Does the Mull-It-Over Sound Barrier Mullion Trim Cap impact the thermal performance of the curtain wall system?
The mullion trim cap has a small impact on the thermal performance of the curtain wall system because the trim cap is thermally isolated from the vertical mullion. The exposed surface of the mullion trim cap will be less impacted by the exterior temperature and will be slightly closer to the ambient room temperature. In installations in cold climates, the mullion trim cap can cause the vertical mullion temperature to decrease as the warm room air is not able to reach the cooler curtain wall mullion. If the relative humidity of the interior space will be increased on cold days and the thermal performance of the exterior curtain wall is low enough to reach interior dew point temperatures, there is a possibility of condensation behind the mullion trim cap. It is recommended that a thermal model of the building be performed prior to installation of Mull-It-Over Sound Barrier Mullion Trim Caps if these conditions exist.