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Mold In Your Home

mold under house

A Perfect Breeding Ground For Mold

Intro to Molds

Molds produce tiny spores in order to reproduce. Mold spores waft through the indoor and outdoor air continually. When mold spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on in order to survive. There are molds that can grow on wood, paper, carpet, and foods. When excessive moisture or water accumulates indoors, mold growth will often occur, particularly if the moisture problem remains undiscovered or un-addressed. There is no practical way to eliminate all mold and all mold spores in the indoor environment...

the way to control indoor mold growth is to control the moisture. 

The “trick” (hard part) is to find the molds that cannot be seen. One way to do this is through the use of infrared thermography (see below).

Mold in the Home

The first thing to understand about mold is that there is a little mold everywhere – indoors and outdoors. It's in the air and can be found on plants, foods, dry leaves, and other organic materials.

It's very common to find molds in homes and buildings. After all, molds grow naturally indoors. 
Mold spores enter the home through doorways, windows, and heating and air conditioning systems. Spores also enter the home on animals, clothing, shoes, bags and on people.

When mold spores drop where there is excessive moisture in your home, they will grow. Common problem sites include humidifiers, leaky roofs and pipes, overflowing sinks, bath tubs and plant pots, steam from cooking, wet clothes drying indoors, dryers exhausting indoors, or where there has been flooding. mold on window frameMany of the building materials used in home construction also provide suitable nutrients for mold, helping it to grow. Such materials include paper and paper products, cardboard, ceiling tiles, wood and wood products, dust, paints, wallpaper, insulation materials, drywall, carpet, fabric, 
and upholstery.

The Importance of Mold in the Real Estate Market Today

Much has been made of indoor mold in advertising and the media lately, so it’s a common concern for homeowners and buyers alike. It's common to find mold even in new homes. Whether you’re selling your current home or looking into buying one, it’s vital to get a mold inspection. The presence of active mold can drastically affect the resale value of any home.

For homeowners, a mold inspection will either put your mind at rest or make you aware of any problems that could otherwise cause delays or break deals once you’ve entered negotiations with a buyer. A professional mold inspection by OxBow Home Inspections will give you a signed report from an expert, before you put the home up for sale.  Imagine being able to show a “clean bill of health” to potential buyers that express concerns – they’ll be impressed by your thoroughness and commitment to your home.

For buyers, getting a mold inspection will ensure that you’re not surprised by costly clean up and the potential health hazards of mold. If any mold is found to be present and active in the home, the mold inspection will allow you to ask the seller to do the clean up prior to buying the home.

Exposure to Mold

Everyone is exposed to some amount of mold on a daily basis, most without any apparent reaction. Generally mold spores can cause problems when they are present in large numbers and a person inhales large quantities of them. This occurs primarily when there is active mold growth.

For some people, a small exposure to mold spores can trigger an asthma attack or lead to other health problems. For others, symptoms may occur only when exposure levels are much higher.

The health effects of mold can vary. The production of allergens or irritants can cause mild allergic reactions and asthma attacks. The production of potentially toxic mycotoxins can cause more severe reactions, and in rare cases death. Should you be concerned about mold in your home?

Yes. If indoor mold is extensive, people in your home can be exposed to very high and persistent airborne mold spores. It is possible to become sensitized to these mold spores and develop allergies or other health concerns, even if one is not normally sensitive to mold.

Left unchecked, mold growth can cause structural damage to your home as well as permanent damage to furnishings and carpet.  According to the Centers for Disease Control*:

"It is not necessary, however, to determine what type of mold you may have. 
All molds should be treated the same with respect to potential health risks and removal."

How do I remove Mold from my home?

First, address the source of moisture that is allowing the mold to grow. Then take steps to clean up the contamination. Here are helpful links to lean more about cleaning up mold in your home.

Ten Things You Should Know About Mold 

  • Potential health effects and symptoms associated with mold exposures include allergic reactions, asthma, and other respiratory complaints.

  • Molds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present. There are molds that can grow on wood, paper, carpet, and foods.

  • There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to control moisture. 

  • If mold is a problem in your home or school, you must clean up the mold and eliminate sources of moisture. Fix the source of the water problem or leak to prevent mold growth.

  • Reduce indoor humidity (to 30-60% ) to decrease mold growth by: venting bathrooms, dryers, and other moisture-generating sources to the outside; using air conditioners and de-humidifiers; increasing ventilation; and using exhaust fans whenever cooking, dishwashing, and cleaning.

  • Clean and dry any damp or wet building materials and furnishings within 24-48 hours to prevent mold growth.

  • Clean mold off hard surfaces with water and detergent, and dry completely. 
    Absorbent materials such as ceiling tiles, that are moldy, may need to be replaced.

  • Prevent condensation: Reduce the potential for condensation on cold surfaces 
    (i.e., windows, piping, exterior walls, roof, or floors) by adding insulation.

  • In areas where there is a perpetual moisture problem (bathrooms), do not install carpeting  (i.e., by drinking fountains, by sinks, or on concrete floors with leaks or frequent condensation).

  • The key to mold control is moisture control. It is important to dry water damaged areas and items within 24-48 hours to prevent mold growth. If mold is a problem in your home, clean up the mold and get rid of the excess water or moisture. Fix leaky plumbing or other sources of water. Wash mold off hard surfaces with detergent or bleach and water, and dry completely. Absorbent materials (such as ceiling tiles and carpet) that become moldy may have to be replaced.

Asthma and Mold

Molds can trigger asthma episodes in sensitive individuals with asthma.  
People with asthma should avoid contact with or exposure to molds.

EPA's Asthma web site
Asthma Brochure
Mold page from Asthma web site

Allergy and Asthma Network/Mothers of Asthmatics (AAN/MA) (800) 878-4403;

American Academy of Allergy, Asthma and Immunology (AAAAI)

American Lung Association: 1-800-LUNG-USA (1-800-586-4872)

Health and Molds 

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 Health Professionals , assists health professionals (especially the primary care physician) in the 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.  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. The EPA Document Reference Number is: 402-R-94-007, 1994.

Allergic Reactions - excerpted from Indoor Air Pollution: An Introduction for Health Professionals section on: Animal Dander, Molds, Dust Mites, Other Biologicals .  

A major concern associated with exposure to biological pollutants is allergic reactions, which range from rhinitis, nasal congestion, conjunctival inflammation, and urticaria 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. Consult the Centers for Disease Control (CDC) website

CDC's National Center for Environmental Health (NCEH) has a toll-free telephone number 
for information and FAXs, including a list of publications: NCEH Health Line is: 1-888-232-6789.

CDC's Molds in the Environment Factsheet
Stachybotrys or Stachybotrys atra (chartarum) and health effects ("Black Mold")

Homes and Mold

The EPA publication, A Brief Guide to Mold, Moisture, and Your Home , is available here in HTML and PDF formats.  This Guide provides information and guidance for homeowners and renters on how to clean up residential mold problems and how to prevent mold growth.  A printed version will be available soon.

Biological Pollutants in Your Home - This document explains indoor biological pollution, health effects of biological pollutants, and how to control their growth and buildup. One third to one half of all structures have damp conditions that may encourage development of pollutants such as molds and bacteria, which can cause allergic reactions -- including asthma -- and spread infectious diseases.  Describes corrective measures for achieving moisture control and cleanliness.  This brochure was prepared by the American Lung Association and the U.S. Consumer Product Safety Commission. EPA Document Reference # 402-F-90-102, Jan 1990.

Moisture control is the key to mold control, the Moisture Control Section from Biological Pollutants in Your Home follows:

Moisture Control

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 exhaust 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 to promote air and heat circulation. Be sure that your house has a source of fresh air and can expel excessive moisture from the home.

  • Pay special attention to carpet on concrete floors. Carpet can absorb moisture and serve as a place for biological pollutants to grow. Use area rugs which can be taken up and washed often. In certain climates, if carpet is to be installed over a concrete floor, it may be necessary to use a vapor barrier (plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem.

  • Moisture problems and their solutions differ from one climate to another. The Northeast is cold and wet; the Southwest is hot and dry; the South is hot and wet; and the Western Mountain states are cold and dry. All of these regions can have moisture problems. For example, evaporative coolers used in the Southwest can encourage the growth of biological pollutants. In other hot regions, the use of air conditioners which cool the air too quickly may prevent the air conditioners from running long enough to remove excess moisture from the air. The types of construction and weatherization for the different climates can lead to different problems and solutions.

  • One sure fire way to reduce the chances of getting mold is to have a good gutter system installed on your home.  Read more about it here.

Moisture On Windows

Your humidistat is set too high if excessive moisture collects on windows and other cold surfaces. Excess humidity for a prolonged time can damage walls especially when outdoor air temperatures are very low. Excess moisture condenses on window glass because the glass is cold. Other sources of excess moisture besides overuse of a humidifier may be long showers, running water for other uses, boiling or steaming in cooking, plants, and drying clothes indoors. A tight, energy efficient house holds more moisture inside; you may need to run a kitchen or bath ventilating fan sometimes, or open a window briefly. Storm windows and caulking around windows keep the interior glass warmer and reduce condensation of moisture there.

Humidifiers are not recommended for use in buildings without proper vapor barriers because of potential damage from moisture buildup. Consult a building contractor to determine the adequacy of the vapor barrier in your house. Use a humidity indicator to measure the relative humidity in your house. The American Society of Heating and Air Conditioning Engineers (ASHRAE) recommends these maximum indoor humidity levels:

Outdoor Recommended Indoor Temperature Relative Humidity

                                                    +20 F.        35%
                                                    +10 F.        30%
                                                    +0 F.         25%
                                                    -10 F.        20%
                                                    -20 F.        15%

Anne Field, Extension Specialist, Emeritus, with reference from
the Association for Home Appliance Manufacturers

  Should You Have the Air Ducts in Your Home Cleaned?

The following is an excerpt on duct cleaning and mold. You should consider having the air ducts in your home cleaned if there is substantial visible mold growth inside hard surfaces such as sheet metal or ducts, or on other components of your heating and cooling system.  There are several important points to understand concerning mold detection in heating and cooling systems:

  1. Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.

  2. You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation.  For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.

  3. If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.

  4. If the conditions that are causing the mold growth in the first place are not corrected, mold growth will return. 

Infrared Thermography

About 50% of mold cases initially go unnoticed because they are hidden behind something (such as a wall). Any Home Inspector will identify and report any visible molds. Problem is…  they normally cannot see the mold that has damaged the wall behind the dishwasher, or destroyed the floor under the bathtub. With the latest technology in mold detection, I am able to see many of those molds that used to remain hidden. This new technology is called “Infrared Thermography”, but is often known as Infrared Thermal Imaging. For example, if the previous owner had a water leak behind a wall… fixed the leak and then replaced the damaged drywall with new stuff, nobody would ever know the difference. But what if his leaking pipe started a mold culture in the framing structures of the wall itself?  The mold actually changes the thermal transferrence capacity of the wood.  With Infrared Thermography technology, I am often able to identify mold growths that before now, would have remained unnoticed.

Infrared Thermography Facts

Moisture behind walls, over ceilings, and under floors is often impossible to detect until the problem is excessive and visible to the naked eye. The investigation of not yet visible mold in structures is often difficult to detect, however with modern technology and infrared diagnostics it is now possible to do what was once impossible.  

Technology has provided a tool that can be used by investigators, remediators and consultants to detect and help eliminate mold infestations. The technological tool is called Infrared Thermography (IRT).  It is a technique that produces an image of invisible (to the human eye) infrared light emitted by objects due to the heat, or lack thereof, in the object called its “thermal condition.”  The most typical type of thermography camera resembles a typical camcorder and produces live television pictures of heat radiation.  More sophisticated cameras can actually measure the temperatures of any object or surface in the image and produce false color images that make interpretation of thermal patterns easier.  An image produced by an infrared camera is called a thermogram.

To understand IRT as a tool it is necessary to understand how it works.  Thermal or infrared energy is light that is not visible to humans because of its wavelength is too long to be detected by the human eye. Thermal or infrared energy (IR) is the part of the electromagnetic spectrum that we perceive as heat. Unlike visible light, in the infrared world, everything with a temperature above absolute zero emits heat. Even very cold objects, like ice cubes, emit infrared.  The higher the object’s temperature, the greater the IR radiation emitted.  Infrared allows people to see what their eyes normally cannot.

IRT cameras produce images of invisible infrared or “heat” radiation.  The IRT camera can provide precise non-contact temperature measurement capabilities.  The existence of moisture (normally cooler than normal construction materials) can be used to detect conditions that promote mold growth.  Mold related problems can be detected before the mold is visible to the eye or detectable by the nose.  IRT cameras are extremely cost-effective, valuable diagnostic tools in construction related problems of water intrusion and mold growth.

But finding a problem with an infrared camera is not a solution.  It is only the start of an investigation that will help the property owner or developer to stop a problem before it becomes serious.  

The use of a thermal imaging camera can provide valuable information during moisture assessments, remediation oversight, energy audits, roof and electrical system inspections and water damage investigations.  Temperature difference caused by evaporation, radiation, thermal bridging, infiltration/exfiltration, and other sources must all be carefully evaluated.  

The time saved using infrared, and the larger areas covered rapidly by an IR camera, can save time and money by providing a faster, more efficient and more reliable survey.  An IR camera can detect moisture located behind interior walls under the right conditions.  The temperature difference created by the presence of moisture on the inside surface of a wall appears differently than the surrounding area.  Sample photos of Infrared Thermography are posted on my "Difference" page.

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