Water Intrusion: An Analysis of Water Sources, Categories, and the Degradation Science of Building Materials

Abstract

Water intrusion into a building envelope describes the unwanted movement of water or vapor into a building, where it causes damage. Various factors dictate water intrusion category determination and classification. These factors include, but are not limited to, the type and degree of water intrusion, the source and route of the contamination, and exposure time, as well as geographical environmental conditions. This comprehensive research paper looked at the literature and the science to explore the bases for indoor environmental professional (IEP) classification and category determination, but also the science behind the effects of water intrusion on building materials (BM). The efficacy of building materials once degradation has occurred and any accelerating effects impacting the efficiency of building materials and their loss of integrity were closely examined in terms of material microstructural and compositional changes. The damaging effects of moisture and heat on building materials are called hygrothermal damage, which compromises the properties and use of materials. Both aspects of building integrity, i.e., water intrusion and structural deterioration, should be of concern when mitigating and remediating the intrusion of moisture. Previous research on the clarification of water categories for water intrusions is lacking. Past approaches to water classification have lacked universal scientific clarity and understanding. In addition to a need to understand the effects that water category might have on building materials and their corresponding degree of degradation, more science and reviews are needed. The need for proper class and category determination for the remediation of water intrusion within buildings is the first step toward achieving correct mitigation to ensure human health and safety. The possible adverse health effects of water intrusion need focus and cohesion for the determination of categories. We know that the final determination of water categories differs according to the degree of contamination over time and the degree of a given class of water intrusion; however, what role do the route and initial water contamination play in the determination of the category? The following paper aims to provide not only a review of the science but also an elaboration of the category determination process and the degradation effects on building materials which should be considered, as well as possible avenues of scientific research.

1. Introduction

To clearly and precisely classify the water source and, eventually, the category of water intrusion in residential and commercial environments, an initial analysis of the water quality must be performed. In water quality determination, several parameters are applied, i.e., dissolved oxygen content, electrical conductivity, nitrogen/nitrate levels, phosphorus levels, and pH. However, in water intrusion, the main parameter for determining the source quality is whether the water is treated, potable or untreated wastewater. This parameter makes it possible to classify the source water quality. An additional analysis of the route and environment further informs the quality and category determination. The route and environmental conditions are important analysis parameters due to the contamination potential observed after intrusion has occurred and water has travelled through possible contamination sources. The EPA has provided an inventory of contaminant sources that characterizes potential contamination sources and the associated contaminants of concern, as identified within a source water protection area (SWPA).

Further research into the indoor environment and contaminant potential would be beneficial for Indoor Environmental Professionals (IEPs). Drawing upon the EPA’s example inventory and list of chemicals of concern with relation to building materials within indoor environments, IEPs could more accurately assess the contamination potential and category during inspections. In order to compile an extensive building material chemical composition list to allow for the examination of contamination potential according to water intrusion threats, manufacturers would also need to be willing to provide the chemical compositions of the materials that they supply.

Water Quality Indexes (WQI) for local treated drinking water are reported to the public as summarized water quality data, also known as Consumer Confidence Reports (CCR) [1]. The WQI ranges from excellent to very bad and is graded annually at each wastewater treatment plant. This initial assessment of the water source is the first step in determining the water quality in cases of water intrusion. A comparable index could be created and utilized, like that of air quality and water quality, for the indoor environment, to properly gage water quality intrusion as well as the degree of building material degradation, taking into account the environmental factors that determine the category of contamination and decay risk. Further research is needed for uniform improvements and consistency. The aim of this paper is to ensure the start of achieving this consistency.

There are three main sources of water contamination: biological, chemical, and physical [1,2].

Each aspect of contamination, for both source water quality and route/environment, must be observed and recorded to properly classify and categorize the water. Components of the environment for water category determination can be simplified according to the level of observation:

• Water Source Quality
• Environmental (Route)
• Building Materials (BM) Time and Effect

These components are equivalent to initial contamination, contamination potential via route, and physical contamination present, which comprise the factors determining classification into Category 1, 2, or 3.

Water, once categorized, must then be properly remediated to protect the home and the health of the occupants. Multiple material science studies have been conducted, and health effect guidelines for remediation and mitigation have been created by agencies such as the CDC, EPA, FEMA, OSHA, and WHO to ensure mold removal, building material improvements, and human health and safety [3,4,5,6,7].

For treated, potable water, or otherwise clear water, both Category 1, or water that has not been wet for more than 24-48 h, the guidelines are dependent on the total surface area and the type of material that has been affected. Water type can be determined as Category 1 if there is no contamination via a given route and no environmental contamination potential, and if there is almost immediate remediation (<48 h) [6]. After the initial microbial germination and proliferation, i.e., after 48 h, and every 24 h after that, the category is moved to the next stage up, increasing by degree and ending in Category 3, i.e., highly contaminated Black Water. These categories are stages 1, 2, and 3. These stages are also referred to as Clear, Grey, and Black Water, respectively, in the literature [8].

Each category or type of building material or furnishing affected with water has different remediation recommendations. For example, for areas greater than 100 ft², or if there is potential for negative human health effects or the likelihood of exposure to microbial presence is increased, then containment is required. Containment is utilized to prevent microbial spread and protect workers/occupants. If building materials have been exposed to moisture or mold has been present and unaddressed for long periods of time, structural damage can occur. “In the case of a long-term roof leak, for example, molds can weaken floors and walls as the molds feed on wet wood. If you suspect that mold has damaged building integrity, you should consult a structural engineer or other professional with expertise in this area” [9].

When a building material is compromised due to water intrusion, the degree or amount of wetting that has occurred and the time in which wetting occurred will influence further classification and categorization, as well as the degree of degradation of the building material. Contamination assessments and potential were seen in an extensive EPA study of the end-of-life management of drywall, in which moisture content, leachability, water-extractable sulfate and inorganic element concentrations, among many other parameters, were observed in water intrusion specimens. Target organic compounds and detection limits were also recorded and analyzed, allotting invaluable scientific data concerning the contamination potential of drywall [10].

Building material degradation occurs in various materials under various saturation and wetting circumstances in the presence of moisture, including relative humidity (RH), and according to temperature. An increase in RH and temperature can initiate and increase the progression of deterioration through microbial degradation and decomposition. “In real-life situations in buildings, different species of fungi often occur together on the building materials, and various fungi occur to different extents on different materials” [11]. Large degrees or amounts of water intrusion on porous building materials can permanently alter their chemical composition, affect structural integrity, produce bioaerosols, and release of airborne chemicals such as VOCs into the indoor air, in conjunction with climate control loss and/or moisture issues, which promote the optimal environment for proliferation, i.e., a moist environment with a lack of air flow [9,12,13].

The science behind moisture content (MC) in building materials (BM), in particular, different wood species and varying material compositions (drywall, vinyl, resins, and glues), enables indoor environmental professionals (IEPs) to evaluate contamination and categorize the final parameters for water category determination. The physical contamination exhibited due to microbial growth or decay, as well as its duration and effect on exposed building materials, aid remediation professionals and engineers in achieving containment and assessing degradation and structural loss in order to ensure proper remedy and mitigation. While previous research has addressed the science of building material deterioration due to water intrusion and decay, little research is available regarding the category and classification of water in an indoor environment. The objective of this study is to bridge the gap between the little research that is available on indoor environmental water intrusions and the further need for discovery.

2. Contaminants

2.1. Biological

Contaminants of the biological type are of biological origin and range from microbes, such as bacteria, viruses, unicellular organisms, fungi, algae, insects, animal epithelia, and byproducts such as endotoxins, mycotoxins, volatile organic compounds (VOCs), to plants and certain building materials which contain biological components. It should be noted that building materials are either derived from outdoor, organic materials, formulated from inorganic materials such as salts and metal oxides, or produced in a manufacturing process from a combination of both organic and inorganic materials. Biological contaminants have been categorized according to whether they are allergenic, infectious, or capable of inducing toxic or inflammatory responses in human beings. At present, there is a lack of awareness about biological contamination in indoor environments and potential sources of the spread of various infections [14].

The identification of contaminants can be achieved with water quality tests, tests for the presence of microorganisms, or by visible observations.

2.2. Chemical

Chemical contamination may occur not only through route exposure of building materials or route exposure to products or materials within the indoor environment, but also through the microbial and chemical transformations water might undergo given different scenarios or conditions. Chemicals from the building materials themselves can also leach into water and travel due to gravity, eventually being released into the indoor environment [15].

In an extensive research paper conducted by the EPA, titled Best Management Practices to Prevent and Control Hydrogen Sulfide and Reduced Sulfur Compound Emissions at Landfills that Dispose of Gypsum Drywall, the leachability of decomposed drywall chemicals was closely examined to determine the degradation and chemical contamination in landfills. This study noted the ability of drywall to produce hydrogen sulfide (H₂S) as a leachate and sulfur compounds which were analyzed in construction and demolition (C&D) debris and municipal solid waste (MSW) landfills. That study was commissioned by the EPA in coordination with EPA Region 5 to achieve better understanding and operational guidance on the emissions and prevention of H₂S pollution at disposal sites. These emissions have been associated with gypsum drywall, although sulfur containing waste and biosolids from municipalities can also contribute to H₂S production; in such cases, the main culprit has been designated as gypsum. “This report provides regulatory agencies, landfill owners and operators, and other interested parties with information regarding the science of H₂S production and emissions at landfill sites, and information on BMPs to prevent and control these emissions. Emission levels are discussed in the context of published health and safety standards and health-based or nuisance-based thresholds” [16]. The study conveyed the importance of gypsum deterioration and degradation in the release of H₂S, which is a poisonous and flammable gas. Its specific gravity is 1.189, making it slightly heavier than air. It therefore has a high accumulation potential in poorly ventilated areas with high levels of degradation occurring. Hydrogen sulfide is commonly tested for during indoor air quality monitoring due to its adverse health effects. The aforementioned study used measurements taken via fixed instruments, i.e., gas collection vent wells and probes. Given the concerns associated with drywall, a similar scientific study was conducted in 2020 to research the chemical composition of drywall products and the chemical constituents that may leach from such products upon wetting or contact with water. That study was also conducted by the EPA to determine end of life management practices. “Drywall product characteristics examined in this study included mineral analysis, moisture content, total sulfur, metal composition, water-soluble sulfur and metal concentrations, trace organic chemical analysis, and two different leaching tests (M1315, and M1316)” [10]. In that extensive study, the methodologies used consisted of, but were not limited to, EPA Method 8260B using gas chromatography (GC)/mass spectrometry (MS) (USEPA, 1996b), USEPA Method 8270C with GC/MS (USEPA, 2014b), USEPA Method 3546 (USEPA, 2007d), EPA Method 8082 with the GC/electron capture detector (ECD) (USEPA, 2007b) EPA Method 3546 (USEPA, 2007d), EPA Method 8315A via high performance liquid chromatography (HPLC) (USEPA, 1996a), EPA Method 3051A and acidic extraction, X-ray diffraction (XRD) analysis, and elemental recovery (%) by nitric acid extraction at 90 °C, in addition to many other techniques and procedures, including calculations. “Overall, the primary constituents and minerals in drywall are quite uniform, but the composition of minor constituents exhibited a large degree of variability. This variability was attributed to differences in gypsum feedstock, conditions at the processing facilities, and sample processing and analysis” [10]. With drywall being the most porous and permeable building material, its ability to hold water, and its manufacturing process makes it more susceptible to degradation through hydrolysis. With preventive measures and the application of chemical agents, for example, fire retardation chemicals and chemical alterations, the risk shifts to leaching if hydrolysis occurs. The leaching of chemical additives is used to try to combat degradation. Specific drywall qualities, for example, fire-resistance, mold-resistance, and soundproofing ability, are achieved through chemical or physical processes in order produce the desired marketing features. These characteristics can also include the thickness and materials used, which alter not only the way in which water intrusion travels, but contaminant transportation as well. Further clarification of the products produced by the manufacturer could aid building engineers and in the designation of residential building codes to help reduce the need for water intrusion mitigation measures. In short, better building materials and better building science, as well as public education on these issues, are required to aid developers and homeowners in choosing products.

Volatile organic compounds or organic chemicals are both naturally made and anthropogenic. They are released naturally from building materials and other household items as well as fuels or decomposing wood in the presence of microbial growth. The most common VOCs are aromatic hydrocarbons (benzene, toluene, xylene and ethyl benzene) and halogenated hydrocarbons (chloroethylene and trichloroethylene), which are cancer causing (cVOCs) [17]. Chemical contaminants (VOCs) include formaldehyde (CH₂O), vinyl chloride (C₂H₃Cl), carbon tetrachloride, trichloroethylene, carbon tetrachloride (CCl4), toluene(C₇H₈), acetone, isopropyl alcohol (CH₃CHOHCH₃), hexanal or hexaldehyde (C₆H₁₂O), carbon disulfide or carbon bisulfide (CS₂), and acetone (CH₃)₂CO. Semivolatile organic compounds (SVOCs) are less likely to become vapors at room temperature and include pesticides, chlordane (C₁₀H₆Cl₈), benzyl alcohol (C₇H₈O), polychlorinated biphenyls (PCBs or PBBs) and phthalates, polybrominated diphenyl ethers, and hexabromocyclododecanes [17]. All of these common chemical contaminants are found in any given indoor environment. Chemical contamination can include, but is not limited to, surfactants from cleaning products, resins, glues/adhesives found in flooring or fiberglass insulation, lead in roofing applications, polychlorinated biphenyls (PCBs), also known as plasticizers, and perfluorinated compounds (PFCs), which are stain and water repellant chemicals found in paints and other fire-retardant products, as well as various chemicals used in the manufacture of building materials. The ANSI manual states that the presence of contaminants does not directly determine a category change; however, the presence of a contaminant would be a factor in an IEP’s final category determination [18].

The identification of contaminants is possible through water quality analyses if applicable, Indoor Air Quality (IAQ) analyses, or by the observation of contamination potential by a skilled professional.

2.3. Physical

The physical characteristics of water normally constitute parameters which are easily assessable through our human senses. These include sight, taste, smell, touch, and correspondingly, color, taste, odor, and temperature [19]. Anything contaminating water which affects these characteristics is considered a physical contamination. This, for example, would include floating debris, a physical smell, or discoloration. Quantifiable identification of this type of contamination is not necessary, since it is observational, i.e., the physical presence of a contaminant is affirmative of physical contamination.

3. Water Category Determination

Water quality can be categorized as potable water, palatable water, contaminated (polluted) water, or infected water [20,21,22]. Such a determination of source water quality is the initial water source analysis for category determination. Next, the route or the pathway the water intrusion has taken is examined to determine further water intrusion contamination potential. The magnitude or degree of wetting influences the classification of water intrusion and aids in the category determination of the IEP’s assessment, as can be seen in the EPAs Mold and Remediation guidelines for surface areas effected by intrusion and containment procedures [9], as well as in the ANSI manual [18] for classification determination. Water intrusion science and remediation drying times would also be other avenues of research; additionally, a literature review is needed in this field of study. Lastly, the time and degree of microbial proliferation of a water intrusion are observed and recorded to make a final determination of the category. If building materials are highly degraded and microbial growth is present, then Category 3 is automatically conferred.

Categories of water intrusion are defined by the range and magnitude of contaminants present within the water. The EPA’s Safe Drinking Water Act (SDWA) “defines a ‘contaminant’ as any physical, chemical, biological or radiological substance or matter in water. Drinking water may reasonably be expected to contain at least small amounts of some contaminants. Some contaminants may be harmful if consumed at certain levels in drinking water. The presence of contaminants does not necessarily indicate that the water poses a health risk” [23]. This is also reiterated in the ANSI manual. Final determination is at the discretion and expertise of the IEP [18].

3.1. Wastewater

Wastewater is the term given to water produced after human activity or use. Wastewater can contaminate an indoor environment through water intrusion via storm water, flooding or wind-driven rain (WDR). Domestic wastewater, or wastewater produced through intrusion, be it residential or commercial, is ranked using three main categories, i.e., 1, 2, and 3. Water intrusion stages can be grouped into three main categories based on water quality at the source, the route that the water has traveled, and any environmental factors that would further contaminate the intrusive water. Water intrusion can occur at three main but dissimilar sources, i.e., from treated potable/clear water (Category 1), from untreated water sources or grey water (Category 2), or through WDR or flood or contaminated/infected water, also known as black water (Category 3) [24,25,26,27,28].

3.2. Clear/Category 1

Category 1 water is potable, treated water. It should be noted that multiple countries and scholars acknowledge the category of yellow water. Water that would be categorized as yellow would contain urine but no other contaminants found in grey or black water [8]. For the purposes of this research, and for simplification, yellow water and grey water are combined into one category specifically referring to extreme biological contamination. This is also reflective of the ANSI manual [18].

3.3. Grey/Category 2

The next stage of water contamination is described as grey water. This type of water contains domestic wastewater (clear water) but with the addition of surfactants (soaps) and some urine. This can include water intrusion or discharge from baths, washing appliances such as dishwashers or clothes washing machines, and bathroom sinks or overflow from toilet bowls with no feces. Gray water is not pathogenic, as any water containing bacteria, viruses, or other microorganisms would be categorized as black water. Grey water can contain various chemicals and surfactants from soaps and detergents but is essentially black water without fecal matter, urine, or particle waste (food or paper). Grey water can be treated for reuse in agricultural sectors but not for potable use.

3.4. Black/Category 3

This type of water is highly contaminated. It is wastewater which can contain urine, fecal matter, surfactants (soaps), food and paper particles, or building material particles. This type of water is dangerous and highly polluted due to biological contamination. Chemical contamination can affect the biological contamination potential of water. In contrast to the chemical chlorine (bleach), which is able to kill pathogenic matter, other chemical components can feed biological matter. This microscopic environment is the final factor in the determination of this category. Wind driven rain is considered Category 3 according to ANSI S 500.

4. Class of Water Intrusion

Restorers post-water intrusion should estimate the amount of humidity control needed to remediate water intrusion on a given project or site. A component of the humidity control is the class of water. The class of water regarding water intrusion classification per degree of wetting and estimated evaporation load are used when calculating the initial humidity control required for remediation. This classification is based on the approximate amount of wet surface area. At initiation of restorative drying, humidity and temperature control must be established to control moisture transfer and increase drying time, thereby prolonging restoration proceedings. The permanence and porosity of the affected materials play a major role in drying. Environmental conditions must be stable to ensure project restoration efficiency. This clarification can be found in the ANSI/IICRC S500 Standard for Professional Water Damage Restoration in Section 10.4.3, titled Class of Water Intrusion: “Information needed to determine class should be gathered during the inspection process. The classes are divided into 4 separate descriptions Class 1, 2, 3, and 4. The determination of class may be dependent upon the restorability of wet materials and access to wet substrates” [18].

• Class 1 is less than ~5% of the combined floor, wall, and ceiling surface area in the space and where materials described as low evaporation materials or assemblies have absorbed minimal moisture.
• Class 2 represents ~5% to 40% of the combined floor wall and ceiling surface area in the space and where materials described as low evaporation materials or assemblies have absorbed minimal moisture.
• Class 3 represents more than ~40% of the combined floor wall and ceiling surface area in the space and where materials described as low evaporation materials or assemblies have absorbed minimal moisture class.
• Class 4 is water intrusion that involves a significant amount of water absorption into low evaporation materials or low evaporation assemblies. Drying may require special methods, longer drying times, or a substantial water vapor pressure differential.

Isolation of the affected area and dehumidification or moisture control are essential to facilitate remediation. The class of water intrusion is essentially the degree of water damage. The environmental factors for remediation and proper thermal control including humidity control should be understood by the restorer or IEP. These factors can prevent additional damage and ensure compliance and control; see 12.3.5, 12.4.2, and 12.5.2 in the ANSI Manual for further information on humidity and contamination. Further study of these topics would be helpful in the indoor environment field for explanatory and clarification purposes beyond the scope of this work. Methodologies for the examination of the extent of water mitigation include the use of moisture sensors, thermo-hygrometers, invasive and noninvasive moisture meters, infrared thermal meters, and thermal imaging cameras [18,19].

5. Route and Receptor(s)

Roofs, windows, doors, and exterior building materials and finishes are used to keep water out of the interior of a home. With water intrusion, failures of building materials allow water to intrude. The route is the pathway that the water takes once inside the home or building. Water transport occurs naturally in ground water and sedimentation transport. The various chemical manufacturing processes used in building materials lead to the presence of an abundance of different chemical compounds that water intrusions can encounter. Water intrusions within an indoor environment take the path of least resistance, i.e., gravity. Once within a porous material, capillary action can also occur, which works against gravity, as is seen in fire or gypsum board. As water travels through building materials and household items, contaminants, including physical, chemical, and biological agents, are absorbed into the water. These routes can be seen on the outsides of building materials through wetting or visual observation but are also located within the materials once water is absorbed, at a microscopic level. The absorption process depends on capillary action or a material’s ability to absorb fluid through space within pores, as well as external environmental conditions that create warm and moist environments that encourage the growth of microorganisms. These conditions alter the spread of contaminants from water sources through building materials. The removal of water, proper airflow, and the correction of thermal conditions (temperature and humidity) will prevent optimal growth conditions from occurring. These conditional requirements ensure proper indoor air quality and prevent mold growth, as per the ASHRAE and EPA standards. These controls, as well as proper maintenance of air control systems, have been proven and utilized in building management practices for decades [20].

Intruding water travels and migrates into and through building materials. Without proper personal protection equipment (PPE) and knowledge of the possible effects, exposure might occur.

Once water interacts with any building material, chemical reactions and the degradation of building materials can occur. Unless immediate remediation occurs, water can continue to move through capillary movement through porous materials, transporting the accumulated chemical or microscopic contaminants released into the water to their destination, ending with gravitational pull.

Chemical leaching can occur as well, leading to poor indoor air quality as the contaminants are released into the air. Further research is needed on the contamination potentials of specific building materials and environmental conditions for better health and safety precautions.

Any chemical, biological, or physical contaminant the intrusive water source encounters gives rise to contaminated intrusive water. The degree of contamination and eventual category are determined by an IEP. This is clearly stated in the ANSI/IICRC Standard and Reference Guide for Professional Water Damage Restoration manual in Section 10.4.1: “categories of water… refer to the range of contamination in water, considering both the originating source and its quality after it contacts materials present on the job site. Time and temperature can affect or retard the amplification of contaminants, thereby affecting its category. Restorers should consider potential contamination, defined by the presence of undesired substances; the identity, location, and quantity of which are not reflective or a normal indoor environment; and can produce adverse health effects, cause damage to structure, systems, or contents, or adversely affect the operation or function of building systems” [18]. Therefore, building material compositions also play a role in the determination of water source potential contaminations. Since an IEP has authority to categorize the water category of a given environment, any contact the source water has with the indoor environment is to be recorded and analyzed. A detailed inspection and investigation into water intrusion-affected building materials, their chemical compositions, the chemicals used in their manufacturing processes, and the environmental factors a water source has encountered, are required according to the risk assessments described in the ANSI manual [18].

As standards are set to protect the young and old or groups whose health may be affected by exposure to pollutants, IEPs have an obligation to protect human health and safety. For example, we can safely determine the category of water intrusion based on the source conditions and indoor and outdoor environmental conditions, i.e., time, visual observations, physical presence of microbial life, and the loss of climate control which would promote microbial growth.

6. Contaminant Fate

When a contaminant enters the environment, its chemical structure may change as it undergoes various biotic and abiotic processes. A change in its chemical structure is referred to as either a transformation or a degradation. When the change is due to microorganisms, it is called primary biodegradation or biotransformation. In relation to chemical changes, degradation depends on multiple factors, e.g., the chemical properties of the contaminant, environmental factors, temperature and humidity, as well as nearby chemicals or microorganisms that can alter or transform the pollutant. Other factors could include the degree, magnitude, or even combination of contaminants that might change the conditions in which degradation occurs. Together, these factors and many more can decide what range of conditions a contaminant can survive within and how it may be transformed or degraded over time. Further research is needed to understand contaminant fate within an indoor environment from a water source intrusion. The most critical factors in water intrusion are amount of wetting, or class of water, in addition to decay promoting environments of high temperature and humidity. In essence, the environment’s ability to promote both biotic and abiotic degradation processes are what influence the rate and extent of degradation. Precise determination is sometimes difficult to unequivocally achieve, as varying combinations of contributing factors may be at play. Case studies and methodologies can be seen extensively in the 2010 work by Van de Meent et all, Ecological Impacts of Toxic Chemicals, Fate and Transport of Contaminants [29]. Further examination of this topic, including water intrusion scenarios that may contribute to degradation processes, would be a great focus for future study.

Mineralization can also occur through the conversion of molecules. “Transformation and mineralization processes alter the physicochemical and toxicological properties and can reduce exposure concentrations of chemicals in the environment. The rate of degradation of a specific chemical depends on its intrinsic sensitivity to undergo chemical transformation (reactivity), the presence of reactants and the availability of the chemical to undergo reaction, i.e., the presence of the chemical in the gas phase of air or dissolved in water. Generally, the availability and reactivity of both the chemical and the reactant depend to a large extent on environmental conditions like pH, temperature, light intensity and redox conditions” [2].

The hydrolysis of building materials can alter the structural integrity and efficacy of the materials. Additionally, the water that encountered those materials is also contaminated with the chemicals that were released through the breakdown of compounds from reactions with water. Determining the water category of water intrusion for building materials within an indoor environment is based on two factors: the outdoor environment (geological conditions and water source) as well as the indoor environment (climate conditions and routes of possible exposure that would promote possible contamination). The degrees or levels of water quality parameters specific for water intrusion, building material degradation science, and hydrolysis once water intrusion occurs, in addition to the possible contamination potential of building materials, are interesting avenues of research. Possible contaminants associated with each building material should be evaluated to make determinations more proficient and universal; given scientific research and data on the effects of hydrolysis and the reactions and emissions of chemicals once degradation has occurred, this information would be vital in the determination process and order to ensure human health is protected.

Percolation refers to the movement and filtering of fluids through porous materials. Water trickles through a porous material, substrate, or multiple substrates; subsequently, that substrate reacts with H₂O and releases compounds through hydrolysis or can be chemically altered, cause leaching or vaporization. Percolation occurring in wood transports chemicals such as CMF within the wood cell walls at between 20–25% moisture content (MC). “The moisture-induced glass transition of hemicelluloses occurs at lower moisture content than wood decay. The range assessed using mechanical spectroscopy is between 60–80% relative humidity [30,31,32] at room temperature, which corresponds approximately with 11–15% wood moisture content (MC). Ionic conduction in polymers is much higher in the rubbery state above their glass transition than in the glassy state below their glass transition [33]. Ionic conduction in wood as a function of moisture content can be fit with a percolation threshold at 16% moisture content” [34,35].

Similarly, moisture content intrusion in the form of water vapor plays an important role in contaminant transport. The effects of relative humidity and temperature vary depending on the building material being observed. Observations of indoor air quality (IAQ) can reveal the presence of aerosolized contaminants, giving an idea of the level of contamination within an indoor environment. In wood-based panels, for example, an increase in either temperature or relative humidity does not result in the release of formaldehyde or TVOC into the indoor environment. “The release trend of formaldehyde and TVOC in wood-based panels does not change with changes in temperature and relative humidity. The release process of formaldehyde from wood-based panels can be divided into three stages: initial rapid release phase, stable release phase, and long-term slow-release phase. The release process of TVOC can be divided into an active period and a stable period in which the amount of release changes significantly with time. Increasing the temperature or increasing the humidity, the release rate of formaldehyde and TVOC in the artificial board increased to different degrees. The change of temperature or humidity has a greater effect on the release of formaldehyde from the artificial board and has less influence on the release of TVOC. Under the combined action of temperature and humidity, the effect of formaldehyde and TVOC release on wood-based panels is more intense” [36].

7. Environmental Conditions

Environmental conditions are factors within a space or area that can alter the category classification. Substances, materials, or elements within a space or area can contaminate the source water further and influence the determination of source water intrusion type. Any water that encounters possibly hazardous or harmful substances, materials, or elements or contains pathogenic or biological contamination that could contaminate the source water and cause human health problems is categorized accordingly by the IEP. Exposure alters the category determination. Further research could be undertaken to obtain an assessment tool that encompasses all contamination potentials; this could then be universally employed by IEPs.

7.1. Outdoor Environmental Conditions

Wind driven rain (WDR) is categorized as Category 3 in the ANSI manual due to contamination from outdoor environmental factors. Flood waters are also Category 3 due to the intrusion potential of untreated wastewater from outdoor ditches and sewage sources. For example, local plants and wastewater treatment facilities, as well as any untreated or contaminated water found in waterways or local water sources such as lakes, rivers, or bayous, can contaminate rain or flood water. Evidence of this can be found in atmospheric dispersion studies, where biological contaminants such as Legionella were found at various locations due to wind travel; this was also the case with land sourced contaminants after hurricanes due to wind driven rain [37,38]. During severe storms, tornados, or hurricanes, power outages cause the loss of a building’s main function, which is interior environment climate control. When power is lost, the ability of the HVAC to function is removed, and the indoor environment increases in relative humidity and temperature, which exacerbate the potential for microbial growth. Water intrusions from storm water or wind driven rain ensure contamination, as these environmental conditions increase the likelihood of the biological contamination of building materials. Determining the initial water quality based on external environmental factors is step one in category and classification determinations. The water quality source can either be contaminated or noncontaminated. Other external conditions, such as geological location and the climate, also contribute to the indoor environmental conditions. For example, tropical climates experience higher temperatures and humidity. In such settings, the base humidity level might rest above the recommended 30–60% for optimal comfort. According to The American Society of Heating, Refrigeration, an Air Conditioning Engineers (ASHRAE) standards, recommendations for acceptable thermal comfort parameters are within temperatures ranges of 23–27 °C (73.4–80.6 °F) in summer and 20–24 °C (68–75.2 °F) in winter [39]. The outdoor temperature and humidity will determine the indoor temperature and humidity, as well as the efficacy of the climate control mechanism to control both parameters. Increased moisture content and relative humidity increase the contamination potential. “High humidity levels result in the absorption of moisture by the building materials to support microbial growth and increase the settling rate of aerosols” [40]. Outdoor air quality is also a factor to consider when evaluating indoor air quality [41].

7.2. Indoor Environmental Conditions

Conditions that determine the indoor environmental quality include indoor air quality (IAQ), temperature and humidity, outdoor air quality and climate, as well as materials that might influence chemical reactions that affect indoor environmental quality. All aspects involving the ecosystem which humans occupy influence the environment in which occupants reside. For example, the science between airborne contaminants or pollutants, indoor air pollutants, outdoor pollutants infiltrating into the home and atmosphere, surface borne contaminants, as well as waterborne pollutants, are all encompassing in determine indoor environmental conditions. The discussion of SVOCs and the presence of chemicals and particles suggests that there are relationships between chemical, biological, and particle pollutants, between indoor and outdoor air, between water quality and air quality, between building climatic conditions and air quality and the role played by HVAC systems, building materials and furnishings, and occupant activities. Recognizing these broad interdependencies and relationships is opening our eyes to the broader reality of indoor environmental quality. And this appreciation has begun to extend to recognizing the vast interrelationships between indoor microbial activity and virtually all aspects of our indoor environment [42]. David H Mudarri PhD, the author of the 2018 EPA Synthesis Paper titled Research, Policies and Program Options for Improving Indoor Environmental Quality, states that damp buildings also may contribute to the indoor chemical surface reactions, even at low levels of relative humidity. He has requested more EPA sponsored research on the potential effects of this phenomenon. “While dampness has been frequently associated with respiratory illnesses, the specific causal factors remain a mystery though frequent reference is made to potential bacterial or fungal causes. Little attention has been focused on the byproducts of possible surface chemical reactions that could take place from sorbed water on surfaces and the presence of aqueous surface films. Sorbed water on surfaces can affect hydrolysis reactions, corrosive reactions, and acid-based chemistry. Phthalate esters (in plasticizers), phosphate esters (in flame retardants, pesticides, and plasticizers) and Texanol Isomes (in latex paint) are all subject to hydrolysis. To what extent does chemical decomposition by hydrolysis increase exposure to these decomposed products. It is also suggested that low volatility organic compounds may be formed by aqueous reactions. Further, microbes that are more prevalent in water sorbed surfaces can remove halogens from some halogenated chemicals, and they can also influence surface pH which can then influence hydrolysis and corrosive reactions” [42].

In addition to the route of water intrusion from an outdoor source, microbiological contamination could occur within the plumbing of the structure itself [43]. Whether commercial or residential, the plumbing and filtration type can influence factors that may affect the water quality at the source of the water intrusion. The type of plumbing pipe used also influences the water quality and contamination potential [44,45,46]. Smaller internal diameter, which restricts water flow [47], and metal pipes create a greater chance of corrosion and biofilm accumulation [48,49]. The source of water intrusion has also been shown to have high contamination potential, even over a short period of stagnation time, such as a weekend stagnation [43,50]. Legionella is a typical plumbing pathogen that can tolerate disinfectants, develop biofilms, survive in waterborne protozoa, and thrive with low levels of nutrients [51]. Prolonged water stagnation can result in the accumulation of nutrients and compromise disinfection, promoting the colonization of pathogens in potable water systems [52].

7.3. Microscopic Environment

Water intrusion can not only be a health hazard but can also degrade building materials, resulting in a loss of efficacy and forced disposal. Determining the water category is done to protect human occupants from exposure to contaminants and to protect human health. There is another aspect of water intrusion that includes the effects water has on the building materials that would cause loss of function. Water intrusion can occur on a mass scale, ranging from gallons of water to intrusions on a microscopic level through water vapor intrusion due to an increase and variations in humidity. This latter is the next environment to be explored here. “The mechanism of water absorption is called capillary action or wicking. Water interacts strongly with the wood cell wall and forms a concave meniscus (curved surface) within the lumen. This interaction combined with the water– air surface tension creates a pressure that draws water up the lumina. The rate of liquid water absorption in wood depends on several factors. The rate of absorption is most rapid in the longitudinal direction (that is, when the transverse section or end grain is exposed to water). The rate at which air can escape from wood affects water absorption, as water displaces air in the lumina” [53]. “Over time, a home or building’s inability to remove moisture can have a detrimental effect on building materials. Wood is dimensionally stable when the equilibrium moisture content is greater than the fiber saturation point. Below MCfs, wood changes dimension as it gains moisture (swells) or loses moisture (shrinks) because the volume of the cell wall depends on the amount of bound water. This shrinking and swelling can result in warping, checking, and splitting of the wood, which in turn can lead to decreased utility of wood products, such as loosening of tool handles, gaps in flooring, or other performance problems. Therefore, it is important that the dimensional stability be understood and considered when a wood product is exposed to large moisture fluctuations in service. With respect to dimensional stability, wood is an anisotropic material. It shrinks (swells) most in the direction of the annual growth rings (tangentially), about half as much across the rings (radially), and only slightly along the grain (longitudinally)” [53].

Temperature and humidity fluctuations play a vital role in not only the decrease in the integrity of building materials, but also in microbial growth potential, as microbes prefer warm and moist environments with food sources. With microbial growth, degradation occurs as the organism consumes the contents of whatever it is using as a food source in addition to water. Food and water are required to support microbial growth [54]. In wood, a higher moisture content over time can reduce the longevity due to biodegradation and rot. Varying species of wood at varying locations throughout a building, and varying degrees of moisture content at varying humidity and temperature levels can result in the occurrence of varying species of mold growth. The main factors affecting mold growth are humidity and temperature, with moisture or water being the most critical requirement; however, growth is a result of interactions within the environment and its ability to support life. “In general, the availability of water in the material is regarded as the crucial element for growth to occur. The water available to microorganisms is often referred to as water activity, aw, which is equivalent to the RH of the air at equilibrium but is expressed as a fraction instead of a percentage. The mold growth on a building material takes place on the surface. At equilibrium, the RH on the surface is the same as that in the surrounding air” [11].

8. Water Intrusion on Building Materials (BM)

Moisture content in building materials increases in environments with higher humidity and temperature. It is the responsibility of the occupants to ensure that mold germination and growth is prevented by proper climate control techniques. These include proper HVAC functionality for humidity and temperature to reduce moisture in the environment, in addition to remediating water intrusions. Reducing the moisture content in the air also reduces the moisture absorption potential in porous building materials, consequently reducing microbial growth potential. If microbial growth does occur, wood loses its strength and structural integrity. Wood decay rate assessments can be utilized by remediation engineers and professionals to assess damage in a quantitative manner [55]. For example, EN 252, which is the European method for field test assessments, identifies varying degrees of wood decay according to a classification system (between 0 and 4), with 4 being failure. The age of the wood and protective measures implemented during manufacturing can provide protection from biological contamination and potential for chemical contamination [56].

An extensive research project exploring the implications of water intrusion or wetting postproduction in timber used during construction was conducted. To assess the hygrothermal performance of a timber structure and its response to environmental loading, the wood moisture content (MC) was recorded and analyzed. The results revealed potential points of moisture vulnerability, preventative strategies, and an observable field moisture response. In conclusion, the hygrothermal performance of timber varies greatly according to the environmental conditions [56].

Hygrometric and Thermal Movement

The movement of building materials comes in three main forms: thermal, hygrometric, and structural movements. Thermal movement occurs with the contraction and expansion of building materials due to temperature variations; hygrometric movement occurs due to the absorption and evaporation of water by the building materials; and finally, structural movement occurs due to dimensional changes and physical shifting of building materials. Common building materials all have varying thermal coefficients. The authors of [57] observed “the relative movement related to changes in both temperature and humidity for some common building materials. It should be noted that the dimensional changes due to variations in temperature and humidity are additive. For example, in drywall applications, if the temperature causes 0.025, movement and the related humidity change causes 0.006 movement, the resulting movement is 0.031”. The detrimental effects of thermal expansion are minimal compared to those of moisture. Increasing the moisture content supplies ample food for life forms, and the relationship between the moisture content (MC) and relative humidity (RH) is vital in determining the water activity as well the as condition of the building materials. This relationship is referred to as the equilibrium moisture content (EMC), i.e., the maximum amount of water that a material can hold, according to a given set of environmental factors. Wood is hygroscopic, which means it can absorb water, which causes expansion, or release water, which causes shrinkage. It can do this in response to the temperature and humidity in its environment in addition to large amounts of water intrusion. Under consistent and direct wetting, moisture can become trapped once the wood species has reached its unique fiber saturation point. Fiber saturation varies per species, but is typically >28%. This microscopic environment is a habitat that is conducive to the growth of decay fungi, which causes structural issues that are associated with building material degradation that may eventually render the product unusable [58].

In an extensive literature review by Thybring, Glass, and Zelinka (2019), the kinetics and the relationship between wood and moisture were examined. Their paper reported that water molecules energetically bind to wood polymers through hydrogen bonds or other intermolecular attractions, since hygroscopic materials can contain water that exists in a sorbed state, where phases of a water molecule transition back and forth from vapor to condensed phases. “The ‘water vapor sorption isotherm’ (or often simply “sorption isotherm” in this context) is the locus of points that describe the relationship between the relative humidity (RH) of the environment and the total amount of moisture in wood at equilibrium at constant temperature. For sorption isotherms, “equilibrium” can be thought of in reference to kinetic theory, where rates of absorption and desorption are identical and there is no net change in mass. This is not a true thermodynamic equilibrium because sorption isotherms are hysteretic, that is, at a given constant RH and temperature, the equilibrium moisture content (EMC) upon desorption from a higher moisture content is greater than the EMC upon absorption from a lower moisture content” [59,60,61]. Moisture content (MC) variations will occur under different environmental conditions and can be measured using a moisture meter. This principle is another example of why multicomponent environmental evaluations are needed for category determinations.

“Wood expansion and contraction can vary depending on the climate. In regions with extreme temperature and humidity fluctuations, such as tropical or desert climates, wood is more susceptible to expansion and contraction. The constant exposure to high heat and humidity levels can lead to significant dimensional changes in wood” [59].

9. Building Material (BM) Degradation

The degradation of building materials can occur through abiotic or biological means. Biotic and abiotic processes are influenced by a variety of conditions in the environment. In relation to contaminations, both biotic and abiotic processes can lead to the degradation of building materials. Biotic processes rely on microbes to achieve contaminant degradation. These biotic organisms or factors include autotrophs, heterotrophs and detritivores. Abiotic factors consist of the degradation of contaminants without the direct involvement of a living organism. These factors include temperature, water, light, soil composition, PH, and salinity. Both biotic and abiotic factors are imperative to the environmental conditions that determine and/or facilitate the degree of degradation of building materials. “The climate strains the buildings are subjected to may be divided into the following climate exposure factors: Solar radiation (i.e., ultraviolet (UV), visible (VIS) and near infrared (NIR) radiation), ambient infrared (IR) heat radiation (the resulting elevated temperature increases the rate of chemical degradation reactions, and also the rate of growth of rot and fungus up to limiting temperatures), high and low temperatures, temperature changes/cycles (relative temperature movements between different materials, number of freezing point passes during freezing/thawing), water (e.g., moisture, relative air humidity, rain and wind-driven rain), physical strains (e.g., snow loads), wind, erosion (also from above factors), pollutions (e.g., gases and particles in air), microorganisms, oxygen, and time (determining the effect for all the factors above to work)” [62]. Even cardinal direction has been shown to have a degradation effect on building exteriors, with south facing south over other cardinal directions [63,64].

Inspections and diagnoses of wood degradation include sensory diagnostic methods, visual observations, as well as quantitative, non-destructive techniques (NDT), e.g., using meters, or instrumental diagnoses using mechanical or biological means to obtain an analysis of the physical properties and condition of building materials. To obtain an idea of degradation using in situ methods, portable devices such as fractometers, resistographs, pilodyns, pin pushing and screw withdrawal resistance meter devices, and Baumann hammers may be used to record the mechanical resistance. In analyses of alterations in wood structures based on chemical and biological factors, ideal analysis methods include mass spectrometry (gas or liquid chromatography), IR, NIR, FTIR, and UV [65]. Indoor air quality meters and bacteria culture tests can also be employed to detect decomposition chemicals and microbes in both the air and on surfaces. “For in-situ diagnosis of timber structures the use of cheap sensory methods is firstly recommended, usually visual and sonic ones, and then “as needed” are also used suitable instrumental methods, usually non-destructive-techniques “NDT”” [66,67,68,69,70,71,72].

Microstructural changes to building materials refer to small scale variations from the original structure (postproduction) within a material under conditions of degradation. A material’s mechanical and physical properties are significantly influenced by its microstructure [73]. The negative influence of water on the strength and structure of building materials, as well as advances in material science (through the use of additives in building materials such as nanoparticles, with the objective of achieving physical and chemical modifications to combat intrusions and degradation) are relevant [74,75]. Microencapsulated phase change materials (PCMs) can be mixed directly with gypsum and transformed into wallboard, which is more energy efficient, as it reduces thermal movement and energy loss [76]. The chemical compositions of building materials are not only vital in terms of function and efficacy but are also closely related to possible degradation and end of life cycle. Advances in building material compositions have yielded positive and negative results. Pure calcium silicate bricks (made from sand, lime, and water), for example, have been produced to achieve high strength and durability against chemical and biological corrosion. These materials are naturally radioactive and have a high heat capacity; however, silicate products deteriorate significantly when heavy wall moisture occurs [77].

10. Building Inspections

As part of assessments of damage due to water intrusion into a building envelope, it is necessary to perform testing in addition to visual observations and photographs. Inspections must be made of the exterior, foundation, attic space, doors, windows, every interior room, rooms with no moisture or limited moisture, wiring, plumbing, fixtures, cabinets, the finish of materials, the level of foundation and cracks in concrete, etc. General camera views and closeup camera views are necessary. Materials must be identified such as sheetrock, paneling, tiles, insulation, trim, floor coverings, ductwork, roof covering, underlays, etc.

Professional engineers along with trained moisture instrument technicians are recommended in terms of reading of instruments such as moisture meters and relative humidity meters and in performing linear length and thickness measurements. This includes the use of thermographs. These data are compiled to help identify and analyze elevated moisture levels, moisture intrusion areas, and the need for drying and/or professional restoration. Recommendations for professional restoration can follow the ANSI/IICRC S500-2021 guidelines.

11. Tools, Technology, and Techniques

Presently, for in situ applications regarding residential and commercial analyses, any presence of organic compounds in the air or on surfaces is confirmation of microbial contamination, i.e., Category 3. This can be determined using the classical meters previously mentioned. However, to reiterate, the need for air sampling would be a last resort, once remediation and maintenance techniques have been utilized [20].

In situ measurements for the indoor and outdoor sampling of air in residential and commercial settings commonly use classical IAQ monitoring equipment, i.e., digital micro/manometers and air velocity meters. Commercial and industrial settings frequently use Fourier Transform InfraRed (FTIR) spectroscopy for continuous measurement of multiple parameters simultaneously. Gas chromatography devices can capture multiple chemical intrusions emitted via the air and are the most popular analytical technology. The decision regarding the meter to be used is based on the preference of the IEP professional. It is recommended that all observations be conducted before costly testing is conducted. Air sampling should be a last resort, and ATP or tests for the presence of microbial life should be used to confirm that remediation measures have been successful. This is because measurements of specific contaminants can be expensive and unnecessary [20].

It has been clarified in this paper that the observation of microbial presence is all that is needed to ensure proper categorization and ultimately protect human health and safety. Any presence is considered hazardous. The type of mold and time of exposure determine variations in health effects. The utilization of both observation and technology is essential in water class and category determinations. Knowledge of indoor environmental testing procedures (for example, sampling within breathable zones, away from windows, etc.) is also imperative for the application and development of techniques to ensure accuracy. Knowledge of meters, building materials, functions, structures, and many more conditions is needed for indoor professionals. These skills and knowledge allow for real-time monitoring and decision-making during a water intrusion event to properly categorize and remediate issues, formulating a plan for mitigation and ensuring the health and safety of the occupants.

12. Conclusions

Water contamination, via mains or point of use (POU), stagnant water conditions, WDR, flood, or route exposure are just some of the possible sources of contaminations. Contamination potential is as endless as the environmental conditions can be. It is to be noted that the water source quality is determined by initial water quality (source water) analysis.

The chemical compositions of building materials also vary across products, with possibly hundreds or even thousands of formulas per product. Making precise evaluations of the chemistry of water intrusions and the corresponding effects of chemical alterations and leachates, which may be unknown due to the unique variables in each municipality, and even plumbing environmental diversity, is obviously very difficult. Each home or building carries a unique set of environmental factors that could potentially affect the determination. Further research could be undertaken to determine baseline levels for water source contamination categories, in addition to category finalization based on indoor environmental factors, such as the chemistry of building materials. In conclusion, the degree or concentration of contaminants within water and their effects on the chemistry of building materials are unknown. Further research would be needed to determine if various concentrations of contaminants would interact differently with the chemical structures of building material products.

Biological contamination can cause adverse health effects; such cases are automatically classified as Category 2 or 3, depending on the biological source. Urine is not deemed Category 2; however, any fecal matter implies Category 3. This is because of the adverse health effects animal and human fecal matter can present to the safety and well-being of the occupants. In other words, there are no threshold values; the mere presence of fecal matter is sufficient. Such assessments are made through visual observations, as per EPA recommendations [20].

Pre-intrusion water type is the first category determination; it changes based on the route and environment. If initial water contamination enters the home as non-contaminated, potable water, Category 1 is applied. This could be from a sink faucet, broken water line, or other treated and non-contaminated water source. Any form of contamination in the water, whether chemical or physical, can be present at safe level thresholds. These thresholds are determined by the Safe Drinking Water Act. However, the science is still being explored on the long-term health effects of consuming chlorine treated water, let alone the chemical alterations that chlorine might effect within a porous building material. This is also not considering other contaminants deemed as “safe” in drinking water for potable use and consumption. The AIHA book titled Recognition Evaluation and Control of Indoor Mold states that “the category of water contamination is not determined by the color of the water; rather, the category is determined by the waters source, contents, history, and characteristics” [19].

Initial sources could be clean, potable treated water or contaminated untreated water. This water quality at the source is the first parameter of intrusion category determination. The second and third parameters must be recorded and analyzed to properly assess the category. The water category can then be determined given the initial source quality and the route of travel the water takes within the indoor environment. Finally, the length of time in which the water intrusion has affected the building materials and the magnitude or degree of wetting and its effect on the building materials are considered as the final environmental conditions. These three factors (water source quality, environmental conditions including route, and the building materials) dictate the water category determination. These factors, among many others, play an intricate role in not only the indoor environment, but also the degradation potential of building materials. Once contaminated water enters an indoor environment, that environment may be assumed to be contaminated; an example of this is highly contaminated hurricane or flood waters. Disinfection and remediation must begin to ensure proper health and safety. Likewise, uncontaminated water such as potable, clean water can encounter building materials which leach or release chemicals, sewage particles, or cleaning supplies, such as surfactants located along a route of water travel, causing it to become contaminated.

Biological contamination has growth potential, chemical contamination has leaching potential, and physical contamination such as salinity has moisture retaining potential. However, observing the environmental conditions, having knowledge of the science of the contamination potential, as well as the microenvironment within the indoor environment, aid IEPs in their determinations. These observations, conducted by an IEP, determine the water category and classification. Clarification on classification and category can be found within the ANSI manual. We have already discussed the reasons why the biodegradation of building materials results in a loss of their efficacy and ability to function. As such, once decay sets in, remediation or remodeling must occur to ensure structural integrity. It is also known that any presence of microbial growth in an indoor environment removes the need to test for species classification or enumeration quantities (severity of mold, investigation or issue). Further research could be undertaken on the classification of water intrusion contamination and the types of molds that may be produced given the nature of the contaminated source water. Interactions between contaminants, as well as the effects observed with multiple contaminants, need further investigation in relation to the introduction of contaminants from a water source, the reaction with building materials, in particular within porous materials, and the eventual effects of building material biodegradation and leaching potential, based on the degree and time of exposure.

The testing and identification of materials including the exterior, foundations, attic space, doors, windows, every interior room, rooms, wiring, plumbing, fixtures, cabinets, finish of materials, level of foundation, and cracks in concrete, etc. must be completed, along with the type of water intrusion.