Water Damage and Mold Remediation

Wayne R. Thomann

October 1, 2003

There are currently no federal or state regulations governing the response to water damage events or mold remediation. However, there are numerous government-associated guidelines that have established new "community standards" for the management of these important issues. In addition, several professional/industry associations have published guidance documents for their practitioners. Unfortunately, there are differences in both the recommendations and interpretations of these guidance documents, which have led to confusion within the community being served.

Moisture control is the key issue in minimizing the potential for mold growth within buildings. Building "stewardship" during the design, construction, start-up and operation of the building can greatly minimize water issues. However, all buildings will experience water intrusion events in the form of flooding, roof, building envelope and plumbing leaks, and/or weather related intrusion. Rapid response is essential for protecting the building and occupants. Guidance documents from the American Red Cross, the Federal Emergency Management Agency (FEMA), the U.S. Environmental Protection Agency (EPA), and the Institute of Inspection, Cleaning, and Restoration provide guidance on response to water damage events, but the recommendations regarding management of wetted insulation materials vary within these documents. The range of suggested approaches for addressing moisture-impacted insulation span simple drying to immediate removal.

One of the potential consequences in failure of moisture management and response may be mold growth that will necessitate a mold remediation project. The primary recommendations for the investigation and remediation of mold growth have been developed by the American Conference of Governmental Industrial Hygienists (ACGIH), the EPA, the New York City Health Department, and the Institute of Inspection, Cleaning, and Restoration. Similarities and differences in the specific guidance regarding environmental monitoring, containment, and personal protective equipment impact the extent of the response effort.

Mycology 101

Fungi are a large group of organisms that form a kingdom of eukaryotic organisms (such as plants and animals) that have cells bound by rigid walls usually formed of chitin and glucans. There are more than 100,000 different species of fungi, and they can be found in virtually every ecological niche. The scientific study of this diverse group of organisms is called "Mycology," from the Greek words "mykes" for mushroom and "logos" for discourse.

Fungi don’t have chlorophyll, so they can’t produce food through photosynthesis as a plant can. Instead, fungi feed by absorption of nutrients from the environment. They secrete digestive enzymes to break down the material (substrate) they are growing on and then absorb the nutrients from that substrate. This process of feeding is very important to the environment, because it’s what allows the fungi to decay the large amount of plant debris that’s produced every year, which may well make the fungi one of the world’s number one recyclers. Unfortunately, fungi don’t restrict their attention to naturally occurring dead wood and leaves. Where there’s a trace of moisture, their omnipresent spores will germinate, and they will attack food, fabric, paper, paint, or almost any other kind of organic matter.

Fungi Growth Requirements

In addition to an appropriate source of nutrients, fungi need certain other environmental conditions to grow. The most important conditions are temperature and water activity.

Temperature Requirements

Fungi will grow at a wide range of temperatures, but most species grow best between 25 and 30 degrees Celsius (C) (between 77 degrees and 86 degrees Fahrenheit [F]). The lower and upper temperature limits are about 10 degrees C and 40 degrees C (between 50 degrees and 105 degrees F). However, certain "thermophilic" fungi will grow at temperatures as high as 50 degrees C (121 degrees F) in composting habitats.

Water and Water Activity

Regardless of the nutrient status of any material, whether a microorganism grows on and in that material or not depends on the availability of water in the material. Every microorganism has its own particular moisture requirements. Its growth depends on enough "free" water being available. Free water can be thought of as the absorbed water that’s not held tightly in chemical union with the material. The term used to describe the amount of free or available water is "water activity." Water activity is an important indicator of a material’s ability to support microbial growth. Theoretical limits for microbial growth lie between water activity levels of 0.65 and 1.0, with 1.0 being saturated. Practically speaking, if water activity in materials is maintained below ~0.75, microbial growth will be limited; below a water activity of 0.65, virtually no microbial growth will occur on even the most susceptible materials. The range of fungi found in indoor environments are able to grow at water activity from a range of 0.70 to 0.80, and even some as low as 0.65. Other fungi, such as Stachybotrys chartarum, are hydrophilic (water loving) and prefer water activity levels greater than 0.90, which is an extremely wet environment.

Reproduction and Spores

Reproduction is the formation of new individuals having all of the characteristics typical of the species. Two general types of reproduction are recognized for the fungi: sexual and asexual. Typically, fungi reproduce both sexually and asexually, although not necessarily at the same time. The sexual and asexual reproductive units of fungi are called spores. Fungal spores are usually enclosed in a rigid wall. Fungal spores differ from plant seeds because the spore does not contain an embryo. In general, asexual reproduction is more important because it results in the production of large numbers of individuals (Alexopoulos 1996). Asexual fungal spores include zoospores, sporangiospores, and conidia. Asexual spores are of particular importance to indoor air quality because they are the reproductive units for species of Cladosporium, Aspergillus, Penicillium, Ulocladium, Alternaria, Fusarium, Trichoderma and Stachybotrys, to name several.

Spores permit rapid dispersal and a kind of scattershot saturation of the biosphere-fungal spores are everywhere. Spores are dispersed by wind, by water or by animal vectors, and they can often survive long periods, sometimes even years, of unfavorable conditions such as freezing, starvation or desiccation. This durability is an important characteristic for the survival of the species, but it also means that spores will remain viable in environment for extended periods. This durability is associated with the mold growth that can occur in buildings that experience water infiltration. That is, spores will contaminate all surfaces in a building and then just "wait" until conditions (water) become right for them to germinate and grow.

Mold Growth Within Buildings

Molds have always grown within our buildings. However, there are increasing numbers of reported health effects associated with continued or extensive mold growth. These reported problems are typically associated with extreme weather events (flood, hurricanes, tornados) or chronic water problems in the building. Previously, most reported mold problems in buildings were associated with issues in the heating, ventilation, and air-conditioning (HVAC) system. We now recognize significant mold growth problems on many other building materials and components within buildings. Remember that most of the environmental conditions necessary to support mold growth already exist in buildings; building materials are already "seeded" with mold spores from natural infiltration, the temperature inside buildings is generally within the optimal range for mold growth, and many building materials either serve as or are contaminated with appropriate nutritive sources for the fungi.

Water Intrusion

Again, water is the limiting factor for mold growth within or on buildings and building materials. Thus, moisture control is the key issue in minimizing the potential for mold growth. Building "stewardship" during the design, construction, and operation of the building can greatly minimize water issues in buildings. However, all buildings will experience water intrusion events in the form of flooding, roof, building envelope and plumbing leaks, and/or weather related intrusion. Additional factors that that introduce water into the building system include improperly sized or operated HVAC systems and occupant activities. Condensation associated with building pressurization problems and inadequate or improperly installed insulation is also a significant source of water in buildings.

Responding to Water Intrusion Events

Rapid response is essential to protecting the building and occupants, because quick drying of building materials is an important mitigation effort that can prevent or limit mold growth in a building. Guidance documents from the American Red Cross, FEMA, the EPA, and the Institute of Inspection, Cleaning, and Restoration Certification (IICRC) provide guidance on response to water damage events, but the recommendations regarding management of wetted insulation materials may vary between these documents. For example, all of these guidelines recommend that wetted cellulose insulation be removed and replaced. However, for fiber glass batt insulation, the American Red Cross and IICRC documents state that the batts may be dried and reused, while both the EPA and FEMA documents recommend removal and disposal. Perhaps more importantly, these guidance documents don’t address the full array of different building materials or insulation products. For example, rigid insulation products aren’t specifically addressed in the EPA or IICRC documents, while the American Red Cross document states "Styrofoam survives best and may only need to be hosed off" and is silent on the other types of rigid insulation.

This conflicting and incomplete guidance is somewhat problematic. The lack of specific recommendations for certain types of insulation products can result in inappropriate management of wetted materials, because the response will be based on the experience and/or bias of the response personnel. Alternatively, certain materials aren’t specifically addressed in the guidance documents, which may lead some to incorrectly conclude that the material isn’t affected/impacted by a water event. An additional concern is that many of the recommendations seem to be based on the performance of the insulation material alone, and not on how the insulation may impact the performance/drying of the associated building elements. For example, does the insulation act as a "vapor barrier" to prevent release of water for a wetted wall cavity?

Until these informational voids are addressed, appropriate response to water intrusion events is compromised. It’s important that the guidance documents provide complete, factual, and consistent recommendations. Therefore, it would seem appropriate for the insulation industry to partner with the mitigation industry/agencies to develop meaningful information regarding the drying and reuse of the full array of insulation products.

Mold Remediation

One of the potential consequences of failures in moisture management and response may be mold growth that will necessitate a mold remediation project. There are currently no state or federal regulations governing mold remediation. However, there are numerous non-regulatory guidelines that serve as a reference for potential mold and moisture remediators. The most frequently cited guidance documents for the investigation and remediation of mold growth have been developed by the ACGIH, the EPA, the New York City Health Department, and IICRC. These guidelines provide a hierarchal approach to remediation, which is based on the extent of water/mold-impacted materials. That is, the more visible mold growth that is present, the more rigorous the control measures required for remediation. Similarities and differences in the specific guidance regarding environmental monitoring, containment, and personal protective equipment impact the extent of the response effort.

This stratified approach makes sense when one considers that the primary focus of these documents is protection of the health of occupants and cleanup personnel. Most of the guidelines also focus on correcting the water problem, drying the building and building materials, and complete removal of all mold growth and residual contamination.

As was the case in the water response guidelines, insulation products are incompletely addressed in the mold remediation recommendations. While the New York City Department of Health guidelines recommend that porous materials such as ceiling tiles and insulation with visible mold growth be removed and discarded, most of the other documents don’t specifically define remediation methods for insulation products with mold growth. General expectations can be inferred from the recommendation that porous materials typically can’t be cleaned and should be removed and discarded, while non-porous materials can be cleaned and reused. Unfortunately, this guidance doesn’t account for the differences in "porosity," resistance to mold growth, and other properties specific to the various insulation materials. Therefore, mistakes in judgment can be made that will result in either wasted resources (unnecessary removal and disposal of "safe" products) or unsafe conditions (mold contaminated products being reused). Again, it seems appropriate that the insulation industry partner with the agencies responsible for these guidance documents to assure complete, factual, and consistent information/recommendation.

Prevention Versus Mitigation or Remediation

Preventing water and mold problems should be easy. We do know how to design buildings, select appropriate products, appropriately manage the construction process, and effectively operate and maintain our buildings. However; we frequently fail to coordinate and integrate these processes. The result is wet buildings with mold problems. Therefore, it’s imperative that insulation manufactures, specifiers, and installers collaborate to optimize the performance of their products. Education and communication are at the core of this collaboration. Manufacturers must provide science-based information regarding the indications and limitations for the products. In particular, how the products perform in relation to other building materials and construction types.

Factual information of how the product performs when wet is also important. Specifically, it’s important to know how/if the material can be dried, how the "installed" material may impact the drying of other adjacent building materials, and how wetting will impact the long-term performance of the material.

Finally, clear recommendations on remediation methods for all insulation materials should be developed. It’s essential to know if and how a product can be cleaned for effective remediation of mold growth.


One certainty related to construction is that water will enter our buildings. The water can result from poor design features, poor stewardship during construction, construction defects, weather events, and the stresses of occupancy. Failure to effectively manage water in our buildings can result in mold growth and degradation of the indoor environment. A key factor in minimizing the impact of water events is the availability of products that perform well within the design and construction constraints of the building. Prevention is the preferred method for protecting our buildings. Prevention involves good construction processes that keep rain and ground water out, allows the building to dry if it gets wet. Insulation systems must contribute to these objectives by enhancing the barriers to water infiltration and facilitating the release of incidental water. In addition, insulation products should be compatible with mitigation strategies that may be required when our buildings get wet. Finally, insulation products should be resistant to mold growth to minimize the impact of long-term or unrecognized water problems.