Caroline Harvey – caroline.harvey@arup.com
Arup
Suite 900
Toronto, Ontario M4W 3M5
Canada
Vincent Jurdic
Chris Pollock
Willem Boning
Popular version of 1aAA13 – The cost of transparency: balancing acoustic, financial and sustainability considerations for glazed office partitions
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0026646
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
I’m an acoustician and here’s why we need to use less glass inside office buildings.
Glass partitions are good for natural light and visual connection but how does glass perform when it comes to blocking sound? What about the environmental cost? These questions came up when my team was addressing problems with acoustic privacy in a downtown Toronto office building. One of the issues was the glass partitions (sometimes called a “storefront” system) between private offices or meeting rooms and open office areas. Staff reported overhearing conversations outside these offices, an issue that ranges from just being distracting to undermining confidentiality for staff and clients.
Glass is ubiquitous in office buildings, inside and out. As a façade system, it’s been a major part of the modern city since at least the 1950s. Inside offices, it often gives us a sense of connection and inclusivity. But as an acoustician, I know that glass partitions are not effective at blocking sound compared to traditional stud walls or masonry walls. How good or bad depends on the glazing design – how thick the glass is, lamination, double panes and air gaps, and how the glass is sealed. When working on fixing the speech privacy problems in the Toronto office, we measured the sound isolation of the glazed partitions by playing random noise very loudly in each office and measuring the sound level difference between that room and the area outside. Our measurements supported the experience of the office staff: conversations are not just audible but comprehensible on the other side of the glass. The seals around the sliding doors often had gaps and sometimes there were joints without any seals – big enough to put your fingers through. Sound is made by tiny fluctuations in air pressure; even small gaps can be a problem.
Figure 1: Example of glass storefront with a sliding door and no seal (Arup image)
This acoustics problem led me to other questions about the cost of transparency in offices, especially the carbon cost. Glass is energy-intensive to produce. Per unit area, ¼” glass can require seven times the embodied carbon of one layer of 5/8” type X gypsum. When Arup compared several glazed partition systems that all had about the same acoustic performance, we found the glass was the greatest contributor to carbon emissions compared to all the other components (see Figure 2). Using these embodied carbon values, we estimated that the carbon cost of all the glazed partitions in this particular office was about 56,800 kgCO2eq, equivalent to driving one-way from New York to Seattle 51 times in an average gasoline-powered car.
Figure 2: Embodied carbon for typical aluminum storefront with three glazing buildups with the same sound isolation rating (Arup research)
So how should these costs be balanced? First, acousticians should be involved early on in space planning and can encourage architects to use less glazing to achieve the design outcomes, including acceptable acoustic performance. Second, we could encourage designers to create a glass aesthetic that uses “less perfect” glass in some locations. Offices may not require the degree of transparency that has become the norm. Where visual privacy is important, glass made from recycled cullet could be specified, leaving the perfectly transparent glass manufactured from virgin silica sand for key locations where a strong visual connection matters. The right balance depends on the project, but asking questions about the multiple costs of transparency is a good place to start.