Airflow is a long journey. Your HVAC system has many components that all work to provide airflow to each room in your building. This can make it daunting task to plan out a commercial HVAC project. Let’s follow the flow and discuss these pieces of equipment. The journey begins outdoors.

Image of louvers and dampers beside a building

Exterior - Louvers

Commercial buildings have openings along their envelope that lead to HVAC ducts. These are the ventilation points of the building, places where the HVAC system can draw in and expel air as needed.

You must protect these openings from rainfall and other harmful elements. Otherwise, your HVAC system will draw in more than air: rain, dust, birds, just to name a few things. We focus primarily on the rain, since raindrops can damage your system when they infiltrate the opening.

Louvers protect the opening while allowing airflow in. Louvers consist of several blades in a frame, with space left between each blade for air to move through. The blades will often have features that capture waterdrops as they move along the airstream.

Other features, like drain troughs and channels, provide a path for the captured water to safely exit the louver. Different types of louvers will provide different protection: a severe weather louver will block heavy rain blown towards the opening by heavy winds, while a drainable louver is better suited for light rain.

Illustration of a louver installed in a wall, deflecting rain drops — It starts at the air intake point. These openings need louvers to protect the interior from water damage.

If you want to know more, we discussed severe weather protection in greater detail in Louver Design 103. We also have other blogs that talk about rainfall protection and louver design.

Ductwork - Dampers

Now that the airflow is in the building, it needs to get through the network of ducts to the HVAC unit. It won’t always be a straight shot from the intake point to the unit. Control dampers direct airflow through the ducts. Dampers consist of several rotating blades in a frame.

Where a louver is designed to protect, a control damper is designed to regulate airflow. The damper’s blades will rotate from close to open when air needs to pass through, then back to close when airflow stops.

Illustration of a control damper in a duct — Air will travel through ducts. Control dampers direct air through ductwork to where it's needed.

The goal of the control damper is directing airflow. When the air is conditioned, the system will pass the air to the rooms that need it. Control dampers will open a path from the unit to the room in need. The dampers will close off ducts that lead to other parts of the building, so that the airflow is concentrated to the rooms that need it. Check out our series on damper design for tips on designing airflow efficient dampers.

Not every damper will open and close the same way. Different damper types will perform specific tasks in your HVAC system. For example, a pressure relief damper will only open to relieve excess air pressure in a duct. Also, certain dampers are designed for highly specific roles. Isolation dampers control airflow for sensitive areas. These dampers close with near-zero leakage. You won’t be using isolation dampers throughout your building.

Balancing dampers help regulate the pressure of air as it flows through the duct. These dampers stay partially open throughout the day. The damper will create static pressure as air moves through its open blades, reducing the dynamic pressure of the airstream.

Illustration of a balance damper in a duct — Balancing dampers keep air moving. Pressure imbalances can lead to airflow issues.

This is commonly referred to as pressure drop. Pressure drop is generally viewed as an airflow issue, because it creates a demand for additional power. System fans will need to spin faster to push the same amount of air through the system. However, balancing dampers can use pressure drop to alleviate airflow issues like cold spots in an office. By balancing the air pressure in the duct, the system can better distribute air through the office.

Rooms - Diffusers

The final stop will be the space receiving the airflow. The duct won’t end directly in the room. A hole in the wall won’t evenly distribute the air through the room. This is why most HVAC systems use diffusers. Diffusers sit over the opening between the duct and the room.

You may notice several large squares with slats when you look up at your ceiling. These are diffusers.

Illustration of a diffuser vent beside the interior of an office — Diffusers distribute air through the room, so that every corner gets enough air.

Diffusers utilize these slats to direct airflow to different parts of the room, typically in two or four directions. This design ensures the system can distribute the air evenly across the room. The entire room can feel the cool air instead of just the area under the duct opening.

HVAC is a continuous journey: drawing fresh air in, conditioning it and sending it to the right room, then drawing it out and sending it out of the building through the exhaust points. The best practice in design is making sure that journey is efficient. Choose louvers and dampers that meet the needs of your HVAC system.

A laboratory technician working in a lab

At AWV, we build everything you need to direct air through your HVAC system. Louvers for your intake points, control dampers for air control, and diffusers for even airflow in each room. Not sure where to start? Contact AWV today and talk to us about your next HVAC project. We can help.

Follow the Flow with HVAC Design