For students at the Turtle River Montessori School in Jupiter, Florida, being “cool” has become a lot easier — and not simply because their clothing is the latest fashion. It’s because the school itself has become cooler.
The students, teachers and staff at the school have the developers of Turtle River to thank for making them comfortably cool in an area of eastern Florida where the average temperature last May was 87 degrees (Fahrenheit).
The school’s developers wanted students to have the best possible indoor air quality, but they also wanted to provide it in the most energy-efficient manner. Looking for suggestions as to how to make this new school’s HVAC system “green,” Brad Brown of KAMM Consulting, the mechanical engineer for the developer, approached Charles Eno, sales engineer for Florida Air Conditioning Distributors, for assistance.
Eno said he immediately thought of an energy recovery ventilation system (ERV) to reduce outside air (OA) load, which is the required rate of heat removal from outside air. He recommended an ERV system that contained an energy recovery wheel (also known as a heat wheel or enthalpy wheel) created by a Massachusetts-based company called Airxchange.
An Ideal Way to Reduce HVAC Costs
With rising energy costs and climate concerns, these wheels were an ideal way for the school to reduce HVAC costs while complying with code-mandated outside air requirements. Airxchange’s ERV wheels reduced this cost by recycling the heating and cooling energy in exhaust air (not the air itself), thereby reducing the load on the HVAC system by as much as 80 percent.
This reduction in load not only translated into significant ongoing cost savings, but also allowed for the downsizing of HVAC equipment, creating an immediate return on investment.
Built to Last: ERV wheels = Big Savings for School
The energy recovery ventilation (ERV) system installed at the Montessori school saved the administration approximately $25,000 in construction costs. Since the school opened in the fall of 2009, it has delivered savings at the rate of approximately $6,000 per year, compared with the utility bills the school would have had with a conventional HVAC system.
Even though the state’s climate is usually quite warm and humid, Eno demonstrated that by recovering 70 percent of the school’s exhaust-air energy and recycling it, the ERV system would allow the architect to reduce the required size of the school’s packaged HVAC unit by half.
The design was modified accordingly, and the ERV system was paired with a high-efficiency unitary air-conditioning unit on a single plenum curb to minimize internal duct connections and to simplify the installation on the roof of the school. The system was also mounted horizontally, keeping the height of the packaged HVAC system to a minimum and preserving the building’s architectural profile.
Easy to Clean and Maintain
Most energy recovery wheels are difficult and time-consuming to clean, and contaminant build-up in the wheels can significantly reduce performance over time.
The Airxchange wheel’s unique design, however, includes lightweight, durable segments (shaped like pie slices) that can be easily removed for cleaning on or off the site. In less than 30 minutes, one person can replace all segments with new or previously cleaned spares and return the wheel to service.
However, if properly filtered, and if the filters are maintained in accordance with the manufacturer’s recommended schedule, and the energy recovery wheels installed rarely need cleaning.
A Hardworking and Low Cost System Keeps it Comfortable
The HVAC system manages all of the outside air ventilation for the whole building, conditioning it and feeding it into the returns of all the air handlers. The air handlers are a part of a building-wide variable refrigerant flow (VRF) system that modulates the refrigerant flowing through the coil. This maintains desired humidity without overcooling the building and prevents the coil from icing up as well.
In effect, the downsizing of the overall HVAC system paid for the ERV system. In addition, thanks to ERV, the school saves approximately $500 every month on its utility bill. Best of all, the students, staff and teachers are now cool and comfortable, everyday, thanks to the system that successfully keeps heat and humidity under control.
“The indoor air quality is excellent. The building is very comfortable, and the air always smells fresh and clean,” said Bubli Dandiya, the building’s owner and principal.
