Architectural Record BE - Building Enclosure

A New World of Acoustics

Current and emerging options offer architects and designers a broad range of choice
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Sponsored by Armstrong Ceiling and Wall Solutions
Peter J. Arsenault, FAIA, NCARB, LEED AP

Green Building Contributions of Acoustic Ceilings

Ceilings are a big part of any building interior so it only makes sense that their sustainability should be addressed. The U.S. Green Building Council's (USGBC) LEEDĀ® rating system contains a number of areas where ceilings can contribute to a higher rating and more sustainability overall. This is true in both current versions of LEED that are in use, namely, LEED 2009 and LEED version 4.

Energy and Atmosphere

When designing an energy-efficient building, there is a tendency to focus on things like insulation and windows, but ceiling systems can also play a role in effective energy conservation. By using a ceiling system that has higher levels of light reflectance, less artificial light may be needed. Typical acoustical ceilings have a Light Reflectance (LR) rating of 0.75 meaning that they reflect 75 percent of the light striking is surface. High LR ceilings are made to reflect up to 90 percent of the light striking their surface. This means that the light coming from either natural daylighting systems or electrical lighting systems can be dispersed and spread farther with a high LR ceiling, thus making the space appear brighter with less light needed. This improves space illumination allowing for fewer light fixtures, a reduced electrical light output, lower maintenance costs, and reduced cooling load.

An innovative and emerging trend in energy efficiency related to ceilings is the use of lower voltage direct current (DC) power distributed through the ceiling suspension system to power electric lights. This concept is being actively promoted by the EMerge AllianceĀ®, an open, not-for-profit industry association leading the rapid adoption of safe DC power distribution in commercial buildings through the development of standards. In particular, the EMerge Alliance standard for commercial interiors integrates interior infrastructures (like ceilings), power, controls and peripheral devices, such as lighting, in a common platform. This is all particularly significant on buildings where on-site solar or wind energy is being generated since the electricity produced in such systems is in DC form. Typically, it would then be converted to alternating current (AC) for use in buildings. However, a DC based grid system can eliminate energy lost from conversion and help accelerate use of DC-based LED lighting that is easy to locate, connect, and operate.

In LEEDv4, there is now a credit in the Interior Design and Construction (ID&C) system for Design Flexibility which recognizes and rewards different strategies that increase the useful life of the project space. Interior ceiling systems that are movable or demountable can directly contribute to this credit along with accessible ceiling systems. The DC powered ceiling system can also contribute to this credit since it offers the ability to safely alter and reuse interior spaces since the lighting can be repurposed and reconfigured without the need for rewiring.

Materials and Resources

Under LEED 2009, MR credit 4, Recycled Content, allows points for recycled material content in a new or renovated building. Mineral fiber, fiberglass, and wood ceiling products have a recycled content from 47 percent to 92 percent depending on the material specified. Additionally, high recycled content suspension systems and grids made from metals are also available. There are also a growing number of ceiling products that are being made from bio-based rapidly renewable materials meaning they may qualify under MR credit 6 for one point. Similarly, if wood ceilings are specified, they may also qualify for an additional point if certified wood is used under MR credit 7. And of course, when any of these ceiling products are manufactured in the USA that means regional material contribution may be possible under MR credit 5. If LEEDv4 is being used, there is a new section of credits on Building Disclosure and Optimization. This new area rewards products that have Environmental Product Declarations (EPDs) disclosing the manufacturers life cycle inventory of a product. The formerly single attributes such as recycled content, FSC certification, recyclable content, etc. are now all part of this life cycle assessment / EPD process. Currently, EPDs are available for some, but not yet all, ceiling system products.

Ceiling manufacturers can provide information about the sustainability of their products to show LEED point contributions and Environmental Product Declaration (EPD) information.

Image courtesy of Armstrong Ceiling and Wall Systems

Ceiling manufacturers can provide information about the sustainability of their products to show LEED point contributions and Environmental Product Declaration (EPD) information.

In cases where an existing building is being remodeled, MR credit 3, Materials Reuse, allows either 1 or 2 points based on thresholds of 5 percent or 10 percent of material being re-used. Many of the ceiling systems discussed already are long lasting and durable or have built-in flexibility meaning that they should be considered for ongoing use as part of a renovation project. However where that is not practical or consistent with other design parameters, then look for a manufacturer that will take back the existing ceilings for recycling and re-use. That will not only be the most appropriate thing for the total life cycle of the ceilings, it can also contribute to 1 or 2 points under MR credit 2, Construction Waste Management by diverting this material from a landfill.

Indoor Environmental Quality

There are a number of ways that ceilings can contribute to improved indoor environmental quality (EQ). We have mentioned the higher light reflectivity option that can aid in extending daylighting into the space. Recent independent studies have shown a 10-15 percent increase in the effectiveness of daylighting designs with the use of these ceilings. That means that indirect lighting is spread further providing higher visual comfort and improving the effectiveness of people working. Beyond this EQ trait, most ceiling products are pre-finished and qualify as low emitting materials due to low or no VOC content in the ceiling panels. Further, no paints, coatings, adhesives, or harmful sealants are typically needed for ceilings so those concerns are eliminated.

One of the growing concerns in green building design is the role that acoustics can play in terms of indoor environmental quality. In particular, LEED for Schools contains both a pre-requisite and a credit possibility for improved classroom acoustics using ANSI Standard S12.60 as the basis for performance. This standard and the IEQ inclusion comes from studies that have demonstrated that excessive reverberation and noise in a classroom interferes with a student's ability to clearly hear their teacher which obviously affects a student's ability to learn. The standard addresses Direct Sound which in this case is the sound of a teacher's voice traveling directly from the teacher to the student. This is always beneficial in terms of speech intelligibility because direct sound is not affected by anything in the room, making it clear and distinct. The standard also addresses Reflected Sound and Reverberation Time as they are specifically related to speech intelligibility. Finally it addresses, Background Noise defined as any sound that is generated outside the building, such as playground activity, traffic, planes, etc. that generally intrudes into the classroom by way of the windows or as noise from within the building such as HVAC system noise and corridor noise. Using ceiling systems that have appropriate NRC, CAC, and STC ratings plus proper RT measurements for different areas of school building will be necessary in order to meet the pre-requisite and the credit point in a LEED for Schools building.

While LEED for Schools is the only version of LEED v. 4 that has a minimum acoustic performance pre-requisite, other LEED rating systems now include a credit for acoustic performance based on acoustic design. These include 1 available point for LEED for New Construction, Data Centers, Hospitality, Warehouses and Distribution Centers, plus up to 2 points in LEED for Healthcare. Ceilings can obviously be used to contribute to the overall acoustic design and earning LEED points in this category.

Designing for Specific Building Types

The principles and characteristics of ceilings for acoustic and visual design are rather universal across all building types. However, the specific needs of different types of buildings will dictate the ways those principles are applied and the choices of final materials and systems. Some of the more common applications are discussed briefly in the following sections.

Workplaces

Good acoustic design in contemporary workplace environments address both quiet concentration and energetic collaboration. Studies have shown that noise at the office reduces worker effectiveness, raises stress, and lowers employee satisfaction. To address these issues, speech privacy and excessive reverberation time can be directly addressed using appropriate acoustical design solutions.

In open plan offices contributors of noise can include employee conversations, benching workstations, speaker phones, etc. To counteract this noise, a balanced acoustical design requires high AC and high NRC products that absorb sound and keep it from spreading very far from its source. Closed plan offices will help contain sound within each office, but there is still the concern of sound transfer from room to room if walls are built to ceiling height only. In this case, high CAC products are a must to prevent sound transfer through the ceilings of adjacent offices. Higher STC ratings are needed in the walls for the same sound containment reason.

Different office spaces can be treated with different ceiling treatments to control acoustical performance.

Photo courtesy of Armstrong Ceiling and Wall Systems

Different office spaces can be treated with different ceiling treatments to control acoustical performance.

Aside from individual workspaces, office buildings may contain other types of spaces as well such as group collaboration areas where teaming activities require open communications within groups. However, there is also a need for some moderate separation between different groups or between these collaboration areas and private offices. That means that high NRC or AC ceilings and perhaps clouds/canopies or baffles are needed to complement low/high furniture systems. By contrast, there may also be a need for quiet or private areas within a workplace setting. In these areas it will be important to minimize the transfer of sound in all directions, hence, high CAC and AC rated ceilings, high STC wall ratings, (high furniture panels in open plan settings), and even the possibility of electronic sound masking (background music or white noise) are all design elements to consider incorporating. Of course, there are always some specialty areas that may require some unique consideration such as retail, lobby, or support spaces that need some other types of treatment such as high NRC ratings all around for higher absorption or moderate NRC ratings to allow for some desired reverberation. In short, by looking at the different acoustic needs of each of the spaces within a workplace building, they can each be designed independently from an acoustic perspective to produce successful results.

Education

Good acoustical design in schools address high performing learning environments for students and for teachers. Excessive reverberation and noise in a classroom interferes with a student's ability to clearly hear their teacher. In fact, studies indicate that students typically hear only 3 out of every 4 words in the classroom. Good acoustical design promoting high speech intelligibility is key to understanding and learning from all of the words.

Acoustically designed classrooms following ANSI Standard S12.60 creates spaces that promote better learning and speech intelligibility.

Photo courtesy of Armstrong Ceiling and Wall Systems

Acoustically designed classrooms following ANSI Standard S12.60 creates spaces that promote better learning and speech intelligibility.

As in workplace situations, acoustical considerations for schools vary by space although all will benefit by being acoustically separated from each other. Classrooms and libraries will generally need to be quieter with higher NRC, CAC, and STC ratings than larger open spaces such as cafeterias, gymnasiums, or auditoriums which may accept more reverberation. As mentioned earlier, ANSI Standard S12.60 is used as a performance standard in the LEED for schools rating system, but it is a useful standard even if the building is not seeking LEED certification. Among the things that this standard establishes is the need to first design the architecture for good speech clarity using acoustically appropriate materials and systems within the space. Then, in order to protect that clarity and high speech intelligibility, it sets standards for low background noise from neighboring spaces and outdoor sources that can also be addressed by acoustical design principles. Altogether, students and teachers who function in an acoustically designed school will be more effective and happier without the distractions of unwanted sound.

Healthcare

Healthcare facilities are increasingly requiring good acoustic design as a functional requirement for speech privacy under the federally mandated HIPAA privacy rule. That means that anywhere patient information is being discussed and there are other people in the vicinity, speech sound must be controlled or absorbed. Hence administrative areas where multiple patients are seen will require areas to meet and talk that have high NRC, CAC, AC, and STC ratings to prevent the unwanted and unlawful dissemination of a patient's private information.

Acoustically isolated spaces in healthcare facilities help control sound transfer and protect privacy.

Photo courtesy of Armstrong Ceiling and Wall Systems

Acoustically isolated spaces in healthcare facilities help control sound transfer and protect privacy.

Beyond this basic sound control need, there is evidence to indicate that optimum patient recuperation occurs when acoustics are taken into account in the design. Excessive noise is created by the 24/7 environment of corridor activity, busy nurse's stations, equipment, alarms, and activity in treatment rooms among other things. Studies indicate that on average, hospital noise levels from all of this activity exceed those set by the World Health Organization. The significance is that these elevated noise levels are attributed to increasing patient stress and having an adverse effect on patient comfort. The design of healthcare spaces can sometimes make this worse by using hard, sound reflective surfaces, by not building walls all the way to the deck above, or by failing to treat and isolate high noise areas. Hence designing to acoustically separate patient rooms from sources of noise and using sound absorptive materials in areas that are generating the sound can directly contribute to the success of the hospital operations. This will not only help patients, but the healthcare staff as well who can benefit from a more pleasant work environment while reducing the possibility of missed communication due to better speech intelligibility.

 

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Originally published in Architectural Record

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