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March 4, 2016

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Acoustical challenges in green buildings

Niklas Moeller, Vice-President of K.R. Moeller Associates Ltd, looks at the ways in which we can make our work environments perform better in terms of acoustic performance in green buildings.

Effective acoustics are essential to workplace satisfaction and performance. As such, they should be a top design priority, particularly in green buildings where the mandate is not only to use fewer resources, but to create an environment that is healthy and nurturing for occupants.

However, for much of its history, the Leadership in Energy & Environmental Design (LEED®) rating system developed by the United States Green Building Council (USGBC) paid little attention to acoustics, weakening the overall performance of green buildings. In fact, post occupancy surveys performed by the Center for the Built Environment (CBE) show that the higher the LEED certification level an office building achieves, the lower occupant satisfaction with acoustics. The majority of complaints relate to lack of speech privacy—in other words, the ability to overhear others and to be overheard.

USGBC is attempting to address this weakness. Under LEED v4, a project can qualify for two points toward an Acoustic Performance credit in the Indoor Environmental Quality (IEQ) section of Interior Design and Construction (ID+C) and one point in the Building Design and Construction (BD+C) rating system.

While credits draw much-needed attention to this important aspect of the work environment, it is also essential to have a good understanding of how particular green choices can impact acoustics.

Open Ceilings

Absorptive materials reduce the volume of noises reflected back into a space, the length of time they last and the distance over which they travel. Because the ceiling is usually the largest uninterrupted surface in a facility, using a good absorptive tile is important. Select a ceiling tile with at least a 0.75 Noise Reduction Coefficient (NRC) for open plans. In closed space, use tiles with a high Ceiling Attenuation Class (CAC) because they are better at containing noise. Ideally, tile coverage should be uninterrupted.

However, many green buildings have open ceilings. It is important to research whether this decision will have the desired heating/cooling or cost benefits and, if an exposed structure is still desired, treat an appropriate percentage of the deck with an absorptive material. Generally speaking, this strategy has an impact, as do vertical baffles. Depending on the building construction, another option is to use a perforated corrugated metal deck with an absorptive material placed behind the perforations before the concrete is poured.

If the space is narrow in order to promote natural light penetration, use absorptive panels on select walls in order to prevent noise from ricocheting between the exterior wall and the core. Use soft flooring to reduce footfall noise, at least in high traffic areas.

Workstation Partitions

Blocking noise is achieved using walls, doors and other physical structures. However, green buildings generally feature more open plan that their traditional counterparts. In these spaces, workstation partitions above seated head height (150 to 165 centimetres; 60 to 65 inches) are essential to attenuate the noises passing to an occupant’s nearest neighbours. If they are shorter, they will do little more than hold up the desks.

Workstation panels should also be absorptive, particularly if there is no acoustical tile. Where daylighting is a concern, use absorptive panels up to a 120-centimetre height (48 inches) and top them with 30 centimetres (12 inches) of glass or another transparent material. The top 12 inches introduces a reflective surface, but the reduction in absorption relative to the increase in blocking is an acceptable compromise. Also, ensure the panels have a high Sound Transmission Class (STC) rating and are well-sealed along any joints, with no significant openings between or below them.

Moveable Walls

If there is no ceiling, build walls to the deck. If there is a suspended ceiling, walls can stop at the ceiling. Walls should have a high STC rating to prevent airborne noise transmission. Ensure the STC rating of doors and interior windows at least meets the wall standard. Do not locate penetrations such as outlets back-to-back on opposite sides of a wall.

Many of these requirements also apply to demountable wall systems, which are often used to enclose spaces in green buildings. These systems may have lower STC ratings than conventional walls and the joints between the panels may provide conduits for noise. Address any gaps along the ceiling, exterior walls and floor during installation or they will easily transmit noise.

Natural Ventilation

The ambient—or background—sound level is already to low in the majority of traditional offices. The use of high-efficiency heating and cooling systems means that it is generally even lower in green buildings. Conversations and noises can easily be heard, even from a distance.

A sound masking should be installed to create an effective ambient level. This technology consists of loudspeakers installed in a grid-like pattern in or above the ceiling, as well as a method of controlling their zoning and output. The loudspeakers distribute a sound most often compared to that of softly blowing air, obscuring noises that are lower in volume and reducing the disruptive impact of those that are higher. Similarly, conversations are either covered or their intelligibility is reduced, improving privacy.

Using a sound masking system can help support other sustainable efforts, especially when included in the project’s design stage. For instance, masking increases noise isolation in open plans. Natural ventilation can be employed without affecting speech privacy and the amount of disruptions occupants experience. It can also pave the way for using demountable wall systems, contributing to the space’s flexibility and reducing waste following future renovations. Most systems also provide paging and background music distribution, eliminating the need for a separate system to be installed.

In conclusion

High LEED scores are not a guarantee of high IEQ. Acoustic goals need to be set or poor noise control and speech privacy will continue to undermine the success of green projects. As noted in “The Green Standard” in Fast Company (Issue 119, October 2007), “You could make a building that’s very energy-efficient by not having any windows in it and having only one elevator, but this is not a building that people are going to want to work in.” Focusing on maximising occupant satisfaction from the outset avoids the costs, not to mention the headaches, which arise when IEQ issues must be fixed later on.

Niklas Moeller head shot_hi res (2)

Niklas Moeller is the vice-president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network sound masking system ( He also writes an acoustics blog at



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Frederic BOTTE
Frederic BOTTE
8 years ago

Another option is to use a perforated corrugated metal deck with an absorptive material placed behind the perforations before the concrete is poured.

NIklas, what is it ? I do not know a perforated metal deck with concrete with mineral wool for absorbing sound do you have a reference ? Arval and others made Roof this way but not with concerte poured ….