Tag Archives: acoustics

Designing Stone Wool Ceiling Assemblies

All images courtesy Rockfon

All images courtesy Rockfon

by Corey Nevins

Specifiers have an increasing number of choices for commercial ceiling systems. Among the performance considerations for selecting the most appropriate for a particular application are acoustics, fire performance, humidity resistance, hygienic properties, dimensional stability, indoor air quality (IAQ), and light reflection. Added to these are choices pertaining to design aesthetics, ease of installation, maintenance, durability, sustainability, and cost.

Stone wool ceiling panels and metal suspension systems meet these selection criteria for both new construction and renovation projects throughout North America. The material was discovered on the islands of Hawaii, where it occurs naturally as a by-product of volcanic activity. The primary rock involved is basalt, the earth’s most abundant bedrock. The igneous material forms by the rapid cooling of lava from eruptions on the sea floor. Seismic activity, including the earth’s volcanoes, produces 38,000 times more rock material than is used by the world’s largest producer of stone wool.

The typical production process for stone wool begins with the fusion of this volcanic rock at a temperature of 1500 C (2732 F). Emerging from the furnace, the melt runs out of the bottom and onto a spinning machine, where wool is whipped into thin strands, similar to making cotton candy. The strands form ‘wool,’ held together with minor amounts of organic binders.

Stone wool ceilings offer good sound absorption, high light refl ectance, fi re protection, and humidity resistance. These panels are well-suited to create modular ceiling designs, such as long corridors.

Stone wool ceilings offer good sound absorption, high light reflectance, fire protection, and humidity resistance. These panels are well-suited to create modular ceiling designs, such as long corridors.

Now a fleecy web, the material is gathered and formed; the number of layers varies depending on the final product’s desired structure and density. The layered fibers then move to a curing oven. Once cured, the wool emerges with non-directional fibers that contribute to its multiple performance characteristics of the stone wool products. In addition to ceiling panels, stone wool’s unique combination of thermal, fire, and acoustic properties make it suitable for:

  • blown insulation in cavity walls;
  • rolls of loft insulation;
  • pre-formed and faced pipe sections; and
  • wall slabs.

A mineral fleece and water-based paint are layered on top of the stone wool to produce the finished ceiling panels. The stone wool products proceed to cutting saws, finishing and packing equipment, or are led to off-line equipment for special treatment. The majority of the waste created during the production is fully recyclable.

Use of suspended ceilings
Since the 1950s, drop ceilings have been the preferred method for concealing HVAC vents, electrical wires, plumbing pipes, phone cables, and security lines in interior commercial buildings. These suspended, interconnected ceiling systems consist of a metal grid comprising cross-tees and main runners.

The main runners are suspended by hanger wires from the structure above, and wall channels or angles provide a clean look throughout the perimeter. Panels are used to conceal the plenum—hiding the visible structure, suspension system, HVAC, and other equipment, while providing simple access for future maintenance.

The suspension ceiling system is selected for aesthetics, maintenance, and specialized performance such as fire resistance, seismic mitigation, or limited accessibility in security applications. For all ceiling designs, specifiers should check the suspension systems are manufactured to ASTM International standards. On request, suspension manufacturers may provide reports from the International Code Council (ICC) and third-party seismic performance testing and certification reports.

Corrosion resistance is also a priority for metal suspension systems supporting stone wool and other ceiling panels. The industry standard is 23.8-mm (15/16-in.) galvanized steel for suspended metal ceiling grids; most may be specified with a minimum of 25 percent recycled content.

While the ceiling panel’s size, orientation, color, finish, and edge largely determine the overall aesthetic, changing the size of the grid’s face also changes the appearance. For example:

  • a 14.28-mm (9/16-in.) narrow face diminishes the distinction between grid and panel for a more monolithic look;
  • adding a 3.17-mm (1/8-in.) slender, center regress with a ‘bolt-slot’ design accentuates the shadow between panel and grid;
  • mitered intersections provide crisp, continuous lines for a uniform ceiling plane;
  • wide-face 34.92-mm (1 3/8-in.) ceiling suspension offers bolder expression of the ceiling grid modules, especially at high elevations; and
  • in curved drywall applications, radius systems create concave and convex shapes, including barrel-vaulted ceilings.
When a sound wave hits a surface, part of the energy is refl ected, part of it is absorbed by the material, and the rest is transmitted. Undesired sound from various potential sources can include noise transmitted into the building from the exterior, or coming in from other interior spaces.

When a sound wave hits a surface, part of the energy is reflected, part of it is absorbed by the material, and the rest is transmitted. Undesired sound from various potential sources can include noise transmitted into the building from the exterior, or coming in from other interior spaces.

The noise reduction coeffi cient (NRC) refers to a surface’s ability to reduce noise by absorbing sound. NRC is important in areas where high levels of noise (like a photocopier) are present.

The noise reduction coefficient (NRC) refers to a surface’s ability to reduce noise by absorbing sound. NRC is important in areas where high levels of noise (like a photocopier) are present.

 

 

 

 

 

 

 

 

 

 

 

Specifying acoustic comfort
According to the World Health Organization (WHO):

noise seriously harms human health by causing short- and long-term health problems. Noise interferes with people’s daily activities at school, at work, at home and during leisure time. It can disturb sleep, cause cardiovascular and psychophysiological effects, hinder work and school performance and provoke annoyance responses and changes in social behavior.1

Therefore, it could be argued design professionals have a duty to create acoustic comfort and well-being for the occupants of their buildings. Stone wool can help with two primary components of acoustic comfort: speech intelligibility and noise reduction.

The material’s airflow resistance and density contribute to its high noise absorption properties. The fibers’ size and non-directional orientation lead to stone wool’s inherent sound-absorbing qualities. The measures and concepts discussed in this article provide a foundation for understanding the relationship between stone wool’s characteristics as a material and achieving acoustic comfort.

Speech intelligibility
One important component of acoustic comfort and sustainability, speech intelligibility refers to a listener’s ability to hear and understand a speaker in a room or space. It is measured as a signal-to-noise ratio, expressed in decibels (dB). For this application, the signal typically is speech and the noise usually is everything else in the background.

Reverberation time
An important factor for creating speech intelligibility, it is defined as the time it takes for the sound pressure level to decrease 60 dB below its original level. In most situations (excluding unamplified music performance), a lower reverberation time improves speech intelligibility and acoustic comfort. For most rooms requiring speech intelligibility, mid-frequency reverberation time should be between 0.50 and 1.00 seconds when the room is unoccupied.

Noise reduction coefficient
The noise reduction coefficient (NRC) indicates a surface’s ability to reduce noise by absorbing sound. It is calculated by averaging the absorption coefficients from the 250-Hz, 500-Hz, 1-kHz, and 2-kHz octave bands. It varies between 0.0 (i.e. absorbs very little sound) and 1.0 (i.e. absorbs a lot of sound). NRC is one of two important variables in determining reverberation time (the other being room volume). A higher NRC indicates more noise reduction (or sound absorption) and leads to lower reverberation times and greater speech intelligibility. Stone wool ceiling products typically have an NRC of 0.85 or higher.

Background noise
Undesired sound from various potential sources can include noise transmitted into the building from the exterior, or coming in from other interior spaces. It can also include sounds generated by the building’s systems or even those reverberating too long inside the room.

Speech intelligibility
Factors influencing speech intelligibility include:

  • speech signal’s strength and clarity;
  • sound source’s direction;
  • level of background noise;
  • room’s reverberation time and shape; and
  • listeners’ hearing acuity and attention span.

Reverberation time depends on two main variables: the volume of the room and the amount of sound-absorbing materials. As volume decreases or as the amount of sound-absorbing materials increases, reverberation time decreases and speech intelligibility generally increases. Since the volume of the room often depends on functional and aesthetic criteria, reverberation time is often solely dependent on the amount and efficacy of sound-absorbing materials.

In many cases, placing sound-absorbing materials on the walls is not desirable due to its tendency to get damaged, dirty, or worn because of occupant contact. As a result, whether speech intelligibility is poor, fair, or good can highly depend on the ceiling specified. This is why acoustic standards and guidelines for schools, hospitals, offices, and other types of facilities have minimum NRCs of 0.70 and up to 0.90. Stone wool ceiling panels, more than other panels made of less-absorbing materials, help ensure projects comply with acoustic performance requirements in these standards and guidelines.

Even if reverberation time is appropriate, speech intelligibility can be low if the background noise in the room is too loud. Speech intelligibility equates to a high signal to noise ratio. Consequently, it is also important to ensure noise from the exterior, other interior spaces, and from the building’s systems is controlled.

Noise reduction
In other rooms or spaces like open offices, cafeterias, libraries, and gymnasia, speech intelligibility is not the primary acoustic goal; rather, the push is for overall noise reduction for stress relief and concentration. Noise reduction equates to an overall decrease in sound pressure level from loud continuous noise (e.g. traffic noise transmitting into the building), as well as event-specific noise (e.g. a crying baby). The sound pressure level in a room depends on the strength of the sound source, the room’s size, and the quantity and quality of sound-absorbing surfaces.

Just 30 decibels of periodic noise can be disturbing to sleep or concentration. Conversational speech is generally between 50 to 70 dB. Noise with sound levels of 35 decibels or more can interfere with speech intelligibility in smaller rooms. This is demonstrated by a phenomena known as the ‘cocktail party effect,’ whereby as noise levels get louder and louder, people try to talk louder and louder to be understood. Despite their efforts, speech intelligibility decreases and acoustic stress increases. It is not until someone leaves the ‘party’ that they realize just how agitated they were as their muscles begin to relax, heart rate slows, and respiration deepens. Stone wool, because of its high noise-absorbing characteristics, also helps achieve the overall noise reduction goals.

Whether sound reduction is needed for speech intelligibility or overall acoustic comfort, blocking noise that could be in the plenum above the ceiling can also be important in some instances. As more acoustics standards and guidelines place minimum noise control criteria on wall constructions (i.e. sound transmission class [STC]), the need for ceilings to block noise from adjacent spaces traveling via the overhead plenum is becoming less frequent. This is because achieving the minimum STC wall requirements necessitates the walls be extended up to, and sealed against, the underside of the deck above them. However, in the cases where the walls do not extend full height, or where there may be noisy mechanical equipment in the plenum, the ceiling also may need to block noise from transmitting into the space below them.

Ceiling attenuation class (CAC) indicates the ceiling’s ability to prevent airborne sound from traveling between adjacent rooms when the demising walls do not intersect with the structural deck above. CAC is also a good measure to judge how much protection is offered against noisy mechanical equipment in the plenum. The higher the CAC value, the greater the ceiling’s blocking capacity. A CAC value of 35 dB is considered to be moderately high and may be specified for stone wool ceiling panels. When even higher sound-blocking capacity is required, stone wool ceiling panels can be specified with a CAC value up to 43 dB in combination with a high NRC of 0.85.

Insulation infl uences the sound level in the receiving space, helping provide more privacy between rooms and better concentration in the adjacent room.

Insulation influences the sound level in the receiving space, helping provide more privacy between rooms and better  concentration in the adjacent room.

In practice, there is a strong link between sound absorption and room-to-room sound insulation. This link may not be accurately refl ected in laboratory testing. In practice, two ceilings with the same ceiling attenuation class (CAC), but different NRCs, produce different levels of perceived sound insulation. The ceiling with the highest NRC will do a better job of lowering the sound pressure in both the sending and the receiving room.

In practice, there is a strong link between sound absorption and
room-to-room sound insulation. This link may not be accurately
refl ected in laboratory testing. In practice, two ceilings with the same ceiling attenuation class (CAC), but different NRCs, produce different levels of perceived sound insulation. The ceiling with the highest NRC will do a better job of lowering the sound pressure in both the sending and the receiving room.

Total sound insulation is the ability of a total construction (e.g. partitions, ceiling, fl oor and all connections) to prevent sound from traveling through the ceiling void and through building elements. Sound insulation of ceilings is measured using CAC, while walls are measured using the sound transmission class value (STC).

Total sound insulation is the ability of a total construction (e.g. partitions, ceiling, floor and all connections) to prevent sound from traveling through the ceiling void and through building elements. Sound insulation of ceilings is measured using CAC, while walls are measured using the sound transmission class  value (STC).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fire performance
Every second counts once a fire has started. Specifiers know choosing the right building materials can delay the spread of fire and provide the vital extra minutes needed to save the occupants and limit the damage.

Given its volcanic origins, stone wool can withstand temperatures up to 1177 C (2150 F). It is non-combustible, will not develop toxic smoke, and does not contribute to the development and spread of fire even when directly exposed to fire.

Ceiling panel products are required to be tested for surface burning characteristics to Underwriters Laboratories (UL) 723/ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials. Testing requires 7.31 m (24 ft) of material to be exposed to a flame ignition source in a Steiner Tunnel Test to determine how far the fire will spread during 10 minutes, and how much smoke is developed during this period.

The test was developed by Al Steiner of UL and has been incorporated as a reference into North American standards for materials testing. The progress of the flame front across the test material is measured by visual observation, while the smoke emitted from the end of the test assembly is measured as a factor of optical density. A Flame Spread Index and a Smoke Developed Index are calculated from these results. Both indices use an arbitrary scale in which asbestos-cement board has a value of 0, and red oak wood has a value of 100.

Many commercial applications require a Flame Spread Index of 25 or less and a Smoke Developed Index of 50 or less. Products labeled “FHC 25/50” (Fire Hazard Classification 25/50) or “Class A” (ASTM E1264, Standard Classification for Acoustical Ceiling Products) fulfill these requirements. Stone wool ceiling panels may be specified to meet the most stringent requirements with a maximum Flame Spread Index of 0 and a maximum Smoke Developed Index of 5.

Humidity and hygienic attributes
Humidity can weaken the structure of certain ceiling materials, causing them to sag and, in extreme cases, even fall out of the suspension system. This often happens in buildings under construction where the building is not yet temperature- and humidity-controlled, or materials have not yet dried. Additionally, humidity levels are naturally high in wet rooms like kitchens and sanitary areas, and moisture problems may occur.

The stone-wool core in acoustic ceiling panels can be specified as hydrophobic, which means it neither absorbs water nor holds moisture. This makes the ceiling panels ‘sag-resistant,’ even up to 100 percent relative humidity (RH) and in temperatures ranging from 0 to 40 C (32 to 104 F). The material is dimensionally stable and does not warp, curl, or cup. It also neither rots nor corrodes. Further, its characteristics remain unaltered over time, maintaining its dimensions and physical characteristics throughout a building’s lifecycle.

Since stone wool is inorganic, it also does not promote the growth of mold or bacteria. North American studies show a relationship between mold and damp conditions, and an increase in allergic reactions, along with eye, nose, and throat irritation.2 They have also been associated with litigious concerns that some commercial building owners have termed ‘sick building syndrome.’

Twenty-three percent of office workers experience frequent symptoms of respiratory ailments, allergies, and asthma. The impact has been an increased number of sick days, lower productivity, and increased medical costs. The economic impact is enormous, with an estimated decrease in productivity around two percent nationwide, at a cost of $60 billion annually.3

Helping maintain cleanliness, stone wool ceiling panels may be specified with a smooth, non-textured finish that can be vacuumed with a soft brush attachment. Specially treated hygienic and medical surface finishes allow cleaning with water and some diluted disinfectants, such as chlorine, ammonia, and quaternary ammonium. In some cases, specially treated surface finishes on stone wool ceiling panels allow for more intensive cleaning, such as steam cleaning twice a year following a defined protocol.

Sustainability
In addition to being composed from the earth’s most abundant bedrock, stone wool ceiling panels can contain up to 42 percent recycled content. When removed, undamaged stone wool products may be reused or recycled for other projects. However, if recycling, one should be observant of recycling plant locations.

Stone wool is an excellent thermal insulator and contributes to energy-efficient buildings. Stone wool ceilings’ reflective, smooth surface also can play a significant role in enhancing energy efficiency through better light distribution. The health benefits of natural light include a more positive mood, improved productivity, and lower absenteeism.4 Maximizing use of natural daylight may allow a reduction in the number of lighting fixtures. The subsequent lowering of electric loads may reduce cooling costs.

Further contributing to sustainable goals, stone wool ceiling panels may be specified with UL Environment’s Greenguard Gold Certification for low-emitting products. Certification is only given to products compliant with the associated requirements, which among others include stringent limits on emissions of more than 360 volatile organic compounds (VOCs).

UL Environment states indoor air can be two to five times more polluted than outdoor air. Greenguard Gold criteria incorporate health-based emissions requirements as denoted by the U.S. Environmental Protection Agency (EPA), the State of California Department of Public Health’s Section 01350, and others.

More than 400 green building codes, standards, guidelines, procurements policies, and rating systems give credit for Greenguard products. Certification also fulfills the low emission requirements of the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) v4 program, and the Collaborative for High Performance Schools’ Criteria (CHPS) for low-emitting materials.

Stone wool, the core material of stone wool ceiling products, can withstand temperatures up to 1177 C (2150 F). It is made from basalt rock and is non-combustible; it will not contribute to the development and spread of fi re.

Stone wool, the core material of stone wool ceiling products, can withstand temperatures up to 1177 C (2150 F). It is made from basalt rock and is non-combustible; it will not contribute to the development and spread of fire.

Stone wool acoustic ceiling products that have been certifi ed to GreenGuard Gold certifi cation standards for low chemical emissions into indoor air during product usage are suitable for environments such as schools and healthcare facilities.

Stone wool acoustic ceiling products that have been certified to GreenGuard Gold certification standards for low chemical emissions into indoor air during product usage are suitable for environments such as schools and healthcare facilities.

Aesthetic design
Beyond sustainability and performance, there are numerous aesthetic considerations in selecting the best stone wool ceiling panels to achieve the desired architectural expression.

Shape
The shape of a stone wool panel’s edge significantly contributes to the ceiling’s overall appearance. Demountable options include:

  • square lay-in—cost-effective, provides easy access to the plenum, and mounts in standard suspension systems;
  • tegular—square or angled, hangs on a visible and recessed suspension system that creates a shadow between the tiles, and mounts in standard suspension systems;
  • semi-concealed—appears to float under the suspension system, the profiled edge and deeply recessed grid profiles presents an elegant shadow (an effect emphasized by specifying the suspension system in black); and
  • concealed—hides the suspension system to create a monolithic appearance, but only some concealed panels are demountable.

Another option is the direct-mount assembly, where ceiling panels are directly bonded to the structural soffit or an existing ceiling surface. These systems are for areas where ceiling heights do not permit the use of the suspension setup.

Panels are not limited to two dimensions of squares and rectangles; they may be formed into three-dimensional cubes. Baffles and clouds provide an alternative solution for rooms where contiguous ceilings are unsuitable. They are suited to thermal mass applications where the soffit needs to be left exposed. They can be used as part of a retrofit or to create a design feature.

A wide range of sizes contributes to the design freedom and flexibility offered with stone wool ceiling panels. By combining different module sizes, even small rooms may seem larger and long corridors can seem less distant. The line of a ceiling impacts the perception of a space and creates focal points that may show direction, outline an object, or divide a large space into more comfortable zones.

Horizontal lines convey stability, grounding, and direction. Vertical lines, on the other hand, also communicate stability, as well as pillar-like attributes of strength and balance. Diagonal lines are perceived as dynamic and transformational with overtones of freedom, while curves are considered playful, organic, and soothing.

Texture and color
Based on today’s design styles, stone wool ceiling panels are preferred in smooth and lightly textured surface finishes. This gives the impression the ceiling is lighter in texture, weight, and color. White and neutral tones are the most popular color choices for interior ceilings. For more vibrant spaces, stone wool ceiling panels can be specified in a breadth of other hues.

A viewer’s perception and relation to a color changes depending on whether it stands alone, is dominating a space, or if it is in play with other colors. It also is influenced by the quality and quantity of light hitting it.

Colors evoke physical and psychological reactions, and the brightness or color temperature creates different moods and ambiance: Warm colors—such as red, orange, and yellow—are considered stimulating. Cool colors—like blue, purple, and light green—generally have a calming effect.

Spatial perception is also affected by color. Lighter hues tend to make spaces seem bigger, while darker ones can make spaces feel more intimate. A dark ceiling will seem lower than it really is, or—when installed high enough above—simply disappears.

Color schemes also can indicate the purpose and usage of a space with boundaries and transitions. Consideration should be given to how the visual stimulation in a space will be perceived by the brain to evoke a desired response. This is of utmost importance in environments where varied spaces have different tasks and functions, to avoid any confusion that can cause stress in the occupants.

Segment-specific demands
Color certainly has a place in educational settings, but aesthetics may need to be secondary to performance requirements. Fire performance and indoor air quality are top-of-mind, and acoustics also need to be of primary importance. Classrooms in the U.S. typically have speech intelligibility ratings of 75 percent or less, meaning every fourth spoken word is not understood.5 Loud or reverberant classrooms may cause teachers to raise their voices, leading to increased teacher stress and fatigue.6

In school activity areas, stone wool ceiling panels may be specified with both a high acoustic performance and impact-resistance. The panel’s reinforced surface withstands tougher-than-average wear and tear, as well as frequent mounting and demounting.

Along with durability and flexibility for future redesign, health care facilities seek products with easy-to-clean surfaces to support infection control. Most Methicillin-resistant Staphylococcus Aureus (MRSA) infections occur in people who have been in hospitals or other health care settings and are resistant to the antibiotics commonly used to treat ordinary staph infections.7

Stone wool ceiling panels designed for medical use have been classified Class 5, or better, in accordance with International Organization for Standardization (ISO) 14644-1, Cleanrooms and Associated Controlled Environments−Part 1: Classification of Air Cleanliness. Those that have specially treated medical and hygienic surface finishes also help mitigate:

  • MRSA bacteria resistant to antibiotics and responsible for post-surgery infections and septicaemias;
  • Candida Albicans, which is yeast responsible for skin infections and pneumonias; and
  • Aspergillus Niger, which is mold responsible for pneumonias.

Noise also contributes to patients’ slower recovery times. Studies show high levels of sound have negative physical and psychological effects on patients by disrupting sleep and increasing stress.8

With respect to auditory privacy, acoustic performance not only is relevant to patient decency and respect, but also to the protection of corporate intellectual property, and to increased concentration levels in working environments. After surveying 65,000 people over the past decade in North America, Europe, Africa, and Australia, researchers at the University of California-Berkeley reported more than half of office workers are dissatisfied with the level of speech privacy, making it the leading complaint in offices everywhere.9

Conclusion
From acoustics to fire performance and aesthetics to sustainability, stone wool ceiling systems provide the versatility and attributes to meet the varied requirements of commercial and institutional buildings’ new construction and renovation projects.

Notes
1 Visit www.euro.who.int/en/health-topics/environment-and-health/noise. (back to top)
2 Visit www.hc-sc.gc.ca/ewh-semt/air/in/poll/mould-moisissure/effects-effets-eng.php(back to top)
3 See William J. Fisk’s “Health and Productivity Gains from Better Indoor Environments,” from the 2000 edition of Annual Review of Energy and the Environment. Visit www2.bren.ucsb.edu/~modular/private/Articles/Fisk%20HealthandProductivity%202000.pdf(back to top)
4 For more, see Vanessa Loder’s article, “Maybe Money Really Does Grow on Trees,” in the May 4, 2014 edition of Forbes. Visit www.forbes.com/sites/vanessaloder/2014/05/04/maybe-money-really-does-grow-on-trees/2(back to top)
5 See Classroom Acoustics, by Seep et al, published in 2000 by the Acoustical Society of America (ASA).(back to top
6 See Tiesler & Oberdörster’s 2008 article, “Noise: A Stressor? Acoustic Ergonomics of Schools,” in Building Acoustics (15 [3]). (back to top)
7 Visit www.mayoclinic.org/mrsa(back to top)
8 See “Sound Practices: Noise Control in the Healthcare Environment?” published by HermanMiller Healthcare in 2009, and “Sound Control for Improved Outcomes in Healthcare Settings,” by Joseph Ulrich, published in 2004 by the Center for Health Design. (back to top)
9 See John Tierney’s article, “From Cubicles, Cry for Quiet Pierces Office Buzz,” in the May 19, 2012 edition of the New York Times. Visit www.nytimes.com/2012/05/20/science/when-buzz-at-your-cubicle-is-too-loud-for-work.html. Also, visit www.cbe.berkeley.edu/research/index.htm(back to top)

Cory Nevins is Rockfon’s director of marketing, leading the company’s continuing education and training programs to keep commercial building team members updated on acoustic stone wool ceiling panels, specialty metal ceiling panels, and ceiling suspension systems. He has nearly 20 years of experience in the building products industry, the majority of which has focused on ceiling systems, and a bachelor’s degree in marketing from Miami University in Oxford, Ohio. Nevins can be contacted at cory.nevins@rockfon.com.

Improving Floor/Ceiling Sound Control in Multifamily Projects: Sound Testing Practices

by Josh Jonsson, CSI

The sound transmission class (STC) and impact insulation class (IIC) are ASTM-derived single number ratings that try to quantify how much sound a stopped by partition being tested.

Laboratory testing involves an ideal setting for the floor/ceiling assembly—it is isolated from the walls, and there are no penetrations for HVAC, plumbing lines, sprinklers, can lights, or electrical boxes. In the field (i.e. F-STC and F-IIC), the floor/ceiling assembly often sits on load-bearing walls, is connected to the structure, and contains many ceiling and floor penetrations for the items just mentioned. Consequently, the code allows for a lower rating for field scores over those in the lab.

The STC rating essentially tells how much noise is stopped from going through a wall. The test involves blasting loud noise at all the measured frequencies in a room. A Level 1 sound meter measures this exact noise in that room level at all frequencies, as well as the sound in the room on the other side of the partition. These two different levels are then essentially subtracted from each other, with some corrections made for background noise.

The IIC rating is not a comparative test like the STC. Rather, it uses an ASTM-specified tapping machine that sits directly on the floor—more specifically, directly atop the finished floorcovering. (Consequently, an IIC rating always lists the floorcovering with which it was tested.)

The machine has five steel hammers that spin on a cam shaft, falling onto the floor from the same height, no matter what or who is testing. These hammers put a consistent energy into the floor. The sound level meter is taken downstairs below the tapping machine and the sound level is measured at all the frequencies called out in the ASTM standard. These sound levels are plugged into the equations in the standard; a single number is generated summarizing how much sound was stopped.

To read the full article, click here.

Improving Floor/Ceiling Sound Control in Multifamily Projects

DSC_1207-2

All images courtesy Maxxon Corporation

by Josh Jonsson, CSI

In recent years, demand has increased for better floor/ceiling acoustics in multifamily construction. This has been driven by consumer desires, new guidelines from code bodies, and stricter enforcement of existing codes. How do design professionals keep pace as the traditional approaches to multi-unit residential sound control evolve?

This article reviews important new guidelines that must be taken into account by architects and specifiers, and examines how construction manufacturers have created new products or enhanced existing ones in the pursuit of achieving higher acoustical performance.

Thanks to product technology improvements and more stringent regulations, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly.

Thanks to product technology improvements and more stringent regulations, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly.

Two of the principal measurement standards for acoustics in multifamily construction are:

  • sound transmission class (STC), which pertains to the amount of airborne sound contained by a given building element (i.e. walls, doors, windows, and floor/ceilings); and
  • impact insulation class (IIC), which deals with impact noise (i.e. footfall, chair scrapes, and dropped objects) transmitted through a floor/ceiling system.

Both these single-number ratings apply to the full assembly of building materials used to separate tenants, including floor/ceiling assemblies.

For more than 50 years, these measurements have helped architectural project design teams quantify the acoustic levels of floor/ceiling assemblies. In fact, the Department of Housing and Urban Development (HUD) wrote A Guide to Airborne, Impact, and Structure Borne Noise: Control in Multifamily Dwellings in 1967, helping reinforce the importance of sound control in multifamily construction. This document, along with the Uniform Building Code (UBC), helped project teams recognize an acoustical threshold was needed in multifamily construction. UBC required an STC and IIC rating of 50 (or 45 if field-tested as F-STC or F-IIC). The higher the rating, the better the performance. (See “Sound Testing Practices.”)

In 1997, UBC gave way to the International Building Code (IBC) as the widely accepted model code. This shift brought greater awareness of acoustical ratings and their deemed thresholds in unit-over-unit construction, however these code levels remained aligned with the UBC’s established minimum requirements of STC and IIC 50 (or 45 if field-tested).

As the multifamily industry became more competitive, developers began offering upgrades in flooring and lighting to tenants as an amenity, yet little to no attention was paid to acoustical performance. This is astounding when one considers acoustics continue to be one of the driving factors in maintaining low vacancy levels, as well as one of the most litigated issues in this type of construction. To compound the subject, many of the amenity upgrades offered, such as hard-surfaced finished floors and canister lighting, can adversely impact a floor/ceiling assembly’s performance.

CS_July_2014.inddUpdating acoustical recommendations
In response to the need for updated acoustical guidelines, the International Code Council (ICC), along with several respected acoustical experts, created ICC G2-2010, Guideline for Acoustics. The guideline recognizes:

the current level and approach of sound isolation requirements in the building code needs to be upgraded. The requirements are currently insufficient to meet occupant needs.

As shown in Figure 1, the guide provides two levels of acoustical performance: ‘acceptable’ and ‘preferred.’ Both exceed code minimums for airborne and structure-borne noise.

These new levels now give a clearer direction on what levels should be targeted for desired acoustical performance, depending on the building type. As the names suggest, when one wants a building that has an acceptable level of acoustical separation, ‘acceptable’ is targeted. When one is designing a building on the higher end of market rate or luxury level, or has tenants or owners sensitive to noise, the desire should be for a ‘preferred’ level of performance.

Components of acoustical design
How do these new recommendations apply to the current approach for multifamily construction? As Figure 2 shows, a commonly specified design for many multifamily projects, which is also recommended by acoustical consultants, includes:

  • hard-surfaced flooring;
  • 25 mm (1 in.) or more of gypsum concrete;
  • 6.4-mm (¼-in.) entangled mesh sound mat;
  • wood subfloor;
  • wood floor trusses or joists;
  • insulation;
  • resilient channel; and
  • one layer of gypsum board.

CS_July_2014.inddThe typical rating for the design would be an IIC 51 to 55 and STC 56 to 60, depending on the floorcovering (e.g. laminate, tile, floating engineered wood), the acoustical performance of which would be listed by the consultant and verified by test reports. These numbers exceed code minimum and exceed the STC requirement for ‘acceptable,’ but only marginally—at best—meet an ‘acceptable’ level for IIC and any nuisance impact noises from upstairs tenants (IIC).

It is important to keep in mind these listed ratings would be achieved by selecting and installing all the components based on proper acoustical design. For example, the resilient channel would need to be a product similar to a proprietary one using steel measuring 0.5 mm (0.021 in.) thick by 38 mm (1.5 in.) wide, as opposed to a similar but lesser design lacking proper acoustical performance. To increase the IIC rating, an upgrade to the sound mat and/or the resilient ceiling system must be made.

Improving IIC ratings with sound mats
Traditional sound control mats with entangled mesh enhance IIC performance through the mesh being attached to fabric, which is loose-laid over the subfloor and then encapsulated with a gypsum concrete topping. The entangled mesh acts as a spring and produces an air space with little surface contact (i.e. three to five percent). Until recently, IIC performance was upgraded by using a thicker sound mat and deeper gypsum concrete.

Sound mat manufacturers have added new technology that allows for higher ratings while continuing to meet industry expectations for the corresponding thickness of the gypsum concrete. Traditional entangled mesh mats are now being manufactured with an additional acoustical fabric—Figure 3 depicts a 6.4-mm (¼-in.) entangled mesh mat with this upgrade. The acoustical fabric is laminated to the underside of the mat, creating an additional vibration break and absorptive layer. This improved product requires the same thickness of gypsum concrete as its standard counterpart. The IIC performance of the system is improved by two to five points without adding any measurable thickness to the floor system.

Another option is to employ the original 6.4-mm entangled mesh sound mat and a secondary topical mat placed between the gypsum concrete and the finished floor. If this option is selected, this secondary mat should be high-quality and thoroughly tested for sound ratings. (The sound test showing this type of product’s performance must be specific to the assembly that is being used versus a sound test from an unrelated design—for example, using concrete test data for a 2×10 joist system.)

CS_July_2014.inddImproving IIC ratings with resilient clips and channels
Properly installed, high-quality resilient channel will improve IIC ratings, but the resilient channel’s effectiveness can be easily lessened through faulty installation. To install traditional resilient channel, proper-length screws are imperative so as not to penetrate the joist or remove the channel’s resiliency.

Penetrations from the drywall into the joist through the resilient channel create flanking paths that transfer sound through a floor/ceiling assembly, as does having a channel affixed tightly to the assembly. For these reasons, new resilient clips that are difficult to install improperly have been introduced to the market. These clips can deliver equivalent performance to properly installed, high-quality resilient channel.

Hanging systems that provide spring and reduce or eliminate resilient channel contact with the joist offer even better performance. Figure 4 shows two such products: the ceiling wave hanger and a spring isolator. Either of these products installed in conjunction with a 6.4-mm (¼-in.) entangled mesh sound mat on the floor above would help the system exceed the ‘acceptable’ level, and approach ‘preferred’ levels for the IIC rating with hard-surfaced floorcovering. See Figure 5 for various assemblies and their acoustics attributes.

How to design for desired acoustical performance
As a specifier or architect team leader, one must first determine the level of acoustic performance to which to design. This should not be a matter of just meeting code—rather, the entire conversation must be approached in a new light. The following questions should be asked:

  1. When considering the amenities offered to tenants, how important are the acoustics of the unit? In other words, how important is the quality of life related to acoustical privacy?
  2. Does the project team want to just meet code because complaints and vacancy rates are unimportant or not a factor? Do they want ‘acceptable’ performance, significantly reducing noise complaints and removing sound control from the vacancy equation? Or, do they want ‘preferred’ performance to meet client expectation and greatly reduce potential for noise complaints?
  3. Once the level is determined, which method makes the most sense for achieving that performance level? Does the sound mat get upgraded to a very high-performing mat (manufacturers offer many styles with differing performances)? Does the sound mat get upgraded while keeping the system as thin as possible? Does the sound mat stay the same and the ceiling hanger system get upgraded? Is a secondary sound mat added while upgrading the primary sound mat and/or ceiling system to reach optimal sound ratings? Or, do the mat and ceiling get upgraded to reach better ratings?

CS_July_2014.inddEven after the desired level of performance has been determined, there are other factors that should be considered, such as whether the project will always be apartments or if they could become condominiums. There is also the matter of whether carpet and pad areas will always have carpet and pad.

Projects that start as apartments and then plan on being converted into condominiums should be approached as if they were condominiums from the beginning. Future owners may tear out carpet and replace it with hard-surfaced flooring.

Sound mat manufacturers receive a high volume of phone calls every year where a condominium project put sound mat only in the hard-surfaced areas. The new owners want hard surfaced flooring throughout and are being told they need to provide levels of performance similar to the ‘preferred’ levels while only being able to add a thin amount to the profile of the floor. As they can only do work in their unit, they are left trying to use a thin, lower-performing sound mat to reach the requested, more stringent criterion.

Acoustic qualities of various fl ooring assemblies.

Acoustic qualities of various flooring assemblies.

Conclusion
Throughout the United States, the wood-frame multifamily industry is paying increasing attention to the acoustics of the floor/ceiling assembly. Innovative architectural acoustic products continue to see greater use in existing metropolitan areas as well as in new areas of the country. It is important specifiers continue to be educated on new products and adapt their specifications to ensure they meet defined levels of sound control that tie directly to the end user’s satisfaction with their living space.

Josh Jonsson, CSI, is an acoustical specialist and West regional manager at Maxxon Corporation. He has more than 15 years of experience in the architectural noise industry and has worked for acoustical and vibration consulting agencies. Jonsson is a member of CSI, Acoustical Society of America (ASA), and ASTM International committee E33 Building and Environmental Acoustics. He can be contacted via e-mail at josh@maxxon.com.

Shapes and Sounds: Designing concert halls with curves

Images courtesy Radius Track Corporation

Images courtesy Radius Track Corporation

by Chuck Mears, FAIA

The marriage of shape and sound are used to create world-class acoustical experiences inside the New World Center, designed by Frank Gehry, and the Kauffman Center for the Performing Arts, designed by Moshe Safdie.

Billowing clouds, curved ceilings, and swooping lines all have dramatic impact on the way concertgoers experience sound. Both architects relied on the use of curved surfaces to diffuse sound and to create the distinctive appearances, each with dramatically different visual results.

Technology has changed how spaces are designed. This image is a 3D framing model for an acoustic ceiling.

Technology has changed how spaces are designed. This image is a 3D framing model for an acoustic ceiling.

Gehry chose to expose the curved elements, enclosing them in a glazed box that allows passersby to glimpse the flowing interiors. Safdie used giant curves to define the shape of his building, composed of two symmetrical half shells of vertical concentric arches, which perch on a magnificent site overlooking the city. However, in both cases, the ability to interpret the acoustician’s nuanced instructions to exacting perfection was the key to creating an acoustical masterpiece in two of the United States’ most important symphonic institutions.

This article deconstructs the delicate balance between shaped walls, curved ceilings, and sound—principles that can apply in any performance space.

A look back in time
Concert halls have historically been designed with the architectural trends of the day. The science of architectural acoustics is just over a century old, but before it was hit or miss. Many of the early European halls, which were heavily ornamented on the walls and surfaces, were fortunate accidents, as the ornamentation served to diffuse sound.

It was not until Wallace Clement Sabine, an assistant professor at Harvard, was called on to correct an acoustically disastrous lecture hall on campus that modern acoustical science was launched. Sabine was able to determine, through experimentation, there is a definitive relationship between the quality of the acoustics, the size of the chamber, and the amount of absorption surface present. In 1898, he formally defined ‘reverberation time’—still the most important characteristic currently in use for gauging a room’s acoustical quality—as the number of seconds required for sound intensity to drop from the starting level by an amount of 60 dB.

In the 20th century, with growing popularity of ticketed concerts, many cities decided to build large-capacity venues, basing them on the parallelepipic form employed in some churches. The first reference model, called the ‘shoebox,’ places the orchestra directly in front of the audience; with musicians and spectators face-to-face. When designing for this type of architecture, acousticians must consider the shape and volume of the auditorium, and the materials used to achieve the ideal acoustic experience. What volume is required? How should the room be shaped?

Most auditoriums built since the 1950s have reproduced or adapted the shoebox model, which has the advantage of being well referenced, and therefore mastered by acousticians. However, contemporary architects like Safdie and Gehry are redefining the old models, and acousticians are learning new ways to incorporate complex design trends with the current knowledge base of acoustical engineering.

Designed by Moshe Safdie, the Kauffman Center for the Performing Arts’ prosceniumstyle Muriel Kauffmann Theater brings world-class cultural events to Kansas City, Missouri. Shown here are both early framing and completed work.

Designed by Moshe Safdie,
the Kauffman Center for the
Performing Arts’ prosceniumstyle
Muriel Kauffmann Theater
brings world-class cultural
events to Kansas City, Missouri.
Shown here are both early
framing and completed work.

IMG_6995IMG_0532The sound (and reverberation) of music
On a clear summer night, an outdoor concert can be entrancing. However, entering a well-designed concert hall can be even more magical, as the audience is enveloped in the music. This is because sound in a concert hall is related to vibrational energy.

Sound results from pressure fluctuations that travel through the medium of air. Various sources, such as an opera singer, a viola, or a horn, generate the air vibrations. The vibrations occur at varying rates, resulting in different frequencies of sound, which are perceived by humans as different pitches.

Low-pitched sounds (like that produced from a bass drum) vibrate at low frequencies, such as 20 to 250 cycles per second, or hertz (Hz). High-pitched sounds (like that of a piccolo) vibrate at high frequencies, such as 5000 to 20,000 Hz. Generally, humans can hear sounds from 20 to 20,000 Hz. These vibrations emanate in sound waves, which travel around the room, becoming reflected, absorbed, or transmitted at the walls or boundaries of the room. This is why the shape and size of the space, background noise, reverberation, as well as its material properties, are important.

In an enclosed environment, sound reflects—or reverberates—for a period after a source has stopped emitting sound. A space with a long reverberation time is known as a ‘live’ environment. Conversely, when sound dies out quickly, it is called a ‘dead’ environment. Speech is best understood in the latter, but music can be enhanced in the former, as the notes blend together.

Adding to an acoustician’s checklist are the different types of music that will be played in a space, as many venues today accommodate various styles. Reverberation time is affected by size and amount of reflective or absorptive surfaces in a space, making it one of the key considerations in a concert hall’s overall design and architecture.

For the Kauffman Center, form meets function—curves are both expressive aesthetic and carefully considered acoustic component.

For the Kauffman Center, form
meets function—curves are both
expressive aesthetic and carefully
considered acoustic component.

IMG_2816IMG_0591

Kauffman Center for the Performing Arts
Kansas City, Missouri’s Kauffman Center landed the Midwestern city among the ranks of world-class theaters like the Berlin State Opera in Germany and Disney Concert Hall in Los Angeles. The approximately 26,500-m2 (285,000-sf) facility has two technically sophisticated performance spaces: the proscenium-style Muriel Kauffman Theatre and Helzberg Hall.

With a seating plan similar to the traditional horseshoe of opera theaters in Europe, the Muriel Kauffman Theatre houses an acoustic infrastructure disguised within the aesthetics of the space, and showcases the integration of the architectural imagination with acoustical engineering.

Architect Moshe Safdie wanted the audience to experience a sense of warmth and intimacy with the performers. Referencing the fanning element of the facility’s north façade, the Muriel Kauffman Theatre curves around the seating pit and balcony; it naturally focuses sound waves to each of the 1800 seats.

Also pictured on page 10 and the cover, Helzberg Hall is one of the performing arts spaces in the Kauffmann Centre. Acoustic bumps were used behind an acoustically transparent mesh.

Helzberg Hall is one of the performing
arts spaces in the Kauffmann Centre.
Acoustic bumps were used behind
an acoustically transparent mesh.

CS_Helzberg_bumps

 

 

The seats were built with materials that narrow down the range between sound reflectance and absorption when occupied and when vacant—a difference of only 0.2 seconds. At the same time, semi-cylindrical bumps were installed behind the louver wall to balance out the acoustical focusing caused by the round shape of the theatre. Further, shallow balcony overhang design helped deliver direct sound to the audience from the stage. In this balancing act of absorption and reflection, shapes and textures have everything to do with the sound quality.

Similar to their design for the Muriel Kauffman Theater, Nagata Acoustics (Los Angeles) designed cylindrical, convex, acoustic elements behind acoustically transparent materials for 1600-seat Helzberg Hall. Similar to drawing a curtain on a messy room, these barriers conceal the bulky framework of an acoustical system, but do not stifle their acoustic properties. As captured so elegantly through Safdie’s design, acoustical materials are no longer an aesthetic obstacle for the architect.

Continuing in Helzberg Hall, architects and acoustical engineers worked against the challenge of maintaining sound intimacy in the face of a large expanse between the audience and performers. By devising a round room in which all the surfaces work together to reflect sound three-dimensionally, the team could channel the direct and clear sound reflections to each audience member.

Surface materials were a key part of the acoustic design in both performance spaces at the Kauffman Center. To channel quality acoustics up to the balcony from the Helzberg Hall stage, Safdie designed a shallow overhang to reflect the sound. Made of plaster with a sandblasted finish, the balcony’s surface materials are essential to the theatre’s ability to diffuse sound.

Performance Contracting Inc. (Lenexa, Kansas) worked with the curved cold-formed steel (CFS) framing provider to devise an advanced, structurally engineered framing approach to support the per-square-foot weight of the plastered acoustic surfaces, which included more than 907,000 kg (2 million lb) of acoustical plaster.

For Helzberg Hall, these curved framing members were engineered to shape and load requirements for acoustic elements that span nearly 30 m (100 ft) from the rear of the stage to the ceiling.

For Helzberg Hall, these curved framing members were engineered to shape and load requirements for acoustic elements that span nearly 30 m (100 ft) from the rear of the stage to the ceiling.

This weight of plaster was used to keep sound from transferring. To achieve this, the plaster on the ceilings had to be 63.5 mm (2 ½ in.) thick to meet the STC rating—1.2 to 1.4 kPa (25 to 30 psf). With nine different density requirements across varying plastered surfaces inside the concert hall, the geometry had to be perfect.

The process of tuning a musical venue has evolved from a ‘close enough’ mentality to extremely precise acoustical methods. In this case, the team’s process used 92 mm (3 5/8-in.) pre-curved studs tied to 19-mm (¾-in.) pre-curved cold-rolled channel framing to provide a precise and acoustically specific profile. Additionally, the perimeter of each of the acoustic elements created with the stud-channel framing methodology was finished with a custom-formed 110-mm (4 3/8-in.) track to provide crisp, clean edges and corners.

Kauffman’s complex geometry required an acoustic design complete with ‘bumps’ of various sizes in specific locations in each hall. For these elements too, the CFS framing provider prefabricated a complete kit of required parts, which was shipped to Kansas City and easily assembled onsite, reducing jobsite labor and installation time.

New World Center
Nagata Acoustics was also involved in the New World Center—Gehry Partners’ Miami project that used billowing shapes and acoustic clouds to render perfect pitch for the main performance space and practice rooms. Home to New World Symphony, the facility provides the noted orchestral academy with the space to “prepare highly gifted graduates of distinguished music programs for leadership roles in orchestras and ensembles around the world.” The centerpiece of the building is an adjustable 757-seat natural acoustic performance space, featuring large, distinctive sail-like acoustical surfaces designed for the ultimate orchestral experience.

Although New World Center is comparable to Helzberg Hall in its stage size and program capacity, the size of the room is smaller. Acoustically, this means less distance between the stage and the audience; therefore, the reflective surfaces are closer.

Sound in a compact space can be perceived as louder. By increasing the ceiling height to 15 m (50 ft), the room volume expanded and the level of sound decreased. The room, and consequently its sound, can be adjusted to a dazzling array of options, as Frank Gehry designed 14 different stage configurations within the hall’s trapezoidal shape. Seats can be retracted to add floor space and satellite platforms allow for performances off the main stage.

Five huge acoustic sails were among the primary tools Nagata’s acousticians used to focus sound. The sails are the focal point of the stage and also serve as video panels that enhance the concertgoer’s experience. The team was challenged to maintain the architectural ‘swoops’ of Gehry’s design and make it work acoustically. Some modifications were made to improve acoustics: tilt angles were adjusted, curvatures were changed slightly, and other tweaks were incorporated to deliver early reflections to the audience.

Such precision meant the CFS framing provider—working closely with Lotspeich Company, the specialty contractor responsible for metal stud framing, drywall, gypsum plaster, acoustical plaster, acoustical ceilings, and wall panels—had to be geometrically precise in fabricating the custom curved framing to create the exact shapes Gehry wanted.

Using 3D modeling, curved studs, curved box beams, curved channel, and knife edges were designed to meet the design intent and acoustic requirements. During this stage, there was also analysis with adjacent systems for clash detection and fit informed the design solution. The entire framing system was coordinated with audiovisual (AV), air-conditioning (AC), and lighting systems to fit seamlessly.

The CFS framing’s 3D model provided the data to fabricate 46,975 m2 (505,638 sf) of material, which included 3432 curved studs, and 2632 curved track framing pieces. Ninety four percent of the materials were created uniquely for the project. The company even developed a proprietary new construction method—knife edges—for corners that were not at right angles (a condition common in Gehry’s design). Every detail was designed with the project’s ultimate goal in mind: marvelous acoustics.

An evening view of the New World Center, featuring The Wall (a 650-m2 [7000-sf] projection wall) and SoundScape (a 1-ha [2.5-acre] multiuse urban space).

An evening view of the New World Center, featuring The Wall (a 650-m2 [7000-sf] projection wall) and SoundScape (a 1-ha [2.5-acre] multiuse urban space).

A view of the Atrium through New World Center’s six-story window wall where abstract forms and curved surfaces above house practice rooms for musicians and offi ces for the venue.

A view of the Atrium through New World Center’s six-story window wall where abstract forms and curved surfaces above house practice rooms for musicians and offices for the venue.

The New World Center’s main performance hall delivers a multimedia experience with crisp acoustic integrity.

The New World Center’s main
performance hall delivers a
multimedia experience with
crisp acoustic integrity.

 

 

 

 

 

 

 

 

 

 


Conclusion

Streamlining the construction process from blueprint to acoustic plaster element or complex ceiling design is achieved with advanced building information modeling (BIM), 3D modeling, CFS fabrication, and framing technology. This combination opens up unlimited acoustical opportunities for performance spaces around the world.

No longer are designers limited by straight lines and right angles. Curved surfaces can bring new levels of acoustic perfection to a space and can be precisely designed and studied prior to construction, as acousticians add subject matter experts like cold-formed steel framing manufacturers (and their tools) to the project team. The results, as patrons of both Kauffman Center for the Performing Arts and New World Center will attest, can be pitch-perfect.

Chuck Mears, FAIA, is the chief design officer and founder of Radius Track Corporation. He is an expert in the design and fabrication of complex cold-formed steel framing. Mears’ work in 3D computer modeling and fabrication technology allows his team to create cold-formed steel structural systems to support any imaginable architectural form. He can be contacted at chuck@radiustrack.com.

Choosing a Rubber Floor for Aesthetics and Performance

Photos courtesy Regupol America

Photos courtesy Regupol America

by John P. Aten

Functionality is the ultimate goal for athletic flooring, and high-performance assemblies can provide durability, shock absorption, acoustics, and aesthetics. Specifiers and designers should explore the various options based on individual projects.

Designers, architects, and specifiers have many questions to ask themselves before selecting facility floors. These include:

  • How much of the project’s budget can be dedicated to flooring costs?
  • Is sustainability an important factor?
  • Is the project new construction or a refurbishment?
  • What are the primary and secondary uses—is it a single-use or multi-purpose floor?
  • According to its use, what are the key athletic floors properties (e.g. shock absorption, energy return [i.e. the energy returned to the athlete after impact], floor deformation, or ball rebound)?
  • What are the aesthetic goals for the space? Is it an ideal location to promote brand recognition?

Now produced from recycled tires, rubber flooring is a high-performance, sustainable material that is often specified for athletic facility floors. The recycled tires are ground with color chips before being combined with a bonding agent. With color consistent throughout the product, the top does not show wear like products with a veneer or thin wear layer.

Before the 1990s, earlier similar products had a strong odor and lacked aesthetic options. Now, recycled rubber is customizable, and meets current South Coast Air Quality Management District’s (SCAQMD) volatile organic compounds (VOC) and indoor air quality (IAQ) standards.

Benefits of rubber flooring

Consisting of 100 percent post-consumer recycled tire rubber, the 25-mm (1-in.) thick flooring at Iowa State University’s facility provides superior performance and durability for the weight room.

Consisting of 100 percent post-consumer recycled tire rubber, the 25-mm (1-in.) thick flooring at Iowa State University’s facility provides superior performance and durability for the weight room.

In addition to a long service life, recycled rubber flooring requires low maintenance of routine damp mopping with neutral pH detergent. Roll and sheet products can be made with a smooth bottom and molded tiles can be manufactured with a waffle bottom to provide optimal shock-absorption for space such as cardio or heavy free-weight areas.

The void created by the waffle bottom adds a level of air-cushioning to the surface. The material’s density, along with the spring surface, is able to compress and then have a cushioning effect. The extra-thick, unique composite structure also provides durability.

Logos and custom color blends allow facilities to incorporate design and even targeted marketing. Produced using high-quality manufacturing standards, the rubber withstand a lot of abuse without losing performance capabilities. Customizable recycled rubber, made of 100 percent post-consumer content, offers aesthetic flexibility. Colleges will often employ team logos and school colors while athletic clubs can display their brand identity. Prefabricated for precision in density, thickness, and physical properties, its modular possibilities provide a range of functions as well as flexibility for various spaces.

For specifiers, recycled rubber flooring is an excellent choice for various areas of a facility. With the manufacturing easily producing both small and large batches, recycled rubber can be specified to fit a small locker room or a large arena.

Recycled rubber flooring uses 100 percent post-consumer tire rubber and post-industrial ethylene propylene diene monomer (EPDM) rubber in its manufacturing.

Flooring specification begins with determining the area’s function. From multi-purpose areas to single-use spaces, performance—including such factors as the level of shock absorption, durability, maintenance, acoustics, aesthetics, and sustainability—is all decided by the desired function. Specifiers must also consider the wear and tear of the space, and choose a surface that provides the best biomechanics to minimize athletic injuries.

For all types of flooring, installation requires an understanding of various factors, including moisture prevention and vapor emissions. Prior to installation, thorough testing of the area must be done to ensure adhesives can properly bond the flooring to the concrete, which will minimize maintenance problems in the future. This testing can be done during the installation and should be conducted by the flooring contractor as certain products have different moisture and relative humidity (RH) specifications.

Strategically designed with a waffle bottom, this floor provides shock-absorption, drainage, and cable routing. Its thick, composite structure is durable with wear resistance.

Strategically designed with a waffle bottom, this floor provides shock-absorption, drainage, and cable routing. Its thick, composite structure is durable with wear resistance.

Sustainability and environmental concerns are becoming a standard part of the specification process. In a large space like a sports facility, this becomes even more important. When maintaining a healthy environment, product’s volatile organic compounds (VOCs) and indoor air quality (IAQ) should be considered. For example, California has the strictest indoor air quality regulations for adhesives and building materials and products are third-party-tested to meet the state’s standards.

By having the products third-party verified, certain emission levels are tested based on organic compounds and formaldehyde, and levels cannot be higher than the threshold. (Throughout the United States, most manufacturers aim to meet California levels.) Though their initial costs may be slightly higher than low cost floor alternatives, the benefits of choosing a product such as recycled rubber flooring are ten-fold.

Measuring the benefits

While it can be difficult to measure the benefits of each type of high-performance flooring, responsibly designed flooring can minimize sports injuries through shock absorption and provide a more enjoyable experience. If the floor is selected based on its intended use, relevant testing data can provide background on how it fits the project. Standardization of safety rulings can aid specifiers in choosing the right surface. Specific sports flooring testing methods are employed to guarantee requirements are met.

There are certain safety requirements everyone must abide by, but some of the test methods are specific to the facility. For example, some are looking for pure performance or aesthetics. Every owner comes to a project with a certain criteria, but tweaks the specifications to fit their facility.

ASTM F2772-11, Standard Specification for Athletic Performance Properties of Indoor Sports Floor Systems, measures various performance characteristics for building products. Flooring is evaluated on four criteria:

  • force reduction;
  • ball rebound;
  • vertical deflection; and
  • surface finish effect.

It is then classified into one of five performance levels. In order to meet the standards of ASTM F2772-11, a floor must maintain:

  • 10 percent minimum shock absorption;
  • less than 3.5 mm (0.13 in.) vertical deformation;
  • minimum 90 percent ball rebound; and
  • between eight and 110 sliding effect value.

A plethora of options
Within the key sports flooring categories—namely vinyl, rubber, wood, and polyurethane—there are many divisions and price points. By knowing the intended use of the floor, specifiers can determine the ideal material based on the benefits.

CS_March_2014.inddDepending on whether this is a new project or refurbishment also plays a role in the appropriate selection. Modular rubber flooring works well for refurbished projects because a lot of floor preparation is not required. It can be laid right over top the current underlayment while other adhered options may require more preparation.

Aside from rubber, vinyl flooring is also a resilient surface, offering performance and design. In fact, vinyl includes the option to be printed as ‘wood grain.’ Cost and other benefits have solidified vinyl’s place in the athletic flooring world and the material is often selected for multi-purpose courts, institutional centers, gyms, and yoga studios.

A great option for hard and cushioned surfaces, rubber flooring comes in virgin sheet rubber and recycled rubber, which negotiates issues of sustainability and cost. Virgin sheet rubber has one of the highest price points, but also offers high performance, durability, and aesthetics.

Given the total cost of ownership, recycled rubber flooring as there are many options available based on use.. For example, in a weight room it is now a realistic option to use recycled rubber flooring. The benefits of employing rubber over carpeting include cleanliness in areas with heavy use. Instead of needing frequent, heavy-duty carpet cleaning, building owners can specify recycled rubber and know their upkeep costs will be lowered.

For a hard surface, wood flooring is a traditional choice, but its challenges include high maintenance costs and less flexibility. Wood flooring is specified by grade, thickness, and width.

Aesthetics and acoustics

Branding, team spirit, and loyalty are paramount in sporting facilities, and athletic directors and facility managers are looking to incorporate team logos and colors into the design. The hard surface of vinyl offers many possibilities, from painting to special printed effects. As discussed earlier, recycled rubber also has many customization and color options, ranging from standard black to numerous vibrant color blends in varying intensity to add color and visual effect.

Franklin & Marshall College (Lancaster, Pennsylvania) employed athletic rubber flooring for its high performance.

Franklin & Marshall College (Lancaster, Pennsylvania) employed athletic rubber flooring for its high performance.

Acoustics are another concern for areas with heavy use. Vinyl and wood do little to filter sound. Recycled rubber, however, is a material that cuts acoustic output and produces a less noisy space. For areas that require quiet, recycled rubber is a great fit.

Noise absorption is achieved by minimizing vibrations from sound. Facilities with multiple levels benefit from reduced sound from upstairs. Impact noise (i.e. when something is dropped on the floor) produces energy resulting in loud disruptions as it vibrates through the floor assembly.

As rubber flooring is not completely a hard surface, the sound is absorbed. Citing the noise reduction coefficient (NRC) can prove the effectiveness of acoustical airborne sound control, and rubber flooring can also reduce the impact sound through transmission to another floor below, also known as impact insulation class (IIC).

Conclusion

For sports and athletic flooring, functionality is understandably the goal. Recycled rubber, suitable for many types of areas, is an excellent choice for all areas of an athletic facility, from cardio areas, weight rooms, spinning rooms, to entryways and corridors. High performance—defined by a great showing in the level of shock absorption, durability, maintenance, acoustics, aesthetics, and sustainability—can be attained by thoroughly knowing the options available.

John P. Aten is the vice-president of sales and marketing for Regupol America. He has spent 23 years in the floor covering business, with an emphasis on the sports and fitness segments. Aten’s experience ranges from installing tracks to working closely on the specification of products for Big Ten athletic facilities. He can be reached at jpa@regupol.com.