Are round grease ducts better than rectangular grease ducts?

One of the most important choices when it comes to commercial kitchen exhaust is during the grease duct installation - on whether to use round or rectangular shapes. Both have pros and cons to consider as below:

Gravity flow

Round ducts are generally preferred for their superior gravity flow characteristics. The circular shape allows grease, particulates, and other debris to flow more freely down the duct thanks to a constant slope. Rectangular ducts can experience buildup in corners if not installed perfectly level and straight. Clogged ducts increase cleaning needs and fire risks.

Physical footprint

The smaller physical footprint of round ducts makes them ideal for tight spaces above drop ceilings or when navigating support beams. Their smaller diameter also means less raw material is needed, saving on both ductwork costs and construction time. However, rectangular ducts offer more usable interior square footage when larger capacities are required. 

Installation & maintenance

From a maintenance perspective, round ducts have a structural strength advantage. Their uniform shape resists crushing or warping better than thin rectangular panels. Dents and damage are less likely to cause blockages over time. However, rectangular sections do allow for easy installation of inspection ports at T-sections and directional changes, improving grease duct fire wrap access.

Airflow

When it comes to airflow, tests show round ducts maintain velocity more efficiently around bends compared to their rectangular counterparts. This prevents deposits and reduces cleaning needs. Still, modern rectangular duct designs with gradual rounded turns and vanes inside now easily match round duct velocity performance.

Given advancements in fabrication technologies, the cost differential between round and rectangular grease ducts is small in many markets today. Specifying one over the other often boils down to installation constraints, required capacity, or preference of the mechanical contractor handling the grease duct installation. 

For most commercial kitchen applications, a round duct system remains the superior and most code-compliant option. But high-performing rectangular options have a place too when capacity, material usage, or physical space must take priority over marginal air velocity improvements. Smart design can overcome any inherent performance concerns. Our Morgan Advanced Materials FastWrap XL, developed specifically for commercial grease and air ventilation systems provides an ideal grease duct fire protection solution.

Competent grease duct sizing, layout, joints, and grease duct fire wrap under an approved UL-listed system will matter far more than duct shape alone in ensuring safe, code-compliant performance for years. An experienced commercial kitchen exhaust specialist like Bin Dasmal General Trading can help evaluate all factors for each unique project.