MOLD AND ENVIRONMENTAL ISSUES
- By Tim Bovard
- March 1st, 2003
Improperly insulated chilled water distribution systems can lead to the growth of mold and mildew, which can be a major problem in occupied buildings. The definition of occupied buildings includes office buildings, government facilities, hospitals, schools and universities, and any other building that houses people for work or housing. In these buildings, mold and mildew can cause serious health and economic consequences. That’s why it’s imperative to specify an insulation that is impermeable to moisture in liquid and vapor forms, and not support the growth and propagation of mold and mildew.
Mold and mildew are a part of nature; these microorganisms can grow anywhere, from the top of a mountain to the bottom of lakes and streams, but they become a problem when they start growing indoors. The air inside can become concentrated with allergenic spores and mycotoxins; chemical toxins that some molds produce.
When airborne mold spores find a damp indoor haven, spores will set up as a colony and start reproducing. When this happens, molds evolve from being merely a nuisance to a full-blown health hazard.
Some molds are more toxic than others, but there is no such thing as "good" mold. All are, in the least, allergenic and can aggravate or ignite an allergy attack in the 50 million or so American allergy sufferers. Many molds can even cause an allergy in a previously unaffected person.
Of the most common molds, the following microorganisms have the most potential for disaster.
Cladosporium and Penicillin can grow to toxic levels, triggering allergic reactions including:
eye and throat irritation.
Stachybotrys, memnoniella and aspergillis versicolor produce airborne toxins that can cause even more serious problems including:
loss of balance and memory,
difficulty speaking, and
Toxic mold is the focus of a growing number of legal cases across the country and is rapidly becoming one of the "hottest areas" in construction defect and toxic tort law.
In Florida, building contractors have been liable for some $70 million in damages after toxic mold was found in two brand-new county courthouses.
Toxic molds have been found everywhere, in all kinds of buildings, all across the country.
Toxic mold is deceptive: it looks just like nontoxic varieties. The spores are microscopic, spread easily through ventilation systems and are inhaled by building occupants.
The presence of mold is of particular concern in occupied buildings such as hospitals, schools and government office buildings. Schools are a specific problem because children can be more susceptible to mold-related illnesses since their lungs and organs are still developing. If the problem becomes too large, trained professionals are required to effectively remove the mold, which is an expensive andtime-consuming process.
The need for mold and mildew abatement became clearly apparent recently at Edgewood Middle School, in Edgewood, Md., when high humidity conditions and resulting mold growth on building components was reported to have occurred during this past Labor Day weekend. The Facilities Management department responded by cleaning and disinfecting the affected surfaces and sought outside expertise in Indoor Air Quality (IAQ). It was determined that suspect microbial growth was growing on ceiling tiles, pipe insulation above the ceiling, on upper walls and various other surfaces. A large portion of the water-damaged ceiling tiles was located under the pipes located in the ceiling space.
Edgewood isn’t the only school that has faced mold and mildew challenges. Several school districts across the country have had to close their facilities for mold and mildew abatement, and some are even facing lawsuits. Here are a few documented cases.
Lower Pottsgrove Elementary School in Lower Pottsgrove, Pa., will close its doors indefinitely — despite spending $600,000 to clean up high levels of bacteria and mold. The Pottsgrove Federation of Teachers sued the school district, saying that nausea, respiratory problems and headaches persisted among teachers and students at the school. When the teacher’s union won the lawsuit, the school was ordered to shut its doors.
Four schools in Grand Rapids, Mich., had to be closed while workers searched for clues as to why seven teachers were sent to the hospital, complaining of nausea and dizziness. They found ventilation shafts full of mold blowing directly into classrooms.
Saline Middle School in Washtenaw County, Mich., spent $500,000 to remove a strain of black mold from the ceiling tiles above 10 classrooms after some staff members complained that their allergies flared up when they entered the building.
Fungal and bacterial growth can be prevented by keeping buildings dry; ideally, indoor relative humidity should be kept below 60 percent. The presence of moisture is the single most important factor for growth, because most fungus spores will not germinate and grow unless the moisture content is at least 25 percent. Once a small area has become wet enough and colonization has occurred, some fungi (especially "dry rot" fungi) can carry adequate water to other parts of the substrate, and the contamination can spread well beyond the initially wet area.
The main culprits in mold problems are water vapor pressure and surface temperatures. Understanding which is the dominating factor in your particular building will help in selecting an effective control strategy. For example, a vapor-pressure-dominated mold infestation may not respond well to increasing temperatures, whereas a surface-temperature-dominated mold problem may not respond very well to increasing ventilation.
How Insulation Can Become a Breeding Ground for Mold and Mildew
Whenever both relative humidity and temperature are high, the selection and installation of chilled water line insulation for commercial and institutional buildings presents special challenges in keeping the systems dry. Water vapor makes up less than 1 percent (by volume) of our air, but it is the only atmospheric gas that can change to a liquid or a solid under normal, ambient air temperatures. Consequently, it can threaten the integrity and performance of an insulation system.
The strong vapor pressure in high-temperature and humidity areas causes water vapor to penetrate permeable insulation materials and condense within them. But, with low-temperature equipment, such as chilled water lines, water vapor migrates to the cold substrate behind the insulation system. Once in contact, the vapor condenses to a liquid. This is a major problem in the Southwest and Southeastern United States, but, as evidenced by the school problems previously mentioned in Michigan, Pennsylvania and Maryland, water vapor absorption is a problem just about anywhere for chilled water systems.
In most environments, once chilled water lines become wet, it’s likely that they will never completely dry out. Because water is an excellent conductor of heat, moisture in a permeable insulation transforms insulation into a thermal conductor. This opens the door for additional problems including dripping pipes that damage ceiling systems, walls, floors, equipment and/or furnishings. This initiates the growth of mold and mildew and the potential for associated health problems and economic losses.
Indoor air quality and health and safety issues demand an insulation that will not provide food, sustenance or living quarters for microbes and fungi. Open-structured materials such as fibrous glass and foamed plastics can represent a source of air quality problems caused by the absorption of dust and moisture, providing the perfect culture medium for microorganisms to develop.
The absorption of moisture translates into several ways in which money is lost. First, the loss of insulating efficiency for insulation materials reduces insulating efficiency and increases energy costs, and this can be quite costly considering the recent increases in energy costs. Costs can also escalate in the form of system maintenance and repair, complete system replacement, corrosion to piping and system equipment, as well as damage to ceiling tiles, furnishings, computers and other contents of the building. In addition, lawsuits and building closure due to mold and mildew infestation can be very expensive.
When it comes to preventing mold and mildew on chilled water lines, cellular glass insulation is the best option.
Cellular glass insulation is the most resistant insulation against mold and mildew because it will not absorb moisture, does not present a medium in which microorganisms can grow and multiply and cannot be physically damaged by the microbial attack.
And, no other insulation material offers such a high safety factor from the damage caused by mold and mildew as does cellular glass insulation. Carefully executed tests and practical experience show that cellular glass insulation is the best defense against microbial agents.