Ductwork Modeling & Fabrication by Using Autodesk Revit MEP

Last Updated November 18th, 2019
Ductwork Modeling & Fabrication by Using Autodesk Revit MEP

Revit overcomes complex ductwork design and fabrication process challenges to ensure seamless operations by easy design intent communication and early clash detection.

MEP engineers working on complex ductwork networks are many a time confronted with design coordination challenges and resultant inaccuracies. These arise largely because of the inability to visualise the entire duct network. Poorly communicated, incomplete or non-self-explanatory ductwork design and fabrication details can potentially cause delays in on-site and off-site fabrication processes.

Revit MEP supported fabrication tools serve as the perfect platform for stakeholders across disciplines to design, estimate and manufacture ductwork in a seamless and cost effective manner. Detailed and design intended Revit MEP models ease the generation of shop drawings to facilitate smooth installation of complex ductwork. These fabrication tools further enhance accuracy and improve collaboration between multiple MEP stakeholders including designers, engineers, manufacturers, contractors and installers.

The argument for and against AutoCAD MEP and Autodesk Revit

Often favoured by MEP technicians for fabrication and ductwork, AutoCAD MEP, a 2D software, has relatively easy to operate tools. Standardized diagrams of MEP symbols created in AutoCAD MEP further ease production of 2D mechanical drawings.

But AutoCAD MEP has its own constraints. It cannot produce building information models. Two dimensional drawings makes it hard to visualize complex ductwork networks with multiple elevations. Limited multi-disciplinary coordination and collaboration also delays the fabrication process.

The benefits of Revit MEP far outweigh the ease of use of AutoCAD MEP. Here are some that make it the preferred choice:

AutoCAD
Multiple data sources are required to collect & retrieve data
2D lines presents real object displays Display dimensions
Single design view
A single user can update only a single file
Modifications are manual and time consuming
Disable to create intelligent parametric objects
Manual design coordination
Revit
Revit collects and stores all project data as single source
3D parametric object with real-life customizable properties
Multiple design view
Multiple users can work in a single file at the same time
Modifications are instantaneous and less time-consuming
Creates intelligent parametric objects
A coordinated BIM model automates the process
  • Revit MEP supports BIM modelling, with features like coordination and multidisciplinary model sharing, generation of analysis and pressure reports, fabrication of models, documentation, quantity take-off and scheduling, all of which significantly enhance productivity and operational efficiency.
  • The ductwork model in Revit allows inclusion of ducts of various sizes, customized frames, complex routing and fittings.
  • Revit editing tools like split controls, and resizing of connected elements also help to develop the model accurately and in less time.
  • Revit MEP allows for the creation of different types of hangers for ductwork which are attached to those structural elements that are the closest, such as floors, roofs, structural framing, slabs, etc.

A US-based engineering firm appointed Hitech CADD Services to produce LOD 400 MEP model of a residential building. The higher LOD model could provide the benefit of hassle-free, seamless fabrication and erection of the MEP component on the shop floor and on site, respectively.

Read also: BIM to Address MEP Challenges for Stadium Projects

So, how do the Autodesk fabrication tools deliver operational advantages?

The fabrication tools help the MEP stakeholders to export the model for designing, estimating, and fabricating mechanical systems like ductwork, pipework, electrical containment, etc.

Directly linking Revit MEP model to the tools eases the designing, material management, installation, estimation and the downstream fabrication process. The tools improve visibility and productivity by providing help in tasks like generation of ductwork network, creation of detailed slope pipes, vertical annotation, and so on.

Autodesk Fabrication Tools

The 3 step fabrication process

1Creating fabrication model

By using content from the Autodesk fabrication product, a design intent Revit MEP model can be converted to a detailed fabrication model within Revit MEP. An individual design element, a run or an entire network of ductwork can be converted into highly detailed fabrication components that contain information for estimating, prefabrication, construction and installation processes. The fabrication model can be modified by the fabrication tools and can be used to generate shop drawing.

Also read: Skills a Revit MEP Professional Must Possess From Building Construction Industry Perspective

2Costing and estimation

Using fabrication database, accurate geometry, information on connection types, material and labor, the fabrication model can be used for bids and estimation. Autodesk ESTmep enrich with features like enhanced database, manufactures content, real-world pricing and costing data, built-in Harrison codes, color coded cost tool and value engineering option tools enables more accurate cost estimates for duct-work and other MEP systems. The tool also records all Adds and Omits on a job to support tracebility and promote accountability for changes.

3Fabrication

Fabrication tools help extracting flat patterns from 3D models part for cutting sheets of various gauges at shops for manufacturing elements. Autodesk Fabrication CAMduct is manufacturing and ductwork fabrication software with project management tool to produce HVAC systems. Features like sheet metal and linear nesting, bar coding and QR coding to labels and worksheets, duct fabrication component library, shared content library and database further facilitates the fabrication process. The tool has built-in post processors to control production line of any size.

The Chicago-based building construction and O&M company, The Hill Group uses BIM to simplify the design-to-fabrication process by using single platform for the processes. The use of Autodesk fabrication tools with Revit MEP right from the beginning helps in the generation of real-world 3D models that provide information regarding material estimate and budget early during the design process. Programmers of manufacturing machines in sheet metal shops can also use this model to extract information for sheet cutting and manufacturing elements of ductwork. Leveraging the information created at the initial stage to streamline the processes of manufacturing eliminates human errors and increases manufacturing accuracy.

Also read: Why MEP Engineering Firms Should Give BIM a Second Thought?

Revit has its own challenges

Having gone over the multiple benefits of Revit for ductwork, it is equally important to understand that the design and modelling advantages are not without operational challenges. There are dependencies related to positioning of ductwork in relation to surrounding elements and related structures.

  • Complex routes with multiple elevations require routing size changes and varied connectors.
  • The generic duct element may not demonstrate the actual weight of a duct, and that will affect the material cost and take-off quantities.
  • Placement of the outlet requires sufficient space for other services and maintenance.
  • Often smaller ducts are not modelled because of the model’s defined level of detail. Because of the absence of such components, some clashes cannot be detected in clash detection, and so, coordination with other MEP services can have errors.

Conclusion

A single file of Revit MEP saves the entire project lifecycle, from design layout to fabrication details, without affecting the original design. The software supports designers, engineers, and contractors across MEP disciplines by facilitating a detailed and coordinated building information model of the HVAC and ductwork project. This model also helps in the estimation, analysis, documentation, fabrication, and installation. The Revit MEP model can streamline the engineering design process and communicate the design intent to stakeholders before construction. Thus, by helping make informed decisions, Revit MEP reduces risk, develops better quality designs, and improves building performance.

Keyuri Patel

About Author: is an American Institute of Architecture associate, a LEED Green Associate and a Masters in Architecture from San Francisco, Keyuri Patel carries wide ranging experience in urban design, architecture and BIM projects. Her insightful industry coverage on building design and construction processes builds on her passion for technology and digitalization.

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