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Why MOLD is a Growing Problem?

“Mold spores are everywhere.” – Richard F. Progovitz (author of Black Mold: Your Health and Your Home)¹

Mold grows everywhere because microbial spores are everywhere. S.S. Block’s article Humidity Requirements for Mold Growth states that “in a discussion of the mildew problem, mold requires for growth and proliferation certain essential physical and chemical conditions. These include satisfactory temperature, adequate moisture, sufficient oxygen, proper pH, and essential nutrients.”² Kathleen Parrott, Ph.D., goes into further detail in her article about mold prevention explaining that “molds digest organic matter as a food source. This includes many materials found in our homes, including wood, paper, textiles, plants, and food. Therefore, there is always a food source for molds in our homes, including many of the materials that we use to build and furnish our homes.”³ Unfortunately, we cannot control most of these factors especially in smaller, tighter envelopes such as apartments, but we can help control the relative humidity. According to Block “the control of moisture through regulation of humidity has proved to be most satisfactory.”²

Contributing factors to mold include:

1. Daily Moisture – 25 Pints

The ASHRAE Handbook of Fundamentals states, “a typical family of four may produce as much as 11.4 L/day (25lb/ day) of water vapor or more if humidifiers, automatic washers, and clothes dryers are used”. ⁴ In other words, on average, a family of 4 produces 11.4 L/ day, almost 25 pints of water per day. Moisture is released into the air from daily activities such as cooking, cleaning, laundry, showering, perspiring, etc. The World Health Organization (WHO) states that “the capacity of building and interior materials to absorb and release moisture has a significant effect on indoor humidity fluctuations and may have consequences for moisture damage and dampness”.⁵

2. Daily Habits

Daily habits differ from person to person. For example, some choose not to run exhaust fans while cooking or showering. Others may not leave their residence often, while others cook all day. Some people choose to house many plants and/or aquariums. According to Stephen Smulski’s article on the Durability of Energy-Efficient Wood-Frame Houses, “water vapor generated by occupants’ activities and released from other interior sources lingers longer indoors. When warm, moist air entering into these spaces is cooled below the dew point, the excess moisture is deposited as condensation on framing, sheathing, and other cold surfaces, creating conditions favorable to mildew, mold, and decay fungi”⁶

3. New Construction = Tighter Envelopes

We are seeing an increase in mold growth due to tighter construction regulations. It is great to be energy efficient but In recent years, there has been an increase in mold growth indoors due to tighter construction regulations. According to John Manuel’s article A Healthy Home Environment “since the energy crisis of the 1970s, builders have concentrated on building tighter homes as a way of minimizing heating and air-conditioning costs. Tighter houses can be healthy houses, but more care must be taken to avoid generating or trapping pollutants indoors”.⁷ High-efficiency HVAC systems are much more efficient and run for shorter periods of time. This is exceptional for HVAC systems, however as a result, moisture does not have an escape route and cannot be cycled out. In reference to Aaron McGill Cooper’s thesis, Mold Susceptibility of Rapidly Renewable Materials used in Wall Construction, “although tighter building construction practices save energy, they can also create an environment of stagnant air that is highly hospitable to mold.”⁸ Cooper goes into further detail about moisture trapped indoors explaining that “undesirable moisture is then introduced by unavoidable activities such as showering, cooking, cleaning, and sweating, along with unplanned events such as spills, overflowing toilets, or plumbing malfunctions”.⁸ Kathleen Parrot, Ph.D., Professor of Housing, states that “to control mold growth in our homes, we must control excess moisture and water!”⁹

4. Introduction of Fresh Air Vents

Many codes, such as the ENERGY STAR® Multifamily New Construction Program, require the introduction of “fresh” air from outside. According to the World Health Organization, “ventilation also affects air and moisture flow through the building envelope and may therefore lead to moisture problems that degrade the structure.”¹⁰ Introducing outside air with high humidity into your property will increase the relative humidity and allow the opportunity for pollutants to come indoors. Biological pollutants are found to some degree in every home, school, and workplace. Referencing John Manuel’s article, A Healthy Home Environment, “biological pollutants are found to some degree in every home, school and workplace. They come from outdoor air in the form of pollen and other allergens, from human occupants who expel viruses and bacteria, from pets that shed dander, from insect pests, and from moist surfaces that allow mold and fungi to grow.”⁷

Humidity Happens…

What’s your Plan to Lower High Humidity?

Source:
1. Progovitz, R. F. (2003). Black Mold: Your Health and Your Home. The Forager Press, LLC
2. Department of Chemical Engineering, University of Florida, S.S. Block, June,1953, ASM Journals, accessed October 2021. <https://journals.asm.org/doi/pdf/10.1128/am.1.6.287-293.1953>
3. Virginia Polytechnic Institute and State University; Robert Grisso, Martha Walker, Phillip Agee, and John Ignosh, Virginia Cooperative Extension, accessed October 2021.
<https://resources.ext.vt.edu/contentdetail?contentid=2227&contentname=Energy%20Series:%20What%20about%20Mold%3F>
4. ASHRAE Handbook of Fundamentals, ASHRAE, Atlanta, GA, 1991.
5. World Health Organization, Ollie Seppänen, Jane Kurnitski 2009, National Center for Biotechnology Information, accessed October 2021.
<https://www.ncbi.nlm.nih.gov/books/NBK143947/>
6. Smulski, S. (1999). Durability of Energy-Efficient Wood-Frame Houses. Forest Prod. J.
7. Focus: John Manuel, July 1999, A Healthy Home Environment, accessed October 2021. <https://ehp.niehs.nih.gov/doi/pdf/10.1289/ehp.99107a352>
8. Cooper, Aaron M. Mold Susceptibility of Rapidly Renewable Materials used in Wall Construction. 2007. Texas A&M University, Master of Science. Core, <https://core.ac.uk/download/pdf/4276521.pdf>
9. Virginia Polytechnic Institute and State University; Kathleen Parrott, Ph.D. 2009, Virginia Cooperative Extension, accessed October 2021.
<https://vtechworks.lib.vt.edu/bitstream/handle/10919/50219/2901-7020.pdf?sequence=1>
10. World Health Organization, Ollie Seppänen, Jane Kurnitski 2009, National Center for Biotechnology Information, accessed October 2021. <https://www.ncbi.nlm.nih.gov/books/NBK143947/>