Three Case Studies: Moisture Control in a Hot, Humid Climate

Abstract

This paper will present case studies of the investigations of three different buildings exhibiting moisture control problems along the Gulf Coast. We will briefly discuss the original, or existing, conditions that led to our involvement, as well as analysis of the problems, and recommendations for correction. Each of these projects would be classified an airconditioned building in a hot, humid climate, and subject to the problems and design issues concomitant with these types of projects. The first case study was a historic residence in Houston that had experienced concealed condensation within the wood-framed floor system located over a crawl space. The floor framing had been insulated with an extruded polystyrene rigid board insulation, but with no vapor retarder. The second case study was a new premanufactured residence located in the pine woods of Southeast Texas. The residence had been occupied for two summers when the occupants began to complain of adverse health effects. Indoor air quality testing revealed the presence of mold spores, which prompted the residents to vacate the premises to allow appropriate remediation. Our investigation occurred simultaneously with the remediation and allowed us to determine the sources of moist air infiltration that had resulted in the wall condensation and mold growth. The final case study was a modern, four-story office building recently constructed in New Orleans, Louisiana. The cladding system consists of a clay brick veneer installed over a #30 felt weather-barrier, ½” exterior gypsum sheathing, metal studs with a glass fiber batt insulation, and interior gypsum board. The interior finishes consisted of heavy duty vinyl wall coverings that had been specified by the architect-of-record. After only two Summer seasons of occupancy, the building began to experience fairly widespread mold growth at specific floor levels. Based upon an extensive evaluation of the exterior building envelope, it was found that there were very limited anomalies pertaining to direct water leakage. Primarily, the mold growth was associated with inward water vapor diffusion and moist air infiltration during the summer months. In addition, it was found that the interior spaces of a large portion of this building were experiencing negative pressure with respect to the exterior conditions. Remediation of this building for indoor air quality purposes allowed confirmation of our initial assessment and appropriate remedial recommendations have been implemented.