Q: What kind of mold issues are incurred in EIFS? What are some of the causes of moisture/mold in EIFS? Is it primarily due to improper installation, or is EIFS truly flawed?

A: EIFS, also known as External Insulation Finish Systems or synthetic stucco, is being installed in all kinds of residential, light commercial and even some commercial projects. The system, involving an impermeable exterior membrane/barrier, has been used for many years in Europe and for about 20 years in the U.S.

Early EIFS systems did not include a drainage plane in the design. It wasn't necessary because the system was used in dry climates (less than 20 inches of rainfall annually). As the use of EIFS expanded to wetter portions of the U.S., mold started occurring.

The problem started with the assumption that sealants around windows, and at joints would work perfectly to keep moisture out. When they didn't, moisture reached the more sensitive construction materials, such as oriented strand board (OSB) and paper-faced gypsum board. These two materials are a prime growth media for mold.

Solutions to the problem that have worked well at reducing mold problems include developing a drainage plane, applying more effective sealants and using less sensitive materials. Regular inspections of the sealants still need to be done, though. Otherwise, rain or excess humidity can still bypass seal failures and work its way into the system.

In the summer of 2003, we worked on one mold project involving a seven-year-old building in Corpus Christi, Texas, that was constructed with EIFS. The building, a telephone call center, had 1,200 linear ft. of wall surfaces, 900 of which were moldy. The problem was caused by moisture leaking into the EIFS at every joint and the seals at window jambs. The moisture got in but didn't have a drainage plane to get out. Consequently, the saturated OSB was like mush by the time we found it. The mold remediation, and repairs to the EIFS system ran almost $800,000, which was about 70% of the building's construction price when new. Most of the problems were initiated by seal failures. They grew worse because the moisture didn't have anywhere to go, i.e., no drainage plane.

Finally, there have been many lawsuits during recent years related to EIFS construction. Entire cities (Vancouver, B.C.) have claimed the problem to be "epidemic" in proportion. Careful research into the design, construction and maintenance of EIFS, however, does show it to be a viable option in the right climate.

Travis West is the president of Building Air Quality Inc., a Houston-based indoor air quality consulting firm. He can be reached at twest@baq1.com, or toll-free at 866-367-1177.

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