Many of our office tenants still have not returned to the workplace, a full eight to 10 months after the start of the COVID-19 pandemic. One of the concerns that we hear from our tenant contacts about coming back is possibly being infected by coworkers. Therefore, it is not hard to see that until we have a widely distributed vaccine and/or people feel comfortable being in close proximity to others outside their immediate families, it is unlikely that we will see workplace occupancy return to pre-COVID-19 levels.
In response to these concerns, designers and manufacturers of HVAC equipment are busily working on technologies designed to reduce or eliminate harmful pathogenic viruses and bacteria from the air inside our buildings. One word of caution from IREM member Wade Conlan, PE, CxA, BCxP, LEED AP, of Hanson Professional Services, Inc. and leader of the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) Building Readiness Team, part of ASHRAE’s Epidemic Task Force, is that building managers, owners, and operating engineers need to carefully research any changes in HVAC design or equipment before attempting to alter the existing HVAC equipment of a building.
With those realities in mind, here are some of the most promising new products and emerging technologies to consider.
Improving air filtration on existing systems
According to the National Air Filtration Association (NAFA), air filtration systems within HVAC systems are not a solution all by themselves but can be a part of an effective overall risk mitigation approach. NAFA advises that in most buildings and situations, filters still may be considerably less effective in slowing COVID-19 spread than social distancing, isolating known causes, and hand-washing. NAFA also warns that high-efficiency filters—those with higher Minimum Efficiency Reporting Value (MERV) ratings—can be counterproductive because they often require more frequent filter changes. They also can cause more air to bypass the filter as it becomes occluded with dust particles, diminishing the effectiveness of the higher filtration and potentially causing other problems in the HVAC system, such as dirty cooling coils.
ASHRAE and the Centers for Disease Control and Prevention (CDC) recommend switching to MERV-13 filters to reduce virus transmission in schools, buildings, and homes, but they do not provide specific guidance for office buildings with HVAC systems designed for higher airflows and minimal outside air intake. The challenge with this approach is in design issues of the existing system and the fact that, depending on location, your HVAC system may not use much outside air. In Florida, for instance, the ambient air is often so hot and humid that many HVAC systems are designed to use close to 100% recirculated air.
Utilizing higher MERV-rated filters (such as MERV-13) or even HEPA-type filters (which are able to capture 0.3µm (micrometers, or microns) particles at a rate of 99.97%) on a system that is not designed for them may cause more problems than they solve. In addition, the cost of the MERV-13 filters is significantly higher than lower MERV-rated filters, and they may require more frequent changes if the air handling unit system cannot handle higher pressure drops. Moreover, installing filters that inhibit airflow can often create a reduction in air delivery to the spaces, change pressure relationships, lead to premature fan failures, or cause occupant discomfort. What sounds like an easy fix may in fact cause a lot of headaches and not solve anything.
Altering the set points for the economizer cycle on air handlers
In parts of the country in which the ambient air is less humid and more temperate, air handlers are often designed with what is known as an “economizer cycle”. This is a system in which the air handlers are equipped with appropriately sized louvers, ductwork, and dampers to allow increased outdoor airflow to enter the supply airstream if certain conditions are met, such as outdoor air temperature measuring between about 32 degrees and 65 degrees Fahrenheit and space humidity measuring sufficiently low. The dampers are usually controlled by enthalpy sensors that read both the temperature and humidity of outdoor and return air, and as the outdoor air is less than the return air conditions, the dampers adjust to increase outdoor airflow. This also allows the building to use more fresh air without significantly compromising energy efficiency.
The problem here is that if the dampers do not restrict outside air intake when that air is too hot, too cold, or too humid, it can result in the system working much harder to heat or cool the ambient air. It sounds attractive to have more outside air in the building, but unless the system is designed for that, it can cause a lot of problems, just like changing to higher-efficiency air filters can.
Ozone is a byproduct of traditional ionization technology and is associated with myriad detrimental health effects. GPS has introduced a new version of this technology called Needlepoint Bipolar Ionization (NPBI), which is different because it does not use high voltages to ionize the particles, but rather a proprietary low-voltage technology to avoid the production of ozone during the ionization process.
NPBI produces both positive and negative ions, which, once produced, have a life span of about 60 seconds, during which they travel with the airflow into the space where finer particles as small as 0.3µm in diameter start sticking to each other, allowing them to be pushed by the airflow to the filters.
According to GPS, NPBI technology has been successfully used in hospitals, offices, airports, schools, and other public venues. Bipolar ionization, and especially GPS’s NPBI technology, is indeed promising, but it is new and may prove to have unknown and unintended consequences over time.
UV (ultraviolet) light technology
Ultraviolet light, particularly UV-C light, is a proven technology for neutralizing certain microorganisms and has been used for over 20 years in various applications. According to an ASHRAE Journal article from 2017—and confirmed by Conlan—ultraviolet germicidal irradiation (UVGI) or light in the UV-C wavelength (253.7 nm) has been used in HVAC equipment since the 1990s to deactivate biological growth on surfaces inside air handlers to save energy, boost airflow, and improve IAQ.
UV-C has long been used in the healthcare industry as an effective method of eliminating or neutralizing certain pathogenic bacteria. ASHRAE conducted studies at several healthcare facilities that showed UV-C systems reduced total bacteria and fungus counts and had a “dramatic effect on the levels of air contamination.” Conlan says that although UV-C is promising for office building applications, continued research is needed in nonhealthcare environments. It appears that UV-C can disrupt virus DNA, sterilizing it and inactivating the virus, even at lower UV-C dosages. UV-C light devices have been shown effective in reducing bacteria, viruses, mold, and fungi on surfaces. According to several studies, UV-C has been proven to kill the SARS-CoV-2 virus that causes COVID-19.
So how should building owners and managers proceed from here? Conlan recommends that we evaluate the specific applications at specific buildings with consideration paid to the design limitations of those buildings’ HVAC systems and not assume that one size fits all. He also suggests that we consider using a team of professionals, such as a building commissioning engineer, building test and balance agent, or others before jumping to a promising technology which may not solve IAQ issues but instead may even exacerbate them.
The COVID-19 pandemic is unprecedented in many ways, including the changes that have occurred in how traditional office users occupy their space. We are all looking for the magic solution that is going to cause our tenants and their employees to regain confidence and reenter the workplace. And despite the pressure that some of us are feeling to do something about the ghost buildings that many of us are experiencing, experts including Conlan caution against jumping on board with a solution that could actually make matters worse. The answer may likely be a combination of some or all of the solutions covered in this article, or it may lie in as-yet untested technologies.