In addition, there is the potential that increasing outside air ventilation without accompanying dehumidification can increase the likelihood of condensation on interior building components such as piping and duc- twork. This can lead to the deterioration of building materials and the potential for future mold problems. Working with your HVAC engineer can help maintenance teams prepare for possible implications of in- creasing outdoor air ventilation through building air handling systems. It’s also critical that facilities staff work closely with school administra- tors to keep abreast of the potential for reduced occupancy loads. Many school systems are evaluating partially digital schedules to reduce the number of students in a facility at a given time, thereby increasing the ability to keep adequate social distance between people. This reduced occupancy will improve the effectiveness of ventilation given that reduced occupancy means less potential contaminant or viral sources within the space as well as essentially increasing outdoor air ventilation rates per person, based on the lower number of occupants in the space. Address shutdown-specific risks CDC recommends specific actions be implemented by facilities staff if the building or systems were shut down, or usage was dramatically curtailed, for prolonged periods of time prior to re-occupying. Unless there was a program in place during the shutdown to regularly “flush" water systems, potential Legionella contamination, must be addressed now. Stagnant water can result in ideal conditions for bacteria like Legionella to grow. While Legionnaire’s disease poses its own risks, it’s important to note that it presents symptoms similar to those seen in COVID-19-infected patients and similarly affects vulnerable popu- lations. Addressing Legionella is a critical safety step and will also reduce the risk of another school closure. The CDC outlines several steps to take to minimize the risk of Legio- nella prior to reopening a school facility. The first step should be to create a water management plan that identifies high risk areas for water to stagnate, such as dead legs or unused taps or showers, and outlines steps to correct each problem. Next, flush the building’s water systems with all terminal devices on a branch opened at the same time for a minimum of five minutes. Ensure hot water systems reach the maximum heat available. If these systems have not been flushed throughout the shutdown, there is a risk of invit- ing residual bacteria into the area where the test is being performed. In this case, be sure to work in a well-ventilated area and wear appropriate personal protective equipment, including a properly fitted N95 respirator. Finally, perform cleaning in all areas where stagnant water is possible. This includes clearing running drains to eliminate standing water, cleaning gym and dormitory showers and checking cooling towers for proper operation and chemical treatment for scale, corrosion and biocide. For buildings or populations at highest risk, consider proactive sampling for Legionella. Options for filtration and air cleaning While maintenance will play a critical role in supporting higher levels of ventilation, schools are also looking to invest in other products to strengthen their infection control response.
ASHRAE advises increasing filtration at the air handling unit to limit the spread of viral particles recirculated through the return air system. The association’s guidance suggests MERV 13 filters as preferable as these filters are able to capture particles as small as 0.3-1.0 microns with reasonable efficiency. However, few of the older school HVAC systems will be able to accommodate the recommended minimum MERV 13 filters. Higher efficiency filters add a restriction to the air- flow and without compensating for this restriction, result in a decrease in airflow. To make up for this, schools are looking to utilize portable air filters with HEPA filtration for each classroom. If this is an option your school is considering, it’s best to act now. Obtaining HEPA filters and portable purifiers could become more challenging in the fall as demand increases. In addition, some schools are exploring UV-C and ionization solutions as a potential avenue for limiting the spread of viral particles. ASHRAE provides guidance on the use of UV-C for in-duct air disinfection and surface disinfection and although there are specific applications where this technology is effective in degrading viruses, the products are not considered plug-and-play solutions. To be effective, a UV-C system must be appropriately designed into the existing HVAC system(s) and its output matched with the system’s airflow. Consult an experienced design professional if considering the use of UV-C. Regarding ioniza- tion, there is limited information about the effectiveness of this tech- nology in commercial HVAC systems and this should be considered when evaluating its use and installation costs. Budget for critical improvements While recommended maintenance activities may stretch school bud- gets, these activities are critical to ensure student and staff safety. For many schools, it will be a matter of bringing mechanical systems up to current code performance and catching up on too long deferred maintenance. For others, it may mean investing in the staff to perform routine maintenance or forging relationships with HVAC contractors or consultants to supplement the in-house team. Schools are also likely to see an uptick in operational costs. Among other recommendations ASHRAE advises extending HVAC system operating hours compared to typical occupied hours to provide an in- creased ventilation rate prior to and after occupants leave the building. This increased energy use can drive up energy bills. However, this is but one more reason why it is critical to outline today the steps necessary to safely reopen and identify the potential impacts of each step. Preparing early gives schools time to brace for budget impacts. It also gives facilities managers time to help project where in- vestments are most needed and how to minimize the overall impact on the building. By preparing today, schools can minimize the impact of COVID-19 on their budgets and their communities and create a build- ing environment that is both welcoming and safe for its occupants.
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august 2020
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