Verification of dynamic buffer zone (DBZ) wall assembly performance using infrared thermography

A new type of exterior building enclosure called the dynamic buffer zone (DBZ) system is being designed and built for both new projects and retrofit of existing buildings. Dry conditioned air is forced into and out of interstitial exterior wall cavities by means of dedicated mechanical systems in such a manner as to constantly ensure positive pressure within the cavities relative to interior environments. The primary reason for implementation of this type of design solution is to ensure elimination of moisture accumulation from either interior or exterior sources within the enclosure assemblies. Enclosure cavities are maintained at such low absolute humidity that the cavity air maintains a dew point temperature below the outdoor temperature for most of the time during winter. Since these types of building enclosures rely on mechanical systems, performance verification and commissioning are key components to the success of the assembly to achieve its objectives. Pressure differential, relative humidity and temperature sensors are necessary to ensure effective operation of these types of assemblies but they cannot determine the performance of all areas of exterior assemblies. Infrared thermography is used in combination with data from these sensors to determine the hygrothermal performance of all areas of enclosure assemblies. This paper will discuss the methodology of DBZ wall commissioning and some of the issues related to detection of improper wall assembly performance.