By Paula Melton
U.S. EPA Radon Zone Map
Zone 1 (red) presents the highest risk for radon, but high concentrations in buildings have been found in every zone.
As awareness about air quality in schools has reached unprecedented levels in the U.S., one major indoor pollutant remains widely unaddressed: radon
It might not be the most trendy topic for building interiors, but soil chemistry hasn’t changed since scientists first discovered high radon concentrations in buildings in the 1980s—nor has the fact that radon is considered the second leading cause of lung cancer deaths in the U.S. (tobacco smoke is number one).
Our standards for airtightness and ventilation have
changed, and both can affect radon concentrations significantly. Many project teams and school officials assume ventilation systems will automatically keep kids safe, but radon experts disagree. Fortunately, forthcoming standards developed by the American Association of Radon Scientists and Technologists (AARST) for monitoring and mitigating radon in schools and other large buildings are designed to take the guesswork out of protecting building occupants from this radioactive carcinogen.
Based on a national survey in the early 1990s, the U.S. Environmental Protection Agency (EPA) estimated that 20% of schools had classrooms with elevated radon levels—and, argues William Angell, Ph.D., a professor at the University of Minnesota College of Design and chair of the World Health Organization’s Radon Prevention and Mitigation Working Group, “there’s no reason it would have changed” since then. And although children are not considered to be at higher risk than adults, he points out, “risk is cumulative with radon over a lifetime. The more we limit exposure to radon early on, the more protective we are.”
In general, like most radon experts, Angell says testing and mitigating homes is the most critical effort for public health, “but it’s also important that schools test—and do so according to the national protocols.” He told EBN
he’d tested schools that had “radon concentrations that were more elevated than you would allow uranium miners to be exposed to.” And, he warned, “The only way to know is to test.”
That’s true even in lower-risk areas. As EPA explains on its Radon Zone map, shown above, elevated radon levels have been found in buildings in all three zones.
Testing schools and other large buildings requires a different process than what’s used for testing single-family homes. When practitioners trained for residential radon mitigation are hired to test commercial buildings, there are two major pitfalls, according to Douglas Kladder, director of the Center for Environmental Research and Technology, which trains radon mitigation professionals in the U.S. and Canada.
First, they may only test a sampling of classrooms, he told EBN
. The problem with that is, “When you have a school with elevated levels in classrooms, it’s rarely all
of the classrooms—the reason being an unbalanced HVAC system. The potential for missing elevated locations is high.” He recommends that all occupied classrooms with ground contact undergo preliminary testing simultaneously. If a short-term, two-day test suggests a problem, “Follow up before you start ripping holes in slabs,” he adds.
The second major pitfall, he claims, is “false positives” during long-term monitoring. “Testing should occur during time periods when kids are there,” he explains. Otherwise, high radon readings could be meaningless because they reflect the state of the school when “the HVAC system is shut down or the fresh-air makeup is shut off.” If the testing devices can instead track hourly measurements, schools often find that radon levels go up at night, when the ventilation system shuts off, “but at 6 in the morning, they drop like a rock” when fresh air starts getting pulled into classrooms again. This means the ventilation system is adequately dealing with a potential radon problem—though regular monitoring is obviously warranted.
EPA recommends periodic testing for all schools because settling can cause foundation cracks that elevate radon levels. The agency also recommends using a long-term (90 days or longer) average in wintertime (when windows are sealed up and negative pressure is typically at a high) as an indicator of elevated radon, but Kladder claims this guidance is out of date. The Canadian government changed its protocols to take hourly readings into account two years ago, he says, and “there is discussion here in the U.S. about revising the protocols.”
If classrooms do test above 4 picocuries per liter (pCi/L) during occupied hours, EPA’s “action level” for radon mitigation, there is also still debate about how to correct the problem.
“It’s been kind of a tussle over the years,” Kladder says. “Do we suck on the dirt with ASD?” (active soil depressurization, the technique typically used in homes). “Or do we mess with the HVAC?” The answer has changed since the 1980s, he explained. “Let’s go after the HVAC system, which doesn’t require any additional capital costs. If you maintain the one you already have, you can deal with radon as well as improving indoor air quality.”
State Radon Policies for U.S. Schools
With legal information collected by the Environmental Law Institute, this table represents the paltry number of state requirements regarding radon in U.S. schools. Among the few states where schools have any obligations at all, only two require a comprehensive program that includes testing, mitigation, and radon-ready new construction.
Ventilation adjustments may not get radon concentrations to acceptable levels, Kladder continues, in which case ASD may be needed, but “in order for those things to work, you have to create a larger vacuum under the slab than what’s being created by the building. That’s not possible if you have an HVAC system that’s not balanced.”
R. William Field, Ph.D., a University of Iowa professor of occupational and environmental health and epidemiology, agrees with Kladder that “anytime you increase air exchange in the schools, the radon levels should decrease,” but he adds a caveat: ventilation can make things worse
“if the make-up air is coming from near a radon source” such as a crawl space—a phenomenon known in the industry as “radon mining.”
Mitigation choices need to be made on a case-by-case basis as well, cautions William Brodhead, proprietor of Pennsylvania-based radon mitigation contractor WPB Enterprises and a consultant to state and local governments about radon policy. Referring to the lack of awareness among design professionals, he said, “Certainly if you talk to an architect or engineer, we shouldn’t have a radon problem because we’re going to be bringing in outdoor air”—but reality can be more complicated.
Science labs might have exhaust fans that create negative pressure, and the stack effect can do the same. “It can happen in any school, even in one that’s well designed,” he warned. If the school is meeting its ventilation requirements and there is still elevated radon, a sub-slab ASD system can provide very consistent results—in part because occupants and facility managers can’t cause imbalances by covering heating grilles or turning off the outdoor air to a classroom.
In an existing school, changing the location of the fresh-air intake or correcting native pressure problems with the mechanical system can be expensive and disruptive. That’s why many radon experts are trying to raise awareness among architects, mechanical engineers, and school officials about the importance of radon-resistant new construction
, or RRNC. Most of the guidelines for new construction make sense—if you think about them—but many commercial design teams just don’t have radon on their minds except in states and municipalities that have RRNC laws for school buildings (which is almost none).
A few choice words from Kladder: “Don’t put return ducts in the dirt.” Also, he notes, “It’s a very common practice to use the ceiling as the return plenum. But walls that go up into the ceiling communicate down into the soil,” and the negative pressure in the plenum can suck radon into the ventilation system.
More mindful system design, along with a properly maintained HVAC system, should protect most children from radon exposure, but RRNC is more about the backup plan: radon “readiness.”
In effect, this means designing an ASD system into the building from day one, explains Brodhead, who is working with the State of New Jersey—one of a handful of states in the U.S. to require RRNC in schools in high-radon areas—to rewrite its radon code for new school construction.
Since its adoption in the 1990s, the radon section of the state building code has required the same system in schools as it requires in residences, with 3" piping every 1,500 ft2
; but this adds unnecessary fans and energy consumption in a large building, argues Brodhead, who’s helping to write guidelines that make sense for commercial construction.
The advantages of built-in piping can’t be overstated, though. If the school turns up with a radon problem, you just have to install the fans and start running them—about a $4,000 fix, Brodhead estimates, rather than $30,000 for a sub-slab ASD retrofit or as much as $150,000 to retrofit a mechanical system.
Unfortunately, most districts are unlikely to test radon levels in their schools in the first place, and without policies in place to require RRNC, testing, or mitigation, that’s unlikely to change. “There are school districts that have been very responsible and not only tested once but tested periodically,” explains Angell, “but there’s a lot of fear on the part of school officials,” who may be worried about the cost of making a fix.
“Some still remember what it cost to remove asbestos,” Kladder says, referring to the mitigation fiasco that some districts have been dealing with since the 1980s. He has reassuring words for these administrators: “We’re not talking anywhere near
those kinds of dollars and cents. Maintenance crews can typically do this.”
The burden of voluntary testing and mitigation shouldn’t fall on school districts, though, argues Field. “The U.S. EPA, Congress, and the various states where high radon levels occur surely could be more aggressive in taking steps to reduce radon in schools and daycares,” he told EBN
. Field has compared going to school in a classroom with elevated radon levels to smoking a few cigarettes every day—something the government, teachers, and parents certainly wouldn’t want kids doing on their watch.
With policymakers slow to act and schools skittish, architects and mechanical engineers may need to play the role of educators when they work on school construction and renovation projects—but first, they must educate themselves about the risks, which are real even in a school with a well-designed ventilation system.
Greater awareness of radon in commercial buildings, and especially in buildings occupied by children and teenagers, is at least as important as other air-quality issues.
December 30, 2013