Prefabrication is one of the most important and impactful trends in the HVAC duct fabrication industry. By leveraging appropriate software with the right machinery in duct prefabrication, sheet metal contractors and manufactures can streamline the manufacturing cycle of project design through installation. With the ability to prefabricate ductwork in the shop, the contractor can save not only money but also time. To help you understand the benefits of HVAC duct prefabrication, we will discuss the steps in the prefabrication process and how they help sheet metal contractors boost efficiency and profits.
What Does the Prefabrication Process Look Like in Practice?
The demand for HVAC prefabrication in a controlled atmosphere has seen rapid growth in lieu of jobsite duct production and assembly. In fact, the methodology of sectioning duct, installing taps and collars, and installing sealant systems in the shop atmosphere has taken nearly 40% of the labor out of jobsite installations. In the sheet metal industry, producing prefabricated HVAC duct takes four major steps.
Step 1: Design
Using appropriately integrated software solutions, architects and designers create the drawings and models necessary to plan a duct fabrication project. Today, the two main solutions used to create complex ductwork systems are BIM and CAD to CAM.
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BIM (Building Information Modeling): A 3D design tool used by professionals in architecture, engineering, and construction (AEC) to design, construct, and manage buildings and infrastructure. Utilizing BIM allows contractors and fabricators to integrate design with ductwork fabrication into a singular workflow, which can automatically adjust when new information is received.
- CAD to CAM (Computer-Aided Design to Computer-Aided Manufacturing): CAD is software used to create a line-by-line drawing of the system during the design process, while CAM translates that digital model into a format that manufacturing machinery can read and use to create components. CAD/CAM software works best in tandem, and are often combined into one program.
Designing and planning a duct project with advanced software is the key to setting up a prefabrication job successfully. With CAD to CAM software interoperability, architects and designers can create complex ductwork systems and ease the installation process by pre-assembling on the floor prior to shipping to the job site. BIM improves mechanical, electrical, and plumbing (MEP) design quality and allows the trades to collaborate in real time to support the project delivery process. Bridging the gap between the drafting table and the shop floor strengthens the whole fabrication process and creates a more powerful and productive unified operation. 
Step 2: Fabricate
Fabricating the product in the controlled atmosphere of the fab shop leads to increased material and labor savings, improved technician safety, and boosted product quality.
Once plans are finalized, the sheet metal contractor can begin fabricating sections of duct. During the fabrication stage, technicians will produce the large duct sections that make up the bulk of the HVAC duct work system. Additionally, any necessary holes will be punches and taps, collars, and access doors installed using shop drawing templates, eliminating time-consuming, offline processes. These will also be sealed per SMACNA Class A sealing requirements.
At this step, choosing the right manufacturing machinery to produce high quality ducts is critical. An advanced coil line, such as our Pro-Fabriduct, enhances the prefabrication process by accepting downloads via CAD/CAM. Within the coil line, a precise, reliable in-line plasma cutter enables more efficient prefabrication by providing less input and greater output with less chance of human error.
Step 3: Assemble
Once duct comes off the coil line, the next key step to the fabrication process is assembly. Using advanced machinery systems to automate processes like connecting joints and inserting corners contributes to additional productivity improvements during this step. Contractors create large sections comprised of multiple pieces of ductwork that are completely sealed in the shop. These sections are then shipped to the jobsite pre-assembled, leading to reduced labor costs, improved safety, and increased ease of installation with fewer risks of human error. Prefabrication in shop vs on-site eliminates searching for parts, missing fittings, and material handling. Workers on-site have less inventory to track in the field, and significantly less labor is required downstream to assemble before installation.
Step 4: Deliver
The final step of the HVAC duct prefabrication process is delivery/installation. BIM software plays a key role at this phase of the project as well, allowing all the trades involved to digitize the site and connect project information through construction and handover. Thanks to the larger sections of completed duct that are ready to connect and hang, installation time is significantly decreased. New hardware hanging options are available to further reduce installation time and labor.
According to the 2020 Prefabrication and Modular Construction SmartMarket Report, construction projects containing prefabricated duct systems experience improved project schedule performance. Trade contractors in particular experience the greatest positive impact on project/construction schedules with prefabricated HVAC duct. Additionally, prefabrication is shown to reduce construction waste thanks to the labor taken out of the field and performed in the shop instead.
Saving Time and Money with Ductwork Prefabrication
Prefabrication of HVAC duct systems lends itself to controlling quality and meeting or beating tight construction schedules. Smart planning, innovative software, and reliable manufacturing machinery seamlessly connect to deliver greater productivity and efficiency than traditional duct fabrication and delivery. Ultimately, the rapidly growing trend of prefabrication delivers a variety of significant benefits, including:
- Manufacturing ductwork quickly and accurately in a controlled shop environment before sending it to a job site saves time, labor, and ultimately, profits.
- Improved quality control and safety in a controlled environment.
- Reduced number of field call backs and mistakes.
- Labor is shifted from field to shop, reducing costs through lower wage rates.
- Leakage tests performed based on pressure class prior to installation in the field.
- Increased ability to deliver under stringent timelines.
As prefabrication becomes the norm in sheet metal fabrication as well as across the wider construction and trade industries, these real-world strategies provide an attractive solution to workflow bottlenecks professionals have dealt with for decades.