Advanced filtration: Healthy indoor air without sacrificing energy

Building owners are using a myriad of extensions to adjust their office settings to mitigate COVID-19 infections.

Deep cleaning, temperature scanning, and other measures are all important, but with the latest advances in research on new coronaviruses, experts have evolved their thinking on priority mitigation measures. The most urgent concern is now focused on how to deal with air droplets (bioaerosols) that remain in the air for much longer than initially suspected. The HVAC system and its supporting ventilation and filtration strategies have become a front-line protection mechanism that building managers can employ to ensure that the facility is safe when employees return to the office.

Expert HVAC recommendations have evolved to accommodate the latest COVID-19 studies. Initially focused on maximizing outside air ventilation, this approach quickly reveals significant drawbacks, especially the high energy penalties associated with HVAC system limitations and their strategies. became.

Adjusting the outside air to achieve comfortable temperature and humidity is the highest cost of operating a commercial HVAC system. The more adjustments you have to make, the more energy is used. This makes maximizing outdoor air both a costly strategy and a strategy that exacerbates building carbon dioxide emissions. Increasing concerns are growing as companies adopt sustainability goals and try to avoid immediate GHG penalties from measures such as Land Method 97.

William Burn Fress, chair of the Epidemiological Task Force of the Association of Air Conditioning Engineers (ASHRAE), shared some enlightening research at a recent webinar entitled “COVID-19 Risk Management Fundamentals”. .. Professor Baan Fress, who also teaches architectural engineering in Pennsylvania, showed that the average relative risk of infection can be equally reduced by filtration or ventilation. According to Professor Baan Fres, “Achieving the same risk of infection using ventilation is much more costly. [than filtration], Mainly due to energy costs due to increased ventilation. The reduction in infection risk associated with the use of high efficiency filters (expressed by higher minimum efficiency report values, or MERV rating) is almost completely consistent at high efficiency levels of the filter, regardless of the number of air changes. To do.

ASHRAE updated its commercial guide in late August to reflect these considerations and recommends the following strategies:

• If the increased outside air for ventilation has a significant impact on energy, use the minimum outside air required by ASHRAE Standard 62.1 with a minimum MERV-13 filter.
• If the outdoor air quality, especially particulate matter, is unhealthy according to Section 4 of ANSI / ASHRAE Standard 62.1-2019, do not open windows or increase ventilation without the use of appropriate filters.
• If possible, maintain relative humidity between 40% and 60%.
• If the room’s outside air is inadequate according to the code requirements and the filtration is below the MERV-13, consider a portable air cleaner.
• Consider UVC light as an enhancement if the space requires additional measures, for example, a space that serves vulnerable residents, or if MERV-13 filtration or 100% outside air is not possible. Please give me.

Enhanced filtration is an important solution to the challenge of maintaining healthy indoor air quality, but it is not always easy. In older facilities, existing HVAC systems may not be able to handle upgrades to more efficient filters. For these situations, ASHRAE recommends indoor high efficiency filtration units.

In addition, there is growing interest in addressing bioburden-intensive spaces such as entrances, conference rooms, elevators, and kitchen / lounge areas. Local filtration devices that can handle viral contamination at the source are also recommended in these spaces.

According to ASHRAE, these indoor units should be placed in the center of the space and not directly sprayed on the occupants of the room. Ceiling-mounted units with high-efficiency filters that operate independently of the HVAC system address these concerns without adding significant cost or stressing the system. It’s set off the floor and out of the way, so you won’t be distracted by meandering cords or fan noise. It cannot be removed or removed as easily as a portable unit. It may also contain a UV light that kills virus particles caught in the filter and can be safely replaced at any time.

Many experts now recommend a “all of the above” approach to viral restoration in an office environment. Additional air purifiers can be used to add enhanced filtration to a practical filtration and ventilation approach. Keep the following in mind when choosing an air purifier:

• Look for an independent test that confirms that the purifier works as claimed.
• Look for ceiling-mounted units to prevent the risk of tripping and removing or moving units in busy shared spaces or meeting rooms.
• Choose rugged, durable, commercial or industrial grade units rather than residential products.
• Pay attention to the ventilation rate per hour (ACH) provided by the unit and combine it with the existing HVAC system to ensure that the facility has 5 recommended ACHs to keep the virus load low. Multiple units may be required to handle the space properly.
• For ease of management, make sure that the ceiling-mounted purifier has a wall-mounted control panel.
• Look at the air filters mounted under the ceiling and consider the peace of mind that they may be provided to the residents of the building. It’s as effective as it would be if installed in Plenum, but a visible air purifier may provide peace of mind.

Protecting building residents from COVID-19 infection is one of the priorities for building owners and their tenants. Building owners can breathe a little easier, knowing that they are protecting building residents with advanced filtration strategies, without the enormous energy penalties associated with advanced outside air ventilation.

Doug Engel is Senior Vice President of Sales and Marketing at enVerid Systems in Boston, Massachusetts.