FAQs – Mull It Over Products

General Installation Manufacturing Thermal STC

General

Why is sound transmission between rooms a problem in buildings with glass facades?
Even though the drywall partition between rooms is properly designed and constructed to stop sound, this partition wall terminates into a vertical mullion that supports the curtain wall or ribbon wall glass. This mullion might appear to be solid, but it is actually a fairly lightweight hollow tube. This mullion is not designed to stop sound transfer. When tested in the laboratory, a drywall partition with an STC rating of 57 that terminated into a curtain wall mullion only has an STC of 28 when tested as an assembly.

What are the typical dimensions for the Mull-It-Over Sound Barrier Mullion Trim Cap?
The Mull-It-Over Sound Barrier Mullion Trim Cap was designed to accommodate most curtain wall manufacturer’s standard systems and allows for construction tolerance during installation. The Classic Mullion Trim Cap will accommodate end of partition wall to interior face of glass dimensions between 1-1/4" and 8". A minimum dimension of 7/8" is required from the exposed face of the drywall to the side of the vertical mullion. The Wide and Flush profiles accommodate most other standard detail requirements. Custom extrusions can be provided to accommodate dimensions that do not fall within the standard range. Please contact Mull-It-Over Products for assistance if custom details are required.

Is the Mull-It-Over Sound Barrier Mullion Trim Cap a unique system?
Yes. The Mull-It-Over Sound Barrier Mullion Trim Cap design is unique and is protected by patent numbers 8,572,914 and 8,782,977 for the United States and countries signatory to the Patent Cooperation Treaty.

Our project is unique. What if my partition wall does not terminate at a mullion? What if the wall is angled? What if my project has full height vision glass and sound transfer between floors is a problem? What if I have a folding partition wall that terminates into a curtain wall? What if my curtain wall mullions are deeper than 8"?
Custom solutions for almost any circumstance are available. Call or e-mail for unique solutions.

A building is constructed with high quality drywall partitions that include sound batt insulation, the walls are sealed tight to the deck and power and data outlets were properly offset. If the drywall partition terminates into a curtain wall mullion at the building perimeter and nothing is done to prevent sound from transferring through the mullion, is the performance of the drywall partition compromised?
Yes. Sound will flank around the end of the drywall partition through the hollow mullion and into the adjacent room. When tested as an assembly, a high STC rated partition wall has a low rating of STC 28 when terminated into an exposed vertical mullion.

Installation

Can the Mull-It-Over Sound Barrier Mullion Trim Cap be installed on an existing building?
The Mull-It-Over Mullion Trim Cap can be installed during initial building construction or added to an existing building. The sound barrier mullion trim cap does slightly decrease the size of the vision glass pocket which may impact the dimension of window treatments.

Who typically installs the Mull-It-Over Sound Barrier Mullion Trim Cap? Does it require special tools and training? When should it be installed during new construction?
Installation is very simple with standard tools. Suggested installation sequence would be after the walls are painted but before window treatments are installed. Mull-It-Over Sound Barrier Mullion Trim Caps are typically specified in Division 09 and it is best assigned to be furnished and installed by the Drywall or Finish Trades.

Is the Mull-It-Over Mullion Sound Barrier Trim Cap easy to install and does it eliminate the need for a trim piece to be installed to cover the exposed drywall partition edge?
Yes. The mullion trim cap can be cut using a non-ferrous carbide saw blade, jigsaw or other non-abrasive metal cutting blade. The mullion trim cap eliminates the need for finishing the end of the drywall partition wall with break metal or C cap trim.

What does the Mull-It-Over Sound Barrier Mullion Trim Cap look like when it is installed? Are Custom finishes available?
The exposed surface is extruded aluminum and is designed to mimic the look of the adjacent curtain wall mullion framing. Fasteners are concealed by a snap on trim piece. Standard finishes include anodized finishes and primed finish for field painting. Custom finishes are available to match any curtain wall color or finish.

Does the Mull-It-Over Sound Barrier Mullion Trim Cap allow for differential movement between the building partition and the curtain wall?
Yes. The Mull-It-Over Mullion Trim Cap attaches to the drywall partition, does not contact the curtain wall mullion, and has a compressible closed cell foam gasket between the end of the mullion cap return leg and the interior face of the glass. When properly installed, the mullion trim cap allows for differential movement in all directions. The compressible gasket is available in ½” and 1” thickness and light gray or dark charcoal colors. Movement between systems should be reviewed and approved by appropriate project engineers.

Manufacturing

Thermal

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.

STC

What is an STC Rating and what is the difference between STC 28 and STC 57?
STC stands for Sound Transmission Class. STC ratings are a numbered rating system used by the building design industry to define how well a partition stops sound from transferring through the partition. An STC of 28 is considered a poor rating as loud voices can be heard and fairly legible between rooms divided by a partition with an STC rating of 28. An STC of 57 is considered an excellent rating as loud voices can only be faintly be heard, if heard at all and conversations cannot be understood. Rough rule of thumb is that the sound is cut in half for every 10 point increase in the STC rating.

Do buildings with curtain wall facades meet minimum STC requirements of the International Building Code and Health Care Construction Guidelines if the partition walls terminate at an exposed mullion? What about concerns about confidentiality and HIPAA guidelines?
Codes vary depending on building type and use. Consult with a licensed design professional or proper code official for project specific questions and answers.

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