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MOLD
How to Prevent it and How to Remove it

Few building maintenance issues have garnered as much attention or concern throughout the nation over the past 10 years as mold growth in buildings. In addition to its infamous reputation as a public health and environmental threat, mold growth has been the catalyst of much controversy and litigation between the building and design industries and their customers.

It is essential to think of these wall assembly elements, from insulation to
joint compound, as one system that works in congruence to provide the
utmost in moisture and mold protection.

It is important to remember that the best strategy to avoid the growth of mold is the implementation of good design and construction practices that prevent water and moisture exposure of building products. However, it is equally important to know how to respond to mold growth and the maintenance problems that lead to it in order to guard the health of the building, as well as those who occupy it.

If unaddressed, mold growth can quickly veer out of control and can affect the structural integrity and aesthetics of buildings, as well as the health and comfort of building occupants. According to the Centers for Disease Control and Prevention (CDC), people who are sensitive to molds may experience such symptoms as nasal stuffiness, eye irritation, wheezing or skin irritation when exposed to mold. And, some people with chronic lung illnesses, such as asthma or obstructive lung disease, may see their existing conditions aggravated1.

With these factors taken into consideration, it is a safe conclusion that the occupants of schools and health care facilities may be more vulnerable to the effects of mold growth. It is therefore important for the facility managers and maintenance personnel of these types of buildings to have a good understanding of the conditions that foster mold growth, as well as the best ways to remove mold and prevent future mold growth.

Sources of Mold Growth
According to mold remediation expert Ed Light, president of Building Dynamics, LLC, an industrial hygiene and mechanical engineering consulting firm in Ashton, Maryland, the potential for mold growth begins during the construction process, especially when mold-susceptible building materials are left exposed to the weather.

“Ideally, the roof and walls should be covered before contractors begin installing mold-susceptible materials, such as standard paper-faced gypsum board,” Light says. “If these building materials are exposed to moisture, it is probable that they will suffer water damage or mold growth. Any water damage or potential sources of moisture infiltration discovered during the construction process must be removed before the project is finished to reduce the potential for future interior mold growth.”

As long as moisture and oxygen are present, mold can grow and feed on virtually any organic substance, such as the cellulose found in wood studs and traditional paper-faced gypsum board. Molds create spores — typically not visible to the naked eye — that are continuously wafting through the indoor and outdoor air. When these mold spores make contact with a damp surface inside a building, such as wet walls and studs, the spores may develop into mold colonies, digesting whatever organic material is found on the surface.

Most often, the sources of the building moisture are plumbing leaks, condensation from pipes and water infiltration through the building enclosure, which result in the wetting of wood studs and drywall. HVAC ductwork also becomes a potential incubator for mold growth when condensation mixes with dust on the interior surface.

Fixing moisture problems early on is considerably more economical than making mold-related repairs farther down the road. However, if mold growth is found at any point, a swift and proper response to it can save the building owner and facility manager a lot of money and headaches.

Discovering Mold Growth
Experienced construction and maintenance professionals will likely be able to identify mold on the surface of building materials, usually as a gray or black stain. Mold will likely be found on damp or previously wet surfaces and appear powdery, differentiating it from scuffs, dye or other more common stains. Although some industry standards recommend sending samples of the mold out for testing, this is unnecessary, Light says.

“You don’t need to test for the type of mold present — the primary health risks are the same for all types of mold,” Light says. “Healthy people exposed to mold generally don’t experience health problems.”

In cases where building materials are moistened, but mold growth is not readily apparent or exposed, Light recommends that maintenance personnel track down the source of the moisture, repair it and dry out the walls to stop mold growth before it starts.

“Cut drying holes in the wallboard, where needed, to allow air to circulate — using fans and dehumidifiers helps speed up the process,” Light says. “It will often dry out quickly and there won’t be any mold growth. You can use a moisture meter to gauge the amount of moisture content in the building material before and after — it’s a good tracking tool”

“If mold growth is not caught early on, though, and the wall sits and stays damp for several days, mold is likely to start growing,” Light says.

Cleaning walls with a simple bleach and water solution can remove minor mold growth. However, if a significant amount of mold is found on walls, school or hospital facility managers should either hire a mold remediation contractor or do the job with their own maintenance personnel, following proper mold remediation protocol. School and hospital maintenance crews may benefit from consulting the EPA’s publication “Mold Remediation in Schools and Commercial Buildings,” available online at http://www.epa.gov/mold/mold_remediation.html.

Mold Remediation
A typical mold remediation project should involve laying down plastic drop cloths and dust curtains to prevent the spread of mold spores and dust during the project. To facilitate cleanup, the mold remediation area and work area can be fully isolated. It is imperative that the building occupants, particularly patients, are not exposed to airborne mold spores and dust during and after remediation.

The next step is the removal and disposal of any mold-infested drywall sheets. Any mold growth found on wood studs should be wiped and cleaned with a diluted bleach solution. Following the mold removal, the crew must carefully clean up all remaining dust and mold spores and sanitize the area. The crew should identify and eliminate the source of the moisture causing the mold growth before new drywall can be installed. If the moisture source is not eliminated, mold problems can recur.

There are varying opinions on the safety equipment that mold remediation workers should wear. Many mold remediation contractors will outfit their crews in full hazardous material (HAZMAT) protective suits as a precaution. Others, however, prefer minimal equipment opting only for the safety glasses and respirators recommended by the Occupational Safety and Health Administration (OSHA).

“Many responses to mold are an overkill and the crews do the job in full HAZMAT suits, and that really isn’t necessary.” Light says. “All you really need is a good dust mask — an N95 disposable respirator is generally fine for most workers. Workers who are repeatedly exposed to mold or those who have allergic reactions to it, however, could wear a suit or use a fitted respirator. Most of this work can actually be done by regular drywall, maintenance and construction
personnel.”

Mold Prevention
The growing awareness of mold and its negative effects has driven more of today’s building owners and managers to request mold-resistant design in new construction and retrofits that help ensure mold will never return to existing buildings. Good design involves analysis of the project performance requirements when specifying insulation and vapor retarders, wall assemblies, and efficient and balanced HVAC systems. In addition, some of today’s gypsum board products are a more formidable opponent to moisture and mold than in the past.

In response to recent mold concerns, building product manufacturers have developed a variety of moisture and mold-resistant products. These include exterior gypsum sheathing manufactured with fiberglass mats and wallboard manufactured with bio-inhibitor-treated paper facings. Bio-inhibitors prohibit mold from growing and feeding on paper facings, while fiberglass mat facings provide natural resistance to both moisture and mold. Completing the wall assembly’s defense are new joint tape and joint compound products that resist both moisture and mold. It is essential to think of these wall assembly elements, from insulation to joint compound, as one system that works in congruence to provide the utmost in moisture and mold protection.

Though some schools and hospitals opt to have moisture- or mold- resistant gypsum boards installed only in moisture- prone areas of the building, such as restrooms and laboratories, some are choosing to have the new gypsum boards installed throughout the whole facility. Garth D. Hall, principal at structural and architectural engineering firm Raths, Raths & Johnson, Inc., in Willowbrook, Illinois, who has ample experience investigating and repairing moisture problems in buildings, recommends installing as many moisture- and mold-resistant materials as the building owner’s budget will allow.

“Selection of moisture- and moldresistant materials for use in building assemblies can help reduce the risk of mold growth or deterioration in the event of moisture problems over the life of the structure,” Hall says. “The benefits of utilizing moisture- and mold-resistant gypsum products in buildings outweigh the higher initial price when considering long-term performance and durability and potential for moisture intrusion. Costs related to repair and remediation of problems and material degradation can quickly exceed any initial cost savings to the owner.”

“It’s a good idea to install only moisture-resistant building materials because you never can truly predict moisture problems,” Light agrees. “Installing moisture-resistant wallboard can save you a lot of money in the long run.”

Of course, equally important in keeping buildings mold-free is a maintenance staff that stays on top of potential mold problems.

“A good maintenance department should continuously be looking at their building, so they can respond to moisture problems quickly when they find them,” Light says. “If they do that, the building won’t have a mold problem.”

Douglas C. Gehring, P.E., CSI is director of marketing, technical services with CertainTeed Gypsum and can be reached at doug.gehring@saint-gobin.com.

1 Centers for Disease Control and Prevention. “Mold: Basic Facts”

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