Displacement Ventilation

 In Blog, Ventilation

We’ve all been in a meeting room, classroom, or office space in the afternoon. If windows aren’t opened to allow a little fresh air in, the existing room air can start to get a little stagnant and stuffy. This can make the occupants a little uncomfortable and start to lose focus. And we really only have ourselves to blame for poor ventilation.

Breathing, body heat, and even computer use all contribute to the stuffiness. There are several different ways to combat this issue, the most popular being mixed air exchanges. These air handling units/HVAC systems are able to take in outdoor air, scrub it, and fill a room while removing the existing air in the same room.

Depending on the size of a room, it can take an hour or two to completely change out the air supply. Air exchangers improve the indoor air quality and the airflow is minimal to reduce distractions. They also remove the humidity of the outside air, keep the room comfortable.

Displacement Systems

Another way to keep the air flowing in a large room is through displacement ventilation. This system slowly brings in cooler supply air from the outside, usually at floor level, and is taken to the ceiling via thermal plumes caused by the existing warm air. As we said above, heat sources include computers, body heat, lighting, and other electrical machines.

As the cool air rises, the occupied zone – where people are working, either at a desk, standing for a presentation, or walking to the water cooler – remains comfortable, although it is warming along the way (the temperature gradient). The warmer the air gets, the more it rises, dragging the new cool air with it.

As the air temperature rises, the warm air is removed through a vent in the ceiling, taking with it pollutants and imperfections. Buoyancy allows the cooler air to spread out before rising in a sheet so to speak. The vent is equipped with a fan. But to save on energy consumption, the return air just naturally rises up and out on its own.

Pros and Cons of Displacement Ventilation

Theoretically, this is a more energy-efficient way to clean the environment than mixing the air as exchangers do. Using the physics of warm air as a catalyst for air distribution, the cooler air supply temperature remains on the floor. As it warms, the air begins to rise on its own without the benefit of a fan. If a fan isn’t used, it doesn’t need energy.

This naturally provides for improved air quality. If installed properly, displacement ventilation should be providing clean air right in the occupation (breathing) zone while pushing the “infected” air out. Air exchangers mix the two together. So the air is cleaner, but it’s not as clean as it could be.

However, displacement systems can be much bigger than air exchangers, making them harder to place within the room. It’s best to locate a displacement system on a wall if possible because of the proximity to outside air. There are systems that can be placed in the middle of a room, but they aren’t as efficient.

While the system does cool down a room, it doesn’t really act like the air conditioning you have in your home. Those can be set to almost any temperature the homeowner wants, where distribution systems can only go so low.

Where is Distribution Ventilation Most Successful?

Although the system can be used almost anywhere, they seem to be at their best when working in large, open spaces where many people congregate. Theaters, restaurants, and supermarkets can all take advantage of this kind of ventilation. It keeps things cool as well as pushes “infected” air out of the room.

We’ve all been at a movie theater where somebody has an incessant cough or at a casino where smoking is allowed. The germ-filled and smoky air is automatically lifted up and away by this system. It leaves behind cleaner, cooler, and more comfortable air.

Hospitals, industrial plants, and other facilities require improved air quality. It’s a matter of employee safety. They would also benefit from this ventilation. Essentially, if the supply air is cooler than the room temperature, the rooms are 10 feet high or higher, and low mechanical noise is desired.

As part of our building and commercial construction, we work with many different types of ventilation systems. Does your industrial facility need a new or upgraded HVAC system? Contact Storee Construction and we can define what system is best for you and get it installed. We have been working with large plants in the midwest region for more than 50 years. We’ll make sure you get the system you need.