Astronomical mold

Most roofing materials manufacturers would jump at the chance to have their products atop a major sports facility. But they probably wouldn't want to face the headache GenFlex Roofing Systems, Maumee, Ohio, has had related to the roof system on Minute Maid Park in Houston.

The ballpark, home to the Houston Astros (and formerly known as Enron Field), is a $250 million facility with a $30 million retractable roof. The 480,000-square-foot (44592-m²) roof system features a GenFlex single-ply white membrane.

The park opened in March 2000. In May 2003, the Harris County-Houston Sports Authority, which leases the building to the Houston Astros, noticed some growth on the membrane. Scientists who tested the growth determined it was Aspergillus, a common mold, coupled with yeast, bacteria and unidentified fungi.

So began a six-month dispute regarding who was responsible for cleaning the roof system—Super Bowl XXXVIII was headed to Houston, and the city wanted all highly visible buildings to be spotless.