As we move toward the reopening of school for in-person instruction on Sept. 14, there have been some questions about the ventilation systems in our schools. We have been inspecting and improving these systems this summer in consultation with Johnson Controls and Technical Building Systems. The Q&A below includes many questions that have been circulating in our state related to school ventilation systems. Much of the information was provided by our HVAC Engineer, Dave Haman of IPD Engineering, as well as from our Facilities Director Tony Lento.
Q: Who maintains the ventilation systems?
A: District personnel
Q: Where are the outside air intakes?
A: At units, exterior walls and roofs
Q: How is the building zoned?
A: Individual room units
Q: What areas are within each zone?
A: Classrooms, offices, cafeteria, media centers, gyms, libraries
Q: Do the buildings have an economizer?
A: Yes, economizer control is either available or can be programmed for the majority of the equipment. At the high school, rooms served by heat pumps do not have economizer capability. The heat pump outdoor air ventilation is provided via dedicated outdoor air units with fixed airflow rates. Areas of the building not served by heat pumps have economizer control capability.
Q: What are the outside conditions under which economizers are used?
A: When it is 3 degrees Fahrenheit below the zone set point and outdoor temperature is below 75 degrees Fahrenheit. If the outdoor temperature drops below the heating enable set point 65 degrees fahrenheit and the discharge air temperature drops below 70 degrees Fahrenheit, the economizer is disabled and normal operation commences.
Q: Is outside air increased to the highest extent possible based on daily weather conditions and at least above the 17 CFM of outdoor air per person, or approximately 20% of outdoor air?
Q: What temperature or humidity levels trigger a change?
No temperature or humidity levels trigger a change. Outdoor air is scheduled based on the occupied/unoccupied cycle.
Q: What rating of filters are used? Are MERV-13 filters used?
A: The majority of air handlers in the district are designed to use a MERV-8 filter. Increasing the density of the filter (MERV-13) in these units will actually decrease the amount of air flow. The increase in pressure from the motor trying to move a specific volume of air through a denser filter will cause the motor to work harder, run hotter and eventually fail. Failure of a ventilation unit is not something that we want to risk at any point, especially this year.
Q: Will the HVAC systems be kept running for longer hours, up to 24/7 if possible, and at least 2 hours before occupants arrive and the last person leaves the building?
A: Yes, the HVAC systems will be kept running for longer hours than usual. We are planning on setting the unoccupied time at 11 p.m. and the reoccupied time at 5 a.m.
Q: Are portable air cleaners with HEPA or high-MERV filters being provided in areas where there is a high occupant load or areas that have poor ventilation.
A: No. It is important to remember that the ventilation systems in our schools were designed for the spaces they are serving, including the particular occupancy of the space. Further, occupancy is being reduced in spaces across the district in light of social distancing guidelines, increasing ventilation/outdoor airflow for those who are present.
Q: Are upper room and/or portable UVGI devices being used in areas where there is a high occupant load?
A: No. The New York State Education Department currently does not allow their use in student-occupied space. Further, we do not anticipate any spaces where there will be a high-occupant load in relation to the capacity for the room. (e.g. a cafeteria that is housing two separate classes, with half of each class in the group, has significantly fewer students than when they are used for lunches during regular circumstances).
Q: Are bypass energy recovery ventilation systems that could leak potentially contaminated exhaust air back into the outdoor air supply deactivated?
A: Yes, however all energy recovery units meet the NYSED requirement to not allow ERV’s that could potentially allow crossover of exhaust air into the outdoor or supply air streams.
Q: Are the temperature and humidity levels maintained within the established ASHRAE seasonal guidelines with temperatures between 68 to 74 degrees Fahrenheit in the heating season and between 72 and 80 degrees Fahrenheit for the cooling system and humidity between 40% and 60%?
A: Yes for the heating season, and yes for zones with air conditioning/cooling capability.
Q: How are conditions monitored to assure they are within the desired ranges for humidity and temperature?
A: Through the direct digital control system. Humidity is not currently controlled, only monitored. Potential humidity control can only be achieved in zones where cooling is available.
Q: Has the ventilation system been inspected/rated to make sure it is effectively moving air in order to mitigate the possibility of virus transmission?
The district maintenance staff along with Johnson Controls and Technical Building Services have been working on air handling units on all buildings this summer. All necessary repairs and preventive maintenance is being done. This has included new belts, motors, controllers, bearings and drives depending on the specific unit.