Air Cleaning Recommendations for All Systems
Regardless of the system type, we suggest extending HVAC unit run times to allow for greater filtration and/or disinfection while attempting to reduce pathogen levels in the air and spaces served, possibly early in the morning prior to occupancy and at the end of the school or workday for a designated period of time.
We recommend for new construction, and HVAC replacement projects, that the design accommodates continuous fan operation during occupancy.
Air Cleaning System Recommendations for Packaged Equipment
For packaged equipment (Split DX, RTUs, & Heat Pumps), ultra-high efficiency units that use an inverter-driven compressor to allow the unit to turn down to match the load and keep the unit running is an optimum solution. These units are typically more expensive but also provide additional humidity control and energy efficiency in addition to the benefit of allowing the air purification system to continue to operate for longer periods of time. There are alternates to the inverter compressor systems to allow continuous unit operation that include hot gas reheat coils or specialized refrigerant control valves.
Air Cleaning System Recommendations for Central Plant Systems
For centralized equipment, VAV air handlers or packaged VAV type Roof-Top Units with terminal boxes allow for the HVAC system to remain energized throughout the occupied period and have similar benefits to those noted for packaged A/C units with inverter-driven compressors.
Air Cleaning System Recommendations for Four-pipe HVAC Systems
For a four-pipe HVAC system with large VAV, constant volume, or multi-zone, air handlers, we recommend installing a UV light system in the air handler where you have the longest exposure available. These systems can be sized for a 99.9% kill rate per air pass, meaning that they effectively eradicate the airborne pathogen from the air that is circulated in the system. This type of centralized UV light system can effectively protect a large area of the building.
However, many air handlers and fan coil units do not have adequate space for a UV light system to be installed inside them. As a result of this, we would recommend installing bi-polar ionization in these units. As long as the space being served is not more than 100 feet downstream of the bi-polar ionizer, a needlepoint ionizer will suffice. For longer duct runs, we would recommend installing either a tube type bi-polar ionizer or multiple needlepoint units closer to the discharge of the ductwork. We would recommend a similar installation of bi-polar ionizers in rooftop air conditioning units. For a water source heat pump system (which would include geothermal systems), we would recommend having needlepoint bi-polar ionizers installed on each water source heat pump while providing a tube type bi-polar ionizer in the 100% outdoor air unit to continuously provide ions into the space for cleaning even when the water source heat pump switches off.
Air Cleaning System Recommendations for Special Use Cases
There are some spaces within buildings that require special attention. The spaces we have identified as special use cases generally fall into two categories. The first are spaces with a high amount of non-occupant or visitor traffic. The other category is spaces where occupants may not wear face coverings due to the activity that happens in that space.
Some examples of special use case spaces are:
- Cafeterias or dining spaces in K-12 schools, higher education campuses, or office buildings
- Health clinics
- Administrative or lobby spaces in government buildings, schools, or offices
- Fitness centers, studios, or gyms within schools or office buildings
- Locker rooms or spas with shower facilities
- Shared housing spaces, such as dormitories on higher education campuses
In these special use case spaces, we would recommend providing space mounted DHP devices. This will provide additional coverage for these higher risk areas in order to provide the maximum effectiveness while minimizing the cost.