Your Duct Size Does Matter (and Material Too) in Commercial HVAC

Anyone who owns a commercial building knows that ductwork is an integral part of the property’s operations. Designing, sizing, and installation is crucial for your HVAC ductwork to operate at maximum efficiency. Proper duct size is often an overlooked feature of commercial HVAC systems. The role duct sizing and material play in maintaining a safe, comfortable environment are important. Having the right size and material for your ducts will maintain comfortable conditions, improve indoor air quality, minimize energy losses, and lower your heating and cooling bills, as well.

How Duct Size Matters

Humidity levels, air temperature, and air pressure within a building all factor into the size of commercial ductwork. When ducts are too large, there is inadequate pressure available to move air to different areas of the building properly. As a result, the furnace or air conditioner will work much harder than usual to maintain a proper temperature, running far more often and far longer than it should. This overuse, as you might imagine, can push energy bills sky-high.

By the same token, when ducts are too small, the air cannot adequately move through to designated areas of the building. This restriction can cause pressure to build up in the HVAC system, causing premature wear and tear and potentially significant damage. Eventually, both sizing issues cause premature wear and tear, breakdowns, and the inevitable early death of HVAC systems. They also create the need for expensive repairs along the way and early replacement costs. If ductwork is leaky, too, these issues are further exacerbated.

HVAC professionals use a specific formula to figure out the proper duct size. This formula considers the size of your HVAC unit, the friction loss, static pressure, square footage of spaces that need air, and the airflow velocity required.

How Duct Material Matters

The most common air ducts are typically aluminum, stainless steel, or galvanized steel. However, they can also be fabricated with fiberglass, flexible plastic, or even fabric, depending on the needed application. The material matters and relies on the building and the conditions of the installation location.

Sheet Metal

Rigid sheet metal is the most common type of material for ductwork, and it’s commonly made of aluminum and galvanized steel. The interior can catch dust and other debris, and the outside is smooth and easy to clean. This type of ductwork material has a greater degree of heat loss than some others. Therefore, higher energy bills. However, it is the most durable. It is also less likely to harbor mold or mildew, and the smooth surface accumulates less dust than some other materials.


Since fiberglass ductwork has the interior lining sealed it doesn’t need as much cleaning as other options. Most fiberglass ducts reduce heat loss, thanks to this additional interior lining. This material is also an option that can reduce the noise that an HVAC system produces, making it a prevalent choice for ductwork material, especially in commercial applications.


Flat boards of compressed glass fibers are what make fiberboard cut material. These fibers are bonded by resin and have an exterior layer of foil to stop water vapor infiltration and leakage. Ducts made from fiberboard typically cost less than those made from sheet metal. They also can reduce noises and resist thermal loss or gain well. However, fiberboard is prone to a greater potential for mold and bacterial growth. In addition, the rough interior surface can reduce airflow.

Call an HVAC Professional for Proper Ductwork Service

Need reliable ductwork service? Trust The Severn Group for all of your ductwork and HVAC needs throughout Maryland and the Washington, D.C. area. Contact us today and let us know how we can help you!