One of the major lessons learned about the Covid-19 pandemic was the role ventilation played in its spread. In the summer and fall of 2020, the World Health Organization and then the Centers for Disease Control and Prevention announced that the deadly virus was largely transmitted through aerosols, not saliva droplets as originally thought, and that the ventilation performance of buildings played a critical role in the health and safety of their occupants. Simply put, people who spent time in poorly ventilated spaces were at higher risk of being infected. The same principle applies to many other virus we are subjected to in our daily lives — from annoying colds to more serious seasonal flu and RSV.
ASHRAE, the association for the heating, ventilation and air conditioning engineering professions, was one of the organizations paying attention to those 2020 revelations. Its Standard 241, Control of Infectious Aerosols, (published in July 2023), establishes minimum requirements to reduce the risk of airborne viral transmission.
When adopted by builders and regulators, it can provide protection against the germs that impact so many of us every year. “With the fall and winter virus season approaching, mitigating the spread of airborne infections will be of even greater importance, and incorporating the guidance in Standard 241 can be a major step forward in addressing clean air flow goals,” commented ASHRAE’s president Ginger Scoggins in the organization’s October 4 news release.
What can it do for you and your household? Are there components you can add to your home to improve your own and your family’s safety even if you’re not building or remodeling? And when might we see 241 incorporated into new single family home communities?
You probably shouldn’t hold your breath, according to Max Sherman, who served as leader of ASHRAE’s Epidemic Task Force Residential Team during the pandemic. “241 is brand new. No one has adopted it yet,” he responded in writing to my request for comment. “It is being evaluated by many,” he added, noting that he anticipates it will be several years before we see it becoming adopted widespread, but it can start showing up in custom homes sooner. “For new single family, it might be more marketing than regulation.” With more buyers saying wellness will be a factor in their selection, adoption of this new standard can definitely be part of a healthy home pitch.
Some local regulators are already looking at 241 as well, according to its author, (as is typical with ASHRAE standards). “Cities are often able to move faster than states or the federal government, so I am optimistic we will see that happening soon,” observed the standard’s task force leader William Bahnfleth, professor of architectural engineering at Penn State, in a published Q&A. He’s seeing indoor air quality interest among New York City leaders that could incorporate components of the standard in its aggressive housing plans, he shared in that interview.
It can’t happen soon enough! The 241 standard provides guidance on HVAC system design, installation, commissioning and maintenance to control the spread of infectious aerosols. It also includes recommendations for ventilation rates, filtration and air cleaning technologies, along with a building readiness plan that documents procedures for assessing existing or new HVAC systems to determine if they are working properly.
For renters and homeowners not planning on remodeling or moving, 241’s guidance on the performance and safety of air cleaners, (which you probably think of as air purifiers), is crucial. Some produce byproducts that are potentially harmful, Bahnfleth pointed out. Is the appliance you’re considering for your home dangerous? You need to know; the standard showing up on product packaging and online descriptions would make that easier.
The engineering professor also shared that the new standard will also address another major health hazard. “Air cleaning systems installed as part of complying with Standard 241 that remove particles from the air also help clean up wildfire smoke that enters a building.” As more regions’ air quality levels are impacted by distant and nearby wildfires, this benefit takes on added importance.
Indoor Air Quality
IAQ, as it’s referred to in the building and design industry, covers all factors that impact the air we breathe at home, from viruses to wildfire smoke to pollution – which is often worse indoors than outside. It can be challenging to address the problems comprehensively, but this is a good start. “Evaluating IAQ is complicated, depending on multiple factors, such as the number of individuals in a space, what activities they may be doing, the capabilities of the ventilation system and pollutants from both indoor and outdoor sources,” noted Rachel Hodgdon, CEO of the International WELL Building Institute, the creators of the respected WELL AP certification for wellness-focused professionals in an email on this issue.
“ASHRAE standards are designed to be adopted by jurisdictions, thereby integrated into the local building code. We’re fortunate that ASHRAE has made good progress, particularly recently, in advancing its suite of IAQ-related standards, helping jurisdictions strengthen their IAQ baselines,” Hodgdon added. The WELL standard works in a complementary way, she noted, while employing IWBI’s own criteria and guidelines.
Many regulators, builders and buyers are looking at heat pumps as sustainable alternatives to traditional HVAC systems. “Heat pumps can be part of a central air system or can also be part of a mini-split system,” Sherman explained, which is good news for homeowners wanting both sustainability and wellness. “To meet 241 the easiest you need a high-MERV filter and sufficient airflow. Easy to do with a central air handler. Mini splits can theoretically do it, if one can get better filters and enough airflow for the total to reach the right number, but heretofore they have not been designed to do that.” This will likely require more complexity and cost.
Eric Goranson, host of the syndicated radio, TV and podcast program Around the House Show, added his insights about 241 for these increasingly popular systems in an email response. “Mini split heat pumps are like a budget-friendly genie for heating and cooling. They swoop in without the need for a major interior renovation, saving you from the duct drama. For those older homes that were once cozy thanks to oil, gas, or steam boilers, these mini split heat pumps are a game-changer!” Now let’s talk integrating 241 into these systems, he added: “That’s a tough nut to crack! Ducted systems? They’re a bit more versatile, giving us the freedom to tag on other cool stuff like UV air filtration or fresh air systems.”
The 241 standard is written to keep people safer from viruses, with the added IAQ benefits, but Goranson has concerns, he shared. “Living up in the Northwest, I’m all too familiar with wildfire season. It’s a real struggle to keep that indoor air pristine when the great outdoors seems to be in a bit of a mess. We need some serious brainpower to cook up smarter systems. I am liking some of the new heated HEPA filtration units that are just coming on to the market. We will have to see long term how well they work out. My concern is creating standards that technology has not caught up with completely.”
There’s nothing wrong with some healthy skepticism. I’m pleased to see that 241 incorporates product standards around air cleaners and emerging technologies, that IWBI is looking at this issue along with ASHRAE, and that builders are likely to see these as potential boons to new home sales, making their benefits available more widely.