
!--          threshold parameter (params_solar_protection), sun protection will 
!--          be activated
             IF ( net_sw_in <= params_solar_protection )  THEN 
                solar_protection_off = 1
                solar_protection_on  = 0 
             ELSE 
                solar_protection_off = 0
                solar_protection_on  = 1 
             ENDIF
!
!--          Calculation of total heat gains from net_sw_in through windows [W] in respect on automatic sun protection
!--          DIN 4108 - 2 chap.8
             phi_sol = (   window_area_per_facade * net_sw_in * solar_protection_off               &
                         + window_area_per_facade * net_sw_in * buildings(nb)%f_c_win * solar_protection_on )    &
                       * buildings(nb)%g_value_win * ( 1.0_wp - params_f_f ) * params_f_w
!
!--          Calculation of the mass specific thermal load for internal and external heatsources
             phi_m   = (eff_mass_area / total_area) * ( phi_ia + phi_sol )          !< [W] Eq. (C.2) with phi_ia=0,5*phi_int
!
!--          Calculation mass specific thermal load implied non thermal mass 
             phi_st  =   ( 1.0_wp - ( eff_mass_area / total_area ) - ( h_tr_w / ( 9.1_wp * total_area ) ) ) &
                       * ( phi_ia + phi_sol )                                       !< [W] Eq. (C.3) with phi_ia=0,5*phi_int
!
!--          Calculations for deriving indoor temperature and heat flux into the wall
!--          Step 1: Indoor temperature without heating and cooling
!--          section C.4.1 Picture C.2 zone 3)
             phi_hc_nd = 0.0_wp
             CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                         near_facade_temperature, phi_hc_nd )
!
!--          If air temperature between border temperatures of heating and cooling, assign output variable, then ready  
             IF ( buildings(nb)%theta_int_h_set <= theta_air  .AND.  theta_air <= buildings(nb)%theta_int_c_set )  THEN
                phi_hc_nd_ac = 0.0_wp
                phi_hc_nd    = phi_hc_nd_ac
                theta_air_ac = theta_air
!
!--          Step 2: Else, apply 10 W/m2 heating/cooling power and calculate indoor temperature
!--          again.
             ELSE
!
!--             Temperature not correct, calculation method according to section C4.2
                theta_air_0 = theta_air !< Note temperature without heating/cooling

!--             Heating or cooling?
                IF ( theta_air > buildings(nb)%theta_int_c_set )  THEN
                   theta_air_set = buildings(nb)%theta_int_c_set
                ELSE 
                   theta_air_set = buildings(nb)%theta_int_h_set 
                ENDIF

!--             Calculate the temperature with phi_hc_nd_10
                phi_hc_nd_10 = 10.0_wp * floor_area_per_facade
                phi_hc_nd    = phi_hc_nd_10
       
                CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                            near_facade_temperature, phi_hc_nd )

                theta_air_10 = theta_air !< Note the temperature with 10 W/m2 of heating

                
                phi_hc_nd_un = phi_hc_nd_10 * (theta_air_set - theta_air_0)                        &
                                            / (theta_air_10  - theta_air_0)            !< Eq. (C.13)
!      
!--             Step 3: With temperature ratio to determine the heating or cooling capacity    
!--             If necessary, limit the power to maximum power
!--             section C.4.1 Picture C.2 zone 2) and 4)
                IF ( buildings(nb)%phi_c_max < phi_hc_nd_un  .AND.  phi_hc_nd_un < buildings(nb)%phi_h_max )  THEN
                   phi_hc_nd_ac = phi_hc_nd_un
                   phi_hc_nd = phi_hc_nd_un
                ELSE
!--             Step 4: Inner temperature with maximum heating (phi_hc_nd_un positive) or cooling (phi_hc_nd_un negative)
!--             section C.4.1 Picture C.2 zone 1) and 5)
                   IF ( phi_hc_nd_un > 0.0_wp )  THEN
                      phi_hc_nd_ac = buildings(nb)%phi_h_max                                         !< Limit heating
                   ELSE 
                      phi_hc_nd_ac = buildings(nb)%phi_c_max                                         !< Limit cooling
                   ENDIF
                ENDIF
       
                phi_hc_nd = phi_hc_nd_ac   
!
!--             Calculate the temperature with phi_hc_nd_ac (new)
                CALL im_calc_temperatures ( i, j, k, indoor_wall_window_temperature, &
                                            near_facade_temperature, phi_hc_nd )

                theta_air_ac = theta_air
       
             ENDIF
!
!--          Update theta_m_t_prev
             theta_m_t_prev = theta_m_t
!
!--          Calculate the operating temperature with weighted mean of temperature of air and mean
!--          Will be used for thermal comfort calculations 
             theta_op     = 0.3_wp * theta_air_ac + 0.7_wp * theta_s
!
!--          Heat flux into the wall. Value needed in urban_surface_mod to 
!--          calculate heat transfer through wall layers towards the facade
             q_wall_win = h_tr_ms * ( theta_s - theta_m )                    &
                                    / (   facade_element_area                  &
                                        - window_area_per_facade )
!
!--          Transfer q_wall_win back to USM (innermost wall/window layer)
             surf_usm_v(l)%iwghf_eb(m)        = q_wall_win
             surf_usm_v(l)%iwghf_eb_window(m) = q_wall_win
!
!--          Sum up operational indoor temperature per kk-level. Further below,
!--          this temperature is reduced by MPI to one temperature per kk-level
!--          and building (processor overlapping)
             buildings(nb)%t_in_l(kk) = buildings(nb)%t_in_l(kk) + theta_op

!
!--          Calculation of waste heat
!--          Anthropogenic heat output
             IF ( phi_hc_nd_ac > 0.0_wp )  THEN 
                heating_on = 1
                cooling_on = 0
             ELSE 
                heating_on = 0
                cooling_on = 1
             ENDIF

             q_waste_heat = (phi_hc_nd * (params_waste_heat_h * heating_on + params_waste_heat_c * cooling_on))!< [W/Gebäudemodell] , observe the directional convention in PALM!
             surf_usm_v(l)%waste_heat(m) = q_waste_heat

          ENDDO !< Vertical surfaces loop

       ENDIF !< buildings(nb)%on_pe
    ENDDO !< buildings loop

!
!-- Determine the mean building temperature. 
    DO  nb = 1, num_build
!
!--    Allocate dummy array used for summing-up facade elements. 
!--    Please note, dummy arguments are necessary as building-date type
!--    arrays are not necessarily allocated on all PEs.
       ALLOCATE( t_in_l_send(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       ALLOCATE( t_in_recv(buildings(nb)%kb_min:buildings(nb)%kb_max) )
       t_in_l_send = 0.0_wp
       t_in_recv   = 0.0_wp

       IF ( buildings(nb)%on_pe )  THEN
          t_in_l_send = buildings(nb)%t_in_l
       ENDIF

#if defined( __parallel ) 
       CALL MPI_ALLREDUCE( t_in_l_send,                                        &
                           t_in_recv,                                          &
                           buildings(nb)%kb_max - buildings(nb)%kb_min + 1,    &
                           MPI_REAL,                                           &
                           MPI_SUM,                                            &
                           comm2d,                                             &
                           ierr )

       IF ( ALLOCATED( buildings(nb)%t_in ) )                                  &
           buildings(nb)%t_in = t_in_recv
#else
       IF ( ALLOCATED( buildings(nb)%t_in ) )                                  &
          buildings(nb)%t_in = buildings(nb)%t_in_l
#endif
       IF ( ALLOCATED( buildings(nb)%t_in ) )                                  &
          buildings(nb)%t_in =   buildings(nb)%t_in /                          &
                               ( buildings(nb)%num_facade_h +                  &
                                 buildings(nb)%num_facade_v )
!
!--    Deallocate dummy arrays
       DEALLOCATE( t_in_l_send )
       DEALLOCATE( t_in_recv )

    ENDDO


 END SUBROUTINE im_main_heatcool

!-----------------------------------------------------------------------------!
! Description:
!-------------
!> Check data output for plant canopy model
!-----------------------------------------------------------------------------! 
 SUBROUTINE im_check_data_output( var, unit )
        
    IMPLICIT NONE
    
    CHARACTER (LEN=*) ::  unit   !<
    CHARACTER (LEN=*) ::  var    !<
        
    SELECT CASE ( TRIM( var ) )
    
    
        CASE ( 'im_hf_roof')
           unit = 'W m-2'
        
        CASE ( 'im_hf_wall_win' )
           unit = 'W m-2'
           
        CASE ( 'im_hf_wall_win_waste' )
           unit = 'W m-2'
           
        CASE ( 'im_hf_roof_waste' )
           unit = 'W m-2'
        
        CASE ( 'im_t_indoor' )
           unit = 'K'
        
        CASE DEFAULT
           unit = 'illegal'
           
    END SELECT
    
 END SUBROUTINE


!-----------------------------------------------------------------------------!
! Description:
!-------------
!> Check parameters routine for plant canopy model
!-----------------------------------------------------------------------------! 
 SUBROUTINE im_check_parameters

!!!!   USE control_parameters,
!!!!       ONLY: message_string
       
   IMPLICIT NONE
   
 END SUBROUTINE im_check_parameters

!-----------------------------------------------------------------------------!
! Description:
!-------------
!> Subroutine defining appropriate grid for netcdf variables.
!> It is called from subroutine netcdf.
!-----------------------------------------------------------------------------! 
 SUBROUTINE im_define_netcdf_grid( var, found, grid_x, grid_y, grid_z )

   IMPLICIT NONE
   
   CHARACTER (LEN=*), INTENT(IN)  ::  var
   LOGICAL, INTENT(OUT)           ::  found
   CHARACTER (LEN=*), INTENT(OUT) ::  grid_x
   CHARACTER (LEN=*), INTENT(OUT) ::  grid_y
   CHARACTER (LEN=*), INTENT(OUT) ::  grid_z
   
   found   = .TRUE.
   
!
!-- Check for the grid
    SELECT CASE ( TRIM( var ) )

       CASE ( 'im_hf_roof', 'im_hf_roof_waste' )
          grid_x = 'x'
          grid_y = 'y'
          grid_z = 'zw'
!
!--    Heat fluxes at vertical walls are actually defined on stagged grid, i.e. xu, yv.
       CASE ( 'im_hf_wall_win', 'im_hf_wall_win_waste' )
          grid_x = 'x'
          grid_y = 'y'
          grid_z = 'zu'
          
       CASE ( 'im_t_indoor' )
          grid_x = 'x'
          grid_y = 'y'
          grid_z = 'zw'
          
       CASE DEFAULT
          found  = .FALSE.
          grid_x = 'none'
          grid_y = 'none'
          grid_z = 'none'
    END SELECT
    
 END SUBROUTINE im_define_netcdf_grid

!------------------------------------------------------------------------------!
! Description:
! ------------
!> Subroutine defining 3D output variables
!------------------------------------------------------------------------------!
 SUBROUTINE im_data_output_3d( av, variable, found, local_pf, fill_value,      &
                               nzb_do, nzt_do )

   USE indices
   
   USE kinds
          
   IMPLICIT NONE
   
    CHARACTER (LEN=*) ::  variable !< 

    INTEGER(iwp) ::  av    !< 
    INTEGER(iwp) ::  i     !< 
    INTEGER(iwp) ::  j     !< 
    INTEGER(iwp) ::  k     !< 
    INTEGER(iwp) ::  l     !<
    INTEGER(iwp) ::  m     !< 
    INTEGER(iwp) ::  nb    !< index of the building in the building data structure 
    INTEGER(iwp) ::  nzb_do !< lower limit of the data output (usually 0)
    INTEGER(iwp) ::  nzt_do !< vertical upper limit of the data output (usually nz_do3d)

    
    LOGICAL      ::  found !< 

    REAL(wp), INTENT(IN) ::  fill_value !< value for the _FillValue attribute

    REAL(sp), DIMENSION(nxl:nxr,nys:nyn,nzb_do:nzt_do) ::  local_pf !< 
    
    local_pf = fill_value
    
    found = .TRUE.
    
    SELECT CASE ( TRIM( variable ) )
!
!--     Output of indoor temperature. All grid points within the building are
!--     filled with values, while atmospheric grid points are set to _FillValues.
        CASE ( 'im_t_indoor' )
           IF ( av == 0 ) THEN
              DO  i = nxl, nxr
                 DO  j = nys, nyn
                    IF ( building_id_f%var(j,i) /= building_id_f%fill )  THEN
!
!--                    Determine index of the building within the building data structure. 
                       nb = MINLOC( ABS( buildings(:)%id - building_id_f%var(j,i) ),   &
                                    DIM = 1 )
                       IF ( buildings(nb)%on_pe )  THEN
!
!--                       Write mean building temperature onto output array. Please note,
!--                       in contrast to many other loops in the output, the vertical 
!--                       bounds are determined by the lowest and hightest vertical index
!--                       occupied by the building. 
                          DO  k = buildings(nb)%kb_min, buildings(nb)%kb_max
                             local_pf(i,j,k) = buildings(nb)%t_in(k)
                          ENDDO
                       ENDIF
                    ENDIF
                 ENDDO
              ENDDO
           ENDIF  

        CASE ( 'im_hf_roof' )
           IF ( av == 0 ) THEN
              DO  m = 1, surf_usm_h%ns
                  i = surf_usm_h%i(m) !+ surf_usm_h%ioff
                  j = surf_usm_h%j(m) !+ surf_usm_h%joff
                  k = surf_usm_h%k(m) !+ surf_usm_h%koff
                  local_pf(i,j,k) = surf_usm_h%iwghf_eb(m)
              ENDDO
           ENDIF 
    
        CASE ( 'im_hf_roof_waste' )
           IF ( av == 0 ) THEN
              DO m = 1, surf_usm_h%ns 
                 i = surf_usm_h%i(m) !+ surf_usm_h%ioff
                 j = surf_usm_h%j(m) !+ surf_usm_h%joff
                 k = surf_usm_h%k(m) !+ surf_usm_h%koff
                 local_pf(i,j,k) = surf_usm_h%waste_heat(m)
              ENDDO
           ENDIF                     
       
       CASE ( 'im_hf_wall_win' )
           IF ( av == 0 ) THEN
              DO l = 0, 3
                 DO m = 1, surf_usm_v(l)%ns
                    i = surf_usm_v(l)%i(m) !+ surf_usm_v(l)%ioff
                    j = surf_usm_v(l)%j(m) !+ surf_usm_v(l)%joff
                    k = surf_usm_v(l)%k(m) !+ surf_usm_v(l)%koff
                    local_pf(i,j,k) = surf_usm_v(l)%iwghf_eb(m)
                 ENDDO
              ENDDO
           ENDIF
           
        CASE ( 'im_hf_wall_win_waste' )
           IF ( av == 0 ) THEN
              DO l = 0, 3
                 DO m = 1, surf_usm_v(l)%ns 
                    i = surf_usm_v(l)%i(m) !+ surf_usm_v(l)%ioff
                    j = surf_usm_v(l)%j(m) !+ surf_usm_v(l)%joff
                    k = surf_usm_v(l)%k(m) !+ surf_usm_v(l)%koff
                    local_pf(i,j,k) =  surf_usm_v(l)%waste_heat(m) 
                 ENDDO
              ENDDO
           ENDIF      
    
        CASE DEFAULT
           found = .FALSE.
           
    END SELECT    

 END SUBROUTINE im_data_output_3d          
!------------------------------------------------------------------------------!
! Description:
! ------------
!> Parin for &indoor_parameters for indoor model
!------------------------------------------------------------------------------!
 SUBROUTINE im_parin
    
    USE control_parameters,                                                    &
        ONLY:  indoor_model
    
    IMPLICIT NONE

    CHARACTER (LEN=80) ::  line  !< string containing current line of file PARIN

    NAMELIST /indoor_parameters/  dt_indoor, initial_indoor_temperature

!
!-- Try to find indoor model package
    REWIND ( 11 )
    line = ' '
    DO   WHILE ( INDEX( line, '&indoor_parameters' ) == 0 )
       READ ( 11, '(A)', END=10 )  line
    ENDDO
    BACKSPACE ( 11 )

!
!-- Read user-defined namelist
    READ ( 11, indoor_parameters )
!
!-- Set flag that indicates that the indoor model is switched on
    indoor_model = .TRUE.

!
!--    Activate spinup (maybe later
!        IF ( spinup_time > 0.0_wp )  THEN
!           coupling_start_time = spinup_time
!           end_time = end_time + spinup_time
!           IF ( spinup_pt_mean == 9999999.9_wp )  THEN
!              spinup_pt_mean = pt_surface
!           ENDIF
!           spinup = .TRUE.
!        ENDIF

 10 CONTINUE
    
 END SUBROUTINE im_parin


END MODULE indoor_model_mod