Coronavirus Prevention: ASHRAE Guidelines for Building Ventilation
This is an article in the series adapting to the pandemic, where we intend to share useful tips for making it through these troublesome times.
Reducing the supply of direct outdoor air, when needed, is the aim of most modern HVAC engineering. Depending on the time of the year, increased airflow can result in an increased workload on the heating or cooling system. In this case, the heating costs are especially high during the hot summer days and high cooling costs during the cold winter days.
However, ASHRAE provides new HVAC ways to help in controlling or preventing the spread of the coronavirus in your building, during and after the pandemic. ASHRAE suggests that buildings should keep outdoor airflow at a maximum. This way, indoor air recirculation is reduced as well as the chances of spreading the virus through indoor air recirculation. You can also take a look at Best Air Purifier Guides to learn more about air purifiers.
Bear in mind that at extreme outdoor temperatures, heating and cooling units may be overwhelmed. Hence, the supply of outdoor air should be limited. The same is the case for too humid or too dry, outdoor air. The relative humidity should be maintained at the 40% to 60% range recommended by ASHRAE. The idea is to maintain maximum outdoor airflow within these constraints.
But how does increasing outdoor airflow prevent the spread of the virus? With an increase in outdoor airflow, the concentration of the virus in the indoor air is removed, without needing to recirculate throughout the building. MERV 13 filter upgrade and using Ultraviolet Germicidal Irradiation can complement this outdoor airflow recommendation.
Of course, ASHRAE is not turning deaf ears to the fact that increased outdoor airflow means higher energy costs. Depending on the local climate, adding an airside economizer can mitigate the increase in energy costs. You can also achieve this by ensuring the exchange of heat and humidity between the supply air and exhaust air using an energy recovery ventilator.
Disabling Demand Controlled Ventilation for COVID-19 Prevention
Modern HVAC systems come with controls that automatically reduce outdoor air supply based on demand or occupancy. In other words, the ventilation system allows for maximum outdoor flow only when there is high demand (full occupancy). This system of ventilation is known as Demand Controlled Ventilation (DCV). However, to prevent the spread of the virus, ASHRAE recommends disabling this system. Allowing for a constant high outdoor airflow.
DCV regulates the workload on every HVAC component; from air handlers, air conditioning units to space heating systems. Although the DCV is effective in ensuring energy efficiency, the priority at this point in time, preventing the spread of the virus in building interiors, outweighs that of maintaining energy efficiency.
Reconfiguring buildings with Building Automation Systems (BAS) or Building Management Systems (BAS) to follow ASHRAE guidelines is advisable for the prevention of coronavirus. And so also is temporarily pausing DCV controls and installing a program that constantly maximizes the supply of outdoor air.
Inspecting Ventilation Systems Before Reopening a Building
Ventilation is important in preventing the spread of the coronavirus. It is therefore important that you ensure your ventilation system is in good condition. Most buildings have been on lock and keys due to the coronavirus lockdown, if yours was, inspecting the ventilation system, and ensuring it is in optimal condition is a must before reopening. There are two main points that must be considered before reopening;
- Technical issues: Ensuring all HVAC units are working correctly
- Health hazards: ensuring all HVAC components are not pathogens and fungi infested
COVID 19 is a new virus, let’s not forget that other health threats exist. More specifically, mold and legionella bacteria can form and multiply in HVAC components, if left unattended to. This can result in different health hazards, for example, mold spores can affect the respiratory system. Also, asthmatic patients and those with rhinitis allergies are vulnerable. While Legionella bacteria are known for causing severe pneumonia cases (Legionnaires disease).
Mold can grow in areas of high humidity ( greater than 60%). Therefore, maintaining humidity within the ASHRAE recommendation of 40% to 60% can control mold growth. However, components like cooling coils and condensation pans usually have high humidity, and maintaining acceptable relative humidity for these components is impossible. In this case, the use of Ultraviolet Germicidal Irradiation or UVG can make mold inactive.
Infestations on HVAC components can be easily spread throughout the whole building, through their ducts. Therefore, mold growth on HVAC components should be given immediate attention. Components most susceptible to mold growth include;
- Air filters
- Cooling coils
On the other hand, Legionella bacteria make habitats of warm temperature stagnant water. They are commonly found in places such as;
- Hot water piping
- Condensation pans
- Cooling towers
Legionella can cause severe health problems, therefore, building owners must take necessary precautions to ensure there are no health risks before reopening the building. Legionella in water droplets can result in an infection if inhaled.