Building Professionals Seeking to Reduce Noise Transfer May Inadvertently Be Causing Moldy Buildings

Building forensics experts have long known that certain climates require a specific approach to building design and construction to avoid failure.

Building forensics experts have long known that certain climates require a specific approach to building design and construction to avoid failure.

Tokyo-based airbag maker Takata made headlines recently as airbag-related fatalities forced the company to announce the largest auto recall in history. Takata had initially recalled faulty airbags in 18 million vehicles, believing the malfunctions to be linked to cars in hot, humid climates. Although the airbags were failing in other climates, as well, they interestingly had higher failure rates when humidity and moisture were involved—drawing a remarkable parallel with the root cause of many building failures.

Building forensics experts have long known that certain climates require a specific approach to building design and construction to avoid failure. Using the same products and techniques indiscriminately across the board creates a recipe for disaster that unfortunately is very common in multifamily complexes, like apartments, which during the past several years have undergone significant expansion and growth as an industry niche.

Some examples of multifamily complex failures resulting from design, construction or material deficiencies include the following:

  • Green, water-based products (which are fine in most climates but often fail in hot, humid climates) have been used, resulting in excess moisture and mold under kitchen and bathroom cabinets and in closets.
  • Air-conditioning units with very little run time and no load have led to surface mold and moisture problems because of reduced dehumidification.
  • In an effort to create high sound attenuation between floors and interior/exterior walls, apartment designers and contractors have inadvertently tightened the building envelope so much that there is significant chance of accumulated moisture.

Each situation resulted from well-intentioned efforts to reduce noise transfer, lessen the carbon footprint and/or decrease energy costs.

Dreaded Mold

This mold growth was created between the base of kitchen cabinets and thickened gypsum-based flooring underlayment installed in a hot, humid climate.

This mold growth was created between the base of kitchen cabinets and thickened gypsum-based flooring underlayment installed in a hot, humid climate.


More than 20 years ago, Stewart Brand predicted in his book, How Buildings Learn: What Happens After They’re Built, “Most new products are experiments and most experiments fail.”

Most new products are experiments? Really? Does Brand mean every time we use a new product or innovative design concept we are in effect running an experiment? Perhaps.

Consider this: A new 300-plus-unit complex in Florida began to experience moisture and mold problems only months after construction completion. The location and frequency of the mold problems were something new to the sophisticated national multifamily construction firm. To the casual observer, this complex was no different than the hundreds of others the firm had built. Except it was.

In an effort to create high sound attenuation between floors, the firm chose to double the normal size of the gypsum-based flooring underlayment. The typical depth of the gypsum-based flooring underlayment is 3/4 inch and this time the team had made it approximately 2 inches. As most know, the gypsum-based flooring underlayment product is poured in a wet condition and over time it will dry, releasing its moisture.

This particular complex’s floor design had the thickened gypsum-based flooring underlayment over a sound mat that impacted the amount of moisture that was released to the floor cavity below (ceiling cavity of the unit below). Traditional gypsum-based flooring underlayment applications do not have the floor mat and, therefore, over time the floor sheathing allows for moisture to release to the floor cavity below, as well as the interior of the unit below.

For those areas with carpet and pad, moisture easily is released into the unit through the carpet and pad. However, for the areas of the floor that had kitchen and bathroom cabinets installed or areas with vinyl laminate flooring, the additional moisture load from the thickened gypsum-based flooring underlayment posed a significant problem.

Thickened gypsum-based flooring underlayment over a sound mat is problematic in hot, humid climates. It can impact the amount of moisture that is released to the floor cavity below.

Thickened gypsum-based flooring underlayment over a sound mat is problematic in hot, humid climates. It can impact the amount of moisture that is released to the floor cavity below.


This moisture was now trapped creating a microclimate that resulted in mold growth. It became clear through direct readings with data loggers that the gypsum-based flooring underlayment was not drying in a manner that could be absorbed into the unit and handled by the units’ individual HVAC systems. In addition, the small areas below the cabinets had trapped enough moisture and resulted in enough mold growth that it manifested in odors about which the unit occupants complained.

The Retrofit

It is important to note that the underlayment’s moisture release could be occurring during a long period of time. Even after remediation, it was critical to get this area communicating with the unit interior so the unit HVAC system could provide effective ventilation of this space with dry air-conditioned air. Therefore, after cleanup and remediation, which required cabinet removal, treatment and, in some cases, replacement, it became necessary to open these small spaces below the cabinets and retrofit them with vents.

Long-term monitoring of these spaces was an additional concern that resulted in the need to install data loggers so the below-cabinet condition could be tracked to make sure it was being maintained at acceptable conditions to reduce the risk of mold recurrence.

Considerations

Architects, engineers, and contractors who design and construct these complexes nationwide and manufacturers who supply materials, systems, or products for these projects often make critical errors that result in catastrophic building envelope and HVAC moisture problems. One simply can’t take a product or technique that works well in one climate and expect it to work the same way when applied in another climate.

PHOTOS: Liberty Buildings Forensic Group

About the Author

George H. DuBose, CGC, and Chuck Allen, AIA
George H. DuBose, CGC, and Chuck Allen, AIA, are forensic building experts with Liberty Buildings Forensics Group, Zellwood, Fla. Combined, they have more than 50 years’ experience in diagnosing, solving and correcting moisture-related mold problems in buildings.

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