Understanding Rot & Mold
WHAT IS DRY ROT?
Summary: Dry rot is a condition of wood in which a fungus breaks down wood fibers and renders the wood weak and brittle. Excess moisture is the root cause of dry rot. Borate treatment wood preservatives can be used to treat and prevent fungal growth in some situations.
Dry rot is a weakening of wood caused by one of several species of fungus. The fungus digests the parts of the wood that give the wood strength and stiffness. Weakened wood is typically somewhat dry, hence the name dry rot, and brittle and may have a blocky appearance. Ironically, dry rot usually results from too much moisture in contact with wood. The dry rot fungus has the unusual ability to transport water from wet areas to dry areas allowing the fungus to grow in, and infect, relatively dry wood. If not stopped the dry rot fungus will so weaken wood that it may eventually disintegrate.
CAN DRY ROT BE CONFUSED WITH OTHER DAMAGE?
Yes. Dry rot is often confused with damage. Carpenter ant damage is distinguished by the removal of wood and formation of clean cavities where the carpenter ants live. Subterranean termite damage is similar to dry rot in overall appearance but the presence of live termites, termite galleries and generally wetter wood will usually separate the two conditions.
HOW DO I PREVENT DRY ROT DAMAGE?
The most important way to prevent dry rot damage is to reduce or eliminate excess moisture This may be as simple as repairing a leaky pipe or as complicated as stopping water infiltration through a basement foundation. A common cause of dry rot and termite damage is wood in contact with soil as occurs with a failed foundation.
If moisture cannot be controlled, or if the dry rot fungus has gained a foot-hold, then wood should be treated to inhibit the growth of the fungus. Borate is an excellent fungicide (a pesticide that kills fungi) against the dry rot fungus. Borate also prevents insect damage. Wood can be treated during construction, repair, or as a remedial treatment to stop an active infestation.
Borates for structural pests like dry rot are generally applied as liquids with some type of sprayer. However, most forms of Borate should not be used if liquid water is present such as outdoors, because borates are water soluble and will wash away in these wet situations. Borate is made for exterior applications. Molds in your home can cause health problems and structural damage to the home. The buying and selling community is abuzz with talk about insurance and liability issues involving stachybotrys chart arum, also known as black mold or toxic mold. Some homeowners have even burned down their homes, and everything in them, because they felt it was the only way to eradicate toxic mold from their surroundings. Juries have awarded huge sums of money to homeowners who initiated lawsuits against their insurance companies, with most awards given to people whose insurer did not pay for moisture-related repairs in time to prevent severe mold problems. Awards have also gone against home builders when juries felt that shoddy workmanship contributed to the mold.
Most homeowner policies now include a clause that excludes or limits payments for mold-related Issues. While mold is a problem, in most instances its growth can be prevented or stopped before it causes excessive damage.
WHAT IS MOLD?
Molds are fungi that reproduce by releasing tiny spores into the air. Spores that land on moist objects may begin to grow. There are thousands of different types of mold and we encounter many of them every day, in our homes and outdoors.
WHAT IS TOXIC MOLD?
Toxic mold is a type of mold that produces hazardous byproducts, called mycotoxins. While individuals with asthma and other respiratory problems may have reactions to many types of mold, its thought that mycotoxins are more likely to trigger health problems, even healthy individuals. These toxins are believed to be linked to memory loss and to severe lung problems in infants and the elderly.
Floating particles of mold are invisible to the naked eye, so it’s impossible to see where they might have landed until they begin to grow. Loose mold particles that accumulate on items within a house are easily inhaled and can be a constant irritation to the people and pets that live there.
The toxic mold we hear most about Is Stachybotrys chart arum, a slimy, greenish-black mold that grows on moisture-laden materials that contain cellulose, such as wood, paper, drywall, and other similar products. It does not grow on tile or cement.
Even if the mold in your home is not toxic mold, it can still be a problem, because any mold growing on organic materials will in time destroy them. And too much mold of any type smells bad and degrades air quality.
MOLD THRIVES IN DAMP HUMID CONDITIONS:
• Bathrooms with poor ventilation. Install an exhaust fan if possible.
• Leaky water pipes. Repair them immediately.
• Roof leaks. Repair them right away.
• Flood aftermath. Repair as soon as possible.
• Clothes dryers and exhaust fans that vent under the house or back into the room. Vent them to the outside.
Houses that have been flooded are at serious risk for molds, especially in areas when high humidity and temperatures are providing the mold with the perfect place to reproduce before cleanup begins. The houses flooded by the aftermath of Hurricane Katrina--some still sitting in water--are the perfect example of homes that will likely suffer extreme damage from mold.
HELP DISCOURAGE MOLD GROWTH:
• Install a dehumidifier in chronically moist rooms.
• Don’t carpet rooms that stay damp.
• Insulate pipes and other cold surfaces to discourage condensation.
• Install storm windows to eliminate condensation on glass.
• Cover crawlspace dirt with plastic and ensure that the area is well ventilated.
Make sure the room is well ventilated before you begin. If the mold covers a small surface area it isn’t too hard to clean it with detergent and water. Allow the space to dry, and then apply a solution of 1/2 cup bleach per gallon of water to help kill the remaining spores. Never combine bleach and ammonia because the mixture produces a toxic gas. There are products available that are designed specifically for mold. The Centers for Disease Control offers many. Remember that the mold will very likely return unless you eliminate the underlying problems that caused it.
PROFESSIONAL MOLD REMOVAL
If your mold problem is severe you will likely need the help of a mold remediation company, someone who specializes in mold removal.
BEFORE YOU BUY A HOME
In the past, air quality testing was ordered primarily to detect radon gas, but mold spore tests are becoming more common. Your home inspector might not perform mold tests, but can probably help you find someone who does. In the Pacific NW area mold testing costs between $300-$500 dollars.
If mold is in the air, find out where it’s coming from. Mold should be removed and repairs should be made to ensure it won’t come back. Talk to your real estate agent or to an attorney to determine if a special exception should be inserted in the contract that will allow you to back out of the deal if toxic mold or other molds are detected and cannot be thoroughly eliminated. Many standard forms used by real estate agents include the option of a mold contingency.
HOW TO IDENTIFY THE CAUSE OF A MOLD AND MILDEW PROBLEM
Mold and mildew are commonly found on the exterior wall surfaces of corner rooms in heating climate locations. An exposed corner room is likely to be significantly colder than adjoining rooms, so that it has a higher relative humidity (RH) than other rooms at the same water vapor pressure. If mold and mildew growth are found in a corner room, then relative humidity next to the room surfaces is above 70%. However, is the RH above 70% at the surfaces because the room is too cold or because there is too much moisture present (high water vapor pressure)?
The amount of moisture in the room can be estimated by measuring both temperature and RH at the same location and at the same time. Suppose there are two cases. In the first case, assume that the RH is 30% and the temperature is 70% in the middle of the room. The low RH at that temperature indicates that the water vapor pressure (or absolute humidity) is low. The high surface RH is probably due to room surfaces that are “too cold.” Temperature is the dominating factor, and control strategies should involve increasing the temperature at cold room surfaces.
In the second case, assume that the RH is 50% and the temperature Is 70°F in the middle of the room. The higher RH at that temperature indicates that the water vapor pressure is high and there is a relatively large amount of moisture in the air. The high surface RH is probably due to air that is “too moist.” Humidity is the dominating factor, and control strategies should involve decreasing the moisture content of the Indoor air.
Water in your home can come from many sources. Water can enter your home by leaking or by seeping through basement floors. Showers or even cooking can add moisture to the air in your home. The amount of moisture that the air in your home can hold depends on the temperature of the air. As the temperature goes down, the air is able to hold less moisture. This is why, in cold weather, moisture condenses on cold surfaces (for example, drops of water form on the inside of a window). This moisture can encourage biological pollutants to grow.
THERE ARE MANY WAYS TO CONTROL MOISTURE IN YOUR HOME:
• Fix leaks and seepage. If water is entering the house from the outside, your options range from simple landscaping to extensive excavation and waterproofing. (The ground should slope away from the house.) Water in the basement can result from the lack of gutters or a water flow toward the house. Water leaks in pipes or around tubs and sinks can provide a place for biological pollutants to grow.
• Put a plastic cover over dirt in crawlspaces to prevent moisture from coming in from the ground. Be sure crawlspaces are well-ventilated.
• Use exhausts fans in bathrooms and kitchens to remove moisture to the outside (not into the attic). Vent your clothes dryer to the outside.
• Turn off certain appliances (such as humidifiers or kerosene heaters) if you notice moisture on windows and other surfaces.
• Use dehumidifiers and air conditioners, especially in hot, humid climates, to reduce moisture in the air, but be sure that the appliances themselves don’t become sources of biological pollutants.
• Raise the temperature of cold surfaces where moisture condenses. Use insulation or storm windows. (A storm window installed on the inside works better than one installed on the outside.) Open doors between rooms (especially doors to closets which may be colder than the rooms) to increase circulation. Circulation carries heat to the cold surfaces. Increase air circulation by using fans and by moving furniture from wall corners
HOW DO MOLDS AFFECT PEOPLE?
Some people are sensitive to molds. For these people, exposure to molds can cause symptoms such as-nasal stuffiness, eye irritation, wheezing, or skin irritation. Some people, such as those with serious allergies to molds, may have more severe reactions. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. Severe reactions may include fever and shortness of breath. Some people with chronic lung illnesses, such as obstructive lung disease, may develop mold infections in their lungs.
EPA’s publication, Indoor Air Pollution: An Introduction for Healthy Professionals assists health professionals (especially the primary care physician) in diagnosis of patient symptoms that could be related to an indoor air pollution problem. It addresses the health problems that may be caused by contaminants encountered daily in the home and office. Organized according to pollutant or pollutant groups such as environmental tobacco smoke, VOCs, biological pollutants, and sick building syndrome, this booklet lists key signs and symptoms from exposure to these pollutants, provides a diagnostic checklist and quick reference summary, and includes suggestions for remedial action. It also Includes references for information contained in each section. This booklet was developed by the American Lung Association, the American Medical Association, the U.S. Consumer Product Safety Commission, and the EPA.
EPA Document Reference Number 402-R-94-007, 1994.
Allergic Reactions - excerpted from Indoor Air Pollution: An Introduction for Healthy Professionals, section on: Animal Dander. Molds Dust Mites. Other Bioloalcals.
“A major concern associated with exposure to biological pollutants is allergic reactions, which range from rhinitis, nasal congestion, conjunctiva inflammation, and urticarla to asthma. Notable triggers for these diseases are allergens derived from house dust mites; other arthropods, Including cockroaches; pets (cats, dogs, birds, rodents); molds; and protein-containing furnishings, including feathers, kapok, etc. In occupational settings, more unusual allergens (e.g., bacterial enzymes, algae) have caused asthma epidemics. Probably most proteins of non-human origin can cause asthma in a subset of any appropriately exposed population.”
DAMP BUILDINGS AND HEALTH
For information on damp buildings and health effects, see the 2004 Institute of Medicine Report, Damp Indoor Spaces and Health, published by The National Academies Press in Washington, DC.