7 Benefits of Factory-Built Grease Duct (And Why It's Worth the Cost)
Factory-built grease duct saves labor, meets UL 1978, and allows reduced clearance to combustibles. Here's why more restaurants are choosing it over field-welded duct.
For decades, restaurant grease duct meant a welder in your ceiling, weeks of field labor, and a leak test that could fail at any joint. Today, more contractors and owners are specifying factory-built grease duct — pre-engineered, UL-listed, double-wall duct that ships in modular sections and locks together on the job site.
Here is why it is worth every penny.
1. Listed to UL 1978 — And That Changes Everything
Factory-built grease duct is tested and listed under UL 1978, the safety standard for grease duct assemblies. That listing is what allows the duct to be installed at reduced clearance to combustibles — often as little as 0 to 3 inches instead of the 18 inches NFPA 96 requires for field-welded black iron (NFPA 96 §7.4).
In a tight ceiling chase or a food truck roof, that clearance difference is the whole project.
2. Dramatically Faster Installation
A field-welded grease duct system can take a certified welder days or weeks to install and pressure-test. A factory-built system uses V-band clamps or twist-lock joints that a two-person crew can assemble in hours. No welder. No hot work permit. No overnight shutdown for welding operations in an occupied building.
3. Guaranteed Liquid-Tight Joints
NFPA 96 requires grease duct to be liquid-tight. With field welding, that comes down to the skill of one welder on one day. Factory-built duct ships with factory-tested welded seams and gasketed joint systems engineered to stay tight for the life of the system.
4. Double-Wall Insulated Construction
Some factory-built grease duct is double-wall — a stainless inner liner surrounded by an insulation layer (typically ceramic wool) and an outer stainless jacket. That construction:
Keeps the outer surface cool enough to run near combustibles
Reduces heat loss (better draft, less condensation)
Provides fire-resistive protection between the duct and the building
5. No Enclosure Required in Many Applications
Traditional single-wall grease duct usually needs a 2-hour rated fire-resistive shaft or wrap when it passes through occupied spaces. Factory-built double-wall duct listed for zero-clearance installation frequently eliminates that enclosure — saving thousands in drywall, framing, and inspection labor.
6. Predictable, Modular Sizing
Factory-built systems come in standard diameters (typically 8" through 24"+) with matching elbows, tees, cleanouts, transitions, and roof penetration components. You order what the drawings call for, it shows up on a pallet, and it fits. No custom fabrication delays.
7. Easier Inspections and Cleaning
Cleanout doors are engineered into the system at code-required intervals, with tight, listed gaskets that hold up to pressure washing. Hood cleaners love it because they can actually reach and reseal every access point without cutting into the duct.
The Trade-Off
Factory-built grease duct costs more per linear foot than raw stainless or black iron. But once you add in welding labor, hot-work permits, enclosure framing, and inspection time, most jobs come out ahead — often significantly. For food trucks, tight urban buildouts, and any project on a schedule, factory-built is the default choice.
Get Factory-Built Grease Duct Shipped to Your Job
Mr. Hood USA stocks UL 1978-listed factory-built grease duct, elbows, tees, and accessories for commercial kitchens and mobile applications. Fast shipping, contractor pricing, and real product support.