Building energy-efficient structures is increasingly important to combat climate change and rising energy costs around the world. Unfortunately, prioritizing energy efficiency can come with unexpected issues – namely, an increase in indoor mold growth.
Mold is endemic to the outside world, so it’s not uncommon for it to sneak its way inside our homes and businesses. However, living or working in a building with an active mold infestation can be very dangerous – even deadly – to humans.
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A 2004 Los Angeles Times article started investigating the plethora of reasons why indoor mold problems have been on the rise. Some architects believe it’s because of newer materials that are more likely to become food sources for microorganisms. Other industry experts blame sloppy construction, while others say it’s simply because energy-efficient buildings are so airtight that they can no longer breathe.
No matter where one may place blame, it’s important to get back to basics. Mold survives when it has three things: water, oxygen, and a carbon food source, says Monica Mazurek, Ph.D., associate professor of civil and environmental engineering at Rutgers University.
“Maximize energy flow, absolutely. But you must consider other factors like better ventilation for air filtration, air purifiers with (high-efficiency particulate air)-certified filters, and dehumidifiers,” Mazurek explained.
A promising technology for indoor air quality is ultraviolet light. When UV light hits airstreams flowing into and out of heating, ventilation, and air conditioning systems, it can disrupt mold’s cell membranes, killing its DNA and preventing it from proliferating. Lowering air humidity means less favorable conditions for organisms to grow. Mold won’t grow where it can’t survive.
“The laws of nature and physics still apply,” Mazurek says. “Organisms don’t have brains.”
2 main factors
Jon Gordon agrees. Gordon is vice president of Maryland-based mold testing and remediation firm MoldGone and has been working in the industry for over a decade.
He says the trend he has seen over his tenure is that energy-efficient structures in the Baltimore-Washington, D.C., area are at much higher risk of indoor mold growth than older buildings, such as homes and government buildings. “Clearly, new structures don’t breathe as well as older buildings,” he said.
The buildings he has been in that are much less likely to have mold are often centuries old or homes from the 1930s or 1940s. “It’s all solid wood or concrete subfloors, solid wood floor joists, and all plaster walls and ceilings,” Gordon said. “The entire building envelope is able to breathe, from the basement, all the way up the wall cavity, into and out of the attic. On a daily basis, I see the contrast between old and new.”
The main culprit to blame for mold problems in energy-efficient buildings, he believes, is insufficient ventilation. Lack of ventilation enables humidity to rise, suffocating buildings and turning them into saunas. This is especially true with home builds that frequently include HVAC systems in attics, which already can become hot and humid.
A close second: too much insulation. These two factors go hand in hand because even if structures are properly designed to have soffit vents and airflow, specifically around HVAC units, sometimes the construction process interrupts this design.
Gordon has treated numerous homes and commercial structures in the last few years for mold growth that began because insulation was inadvertently placed over vents during construction, blocking their function. If that happens and inspectors don’t catch it, conditions become ripe for quick problems.
“A mainstay I would recommend to every building and homeowner is humidity control,” he said. “Especially in an attic with an HVAC system or in a basement, which are areas already known for mold problems, a $250 dehumidifier can do wonders for mold prevention,” Gordon explained.
Testing for mold
The easiest way to know if there is mold present in a structure, Gordon believes, is a “smell test.” MVOCs, or microbial volatile organic compounds, will often result in a musty odor that is a strong indicator of an existing or developing mold problem. If there’s been a water leak or some other water infiltration incident that leaves an obvious water spot, and then a musty, early smell develops, it’s time to get inspected for mold.
Mold testing companies will often start with air sample tests, conduct visual and thermal imaging inspections, and measure airbourne mold spore counts before making specific remediation recommendations.
“Free full home inspections, while appealing from a marketing standpoint, often mean money will be asked for at some point, just not up front,” Gordon said.
For initial testing, Gordon suggests considering a company that does only air quality testing to ensure a project is correctly and thoroughly completed. The testing company would create a protocol that then a mold remediation company would come in and implement.
“Every indoor environment will always have some mold because it’s naturally outdoors,” Gordon said. “So, if air quality testing is completed and finds the mold spore count lower inside than outside, that would be considered normal fungal ecology.”
A civil engineer’s role
Gordon believes energy efficiency is a necessity, but engineers must go into projects making sure they don’t accidentally cause problems in the name of energy efficiency. “Consulting people who see the other side of it and collaborating between design and construction – and also the mold remediation side – is a great first step at prevention,” he said.
He also encourages construction companies and inspectors to make sure they’re doing their jobs well, so that building occupants benefit from energy efficiency and the architectural designs that ensure occupant safety.
