Volume 39, Issue 2 (March 2011)
Case Study of Mechanical Control of Condensation in Exterior Walls
An electronics manufacturing facility in Colorado was constructed with typical commercial steel framing containing fiberglass batt insulation with foil-facing as the vapor retarder. A large portion of the facility required constant positive space pressurization and an indoor relative humidity (RH) of 48 % RH at 21°C (70°F). Due to a lack of containment of the moist interior air, condensation formed in the exterior walls, in the roofing, on the window and door systems, and on the skylights of the facility, particularly along the north and east elevations of the building, which resulted in significant damage to the wall components and the inability of the HVAC system to remain properly balanced. The as-constructed exterior wall systems were evaluated for performance relative to the existing building mechanical system. It was determined that the as-designed and as-constructed exterior wall assemblies and components could not perform satisfactorily under the necessary indoor environmental requirements. Options were explored to improve the performance of the exterior wall assemblies and related details. Due to a number of constraints, it was decided that constructing new walls inside the as-constructed exterior walls and windows, thereby creating an “interstitial” space to separate the exterior walls from the interior building space for their full height and mechanically supplying warm, dry air to this interstitial space, was the desired method to correct the condensation problems that were occurring. These repairs have proven to be effective. This paper discusses the original design and construction, the method of evaluation of the condensation problems that occurred, and the design and results of the implemented repairs.