by Neil B. Hall, PhD, AIA, PE
Certified Microbial Remediation Supervisor

Most architects are oblivious not only to the problem of indoor mold, but to the very thought of its existence. This shouldn’t come as a surprise. As students, few of us took Biology 101. As interns, we were busy learning the trade. As practitioners, we work in the real world of economic interest. We speak in theory of holistic design and life-cycle costing, but we build under the watchful eyes of political regulation and budget constraint. Model building codes traditionally have dealt with issues of safety and health while ignoring maintenance and serviceability. With notable exceptions, architectural design has followed suit.

Our blissful ignorance of indoor mold and other microbial contaminants is about to end. Public interest is growing. Politicians are taking interest. Codes are changing. Architecture is being argued not in design studios but rather in courtrooms. Even before indoor mold, headlines about Legionnaire’s Disease, formaldehyde, and tobacco smoke changed the way people began to look at indoor environments. The quest for healthy bodies became the paradigm for healthy buildings.

Why the concern?
The problem of mold exploded on the scene in 1996 when preliminary studies by the Center for Disease Control and Prevention (CDC) suggested that a mold called stachybotrys atra (chartarum) was responsible for the death of 16 children in Cleveland. Popularized as “black mold” in newspaper accounts, stachybotrys is capable of producing metabolites called mycotoxins. The mycotoxins are suspected to cause a condition in infants called pulmonary hemosiderosis, which causes lungs to fill with blood. The CDC later retracted the claim, stating that the original studies were methodologically flawed. With less fanfare than its well-known retraction, the CDC recently announced a five-year study program (2002-2007) to determine if mycotoxins produced by indoor mold affect human health.

Starting with the famous Ballard case in Texas, indoor mold became a highly contentious legal issue. Architects were at first insulated from such litigation because plaintiff attorneys went after deeper pockets, i.e., insurance companies that covered property damage. Most insurance companies paid for mold as long as it ensued from a “covered peril,” such as a plumbing leak, sewer back-up, or roof leaks resulting from wind damage. As long as the plaintiff was satisfied with the offered settlement, there usually wasn’t a lawsuit. If the insurance company declined to subrogate against other parties with potential liability—such as the architect who designed the leaky roof—issues of design liability remained moot.

However, times are changing. In response to the rising cost of mold remediation, more and more insurance companies have excluded mold as a “covered loss” regardless of whether or not it resulted from a “covered peril.” Consequently, policyholders and commercial risk managers have been forced to look elsewhere for indemnification. As building designers, construction managers, and representatives of the owner, architects top everyone’s short list of prospective defendants. Delegating the problem to risk managers, consulting engineers, and general contractors won’t help. In litigation, delegation is not a foolproof defense.

Is mold really new?
Of course, mold has been around for billions of years. But in recent years the problem of indoor mold has been commercialized by the multimillion dollar Ballard case, popularized by 48 Hours, and glamorized as “celebrity mold” by Erin Brockovich, Ed McMahon, and Bianca Jagger. The only thing more ubiquitous than mold spores is the growing number of mold experts, mold products, mold laboratories, mold attorneys, and, yes, mold articles like the one you’re now reading.

All of this aside, the problem of indoor mold cannot and should not be trivialized. Sure mold is ubiquitous, but so is radon. There may be a paucity of evidence to prove that mold is injurious to one’s health, but that’s what the scientific community once said about asbestos. The CDC’s insistence on peer-reviewed science should not be seen as obsessive-compulsive behavior by nerdy lab rats. The mere fact that the CDC has embarked on a five-year study is pause for concern. Following suit, architects should not address indoor mold as a litigious hot potato but as a design issue worthy of serious thought and proper consideration.

What is mold anyway?
Molds are part of the Kingdom Fungi, which is divided into yeasts, mushrooms, and molds. There are approximately 60,000 described species of molds, the majority of which are saprobes, i.e., they use dead, decaying organic material for food. Molds develop from microscopic seed-like structures called spores. Some spore structures resemble a string of beads while others look like dandelion heads. For anyone who has ever broken a pearl necklace or made a wish on a dandelion, the image is obvious. As the spore structures break open, individual spores are transported afar by air currents, raindrops, and insects. Contrary to what is generally believed, some fungi require exposure to light to stimulate spore production.

Under the right conditions of moisture and temperature, settled spores form root-like structures called hyphae that weave into tangled mats called mycelium. Hyphae grow over and under the decaying material used as a food source. When we see mold with the naked eye, what we really see is mycelium. Well-established mycelium growth is called colonization.

Although molds require oxygen, the best way to control colonization is to manage moisture and food. Moisture is required for mold spores to germinate. After germination, moisture is required for hyphae to secrete digestive enzymes that break down the food source for use by the mold. This process takes place in as little as one to two days for some molds.

Why should we care?
As molds feed, they produce byproducts that include microbial volatile organic compounds (MVOCs) responsible for the musty odor associated with indoor mold. They also produce mycotoxins, antibiotics, and glucans. Mycotoxins are the most controversial mold byproduct. Aflatoxin, a mycotoxin produced by aspergillus flavus, is considered to be a carcinogen. Mycotoxins produced by stachybotrys chartarum not only are suspected of causing pulmonary hemosiderosis, they are known to irritate skin and mucous membranes.

Architects have a specific responsibility for structural health and the maintenance of healthy buildings. The adverse effects of mold on the indoor environment are many. First, mold looks bad. Secondly, mold smells bad. These problems alone should raise the interest of any architect concerned with habitability.

Unfortunately there’s more. The major food source for indoor mold is the building itself, especially drywall, vinyl wallpaper, cellulose products, ceiling tiles, fiberglass ductwork, and carpets. Unless mold is removed in time (usually before sporulation leads to hyphal growth), it may not be possible to clean mold from porous materials like drywall. Molds and mold by-products can be toxic, pathogenic, or allergenic. Since mold serves as an indicator of water damage, its discovery may require additional good faith investigation for rot, corrosion, and other forms of decay. Some fungi release chemicals that attract foraging termites. In addition to all of these material problems is the legal issue of stigma. Whether or not mold has physically damaged a building, if the presence of mold diminishes the building’s value, there may be a loss recoverable through litigation.

How do architects avoid “designing for mold”?
I once gave an eight-hour presentation on mold, after which a disappointed architect told me, “Where’s the flashing details? I came for the flashing details.” He was right. I had said nothing about them. But surely he already knew how to design flashing details. We don’t specify “mold flashing” like we do “termite shields.” His question, however, underscored a behind-the-scenes battle among designers, builders, and code officials. Do we strive to keep water out of the building? Or do we specify mold-resistant building products in case water gets in?

Everyone agrees that mold needs water. Simply put, the argument is that indoor mold became a problem back in the ‘80s when architects responding to the energy crisis made buildings so tight that they couldn’t breathe. This is a good quip except that at the same time, a lot of plaintiff attorneys got rich suing architects for leaky roofs. Besides, more than 95 percent of residential building stock isn’t even designed by architects.

So which is it? Is the building envelope too tight or does it leak like a sieve? The actual problem is not that buildings let water in, but rather that they don’t let water out. Thus, proper water management is essential to preclude mold colonization in buildings and building envelopes.

How do we find mold?
While a few states have passed mold legislation, generally there are no legal requirements for the qualifications of a “mold professional.” A variety of individuals are qualified to sample, analyze laboratory reports, and recommend remediation plans. These individuals are members of organizations such as the:

• American Indoor Air Quality Council (AmIAQ)
• Indoor Air Quality Association (IAQA)
• American Industrial Hygene Association (AIHA)
• American Council of Governmental Industrial Hygienists (ACGIH)
• Association of Specialists in Cleaning and Restoration (ASCR)
• National Air Duct Cleaners Association (NADCA)
• Institute of Inspection, Cleaning and Restoration Certification (IICRC).

The best experts fully understand not only mold but the science of psychrometrics, architectural design, HVAC systems, construction techniques, and, most importantly, how moisture moves through the building envelope. In fact, the AIHA—a group that tests and designates “certified industrial hygienists”—asserts that an “informed inspection” for indoor mold contamination is best “performed by someone experienced in the design and maintenance of building systems.”

Most investigators reference the New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments (April 2000), the EPA Standards for Mold Remediation in Schools and Commercial Buildings (May 2001), Health Canada’s Fungal Contamination in Public Buildings, or ACGIH Bioaerosols: Assessment and Control (1999). An exhaustive approach is provided by the AIHA’s Field Guide for Determination of Biological Contaminants in Environmental Samples (1996). Scheduled for release in November 2003 is the IICRC S520 Mold Remediation Standard, a companion guide to the IICRC’s S500 Standard and Reference Guide for Professional Water Damage Restoration. Don’t expect S520 to be the industry’s last word. The same month that the S520 is released, the ACGIH hosts a four-day program titled Mold Remediation: The National Quest for Uniformity Symposium.

How do you measure mold?
Field techniques fall into two categories: visual investigation and sample acquisition. Sampling includes air samples and material samples. Air samples bifurcate into testing for viable and non-viable mold spores. Viable spores are capable of growth. Non-viable spores are not capable of growth, although they may still possess allergenic and toxic properties. Viable spores are captured on a collection plate using a high-volume air pump. The collection plate contains a nutrient source for the spores. A laboratory grows the spores and they are counted in terms of colony-forming units per cubic meter of air (CFU/m3). Non-viable spore sampling is a misnomer; in fact what is captured is a total representation of aerosolized spores without discrimination as to viable or non-viable properties. These spores are captured on a sticky slide using a high-volume air pump and counted in terms of total particles per cubic meter of air (particles/m3).

Material samples are acquired in bulk, as dust samples measured by gram or as surface samples acquired with clear tape or sterile swabs. Tape samples count total spores; swab samples are cultured to count total CFUs.

Hidden mold in wall cavities normally is detected by drilling a small hole in the wallboard and pumping air from the cavity. Until recently, this method acquired total spore counts only. Newest technology allows for the analysis of viable mold in wall cavities.

How do we know what we’ve found?
Often the most frustrating part of mold investigation is not finding mold but defining whether or not the mold is “mold contamination.” In insurance issues, the term may mean “mold ensuing from a covered loss” to the plaintiff and “mold of a quantity greater than an acceptable amount” to the defendant. Complicating this dispute is the issue of “contributory cause.” Did any of the discovered mold “pre-exist” the date of loss? Were old “dormant spores” activated by new water activity? Did spores from new mycelial growth transport through the HVAC system to areas made wet by other mechanisms than the covered peril? You quickly can see how, to answer these questions, an investigator must know buildings as well as mold. Mold in a building isn’t mold in a Petri dish.

One aspect of “contamination” is the establishment of a threshold below which the presence of indoor mold is tolerable and above which the presence of indoor mold requires some sort of intervention. For wall surfaces the generally accepted guideline is the presence of “visible mold.” Air must be sampled and tested for the presence of spores and hyphal fragments. Similar to OSHA’s legal permissible exposure limits (PEL), the ACGIH sets recommended threshold limit values (TLV) for worker exposure to hazardous materials. But there are neither PELs nor TLVs for mold spores. CFM/m3 standards for viable mold appeared in the 1996 edition of the NYC Guidelines and the first edition of the ACGIH Bioaerosols handbook, but were subsequently dropped in the second edition of each publication because of the diversity of mold types and the lack of definitive studies linking indoor mold to specific health problems. The National Allergy Bureau (NAB) uses a sliding scale for mold spore levels to determine the effect on allergy sufferers based on their sensitivity to mold spores. Proponents of the NAB criteria argue for its adaptation as a “mold PEL,” which can be lowered for predominantly toxigenic species.

How to get rid of it
There is general agreement that visible mold must be removed by cleaning or replacing the contaminated material. In the case of contaminated material, porous materials are removed and replaced, although some success has been achieved blasting drywall with baking soda or dry ice. Semi-porous materials such as unfinished wood may need to be cleaned by blast cleaning or hand sanding assisted by a HEPA-vacuum. Nonporous materials such as finished wood, metal, and glass are usually HEPA vacuumed and damp wiped with a suitable cleaning agent.

The most widely accepted remediation protocol is the New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments (April 2000). The Guidelines address five levels of remediation.

• Level I concerns small isolated areas of less than 10 square feet with visible mold. Remediation can be conducted by building maintenance personnel who have been properly trained and equipped with disposable respirators, gloves, and eye protection.
• Level II concerns midsize isolated areas of 10-30 square feet with visible mold, such as individual wallboard panels. In addition to the precautions established for Level I remediation, the workspace should be contained with plastic sheets taped to contain dust and debris. The work area should be HEPA vacuumed.
• Level III concerns large isolated areas of 30-100 square feet. Only personnel specifically trained in the handling of hazardous materials are to be utilized in Level III remediation.
• Level IV concerns extensively contaminated areas with more than 100 contiguous square feet of visible mold. Personnel are to wear full-face respirators with HEPA cartridges as well as disposable protective clothing. The work area is to be fully isolated using plastic sheeting and equipped with a HEPA exhaust fan to generate negative pressurization. Airlocks and a decontamination room are recommended. Air monitoring should be conducted prior to occupancy to determine if the area is fit to reoccupy.
• Level V concerns the remediation of HVAC systems. While the NYC Guidelines are still cited for HVAC cleaning, a more complete protocol is the ACR-2002 Assessment, Cleaning, and Restoration Specification published by the National Air Duct Cleaners Association (NADCA).

Staying proactive
As an architect, you may still think that indoor mold is not your problem. Then chances are you’re an architect who has never had the misfortune of being sued. Maybe you did nothing wrong. Unfortunately, it is not your liability but your exposure (i.e. your potential or alleged liability) that brought you into the lawsuit. Proving you have no liability can be an expensive proposition.

Here are a few ideas to help you limit your liability and perhaps your exposure as well.

1. Understand the principles of building science and moisture dynamics.
2. Properly design the building envelope.
3. Ensure that the contractor does not use mold-contaminated materials.
4. The building codes require that wood components contain less than 19 percent moisture. Enforce this simple rule using a moisture meter.
5. Before signing beneficial occupancy, have the building inspected for mold.
6. Instruct the owner as to the proper inspection and maintenance for moisture and mold.
7. Be proactive should the owner call about a “mold problem.”

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