Hard surfaces, open concept design, windows to the outside, concrete walls and wooden flooring are some of the characteristics of Green Office Buildings that contribute to them being noisier than traditional office building. Poor acoustical design is eroding what is otherwise considered to be a superior indoor environment with good air quality and light conditions factors that have facilitated the higher productivity of Green Building office workers.
The lack of consideration for the acoustical properties of Green Buildings has become a concern for the design and development community. While it is not a new issue, as open concept buildings whether green or not are known to have high volumes of interior sound, the absence of acoustical guidelines in the Leadership in Energy and Environnmental Design (LEED) rating system is drawing attention.
This week the Ottawa Green Building Council held an educational event to raise awareness about the issued billed as Acoustics and Green Buildings. Renée Gratton, LEED Accredited Professional of RG Integration and a member of the Board of Directors for the Canada Green Building Council and Tony Barr of Environmental Acoustics Inc. led the event.
Gratton’s presented research that showed occupancy evaluations of Green Buildings have consistently found workers are dissatisfied with the acoustical qualities of open concept office environments.
Workers in cubicles with both high and low partitions identify speaking on the phone and overhearing private conversations as the main source of dissatisfaction with the acoustics. Talking in corridors, telephones ringing, office equipment and street noise from open windows are cited as other sources of disturbing noise.
An Acoustical Evaluation of 6 Green Office Buildings conducted by Murray Hodgson, at the University of British Columbia and a survey of workers in LEED buildings about indoor environmental quality by the Centre for the Built Environment in Berkeley, California both arrived at this conclusion.
LEED for Schools offered by the US Green Building Council has established the only LEED guidelines for sound levels by making points available for achieving a quieter environment. Gratton said that apart from LEED for Schools, under the Innovated and Design category of other LEED programs offered in Canada a building could generate points from improved acoustical design. Otherwise there is essentially 'a disconnect between acoustics and LEED'.
According to Tony Barr reducing sound levels in an office building requires a two-step approach. The first step is to absorb and block excessive sound and the second is to mask the sound that remains.
Absorbing noise is accomplished by installing a suspended ceiling or strategically placed ceiling panels with an absorbent surface sometimes referred to as clouds. Wall panels adjacent to areas with higher sound levels such as cafeterias, workstation panels, acoustical flooring, carpets and curtains.
Blocking is achieved by construction office walls with proper STC ratings, plenum barriers, transfer ducts, workstation panel height and other measures that serve to create a barrier or redirect sound.
Once sound volumes are reduced to a level where voices can be heard across a room, then a more controversial practice of covering or masking sound is employed. Masking is the introduction of electronic devices that generate sound at a specific frequencies and volume that cover, or break up voices and other sounds that can be distracting to someone working.
Masking is controversial in green buildings as many of the older systems use additional energy to produce a specific and unadjustable background sound that can often be disturbing. It is a practice that some argue would not be necessary if the building was designed differently in the first place.
Newer masking technologies use as little as 12 volts and the sound emission is neutral. They are adjustable to design of the space, variable according to occupant requirements and they can be combined with public announcement and music systems.
Green roofs have been found to be acoustically beneficial to buildings by increasing the mass of the roof with improved sound isolation. Earth berms that block and divert traffic sound, window glazing with acoustical properties and solar sources of power that are essentially silent are other ways of making green buildings quieter.
"The ideal way to address acoustical issues in new construction projects is by inviting an acoustical engineer to participate at the earliest stages of an integrated design process," according to Renée Gratton.
Gratton said, "the goal for Green Building designers is to find a balance between the competing priorities of sustainable design and creating a comfortable acoustical environment for workers."
Green buildings and acoustics is a topic that is going to be address at this year’s National Summit of the Canada Green Building Council to be held in Montreal in June.