Basic Information about Mold in Homes

Mold has received a lot of attention of late due to high profile lawsuits and television news broadcasts that have highlighted the potential hazards and liabilities associated with indoor mold.

What is mold?

Mold on an interior wall.

Molds, along with mildews, yeasts, and mushrooms, all belong to the kingdom Fungi. Fungi are unicellular or multicellular organisms that primarily use absorption as a means to obtain energy from their environment, unlike green plants, which use chlorophyll to obtain energy from sunlight. The term “mold” is a generally-used word for unwanted visible fungal growth. “Mildew” is fungi that grows on fabrics and outdoor siding, or that causes plant disease. The term “yeast” is used to describe fungi that are unicellular when cultured.

Molds reproduce by way of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air. Indoors, mold may begin growing when the spores land on surfaces that are wet. There are many types of mold, but none of them will grow without water or moisture. Keep in mind that in addition to mold growing on wet surfaces, mold can also grow under high humidity conditions even without the presence of liquid water. This tendency is increased by a lack of air movement, which can create pockets of high humidity air. Also, once mold has established, it can survive under less favorable conditions than those required for it to become established.

Where are molds found?

Molds are part of the natural environment. They can be found everywhere in indoor and outdoor environments. Outdoors, molds play a large role in nature by breaking down dead organic matter such as fallen leaves and dead trees, but indoors, mold growth should be avoided. More than 1000 different kinds of indoor molds have been found in U.S. homes.

How do molds affect us?

Fungi can act as allergens, toxicants (toxic agents), irritants, or infectious agents. It is believed that all forms of fungi are potential allergens to man. Some fungal species are known to produce specific metabolic products (mycotoxins), which are toxic to man and animals. Some, if not most, fungal species can produce metabolic products that are irritating to the mucus membranes (eyes and the lining of the nose and throat). Some fungal species are known to be infectious to humans and animals.

How do you control mold?

The key to mold control is moisture control. Fix any water leaks promptly. It is important to dry water-damaged areas and items within 24-48 hours to prevent mold growth.


Controlled ventilation with air recovery ventilation or heat recovery ventilation.

Do “tight” houses make indoor air pollution worse?

Many pollutants that can affect indoor air may be found in the home. Generally, these pollutants fall into three broad categories: physical (heat, moisture, light); chemical (radon, combustion products, lead, asbestos, organic gases); and biological (viruses, bacteria, mold, mites, insects and their excertions, pollen, etc.).

Some people incorrectly assume that energy conserving or “energy tight” homes are more susceptible to indoor air pollution than homes kept deliberately leaky. These people may be surprised to learn that properly designed and maintained energy efficient homes can have better quality indoor air than leaky, drafty homes. This is because in new, energy efficient homes, and in older homes that have had energy conservation features correctly installed, many pollutants are less likely to enter the homes, and those that do can be removed with controlled ventilation. Remember, in a home that is left intentionally leaky, there is no way to control the air that enters through cracks and other openings. That air flow is affected by wind speed, topography, vegetation, and many other factors. On the other hand, energy efficient homes using properly designed heating, ventilation, and air conditioning systems, exhaust fans to remove excessive moisture and cooking odors, provisions for the introduction of fresh air, and a tight building shell can ensure that potential toxins do not enter or accumulate in the home.

What is a C.L.U.E. report?

If you suspect a major water leak has occurred in a home you’re considering buying, ask to see a copy of the homeowner’s C.L.U.E. report. C.L.U.E. stands for Comprehensive Loss Underwriting Exchange, which is a claim history information exchange that enables insurance companies to access prior claim information in the underwriting and rating process. The report contains up to five years of personal property claims, and can include claim information such as date of loss, type of loss, and amounts paid. More than 90% of insurers writing homeowner’s coverage provide claims data to the C.L.U.E. Personal Property database. Note that the homeowner will have to order the report. Also note that when you apply for home insurance, your insurer will request a C.L.U.E. report to determine whether you or the home seller have filed any claims during the past five years.

New York City Department of Health and Mental Hygiene’s publication “Guidelines on Assessment and Remediation of Fungi in Indoor Environments” – provides detailed background and offers remediation advice –

CLUE Report explained