What Affects the On-Site Performance of Glass Partitions?

We asked our Fire and Certifications Director, Peter Long, some of the most frequently asked questions about the on-site acoustic performance of glass walls.

Will the on-site performance of a glass wall be the same as in the laboratory?

Not necessarily.

Laboratory testing is carried out under controlled conditions, with the test sample isolated from other sound paths. Once a glass wall or door is installed within a completed building, its measured performance can also be influenced by the surrounding construction.

This is known as flanking transmission. Sound can bypass the wall through ceiling and floor plenums, curtain wall mullions, abutments, service penetrations and around door openings.

For this reason, a field test result may be lower than the laboratory STC rating of the wall itself. The field result reflects the performance of the completed room enclosure, not just the glass wall.

What can be done to help control flanking sound transmission?

There are several areas that should be considered as part of the acoustic strategy.

Flanking through the ceiling plenum

Solution: Where the ceiling provides less sound isolation than the glass wall, an acoustic barrier may be required within the ceiling void to reduce sound transmission above the wall line.

Flanking through the floor plenum

Solution: The need for additional treatment depends on the acoustic performance of the raised floor and the wall system. Higher-performing glass walls may require an acoustic barrier within the floor void to limit flanking transmission.

Flanking through curtain wall mullions

Solution: Curtain wall mullions can provide a path for sound to travel between spaces. Additional acoustic treatment may be required around or behind the mullion to reduce transmission through the façade interface.

Flanking through abutments

Solution: The junction between the glass wall track and adjoining construction should be properly sealed. PurOptima abutment tracks incorporate foam tape to help close potential air paths, while additional acoustic sealant may be required where surrounding surfaces are uneven.

Sound passing through HVAC penetrations

Solution: Where ductwork crosses an acoustic barrier, appropriate attenuation should be considered as part of the mechanical and acoustic design.

Unsealed penetrations

Solution: Openings through acoustic barriers should be fully sealed using a treatment appropriate to the required sound isolation of the surrounding construction.

Flanking through doors

Doors can have a significant influence on the acoustic performance of the complete room front.

Attention to the door leaf, frame and perimeter seals is important if the door is to achieve its intended acoustic performance. Poorly sealed gaps can provide a direct path for sound transmission and reduce the overall performance between rooms.

In practice, the measured room-to-room result will reflect the combined performance of the glass wall, door and surrounding construction.

How does PurOptima support acoustic performance on site?

PurOptima project teams consider acoustic detailing as part of the wider coordination and installation process.

Potential flanking paths, wall interfaces, door seals and surrounding construction should be reviewed during the project rather than treated as an issue only after testing has taken place.

A coordinated approach between the glass wall installer, general contractor, mechanical trades and other relevant parties can help reduce avoidable sound paths and support the intended acoustic performance of the completed space.