When IEQ Problems Arise

Overview Consistent Air Temperature Noise Control Condensation Control Energy Conservation When IEQ Problems Arise Poor or Inadequate Ventilation Mold Growth and the Built Environment Moisture and Duct Systems Exposures to MMVFs Air Handling Issues

Poor or Inadequate Ventilation

Inadequate ventilation has been cited as the major source of poor IEQ. It can lead to moisture accumulation within a building structure causing significant damage. Moisture accumulation can cause problems such as water stains, ice damage, peeling paint, wood deterioration, mold and mildew. It is important to provide sufficient ventilation to reduce excessive water vapor build-up within a building. In addition to providing proper ventilation, it is important to use vapor retarders to limit water vapor transmission into building cavities. When used with insulation, vapor retarders limit the migration of water vapor from warmer areas to the cold surfaces in walls, roof/ceilings. Vapor retarders reduce the amount of water vapor available for condensation.

The vapor retarder facing on insulation should be installed as close as possible to the warm-in-winter (heated interior) surface of the building so the moisture vapor flow is restricted before it has a chance to condense to water. Good construction practice calls for installing a vapor retarder in walls of all new buildings.

Mold Growth and the Built Environment

Requirements for Mold Growth

Mold will grow on virtually any surface where a food source, water and a conducive temperature exist. Since conducive temperatures and food sources like dust and dirt exist in most buildings, the key to controlling mold is to control the moisture.

Reducing the Opportunity for Mold Growth

Wet or damp construction cavities, attics and plenums are a major source of mold. These conditions do not normally occur in properly designed, built, and maintained buildings. Given that moisture is a major contributor to mold growth, insulation products should therefore be installed dry and kept dry. If leaks occur because of defects in construction and/or poor maintenance, the source of the leak should be identified immediately and fixed. Owners should check for condensation problems as well as water leaks.

Replacing Wet Insulation

Whether or not insulation or other building materials should be replaced after getting wet depends on several factors, and opinions differ on the subject. Although fiber glass insulation can be reused in many circumstances, NAIMA suggests consulting the Federal Emergency Management Agency (FEMA), the U.S. Environmental Protection Agency (EPA), the American Red Cross or other reputable sources for specific guidance and definition of terms before taking any remedial action. Any remedial action will depend on a number of unique circumstances which makes general guidelines difficult to provide. For guidance on remediation of wet building insulation, click here.

Moisture and Duct Systems

By helping to reduce condensation, fiber glass insulated ducts actually help minimize microbial growth. A 1997 Duke University study showed that mold is no more likely to grow on fiber glass than on any other surface in the duct system.

Duke University Study (Summary)

A 1997 study was commissioned to do the following:

1. Gain a better understanding of the mold growth in HVAC systems.

2. Determine the role of environmental factors, such as temperature, humidity, airflow, operating hours and the presence of liquid water, in the enhancement of microbial growth in the ventilation systems.

The study revealed that the presence of high humidity conditions in HVAC systems are not necessarily associated with microbial amplification. It is the presence of water that becomes the determining factor. When the surfaces of HVAC materials were examined, fungal growth was rarely observed on surfaces that are regularly exposed during the movement of high humidity air. In comparison, microbial amplification was regularly seen in “wet” zones of the system such as areas close to the cooling coils, mixing boxes and where cold air is mixed with hot, humid air and condensation occurs.

In addition, whenever water was available, microbial growth could be found on all surfaces of the HVAC system, including metal flex duct, the flat surfaces of metal ducts, plastic-lined flex duct, caulks, sealants, conditioning coils, metal sound attenuators, mixing box dampers, and internal insulation or equipment and duct liner. Since humidity is not necessarily the controlling factor, keeping the surface temperature above the dew point can greatly reduce the ‘water’ conditions needed for microbes to grow.

Exposures to MMVFs

Despite the fact that fiber glass duct liner and fiber glass duct board are manufactured and tested to handle air velocities well above normal operating conditions, some people believe that glass fibers can erode from the airstream surface and can be an irritant to people in the occupied space.

A study by the University of Nevada, Las Vegas confirmed that fiber content in the indoor air from fiber glass lined systems is insignificant and does not adversely affect the health of building occupants.

University of Nevada Las Vegas Study (Summary)

A 1996 study by the University of Nevada Las Vegas (funded cooperatively by the Environmental Protection Agency [EPA], DOW Corning, and NAIMA) was designed to address the questions raised about the potential exposure to building occupants from man-made vitreous fibers when fiber glass insulation is used in air handling systems.

The study was performed under controlled environmental conditions using an experimental room to simulate a residential environment. Air samples were taken from the room when it was supplied by new rigid fiber glass duct work and the results were compared to those obtained from the room when it was supplied by bare metal ductwork.

Results of the study which were published in ASTM’s Standard Technical Publication in 1996 confirm the results of numerous earlier studies which showed that fiber content in the indoor air from fiber glass lined systems is insignificant (below detection) and no greater than metal ductwork or ambient background air.

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