Water Infiltration/Mold
Mold is the generic name for a large group of organisms from the fungi kingdom. Unlike organisms in the plant kingdom, fungi do not contain chlorophyll, and therefore, light is not a necessary condition for their growth. Instead, most fungi are considered to be organisms of decay and primarily obtain their sustenance by chemically breaking down organic matter. Without molds and other fungi, the environment would be quickly overwhelmed by the accumulation of the byproducts of plant and animal life.
Under certain conditions, some molds will secrete a substance known as a mycotoxin. These secretions are defensive in nature and are intended to ward off other molds or bacteria that might otherwise harm the subject organism. Most of the concerns raised about the health risks from the exposure to molds have these secretions as their basis.
Although some believe it has been scientifically proven that these secretions cause harm to otherwise healthy humans, this is not the case. Some animal studies using ingestion as the exposure pathway have shown some possible links, but no confirmed human health effects have been found. More importantly, no studies are known to have shown that inhalation of these secretions has caused harm to otherwise healthy individuals. It is likely, however, that the elderly, infants, and those already suffering from a debilitating illness are more susceptible to exposure to molds.
The conditions necessary for mold growth are wide-ranging, but the conditions may be found in almost any environment that is also desirable for humans. In particular, mold growth requires a surface grow on, spores, nutrients, moderate temperatures, excess moisture, low light levels, and minimal ventilation. Once these conditions are met, mold growth can appear within two or three days. If some of the necessary conditions are removed, the mold will simply go dormant and await the return of a more favorable environment. Donan Engineering’s team of professional engineers specializes in diagnosing not only whether mold is present, but in answering the tough questions of why it is there and what needs to be done to eliminate its presence.
Growth Surface:
Molds require a surface for their spores to settle and grow on. Some surfaces seem to be more conducive to the establishment of mold growth than others. Commonly, rougher and more porous surfaces are more favorable for mold growth than hard, smooth surfaces. For this reason, tile grout provides a much better surface than the adjacent glazed, ceramic tiles. The surface does not need to be a solid, as molds will often grow on the surfaces of liquids and gels.
A common misconception about mold is that it can somehow eat its way through the surfaces upon which it is found growing. Typically, homeowners are concerned that mold growth found within a wall cavity or beneath a floor will somehow be able to penetrate the drywall or wood and have an impact on the house’s interior. Some fungi, such as the group responsible for what is commonly referred to as wood rot or dry rot, will eventually penetrate and consume the materials on which they had first grown. These fungi can only survive if the host material contains high percentages of moisture usually exceeding 20%. However, molds are typically sustained by the nutrients and moisture that are only found at the surface of the materials on which they grow. As a result, molds can often be cleaned away without leaving behind any evidence of their former presence. However, if conditions are favorable, molds can spread to these other surfaces via spores.
Mold Spores:
Spores are essentially microscopic seeds that are released by billions by mature fungi growths. Provided with the proper conditions, each spore has the potential to form its own mold colony. The microscopic size of a spore allows it to be easily transported large distances as a result of even the lightest air current. A measurement of the number of these spores within a given air volume is typically given in terms of colony forming units (cfu). The ultimate life span of a mold spore is unknown, but reportedly, some spores found in ancient Egyptian tombs have sprung to life after centuries of dormancy once properly incubated.
Spores will be found in almost any environment without regard to the presence of active mold colonies. Any home, office, or other inhabited space will test positive for the presence of mold spores. There are no established guidelines regarding human exposure limits to mold spores. However, mold spores are allergens and can affect individuals in a fashion similar to plant pollens. Additionally, prolonged exposure to high levels of mold spores can cause a person who formerly had no known allergies to become sensitized and develop allergic respiratory reactions.
Allergic reactions to mold are the most common human health consequence of their presence; if tested, most individuals will show a reaction to some molds. Because of this and a growing awareness of mold, homeowners and other concerned individuals often assume that any health issue they or their family is experiencing is the result of mold or its spores. They tend to dismiss any notion that other indoor air pollutants or other environmental factors could be the illness’s cause.
Although there are no standards for mold spore quantities in a home’s atmosphere, often a comparison between the density of mold spores in the interior air is contrasted with a similar sample taken from the exterior. In general, the number and types of spores found in the interior sample should be less than those found in the exterior ambient environment. However, this rule is discounted if the exterior sample has been taken after a recent rain because the atmosphere may have been rid of a large percentage of the airborne spores – at this time, such a comparison will be faulty.
There are two basic methods employed to sample and identify the quantity and types of mold spores in the air. One method utilizes a small pump to pull a known quantity of air through a specially designed sampler. The air impacts a Petri dish containing a growth medium that is typically potato dextrose agar (PDA), a gelatin-like substance that provides an ideal growth medium for the mold spore. The spores in the air collected by the pump will stick to the agar. After a specific time, the Petri dish is removed and then taken to a laboratory for incubation in a controlled environment. Once the collected spores have been incubated, the number of resulting mold colonies can be counted, and then this number and the pump’s air flow data can be used to determine the number of cfu in a given quantity of air. Next, a trained technician can view each of the colonies microscopically to visually identify the exact type of each mold. This information can then be used to determine the breakdown of the types of spores found in the sampled environment.
A second method utilizes a fine filter and air pump to collect airborne spores from an environment. The collected spores are then examined under a microscope, and a determination of the type mold is made. The number of spores on the filter is also counted and a mold spore density in the air can be obtained. This method is quicker and less expensive than the first, but because mold spores are less unique than the molds they produce, the determination of the type is cruder. No matter which method is used, the data produced is no more than a snapshot of the conditions that existed at the time the samples were collected – samples taken in the same location at a later date can be significantly different.
Bulk samples are gathered from a piece of material that contains obvious or suspected mold colonies. Spores from such a sample can be collected in the laboratory and then cultured to determine their types. Quantity information can also be obtained, but airborne spore data cannot be extrapolated from this data. The number of cfus that will be detected from a bulk sample will be much higher than in air samples from the same environment.
Nutrients:
Molds must have nutrients to grow and propagate. However, fungi, unlike most plants and animals, have very minimal energy requirements, and their need for nutrients is small. Almost any carbon-containing substance can provide sufficient nutrients for mold growth. Even in a spotless home or office one can find enough cooking vapors or grime to sufficiently supply mold with adequate sustenance. On furniture, mold growth will occur preferentially at locations of handprints and spills as a result of the nutrients these provide. Similarly, carpeting will display mold growth at locations of former spills.
Temperature:
In general, any temperature where humans can survive is also desirable for certain mold species. The temperature of a particular environment will dictate which types of mold will likely grow there. Some cool-temperature molds, such as Penicillium, are much more likely to be found in refrigerators and basements as compared with others, such as Cladosporium, that prefer warm climes. Temperature considerations are more important with regard to humidity and dew point.
Moisture:
A moisture source is the most critical requirement for mold growth. Liquid water or humidity levels of 60% or greater must be present and persistent in order for molds to grow and flourish. Efforts to determine the cause and control of any mold growth problem must first determine the source of it prerequisite moisture. Any attempt to remediate a mold problem without first removing the moisture’s source will fail.
Moisture sources fall into two broad categories: point and non-point sources. Point sources include leaks from plumbing, roofs, appliances, foundations, etc. Mold growth that is the result of a point source will commonly be found in close proximity to the leak. Usually, these problems are the easiest to diagnose and correct.
Non-point sources are often related to humidity and resultant condensation, and there is no readily identifiable source. As a result, the cause of molds promoted by a non-point source is much more difficult to diagnose and control.
Condensation:
The amount of moisture that can be contained within a given volume of air is dependent on the energy it contains. Simply stated, warm air has more energy than cold air. Relative humidity percentages reflect the amount of water vapor contained in a given amount of air at a specific temperature, as compared with the maximum amount of vapor that the air potentially could hold at that temperature. For example, a relative humidity level of 80% at 70° F means that the air could potentially hold 20% more moisture at that temperature. If the temperature was to rise while the water vapor quantity remained the same, its percentage of the capacity would drop, and the relative humidity value would be lowered. In other words, 8 ounces of water in a 10-ounce glass takes up 80% of the volume available. The same 8 ounces in a 16-ounce glass only uses 50% of the volume. In these analogies, the glass size is comparable to air temperature (energy) and the water is equivalent to the available water vapor.
Dew point temperature (dew point) is a more useful tool for understanding condensation. The dew point is the temperature where the available water vapor equals 100% of the air’s capacity to hold it. Using the previous analogy, dew point occurs when the glass size and the amount of water are equal. Condensation occurs at or below the dew point temperature.
The likelihood of condensation is dependent on how much of the air’s capacity to hold moisture is already utilized and on the change in temperature necessary to achieve the dew point. If the 10-ounce glass has 8 ounces of water, the size needs to be reduced by 2 ounces to achieve 100% full. The 16-ounce glass must be shrunk by 10 ounces to achieve the same results. In this case, the dew point temperature is analogous to the 8-ounce glass size that must be achieved before the glass can overflow (condensation).
Condensation will occur at warmer temperatures depending on the amount of moisture that is in the air. Therefore, in some instances, a surface temperature of 40° F may be necessary to create condensation while in others 60° F may be sufficiently cool.
When a surface is at or below the air’s dew point temperature, condensation will form. When condensation forms, mold has the opportunity to flourish. In houses with un-insulated or poorly insulated walls, condensation is a problem, particularly during the winter. Mold is often found behind furniture, where beds abut exterior walls, and in closets adjacent to outside walls.
In houses with generally well-insulated walls, condensation will occur at locations where the placement of insulation is difficult or is simply missed. Such a problem should be suspected if an isolated area has mold and condensation, particularly if it forms a geometric pattern. A similar problem can occur when penetrations, such as the house’s electrical supply, enter the house. Such locations can cause the adjacent interior area to cool to the dew point temperature.
Condensation and resulting mold are also found at the intersection of ceilings and exterior walls. To provide attic ventilation, little or no insulation is placed in the roof’s soffits, and therefore, the room corners below are cooler and more susceptible to condensation and resulting mold growth.
During summer months, attic air conditioning ductwork can provide a cool surface on which condensation will form. When insulated ductwork is used, the location where ductwork connects to the register is un-insulated and therefore creates an area where condensation can form.
The best money a do-it-yourself homeowner with a crawlspace can spend is on a competent vapor barrier over the space’s earthen floor. Such a vapor barrier will minimize moisture entry into the house and its floor structure.
Crawlspace ventilation can also play a role in the control of a house’s moisture. Often, ventilation is blocked or ineffective as the result of additions, constructions, or the covering of vents to prevent pipe-freezing in winter months; the covers are often left on the vents during warmer weather. In some instances, the only method available to enhance crawlspace ventilation is via a powered blower.
Crawlspaces:
Crawlspaces are the source of more—and more severe—problems in houses than any other feature. Studies suggest that most homeowners seldom, if ever, venture into their crawlspaces. These areas are usually difficult to enter and move within, are dark, contain spider webs and other less than appealing obstacles, are often wet and muddy and sometimes harbor creatures that most would rather avoid. Because these impediments curtail most homeowners’ entry into the crawlspace, conditions can exist there for many years before their consequences become known. Persistent water in a crawlspace is the most damaging condition that can exist there. The water’s source can be from plumbing leaks, but more commonly surface water runoff and drainage are to blame.
Water in a crawlspace in almost any amount is sufficient to promote fungal activity there. Even apparently dry crawlspace floors can emit sufficient water vapor to cause problems for an unsuspecting homeowner. Problems often arise during summer months when the house and its floor are cool as the result of air conditioning. The warm, moist air in the crawlspace comes into contact with the house’s subflooring and condenses. Mold results in the short-term, but if the problem persists, other fungal forms such as wood rot, dry rot, or wet rot will attack the wood. These fungi consume the wood and will compromise its structure; sagging and collapse can result.
Lighting:
None of the previously described conditions for mold growth can practically be controlled in a typical residential environment, and therefore, they hold little promise as a prevention or remediation tool. In some cases, however, lighting modification is often an effective component of a mold-control regimen. Additionally, understanding an area’s lighting can provide clues to a mold growth’s cause.
Molds prefer areas with little or no lighting. They particularly do not like natural sunlight or its ultraviolet component. For this reason, molds will often be found in those areas where furniture or other objects block light. A mold problem will sometimes occur after a homeowner has gone away for an extended period and closed all the blinds.
Ventilation:
Ventilation control is another practical method to control and determine the causes of mold growth. Mold growth requires areas with very limited air movement. For this reason, unventilated closets are one of the most common areas where mold growth is found. In areas where both the air flow and lighting are minimized, such as the spaces behind couches and other furniture, mold growth is more likely.
The amount of air movement necessary to limit the growth of mold is very small. Employing the use of a simple oscillating fan may be sufficient to limit or prevent mold growth in a little-used area such as a basement.
Modern Houses:
House construction today almost universally includes air conditioning and some form of central heating. Energy efficiency desires have further prompted contactors to wrap the house with vapor or moisture barriers and to plug any unintended air leaks, which in turn minimizes infiltration. Additionally, modern windows and doors are constructed with very effective seals to prevent drafts. As a result of these changes, today’s houses are very “tight,” and ventilation design becomes a more critical element of its construction than in the past.
Condensation issues related to ventilation can occur in modern houses just as they do in older houses. Today’s building codes direct builders to include ventilation that will prevent moisture problems. Unfortunately, codes only dictate quantities of ventilation but not its desirable placement or effectiveness. As a result, some aspects of an otherwise well-ventilated attic can suffer.
Perhaps the most problematic areas occur in vaulted or cathedral ceilings. These design features typically have little or no ventilation within their inaccessible and miniscule attics. As a result, condensation can build up. Similar problems can also occur in dormers and other architectural features that escape the application of ventilation or other moisture-control techniques during their construction.
Make-up air is often a difficult problem to diagnose in a tight modern house. Make-up air is the air that is consumed by the combustion of wood, gas, kerosene, coal, or similar fuels in appliances or fireplaces. Furnaces, water heaters, ranges, fireplaces, kerosene heaters, exhaust fans, and any other similarly fueled appliance consumes air that must be constantly replaced while it is operating. Unless an exterior source for this air is provided, it must come from the interior. Air pressure is then lowered inside the house, and suction is created that will attempt to stabilize the pressure through any available opening in the structure. Air can be pulled into the house through flues, the attic, plumbing stacks, cracks, and any other pathway to the exterior. Dust carried by the air flow will stain the carpet and streak walls it passes.
Soiling as a result of make-up air infiltration is often confused with mold. Unlike mold, these problems are more uniform in appearance and will typically be found along the edges of carpeting, around floor registers, and beneath closed doors.
A lack of make-up air can also lead to other conditions that homeowners often suspect as being from mold. Unvented appliances, such as kerosene heaters; some fireplaces; and other similar conveniences require a very closely controlled combustion process so that they can be used safely. The only byproducts of complete combustion are heat/light, carbon dioxide (CO2) and water (H2O). If sufficient air is not available, then complete combustion cannot occur. Incomplete combustion also produces heat/light, CO2, H2O, along with carbon monoxide (CO), soot, and other miscellaneous pollutants depending on the fuel used. Soot is nothing more than a fine particulate of carbon that will disperse throughout the house. As with soiling mentioned above, soot is often mistaken for mold, though its location and appearance have recognizable characteristics.
Soot that clings to the drywall surfaces preferentially at the location of joists or studs is known as shadowing. The mass of the joist or stud as compared with the open spaces on either side can allow small amounts of condensation to occur that traps the soot. Eventually the location of the studs or joists becomes visible. Sampling and analysis of suspected soot can confirm its presence and provide clues about its source.
Life Style Issues:
Some of the most difficult mold and moisture source investigations occur when some change in the homeowner’s lifestyle or condition is discovered. These are particularly problematic because the homeowner doesn’t usually consider these changes as being related to the mold problem he or she is experiencing. Additionally, because the investigator is unfamiliar with the family, he must be willing to talk with the homeowner in order to gather information that can lead to the problem’s origin.
As previously indicated, homeowners often find mold growth in areas where air movement and lighting are minimized and where mold growth has become more likely.
As homeowners increase the temperature in a house, such as during the winter months, problems are created that can promote mold growth. The house’s warmer temperature means that its air can contain more moisture. Additionally, the desire for warmer temperatures means the air conditioner is run less often, and its primary function as a dehumidifier is curtailed, leaving more moisture in the house.
Additional inhabitants release moisture due to normal activities such as breathing, bathing, cooking, and laundering. Always check the clothes dryer’s exhaust vent for problems if an increase in the house’s population corresponds with a mold problem.
Hobbies or home businesses can emit large quantities of moisture into a house or cause other changes that can result in mold. As examples we once discovered that a homeowner had begun a large candle-making operation in her basement using a large double boiler to melt the paraffin. During the candle-making process, large quantities of moisture were released that eventually condensed on upstairs windows and caused mold growth.
Conclusions:
Problems and claims arising as the result of molds and other fungi will continue to be an issue for the forensics industry in the foreseeable future. Some relationships between the presence of mold and human health issues are likely to be more strongly established, though it is unknown how severe their consequences will be. The cause of mold, its consequence, and control can be understood through a logical and methodical study of the evidence. Donan Engineering’s team of engineers has the knowledge and skills necessary to properly diagnose mold and water infiltration matters.