A shortened version of this was first published at Facilities.Net – Building Operating Management in 3 parts:
Here’s the full version:
Air quality sits at the intersection of sustainability, energy efficiency, health/wellness, productivity, climate change, and inequity. Even prior to 2020, this huge nexus of multi-level, overlapping issues centered on air quality drove a growing recognition of the need to conduct more research and spend more resources addressing air quality outdoors and indoors. And then a novel airborne virus, jumping from bat to human, sparked a global pandemic, placing indoor air quality and its impact on our health/wellness under a bright spotlight, even if that spotlight was primarily illuminating the threat of airborne pathogens.
Just look at how existing building certification systems have pivoted over the last year to provide specific indexes, modules, seals, dashboards, etc., focused on obtaining, monitoring, and communicating aspects of indoor air quality in general and specific to pathogens. Many of the strategies for COVID safety promoted by these certification systems, consultants, and other experts also improve indoor air quality overall. As we move past the pandemic, it will be important for our facilities to carry forward this focus on air quality, and health/wellness overall, while also addressing construction and operational resource consumption and associated greenhouse gas emissions.
We’ve roughly divided many of these strategies discussed over the last year into primary and secondary strategies. Primary strategies generally align with more common building system strategies and have other health and wellness benefits while secondary strategies potentially add operational complexities and costs that many facility managers are less familiar with and/or are not as applicable to as wide a variety of contexts. Obviously, there are other critical risk mitigation strategies besides those focused on building systems not covered here, such as mask wearing, de-densifying, and conducting activities outdoors.
Building Systems – Primary Strategies.
- Increased Ventilation (mechanical and natural): By ventilation, we specifically mean outside air as opposed to total air changes per hour consisting of both outside air and recirculated air. For the elimination of airborne viral pathogens, 4 to 6 air changes per hour (ACH) of ventilation, or equivalent ACH taking other strategies into account, have generally been recommended. It’s also important to point out that any associated increase in energy consumption with increased ventilation can be offset through other strategies like the use of energy recovery ventilators, improved building envelopes, etc.
- Increased Filtration: For most building systems, a minimum filter rating of MERV 13 is generally recommended. And higher MERV ratings do not automatically equate to increased pressure drop (and therefore increased energy usage), as there are many filters with lower pressure drops and higher efficiency. Portable HEPA filter units are also an effective local filtration strategy to supplement building system filtration, particularly if the system isn’t capable of using MERV 13 filters (or achieving an equivalent MERV 13 rating with pre and final filters). However, the noise produced from these units should be accounted for, as they may create distracting levels of noise and intelligibility issues.
- Isolation: Isolating rooms/areas from each other via negative pressure and zoning (in general and specifically w/ respect to isolation rooms or areas designated for testing) can limit the movement of airborne pathogens within buildings.
- Temperature: Thermal discomfort negatively impacts the efficiency of the human immune system and exacerbates the impacts of illness, so it’s important to take temperature and resulting thermal discomfort into account. However, most temperature ranges found within buildings won’t significantly impact the viability of most pathogens themselves. Though this isn’t the case for facilities like meat packing plants that must operate at lower temperatures.
- IAQ Monitoring: Monitoring different IAQ parameters will provide an indication if adjustments to strategies need to be made – increasing ventilation, increasing filtration, changing occupant density levels and/or activities, etc. Examples of parameters to monitor include CO2, particulate matter, TVOCs, RH, and temperature. Such monitoring, if made visible through dashboards, phone apps, etc., and acted upon, can also provide a measure of reassurance and trust among building occupants as well as maintenance staff.
Building Systems – Secondary Strategies
- Humidity: Targeting levels between 40% and 60% is both beneficial to the human immune response (by increasing the effectiveness of our physiological barriers to viruses) and detrimental to the viability of many viruses (by creating a droplet/droplet nuclei environment less conducive to viruses), including SARS-CoV-2 and Influenza. However, in addition to an increase in energy consumption, increasing humidity levels can create situations leading to moisture damage and mold, depending on the climate, building envelope, and HVAC system. Implementing this as a strategy must be carefully thought through. But if they can be navigated, it could be considered a primary strategy.
- UV at HVAC Units: This refers to the use of UV lamps at the air handling unit itself to sterilize the air stream as it passes through the air handling unit. But centralized air disinfection strategies like this are also less effective than in-room strategies. They do relatively little to directly protect occupants in the same room with an infectious source. In-room strategies in essence reduce the exposure time compared to centralized strategies. While that same general criticism applies to building system filtration, building filtration also removes particulate matter (improved w/ increasing MERV levels), further positively impacting human health. In addition, the higher UV irradiance values required due to the airflow speed through the AHU result in greater potential hazards for the maintenance staff compared to upper room UVGI systems (discussed below). They also add additional maintenance tasks for operations staff that many are less familiar with.
- Upper Room UVGI (ultraviolet germicidal irradiation): This refers to traditional applications consisting of perimeter or wall mounted UV-C fixtures (typically 254 – 280 nm), mounted high in a space, used to irradiate an upper zone while shielding the lower occupied portion from exposure. Significant research exists demonstrating the effectiveness of this type of application, but it can be costly to implement, requires specialized expertise to design, requires additional training for facilities staff to operate and maintain, and presents a small risk to facilities staff and occupants if installed or operated improperly. More widespread use of UVGI could also have a negative impact in the built environment’s microbiome, something we’re only now beginning to look at.
It should also be noted that recent efforts to incorporate UV technology within a variety of ambient luminaire types and ceiling fans, including those that directly expose occupants to far UV-C radiation (208 – 222 nm), should be avoided in our opinion. These applications lack sufficient third-party testing and peer reviewed research demonstrating effectiveness in a variety of real-world settings. And regarding direct exposure to far UV-C wavelengths more research is needed demonstrating that this exposure doesn’t have negative health impacts, particularly if that exposure is chronic/repeated over a long period of time.
We also generally recommend avoiding multiple types of electronic air cleaning technology currently being aggressively marketed by their manufacturers and suppliers. This includes needlepoint bipolar ionization (NPBI), dielectric barrier discharge (DBD) bipolar ionization, photocatalytic oxidation (PCO) to a lesser degree, among other types, designed for both portable and building system applications. While manufacturers like to promote “reduced infectivity of certain viruses by 90% or more,” such statements are based on laboratory studies with tightly controlled variables not reflective of real-world conditions. In actuality there is a dearth of peer reviewed research demonstrating the effectiveness of these technologies in various built environmental conditions.
These technologies can also expose occupants to ozone, reactive oxygen species, and various harmful byproducts like TVOCs in quantities that we know are harmful. And claims by a manufacturer that their particular piece of technology doesn’t produce these harmful chemicals isn’t typically backed up by field studies. Some of this technology also floods occupied spaces with negative or positive ions as part of the process. Here again, there is limited peer reviewed research looking at the health impacts of such exposure, and most of the studies that do exist suggest negative health impacts. All of this is why ASHRAE, the CDC, and the UK’s Environmental Modeling Group advise caution when using these unproven technologies.
The same goes for hygiene theater. Extensive surface cleaning with chemicals to eliminate a virus predominantly transmitted through the air is simply a waste of resources (and harmful). And flooding the air with chemical laced aerosols simply adds yet another hazard our bodies must navigate, exacerbated by the all-too-common under-ventilated conditions found in many buildings. Our physiologies didn’t evolve to breath in and be exposed to ozone, free radicals, TVOCs, and other chemicals at these concentration levels – nor did the planet’s varying ecosystems, including the built environment’s microbiome. These technologies, applications, and cleaning methods create an evolutionary mismatch with how our physiologies evolved to function.
Knowing generally what to do and not do, the question then becomes how to determine the best contextual solution drawn from these primary and secondary strategies to mitigate risk as we continue to reopen. Generally, it’s important to gain an understanding of how your building systems are currently performing. Are your outside air dampers locked shut even though the building management system shows them open? What actual ventilation rates are found in your various spaces? What’s the maximum ventilation rate you can achieve with your system? There are multiple sources of information out there to help you gain this understanding as well as navigating how to implement these strategies. Some of these resources include the ASHRAE COVID-19 (CORONAVIRUS) Preparedness Resources, the 5 Step Guide to Checking Ventilation Rates in Classrooms, the AIA Re-Occupancy Assessment Tool, and the REHVA COVID-19 Guidance. You may also need to engage consulting engineers, commissioning agents, test and balance consultants, among other experts to help you navigate this.
In addition to these resources, there are also freely available risk calculator web applications that can be used to assess the relative benefit of various strategies for reducing the probability of infection for your specific building. One of these is BranchPattern’s Facility Infection Risk Estimator™. Taking things like mask wearing, vaccination rates, activity levels, age, etc., into account along with existing and proposed ventilation rates, filtration levels, the use portable HEPA filter units, etc., you can estimate how effective various strategies will be at reducing the probability of affection. You can also use these tools to determine and then post maximum exposure times and a maximum number of occupants relative to the strategies employed for a given space. The results can also be used to communicate the importance of various strategies (like mask wearing) as well as demonstrate the additional safety achieved by implementing the risk mitigation strategies.
By focusing on the above strategies to mitigate risk from SARS-CoV-2 infection, facility managers and building owners are also setting themselves and their occupants up for success beyond the pandemic. This essentially readies facilities for future airborne epidemics and pandemics. It also decreases the risk from other seasonal airborne viruses, like Influenza. And the reduction in TVOCs, particulate matter, CO2, etc. within our built environments resulting from these strategies will have a wide range of positive health and productivity benefits – everything from increased cognitive performance to reductions in cardiovascular disease and various cancers. Not to mention the positive influence that increased satisfaction of indoor air quality can have on occupant complaints, engagement, and workplace satisfaction. And as we alluded to above, implementing these strategies doesn’t automatically result in a net increase in energy or water consumption, utility costs, or other operational costs. It is possible to create healthy, productive buildings that are also energy efficient, and even Net Zero.
Nor do such strategies automatically result in higher initial construction costs. But even when they do, they are dwarfed by the health and productivity costs resulting from not implementing them. This is why it is important to integrate health and productivity costs into life cycle cost analyses. For example, a previous corporate client, as part of their tenant fit-out of an office building, was very interested in using an underfloor air distribution (UFAD) system, particularly due to the associated increase in personal agency over thermal comfort that such a system would provide for their employees. However, the additional $2.6 million required compared to a baseline mechanical system had to be addressed.
Just considering the $121,000 in annual energy savings only resulted in a simple 21-year payback – not very enticing. But after reviewing relevant peer reviewed research, taking all of their employees into account, and making use of our happē™ tool (including an early version of the Facility Infection Risk Estimator™ module), we could also present them with the following estimated productivity and health impacts.
- Improved local temperature control = Increased annual productivity of $1.08 million
- Improved IAQ perception = Increased annual performance of $3.6 million
- Reduced Influenza transmission = 16.7% reduction of infection risk
Each one of these individually results in a simple payback under 2.5 years, which was sufficient to justify the use of a UFAD system.
The end of the worst of the pandemic is in sight. Soon we’ll be able to re-occupy our buildings at greater density levels for longer lengths of time more consistent with how things were pre-pandemic. Let’s build on these primary pandemic strategies to create and operate more healthy and productive environments for all of the occupants we serve. But our ability to provide good indoor air quality is constrained somewhat by the quality of the outdoor air available to us, which is partially impacted by the amount and type of energy we consume. This means we need to achieve these indoor health and productivity goals while continuing to reduce the emissions our buildings produce.