Create a new CFAST model with its first compartment and register it.

A CFAST model must contain at least one compartment, so creation includes the first one. Add materials, further compartments, wall vents and fires with the add_* tools, then use inspect_model and run_model.

Parameters

title : str Title of the simulation. May consist of letters, numbers, and/or symbols and may be up to 50 characters. room_id : str Unique alphanumeric name of the first compartment, referenced later by fires and wall vents. room_width : float Width of the compartment as measured on the X axis from its origin. Default units: m. room_depth : float Depth of the compartment as measured on the Y axis from its origin. Default units: m. room_height : float Height of the compartment as measured on the Z axis from its origin. Default units: m. time_simulation : int, optional Length of time over which the simulation takes place. Default units: s, default value: 900 s. interior_temperature : float, optional Initial ambient temperature inside the structure. Default units: °C, default value: 20 °C. exterior_temperature : float, optional Initial ambient temperature outside the structure. Default units: °C, default value: 20 °C. relative_humidity : float, optional Initial relative humidity, only specified for the interior. Default units: % RH, default value: 50 %.

Returns

str The new model_id, the model summary, and any warnings.

Return a model summary, and optionally the CFAST input file.

Parameters

model_id : str Id of the model to inspect. show_input_file : bool, optional If True, save the model and return the contents of the generated CFAST input (.in) file after the summary. Default value: False.

Returns

str The model summary, optionally followed by the input file.

Run the CFAST simulation for a model and summarize the outputs.

Requires the CFAST executable, resolved via the CFAST environment variable or cfast on the PATH. Results are stored in the registry so get_results can read them without re-running.

Parameters

model_id : str Id of the model to run. timeout : int, optional Maximum CFAST run time. Default units: s, default value: 120 s.

Returns

str A bounded summary of the produced output sets.

Read stored run results for a model (bounded; never a full dump).

Call run_model first. Without a column, returns a small preview (shape, columns, first rows) of the key. With a column, returns min / max / final value and time of max for that column — for example an upper-layer temperature column such as "ULT_1" in the "compartments" output.

Parameters

model_id : str Id of the model whose results to read. key : str Output set, one of: compartments, devices, masses, vents, walls, zone, diagnostics. column : str or None, optional Column name within the key. If None, a bounded preview of the key is returned instead.

Returns

str Either a bounded preview of the key or single-column statistics.

List the on-disk files for a model and their directory.

Use this to locate the input (.in), output (.csv) and log files so you can open them yourself. Files appear once the model is saved or run (run_model, or inspect_model with show_input_file=True); before then the directory is empty.

Parameters

model_id : str Id of the model whose files to locate.

Returns

str The working directory and the names of the files belonging to the model.

Update the simulation environment (scenario and ambient conditions).

A model has a single simulation environment, set at create_model; this changes only the parameters you provide; any left as None is unchanged.

Parameters

model_id : str Id of the model to modify. title : str or None, optional Title of the simulation. May consist of letters, numbers, and/or symbols and may be up to 50 characters. None leaves it unchanged. time_simulation : int or None, optional Length of time over which the simulation takes place. Default units: s. None leaves it unchanged. interior_temperature : float or None, optional Initial ambient temperature inside the structure. Default units: °C. None leaves it unchanged. exterior_temperature : float or None, optional Initial ambient temperature outside the structure. Default units: °C. None leaves it unchanged. relative_humidity : float or None, optional Initial relative humidity, only specified for the interior. Default units: % RH. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a material to a model.

A compartment can reference this material by id for its ceiling, wall or floor surfaces, or a target.

Parameters

model_id : str Id of the model to modify, as returned by create_model. id : str A one-word (no more than 8 characters) unique identifier for the material, used in other inputs to reference it. material : str A descriptive name for the material. conductivity : float Thermal conductivity for the material. Default units: W/(m·K). density : float Density for the material. Default units: kg/m³. specific_heat : float Specific heat for the material. Default units: kJ/(kg·K). thickness : float Thickness of the material. Default units: m. emissivity : float, optional Emissivity of the material surface; the fraction of radiation that is absorbed by the material. Default units: none, default value: 0.9.

Returns

str Confirmation, the updated model summary, and any warnings.

Update thermophysical properties of an existing material.

Selects the material by material_id and changes only the parameters you provide; any left as None is unchanged. The material's id is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. material_id : str Id of the material to update. conductivity : float or None, optional Thermal conductivity for the material. Default units: W/(m·K). None leaves it unchanged. density : float or None, optional Density for the material. Default units: kg/m³. None leaves it unchanged. specific_heat : float or None, optional Specific heat for the material. Default units: kJ/(kg·K). None leaves it unchanged. thickness : float or None, optional Thickness of the material. Default units: m. None leaves it unchanged. emissivity : float or None, optional Emissivity of the material surface; the fraction of radiation that is absorbed by the material. Default units: none. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a compartment to a model.

Any surface material id given (ceiling, wall, floor) must already exist in the model — add it first with add_material. If the thermophysical properties of a surface are not included, CFAST treats it as adiabatic (no heat transfer).

Parameters

model_id : str Id of the model to modify. id : str Unique alphanumeric name of the compartment, referenced later by fires and wall vents. width : float Width of the compartment as measured on the X axis from its origin. Default units: m. depth : float Depth of the compartment as measured on the Y axis from its origin. Default units: m. height : float Height of the compartment as measured on the Z axis from its origin. Default units: m. ceiling_mat_id : str or None, optional Material id defining the ceiling surface. Default value: Off. ceiling_thickness : float or None, optional Thickness of the ceiling surface. Default units: m, default value: thickness of the material. wall_mat_id : str or None, optional Material id defining the wall surfaces. Default value: Off. wall_thickness : float or None, optional Thickness of the wall surfaces. Default units: m, default value: thickness of the material. floor_mat_id : str or None, optional Material id defining the floor surface. Default value: Off. floor_thickness : float or None, optional Thickness of the floor surface. Default units: m, default value: thickness of the material. origin_x : float, optional Absolute x coordinate of the lower, left, front corner of the room. Negative values are not allowed. Default units: m, default value: 0.0 m. origin_y : float, optional Absolute y coordinate of the lower, left, front corner of the room. Negative values are not allowed. Default units: m, default value: 0.0 m. origin_z : float, optional Height of the floor of the compartment with respect to the station elevation. Default units: m, default value: 0.0 m.

Returns

str Confirmation, the updated model summary, and any warnings.

Update parameters of an existing compartment.

Selects the compartment by comp_id and changes only the parameters you provide; any left as None is unchanged. Use this to attach surface materials to the first compartment (created bare by create_model) or to revise any compartment later. Any surface material id given must already exist in the model — add it first with add_material. The compartment's id itself is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. comp_id : str Id of the compartment to update. width : float or None, optional New width of the compartment as measured on the X axis from its origin. Default units: m. None leaves it unchanged. depth : float or None, optional New depth of the compartment as measured on the Y axis from its origin. Default units: m. None leaves it unchanged. height : float or None, optional New height of the compartment as measured on the Z axis from its origin. Default units: m. None leaves it unchanged. ceiling_mat_id : str or None, optional Material id defining the ceiling surface. None leaves it unchanged. ceiling_thickness : float or None, optional Thickness of the ceiling surface. Default units: m. None leaves it unchanged. wall_mat_id : str or None, optional Material id defining the wall surfaces. None leaves it unchanged. wall_thickness : float or None, optional Thickness of the wall surfaces. Default units: m. None leaves it unchanged. floor_mat_id : str or None, optional Material id defining the floor surface. None leaves it unchanged. floor_thickness : float or None, optional Thickness of the floor surface. Default units: m. None leaves it unchanged. origin_x : float or None, optional Absolute x coordinate of the lower, left, front corner of the room. Negative values are not allowed. Default units: m. None leaves it unchanged. origin_y : float or None, optional Absolute y coordinate of the lower, left, front corner of the room. Negative values are not allowed. Default units: m. None leaves it unchanged. origin_z : float or None, optional Height of the floor of the compartment with respect to the station elevation. Default units: m. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a wall vent (door, window or opening) between two compartments.

Wall vents connect compartments that physically overlap in elevation, or connect a compartment to the outside. Both compartments must already exist in the model; comp_b may be "OUTSIDE" to vent to the exterior. All specifications of the vent are made relative to the floor of the first compartment.

Parameters

model_id : str Id of the model to modify. id : str Unique name of the vent. comp_a : str First compartment id; the reference for all vent specifications. comp_b : str Second compartment id, or "OUTSIDE" for the exterior. bottom : float Position of the bottom of the opening relative to the floor of the first compartment. Default units: m. height : float Height of the opening relative to the bottom of the opening. Default units: m. width : float Width of the opening. Default units: m. face : str The wall on which the vent is positioned. Choices are FRONT, REAR, LEFT, RIGHT; Front and Rear faces are parallel to the X axis, Left and Right to the Y axis. offset : float, optional For visualization only, the horizontal distance between the near edge of the vent and the origin of the axis defined by the selected face. Default units: m, default value: 0 m.

Returns

str Confirmation, the updated model summary, and any warnings.

Update an existing wall vent.

Selects the vent by vent_id and changes only the parameters you provide; any left as None is unchanged. The vent's id is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. vent_id : str Id of the wall vent to update. comp_a : str or None, optional First compartment id; the reference for all vent specifications. To change the connection, provide both comp_a and comp_b. None leaves the connection unchanged. comp_b : str or None, optional Second compartment id, or "OUTSIDE" for the exterior. To change the connection, provide both comp_a and comp_b. None leaves the connection unchanged. bottom : float or None, optional Position of the bottom of the opening relative to the floor of the first compartment. Default units: m. None leaves it unchanged. height : float or None, optional Height of the opening relative to the bottom of the opening. Default units: m. None leaves it unchanged. width : float or None, optional Width of the opening. Default units: m. None leaves it unchanged. face : str or None, optional The wall on which the vent is positioned: FRONT, REAR, LEFT or RIGHT. None leaves it unchanged. offset : float or None, optional For visualization only, the horizontal distance between the near edge of the vent and the origin of the axis defined by the selected face. Default units: m. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a ceiling/floor vent (vertical flow opening) between compartments.

Vertical flow vents connect compartments stacked in elevation, or a compartment to the outside (e.g. a hole in a roof). Both compartments must already exist in the model; comp_bottom may be "OUTSIDE".

Parameters

model_id : str Id of the model to modify. id : str Unique name of the vent. comp_top : str Top compartment id, where the vent is in the floor. comp_bottom : str Bottom compartment id, where the vent is in the ceiling, or "OUTSIDE" for the exterior. area : float Cross-sectional area of the vent opening. Default units: m². type : str, optional Type of ceiling/floor vent: FLOOR or CEILING. Default value: FLOOR. shape : str, optional Shape factor used to compute the effective diameter and flow coefficients: ROUND or SQUARE. Default value: ROUND. offsets : list[float] or None, optional For visualization only, [x_offset, y_offset] horizontal distances between the center of the vent and the origin of the X and Y axes in the upper compartment. Default units: m, default value: [0, 0] m.

Returns

str Confirmation, the updated model summary, and any warnings.

Update an existing ceiling/floor vent.

Selects the vent by vent_id and changes only the parameters you provide; any left as None is unchanged. The vent's id is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. vent_id : str Id of the ceiling/floor vent to update. comp_top : str or None, optional Top compartment id, where the vent is in the floor. To change the connection, provide both comp_top and comp_bottom. None leaves the connection unchanged. comp_bottom : str or None, optional Bottom compartment id, or "OUTSIDE". To change the connection, provide both comp_top and comp_bottom. None leaves the connection unchanged. area : float or None, optional Cross-sectional area of the vent opening. Default units: m². None leaves it unchanged. type : str or None, optional Type of ceiling/floor vent: FLOOR or CEILING. None leaves it unchanged. shape : str or None, optional Shape factor: ROUND or SQUARE. None leaves it unchanged. offsets : list[float] or None, optional For visualization only, [x_offset, y_offset]. Default units: m. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a mechanical vent between two compartments.

Mechanical ventilation moves air at a user-specified volume flow between two compartments, or between a compartment and the outside. Both compartments must already exist in the model; comp_from or comp_to may be "OUTSIDE".

Parameters

model_id : str Id of the model to modify. id : str Unique name of the mechanical ventilation system. comp_from : str Compartment from which the fan flow originates, or "OUTSIDE". comp_to : str Compartment to which the fan flow terminates, or "OUTSIDE". flow : float Constant volumetric flow rate of the fan. Default units: m³/s. area : list[float] or None, optional Cross-sectional area of the opening for each connection [area_from, area_to]. Default units: m², default value: [0, 0] m². heights : list[float] or None, optional Height of the midpoint of the duct opening above the floor for each connection [height_from, height_to]. Default units: m, default value: [0, 0] m. orientations : list[str] or None, optional Flow orientation for each connection, HORIZONTAL or VERTICAL. A horizontal diffuser implies vertical flow through the ceiling or floor; a vertical diffuser implies horizontal flow through a wall. Default value: ["VERTICAL", "VERTICAL"]. cutoffs : list[float] or None, optional Pressure control values [begin_drop_off_pressure, zero_flow_pressure]: above the first the flow drops off, above the second it is zero. Default units: Pa, default value: [200, 300] Pa. offsets : list[float] or None, optional For visualization only, [x_offset, y_offset] horizontal distances between the center of the vent and the origin of the X and Y axes in the first compartment. Default units: m, default value: [0, 0] m. filter_time : float, optional Time at which mechanical vent filtering begins. Default units: s, default value: 0 s. filter_efficiency : float, optional Portion of soot and trace species mass removed from the flow, specified as a percentage (0-100). Default value: 0.

Returns

str Confirmation, the updated model summary, and any warnings.

Update an existing mechanical vent.

Selects the vent by vent_id and changes only the parameters you provide; any left as None is unchanged. The vent's id is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. vent_id : str Id of the mechanical vent to update. comp_from : str or None, optional Compartment from which the fan flow originates, or "OUTSIDE". To change the connection, provide both comp_from and comp_to. None leaves the connection unchanged. comp_to : str or None, optional Compartment to which the fan flow terminates, or "OUTSIDE". To change the connection, provide both comp_from and comp_to. None leaves the connection unchanged. flow : float or None, optional Constant volumetric flow rate of the fan. Default units: m³/s. None leaves it unchanged. area : list[float] or None, optional Cross-sectional area of the opening for each connection [area_from, area_to]. Default units: m². None leaves it unchanged. heights : list[float] or None, optional Height of the midpoint of the duct opening above the floor for each connection [height_from, height_to]. Default units: m. None leaves it unchanged. orientations : list[str] or None, optional Flow orientation for each connection, HORIZONTAL or VERTICAL. None leaves it unchanged. cutoffs : list[float] or None, optional Pressure control values [begin_drop_off_pressure, zero_flow_pressure]. Default units: Pa. None leaves it unchanged. offsets : list[float] or None, optional For visualization only, [x_offset, y_offset]. Default units: m. None leaves it unchanged. filter_time : float or None, optional Time at which mechanical vent filtering begins. Default units: s. None leaves it unchanged. filter_efficiency : float or None, optional Portion of soot and trace species mass removed (0-100 %). None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a fire to a compartment of a model.

A fire in CFAST is specified via a time-dependent heat release rate (HRR). The compartment comp_id must already exist in the model. Fire properties are linearly interpolated between specified time points; if the simulation time is longer than the total duration of the fire, the final values are continued until the end of the simulation.

Parameters

model_id : str Id of the model to modify. id : str Unique name of the fire instance. comp_id : str Name of the compartment where the fire occurs. fire_id : str Unique name of the fire definition (fuel composition and HRR curve). May be the same as id. location : list[float] Position [x, y] of the center of the base of the fire relative to the front left corner of the compartment. Default units: m. data_table : list[list[float]] Time-dependent fire properties: one row per time point, with columns [TIME (s), HRR (kW), HEIGHT (m), AREA (m²), CO_YIELD, SOOT_YIELD, HCN_YIELD, HCL_YIELD, TRACE_YIELD], yields in kg/kg. Example for a fire growing to 1000 kW at 300 s: [[0, 0, 0, 0.3, 0.005, 0.02, 0, 0, 0], [300, 1000, 0, 0.3, 0.005, 0.02, 0, 0, 0]]. carbon : float, optional Number of carbon atoms in the fuel molecule. Default value: 1. chlorine : float, optional Number of chlorine atoms in the fuel molecule; assumed to completely react to form HCl. Default value: 0. hydrogen : float, optional Number of hydrogen atoms in the fuel molecule. Default value: 4. nitrogen : float, optional Number of nitrogen atoms in the fuel molecule; assumed to completely react to form HCN. Default value: 0. oxygen : float, optional Number of oxygen atoms in the fuel molecule. Default value: 0. heat_of_combustion : float, optional The energy released per unit mass of fuel consumed. Default units: kJ/kg, default value: 50000 kJ/kg. radiative_fraction : float, optional The fraction of the combustion energy that is emitted in the form of thermal radiation. Default units: none, default value: 0.35.

Returns

str Confirmation, the updated model summary, and any warnings (for example a fire located outside the compartment footprint).

Update an existing fire.

Selects the fire by its instance id and changes only the parameters you provide; any left as None is unchanged. The fire instance id is the selector and is not changed here. Changing comp_id moves the fire to another compartment, which must already exist.

Parameters

model_id : str Id of the model to modify. id : str Id of the fire instance to update. comp_id : str or None, optional Name of the compartment where the fire occurs. None leaves it unchanged. fire_id : str or None, optional Name of the fire definition (fuel composition and HRR curve). None leaves it unchanged. location : list[float] or None, optional Position [x, y] of the center of the base of the fire relative to the front left corner of the compartment. Default units: m. None leaves it unchanged. data_table : list[list[float]] or None, optional Time-dependent fire properties: one row per time point, with columns [TIME (s), HRR (kW), HEIGHT (m), AREA (m²), CO_YIELD, SOOT_YIELD, HCN_YIELD, HCL_YIELD, TRACE_YIELD], yields in kg/kg. None leaves it unchanged. carbon : float or None, optional Number of carbon atoms in the fuel molecule. None leaves it unchanged. chlorine : float or None, optional Number of chlorine atoms in the fuel molecule; assumed to completely react to form HCl. None leaves it unchanged. hydrogen : float or None, optional Number of hydrogen atoms in the fuel molecule. None leaves it unchanged. nitrogen : float or None, optional Number of nitrogen atoms in the fuel molecule; assumed to completely react to form HCN. None leaves it unchanged. oxygen : float or None, optional Number of oxygen atoms in the fuel molecule. None leaves it unchanged. heat_of_combustion : float or None, optional The energy released per unit mass of fuel consumed. Default units: kJ/kg. None leaves it unchanged. radiative_fraction : float or None, optional The fraction of the combustion energy that is emitted in the form of thermal radiation. Default units: none. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings (for example a fire located outside the compartment footprint).

Add a device (target or detector) to a compartment of a model.

Devices are either targets (PLATE, CYLINDER), which heat up and report temperature, or detectors (HEAT_DETECTOR, SMOKE_DETECTOR, SPRINKLER). The compartment comp_id must already exist. Required fields depend on the type: targets need material_id (already added with add_material) and exactly one of normal or surface_orientation; HEAT_DETECTOR and SPRINKLER need setpoint and rti (SPRINKLER also spray_density).

Parameters

model_id : str Id of the model to modify. id : str Unique name of the target or detector. comp_id : str Compartment in which the device is located. location : list[float] Position [x, y, z] as distances from the left wall, the front wall, and the floor. Default units: m. type : str One of PLATE, CYLINDER (targets), HEAT_DETECTOR, SMOKE_DETECTOR, SPRINKLER (detectors). material_id : str or None, optional What the target is made of; must already exist in the model. Required for target types (PLATE, CYLINDER). surface_orientation : str or None, optional Predefined surface orientation for targets: CEILING, FRONT WALL, BACK WALL, LEFT WALL, RIGHT WALL or FLOOR. Provide exactly one of surface_orientation or normal for a target. normal : list[float] or None, optional Unit vector [nx, ny, nz] perpendicular to the exposed target surface (e.g. [0, 0, 1] faces the ceiling). Provide exactly one of normal or surface_orientation for a target. thickness : float or None, optional Thickness of the target material; if None, the material's value is used. Default units: m. temperature_depth : float, optional Depth at which the internal target temperature is reported. With depth_units="M" (default) an absolute depth in meters from the front surface, which must be > 0 and less than the material thickness; otherwise a fraction of the thickness in [0, 1]. Default value: 0.5. depth_units : str, optional Units for temperature_depth: "M" for meters. Default value: M. setpoint : float or None, optional Temperature at or above which the link activates. Default units: °C. Required for HEAT_DETECTOR and SPRINKLER. rti : float or None, optional Response Time Index for the sprinkler or detector. Default units: (m·s)^(1/2). Required for HEAT_DETECTOR and SPRINKLER. obscuration : float, optional Obscuration at or above which a SMOKE_DETECTOR activates. Default units: %/m, default value: 23.93 %/m. spray_density : float or None, optional Amount of water dispersed by a sprinkler. Default units: m/s. Required for SPRINKLER.

Returns

str Confirmation, the updated model summary, and any warnings.

Update an existing device (target or detector).

Selects the device by device_id and changes only the parameters you provide; any left as None is unchanged. The device's id is the selector and is not changed here.

Parameters

model_id : str Id of the model to modify. device_id : str Id of the device to update. comp_id : str or None, optional Compartment in which the device is located. None leaves it unchanged. location : list[float] or None, optional Position [x, y, z] from the left wall, front wall and floor. Default units: m. None leaves it unchanged. type : str or None, optional One of PLATE, CYLINDER, HEAT_DETECTOR, SMOKE_DETECTOR, SPRINKLER. None leaves it unchanged. material_id : str or None, optional What the target is made of; must already exist. None leaves it unchanged. surface_orientation : str or None, optional Predefined surface orientation for targets. None leaves it unchanged. normal : list[float] or None, optional Unit vector [nx, ny, nz] perpendicular to the target surface. None leaves it unchanged. thickness : float or None, optional Thickness of the target material. Default units: m. None leaves it unchanged. temperature_depth : float or None, optional Depth at which the internal target temperature is reported (meters when depth_units="M", else a fraction in [0, 1]). None leaves it unchanged. depth_units : str or None, optional Units for temperature_depth: "M" for meters. None leaves it unchanged. setpoint : float or None, optional Activation temperature for HEAT_DETECTOR and SPRINKLER. Default units: °C. None leaves it unchanged. rti : float or None, optional Response Time Index. Default units: (m·s)^(1/2). None leaves it unchanged. obscuration : float or None, optional Obscuration at or above which a SMOKE_DETECTOR activates. Default units: %/m. None leaves it unchanged. spray_density : float or None, optional Amount of water dispersed by a sprinkler. Default units: m/s. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.

Add a surface connection between compartments.

Surface connections transfer heat through solid boundaries between two compartments. Both compartments must already exist in the model. Unlike other components, a surface connection has no id; refer to it by its position (index) when updating. For WALL connections you should add one in each direction (comp_id -> comp_ids and comp_ids -> comp_id).

Parameters

model_id : str Id of the model to modify. conn_type : str Type of connection: WALL for horizontal heat transfer through vertical surfaces, FLOOR for vertical heat transfer through horizontal surfaces. comp_id : str First compartment id. For WALL, the compartment whose wall area fraction is given; for FLOOR, the top compartment (through its floor). comp_ids : str Second compartment id. For FLOOR, the bottom compartment (through its ceiling). fraction : float or None, optional Fraction (0-1) of the first compartment's vertical surface area that connects the two compartments. Required for WALL connections; must be None for FLOOR connections.

Returns

str Confirmation, the updated model summary, and any warnings.

Update an existing surface connection.

Surface connections have no id, so they are selected by index (their 0-based position in the order they were added). Only the parameters you provide change; any left as None is unchanged.

Parameters

model_id : str Id of the model to modify. index : int 0-based position of the surface connection to update. conn_type : str or None, optional Type of connection: WALL or FLOOR. None leaves it unchanged. comp_id : str or None, optional First compartment id. None leaves it unchanged. comp_ids : str or None, optional Second compartment id. None leaves it unchanged. fraction : float or None, optional Fraction (0-1) of connected vertical surface area, for WALL connections. None leaves it unchanged.

Returns

str Confirmation, the updated model summary, and any warnings.