How do I size ductwork automatically in Revit?

First, create a fully connected air system by linking your AHU to all terminals through ductwork. Select the air system or a duct in the system, then click Duct Sizing in the contextual ribbon. Set the sizing method (Equal Friction is most common — use 0.08 to 0.10 in.w.g. per 100 feet), set maximum velocity limits, and click OK. Revit recalculates all duct dimensions to carry the assigned airflow. Review results in a duct schedule filtered by system name.

What is the Revit System Browser and how do I use it?

The System Browser (View > System Browser, or press W then S) is a tree view of all MEP systems in the model, organized by discipline: Mechanical (air systems), Electrical (power, lighting, data), and Piping (domestic water, sanitary, fire protection). Each system shows connected elements and highlights open circuits or disconnected elements in red. Use it to verify system completeness before exporting for coordination or running load calculations.

How do I create a panel schedule in Revit?

Go to View > New > Panel Schedule and select the panelboard family placed in your model. Revit automatically generates the panel schedule from circuit data — listing circuit numbers, phase, load descriptions, amperage, and calculated demand load. The schedule updates automatically when you add, modify, or delete circuits connected to that panel. Place the panel schedule view on a sheet like any other view.

How do I model sloped sanitary drain pipe in Revit?

Select the Pipe tool (Systems > Plumbing & Piping > Pipe), choose your pipe type (DWV copper or PVC), and in the Options Bar click the Slope dropdown. Enter the slope value: 1/4 inch per foot (2.08%) for pipes 3 inches and smaller, or 1/8 inch per foot (1.04%) for 4-inch and larger per IPC requirements. Draw the pipe in plan view and Revit automatically adjusts the downstream end elevation based on the run length and slope.

What MEP connector types are used in Revit families?

Revit MEP families use connector objects to define how equipment participates in systems. Duct connectors define air system type, CFM, and connection shape. Pipe connectors define pipe system type, size, and flow. Electrical connectors define voltage, poles, apparent load, and load classification. Conduit connectors define conduit size and system. Without correctly configured connectors, equipment cannot be connected to systems and will not appear in the System Browser.

How do I export a Revit MEP model for Navisworks clash detection?

Go to File > Export > NWC. Set coordinates to Shared Coordinates so the MEP file aligns with architectural and structural NWC files. Enable 'Convert linked files' if your MEP model contains architectural or structural links. Under Export scope, choose Entire Project. Import the resulting NWC into Navisworks by going to Home > Append and selecting your NWC file. Repeat for each discipline file, then save the combined model as an NWD for coordination.

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Engineering·12 min read·June 19, 2026

⚙️ MEP Modeling in Revit: HVAC Ductwork, Electrical Circuits, and Plumbing Systems

A complete guide to MEP modeling in Revit — setting up mechanical, electrical, and plumbing systems, routing ductwork with auto-sizing, building electrical circuits and panelboards, modeling pressurized and gravity plumbing, and preparing MEP models for coordination and clash detection.

MEP Template Setup: The Foundation of a Productive Model

MEP modeling in Revit begins with the right template. Autodesk ships three MEP-specific templates with Revit: Mechanical-Default.rte, Electrical-Default.rte, and Plumbing-Default.rte. Most firms start from one of these and customize it extensively. Alternatively, some firms maintain a single combined MEP template that includes all three disciplines, simplifying coordination when one team handles all MEP work.

Critical template settings to configure before modeling begins:

Mechanical Settings (Manage > MEP Settings > Mechanical Settings): Set duct sizing method (Friction, Velocity, or Equal Friction — Equal Friction is the ASHRAE-recommended default for most systems), rectangular and round duct pressure class, fitting angle increments, and conversion factors for units. These settings govern automatic duct sizing behavior throughout the project.
Electrical Settings (Manage > MEP Settings > Electrical Settings): Define voltage definitions (120/208V, 277/480V, etc.), distribution systems (single-phase 2-wire, three-phase 4-wire delta, three-phase 4-wire wye), wire types with impedance values for voltage drop calculation, and conduit and cable tray standard sizes.
Pipe Settings (Manage > MEP Settings > Pipe Settings): Configure pipe segments (material, schedule/class, Hazen-Williams C-factor), fittings conversion table, and slope display options. Set up all piping materials you will use: Schedule 40 steel, Type L copper, CPVC, DI, HDPE.
Shared Parameters: Establish a firm-wide shared parameters file containing MEP-specific parameters such as Equipment ID, Maintenance Zone, BAS Point, and Insulation Type. These parameters drive schedules, tagging, and data export to building automation system databases.

HVAC Systems: Air Handling Units, Fan Coil Units, and Ductwork

HVAC modeling in Revit is system-centric: every element belongs to a named air system that connects supply air sources (AHUs, FCUs, VAV boxes) through ductwork to air terminals (diffusers, grilles, registers). The system model drives automatic duct sizing, airflow balancing, and the System Browser — Revit's MEP-specific tree view of all system connections.

Placing Air Handling Equipment

Air handling units (AHUs) and fan coil units (FCUs) are loadable Revit families placed like any other component. Before placing, verify the family has correctly defined MEP Connectors — connector objects that define the supply air opening (flow direction: out), return air opening (flow direction: in), and any outdoor air or exhaust connections. Without properly configured connectors, the AHU cannot participate in a Revit air system.

After placing the AHU, select it and use the connector grip handles to start drawing supply ductwork. When you connect a duct to an AHU's supply connector, Revit automatically creates an Air Supply System. The system appears in the System Browser (View > System Browser, or keyboard W-S) under Mechanical > Air Systems.

Drawing Ductwork

Navigate to Systems > HVAC > Duct (keyboard: DT). The Options Bar and Properties panel let you set:

Duct type: Round, Rectangular, or Oval. Round duct (typically for branch runouts) and rectangular duct (for mains) are most common. The duct type controls fitting preferences and insulation parameters.
Width and Height (rectangular) or Diameter (round): Enter dimensions manually or let automatic sizing calculate them after system creation.
Offset (elevation): Bottom of duct elevation above finished floor. Coordinate this with structural drawings — know your available ceiling plenum depth before routing.
System Type: Supply Air, Return Air, Exhaust Air, Outside Air, or a custom type. Revit uses system type to color-code ducts and keep systems separate in the System Browser.

When drawing ductwork, Revit auto-inserts fittings (elbows, tees, transitions) at connections and direction changes based on the Routing Preferences defined in the duct type. To modify routing preferences, open the duct type properties and expand the Routing Preferences section — assign preferred elbow, tee, cross, and transition families for each connection angle.

Air Terminal Systems and Duct Sizing

Place diffusers and grilles from the Systems panel. Each air terminal family has a Flow parameter (CFM or L/s). After placing terminals, select all terminals in a zone and create a system: right-click > Create System > Supply Air. Revit creates an Air Supply System and displays a system tag showing total CFM.

With the system selected, click Duct Sizing in the contextual ribbon. Set the sizing method (Equal Friction recommended: target 0.08–0.10 in.w.g./100 ft pressure drop for most commercial systems), maximum velocity constraints (1,000–1,200 FPM for supply mains, 700–800 FPM for low-velocity systems), and click OK. Revit recalculates all duct dimensions to carry the assigned airflow within the specified pressure constraints. Review the results in a duct schedule — filter by system name to see sizing for each branch.

Electrical Systems: Devices, Circuits, and Panelboards

Revit's electrical modeling builds a complete single-line circuit database — useful not only for BIM coordination but also for generating load calculations, panel schedules, and circuit directories automatically.

Placing Electrical Devices and Equipment

Electrical devices (receptacles, switches, data outlets) are typically wall-hosted families placed by selecting the wall and clicking position. Each device family must have an Electrical Connector defined in the family editor specifying voltage, number of poles, load classification (Receptacle, Motor, HVAC, Lighting, etc.), and apparent load in VA.

Panelboards and switchboards are placed as loadable equipment families. The panelboard family must have connectors defining the system voltage and distribution system (matching your Electrical Settings). When you run circuits to the panelboard, Revit tracks the load on each circuit and calculates panel demand load for the schedule.

Creating Electrical Circuits

Select one or more devices, then go to Systems > Electrical > Power. Revit prompts you to select a panel. After selecting the panel, the circuit appears in the System Browser under Electrical > Power. You can then draw conduit between devices and panel to complete the physical routing, or leave it as a logical circuit for load calculation purposes without modeled conduit.

Key electrical modeling best practices:

Use the Electrical Analytical view template to see circuits color-coded by panel — invaluable for verifying circuit routing before coordination.
Run Systems > Electrical > Check Circuits to identify orphaned devices (devices not on any circuit) and open circuits (circuits without a panel connection).
Panel schedules generate automatically from the circuit data: Place a Panel Schedule view on a sheet (View > New > Panel Schedule), select the panelboard, and Revit populates circuit descriptions, loads, phases, and calculated demand.

Plumbing Systems: Fixtures, Pipe Routing, and Slopes

Plumbing in Revit covers pressurized systems (domestic cold water, domestic hot water, recirculation) and gravity systems (sanitary waste, storm drainage, vent). The distinction matters for pipe slope — gravity lines must be drawn with a defined slope, not horizontal.

Plumbing Fixture Connectors

Every plumbing fixture family (lavatory, water closet, floor drain) must have pipe connectors defined for each connection point: typically a cold water connector, a hot water connector, and a sanitary connector. The connectors define pipe size, system classification (Domestic Cold Water, Sanitary, etc.), and flow rate (in GPM for pressure systems or fixture units for drainage).

When you select a fixture and draw pipe from its connector, Revit creates a piping system. Verify connector sizes match your plumbing design — a connector set to 1/2" will prevent you from connecting 3/4" pipe without a transition.

Drawing Pipe with Slope

For sanitary drainage, go to Systems > Plumbing & Piping > Pipe. In the Options Bar, set the slope: click the Slope icon and enter the slope value (1/4" per foot = 2.08%, the minimum for 3" and smaller DWV per IPC; 1/8" per foot = 1.04% for 4" and larger). Draw the pipe in plan view; Revit automatically adjusts the far-end elevation based on the slope and the pipe run length.

Use Pipe Placeholder lines in early design phases when routing logic matters but exact sizes are not yet determined. Convert placeholders to actual pipe when ready for coordination.

Fire Protection: Sprinkler Systems

Fire protection sprinkler modeling follows the same system paradigm. Place sprinkler families from the Architectural Equipment category or from MEP-specific sprinkler families. Connect sprinklers to a fire protection pipe system (System Type: Wet, Dry, Pre-Action, or Deluge).

NFPA 13 spacing rules govern sprinkler placement — light hazard occupancies allow up to 200 SF/head with maximum 15-foot spacing. Revit does not enforce NFPA 13 automatically, but you can create a Sprinkler Coverage Area parameter check using Dynamo to flag heads that exceed design area thresholds.

Sprinkler pipe is typically drawn from the branch lines (1" to 2" wet pipe) up to feed mains (2.5" to 4") connecting to risers. Size per hydraulic calculation — Revit's pipe sizing for fire protection uses the Hazen-Williams equation with the C-factor defined in the pipe segment type (C=120 for Schedule 10 steel, C=140 for Schedule 40 steel).

System Color-Coding and Clash Detection Readiness

Before sending MEP models to coordination review, verify your system color-coding is consistent with the project BIM Execution Plan. Create View Filters (View > Filters > New) based on System Classification parameter to color each MEP system — for example: supply air (blue), return air (green), exhaust (yellow), chilled water supply (cyan), chilled water return (dark blue), sanitary (brown), domestic cold water (light blue), conduit (orange).

Apply these filters to your coordination view templates and save them. When the model is exported to Navisworks or uploaded to ACC, the color-coded systems help coordination reviewers instantly identify which discipline owns each element in a clash pair, dramatically speeding up clash resolution meetings.

Topics covered

Revit MEP modelingRevit ductwork routingRevit HVAC systemsRevit electrical circuitsRevit plumbing systemsRevit System BrowserRevit duct sizingMEP Revit familiesRevit fire protection sprinklersRevit MEP templateRevit panelboard scheduleMEP BIM coordination

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