Although COVID-19 may have highlighted issues regarding ventilation, careful HVAC system selection has always been crucial in educational settings. While there are several types of classroom air conditioner units, they work in different ways and have differing requirements for installation. This covers some of the basics about each type and their potential roles in a larger HVAC system.
While there are a number of HVAC options available, engineers have a baseline for assessing the systems that they design through three standards from the American Society of Heating, Refrigerating and Air Conditioning Engineers, or ASHRAE. For reference, ASHRAE 90.1 covers energy usage, 62.1 covers indoor air quality, and 55 covers thermal comfort in terms of both temperature and humidity.
Each has a number of requirements, but the ones most crucial to specifying engineers are the minimum efficiency, minimum ventilation rates for rooms based on activity and occupant load, and comfort zones. These must be used along with the available space, budget, and other factors to properly select the right classroom air conditioner units.
There are four main types of air conditioner units for classrooms, ranging from the venerable unit ventilator to variable refrigerant flow systems and two variable air options.
First introduced in 1917, unit ventilators (UVs) are the most commonly chosen and established way to bring fresh air into educational environments. A fan, run through a heating or cooling circuit, brings in outside air to meet the desired temperature. Because UVs function discretely (one unit per room), one room’s heating and cooling system can malfunction without affecting the rest of the building. Sometimes on a retrofit Job with Existing UV’s replacing like for like is the least costly alternative due to the fact UV’s have been around for so long and they haven't changed much over the years.
However, UVs are not without their drawbacks. They don’t affect the level of moisture in air, which means that students and educators are still impacted by seasonal drops and increases in humidity. Additionally, because they use a single unit to heat or cool a room, any blockage or issue significantly reduces a unit’s effectiveness.
Variable refrigerant flow systems operate on principles much like that of a heat pump. With the proper controls and piping, refrigerants can move around and into dozens of indoor units to provide heating and cooling without the need for large ducts or piping. While they are extremely efficient compared to other options, they may not be as great a fit for interior classrooms and spaces that require significant ventilation.
Single-zone variable air volume systems are increasingly common in educational settings. They can be quieter than unit ventilators because they can operate at significantly reduced fan and compressor speeds. This can also help with humidity control, especially during changes in occupancy levels. However, they also require ducting throughout individual classrooms and carry more of an initial cost.
As opposed to a single-zone system, a larger variable air flow system may also be able to provide heating, cooling, fresh air, and dehumidification to classrooms throughout a building. While this is less expensive in terms of both first and ongoing costs, there are key considerations. The system must be able to direct fresh air to spaces at varying rates depending on ventilation needs of windowed and non-windowed rooms. In addition, there must be enough space for the ducting to be able to bring fresh air into a classroom, not feasible for some retrofit projects.
Classrooms in schools can occupy any number of spaces, which can make for some real headaches when trying to establish proper temperature, humidity, and ventilation levels through system design. So, whether considering a major upgrade or as part of new construction, engineers must understand:
Windy City Ventures represents leading manufacturers of the systems above that serve as classroom air conditioner units and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying these units. Contact us today for a quote or bid.
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