Displacement Ventilation Systems for Schools
Morrison-Maierle’s team of mechanical engineers recently toured a research facility to understand better how displacement ventilation systems could work in schools. Morrison-Maierle has provided the mechanical engineering design on several new educational projects from K-12 to higher education.
A few of our team members recently attended a session that showed how displacement ventilation systems can create environments with the extremely high indoor environmental quality necessary in school environments and other public facilities.
Project Use Cases
After the tours, we asked mechanical engineers Lukash Hoff-Pruss, PE, and Eric Webber, PE, a few questions about displacement ventilation and how it might work in their future projects.
Q: What is the difference between a displacement ventilation system and a traditional HVAC system?
Lukash: Traditional HVAC systems supply air from the floor or ceiling and allow it to mix with the room air to heat/cool and ventilate the space. This type of system is called a mixed ventilation system. An alternative type of system, called displacement ventilation, offers some key advantages over a mixed ventilation system.
In a displacement ventilation system air is supplied near the floor at low velocities and conditions the space by pushing hot room air up out of the occupant zone. Due to the low air velocity and its properties of buoyancy, the supply air and room air don’t mix. This allows the hot room air and its contaminants to stratify and push up into the ceiling space where it’s returned to an air handling unit and reconditioned.
Q. What are the benefits of using a displacement ventilation system?
Lukash: Displacement ventilation systems are highly effective in providing ventilation to a space. By extracting the stagnant and contaminant-filled room air from above the occupied zone, displacement ventilation provides fresh air more efficiently compared to a mixed system. By providing more effective ventilation, the overall amount of ventilation required is decreased. Less ventilation means less energy spent conditioning that air, which translates to significant savings for the building owner.
Q. What types of projects (or architectural designs and features) would be ideal for displacement ventilation systems?
Eric: Typical applications for displacement ventilation systems are schools, healthcare facilities, and large public spaces, not only because they are efficient, but they are quiet and offer superior air quality at the same time. Displacement ventilation is also a good solution for cafeterias and kitchens to ensure that clean, fresh air is delivered while removing contaminants and odors. Low-velocity air doesn’t disrupt exhaust hoods either, as heat generated by cooking equipment rises to the ceiling rather than recirculated through the facility. Additionally, areas with high ceilings, like gymnasiums, theaters, and libraries, also benefit from the economic efficiency of displacement ventilation systems.