Tag Archives: acoustics

Designing Sound Isolation in Multi-family Living

Acoustic_Rendering Twenty 20 Credit CBT Architects

Twenty20 is a 20-floor, 355-unit luxury apartment building in the NorthPoint section of Cambridge, Massachusetts. In addition to the residences in the tower, the project features 807 m2 (8690 sf) of retail space. Image courtesy CBT Architects

by Alicia Larsen, Benjamin Markham, LEED AP, 
and Jeffrey A. Zapfe, PhD
Imagine moving into a new condo, only to realize the TV next door, the dog barking across the hall, and the neighbors walking around upstairs can all be easily heard. Acoustical consultants would love to help, but unfortunately there is little that can be done at this stage without significant cost and intrusion. Sound isolation issues are most effectively addressed before construction, during the design phase.

What can designers of multi-family buildings do to meet the sound isolation expectations of their client and future residents? Acoustical consultants use several techniques to address these issues. However, before delving into them, one must first understand a little bit about sound.

Every sound isolation problem has three elements—a source, a path, and a receiver. The ‘source’ is the noise generator. It could be anything from a fourth-grader practicing her saxophone to a piece of building mechanical equipment. In many cases, the most effective means of mitigating a noise concern is to choose a quieter source if possible (e.g. quieter mechanical equipment), or to increase the distance between the source and sensitive receivers (i.e. lengthen the path).

Unfortunately, many times the source is an element that cannot readily be changed. No matter how many rules you put in place, there is no guarantee the student will stop practicing her saxophone at odd hours or the man next door will not fall asleep with his TV on again.

The ‘path’ is the element designers have the most control over, and so it is what frequently receives the most focus during the design. Both the path’s length and the building constructions intervening between source and receiver (position and composition) can be controlled. The performance of those building components is predictable and does not rely on residents’ behavior to be successful.

Finally, the ‘receivers’ in a multi-family building are the residents. Individual sensitivity to noise or vibration varies, so designers have little control over this piece of the sound isolation puzzle. One exception is the background noise level in a residence—designers can control this aspect by introducing steady, broadband (full-spectrum) ambient sound that masks the intruding sound, similar to the ‘white-noise’ machines some people use in their bedrooms to help them sleep. The bottom line is ‘quiet’ does not equate to ‘private’—in fact, it is just the opposite: there is greater privacy when there is a steady (but pleasant) level of ambient sound present.

Given the design team has the greatest control over the path, this article focuses on this design aspect—namely, how to design building components that provide substantial sound isolation. To add just a little more complexity, there are really two types of sound transmission to be considered in multi-family buildings: airborne and impact.

Airborne sound transmission
Airborne sound is generated, and primarily travels to the receiver, in the air. This is most of the sound heard on a daily basis, with examples including people talking or a loud stereo system. In a room-to-room situation, airborne sound can transmit either through a gap in the construction (e.g. a door undercut) or directly through a wall by causing the intervening construction to vibrate and re-radiate the sound energy on the other side.

Figure 1

Acoustic_Acentech_Figure 1

Sound transmitting through a partition. Image courtesy Acentech

For example, with a single-stud partition, one side (the source side) can be thought of as a microphone, and the other side (the receiver side) as a loudspeaker (Figure 1). The sound energy travels through the air and gets picked up by the ‘microphone,’ transmits through the structure, and is re-radiated by the ‘loudspeaker’ into the air on the other side of the partition.

In this case, there are three primary methods to improve sound isolation:

  1. 
Seal all gaps, cracks, and leaks. This is the easiest and most effective means to isolate sound. Sound will always find the weakest path—other attempts to improve sound isolation will be ineffectual if the gaps are not sealed first.
  2. 
Increase the mass of the construction. This makes it more difficult for the airborne sound to cause the partition to vibrate. In the microphone/loudspeaker analogy, this corresponds to making the microphone and loudspeaker less effective or efficient.
  3. 
Introduce decoupling into the construction. This allows one side to vibrate without transferring the vibration as easily to the other side. This is analogous to cutting the physical connection between the microphone and loudspeaker.

In many cases, all three methods are necessary.

Closing gaps
ASTM C919, Standard Practice for Use of Sealants in Acoustical Applications, contains recommendations on how to apply caulk in acoustical applications. Ideally, all penetrations should be sealed. Back-to-back electrical boxes should be staggered, preferably in different stud bays, and caulked. Walls should be caulked with one bead on each side of the partition. (A second bead of caulk on one or both sides of the partition does not result in a substantial improvement in sound isolation.)

Windows and entry doors should be effectively gasketed. Poorly sealed entry doors (particularly those that have a substantial undercut) can be a significant source of noise intrusion from corridors into residences.

Acoustic_Concord Park Residential Multi-Unit

Concord Park (West Concord, Massachusetts) houses senior residences in senior and assisted living accommodations for the Volunteers of America Organization. Recommendations were made for sound-isolating materials to lessen the train noise. In addition to the exterior sound isolation options, upgrades to the exterior windows were also suggested. Photo courtesy TAT/The Architectural Team

Increasing mass
A substantial increase in mass is necessary to have a meaningful effect on a partition’s sound isolation performance. (‘Substantial’ normally means in terms of a factor of two times heavier.) This could be accomplished by upgrading from one to two layers of gypsum board on each side of a stud partition, or using plaster rather than gypsum board. (Plaster has roughly three times the mass of gypsum board.) If partitions are concrete masonry unit (CMU), increasing the density or thickness, or filling the CMU cavity with grout, can effectively increase the mass.

Introducing decoupling
The goal is to eliminate rigid connections between one side of the construction and the other. The most effective way to do this is by using a double-stud or double-width construction with an air cavity between the two sides of the wall. When double walls are not possible due to cost or space constraints, other methods such as specialty resilient fasteners can be acceptable alternatives. In general, resilient clip products tend to be more reliable than resilient channels, but either product can be compromised in real-world applications, particularly if cabinets, TVs, or other wall-mounted elements must be anchored directly to the studs. Such complications are less prevalent in suspended ceiling applications in place to increase up-down sound isolation.

Impact sound transmission
Impact sound is produced by forces applied directly to the structure or partition. The most common example of this is people walking on the floor above, but things like chairs scraping along the floor and the thump of people ascending/descending stairs are also prevalent in multi-family buildings.

The sound isolation methods that are discussed for partitions can also 
be used in order to mitigate impact sound. A few others are discussed in the following paragraphs.

Increase the structure’s stiffness
Floor stiffness is an important first step in mitigating impact sound (particularly the low frequency ‘thuds’). Unfortunately, increasing the structure’s stiffness can be challenging when the construction is already determined. As a rule, the stiffer the structure, the more effective the sound and vibration isolation will be, particularly at low frequencies. Structures that are not stiff do not generally isolate the low-frequency content of impact sounds, no matter what other mitigation means are employed.

Decoupling
Decoupling works like a shock-absorber on a car. Energy is applied to one side of the construction, but the way in which the sides of the construction are connected prevents the energy from being efficiently transmitted to the other side (the sides of the construction are often connected by a device such as a spring or a resilient pad). A car can go over a bump, but since the wheels attached to the shock absorber move up and down relatively freely, the passengers do not feel the bump to the same degree in their seats.

Acoustic_Berklee Tower - (c) Robert Benson Photography

Berklee College’s new multi-use 16-story tower houses 173 residence hall rooms for 369 students, 23 practice rooms, six two-story common areas, a fitness center, and a 400-seat dining hall that doubles as a performance space. The authors’ firm provided architectural acoustics for the tower, with emphasis on room acoustics, sound isolation, and mechanical systems noise control. Photo © Robert Benson Photography

Carpeting and other ‘soft’ floor finishes significantly cushion impact sounds, preventing the floor/ceiling assembly from becoming energized in the first place. Most impact sound problems occur with hard floor finishes like wood or tile. In most cases, addressing this issue with decoupling is the most sensible option, as it often has the fewest implications on the project.

The structure’s stiffness is typically decided in the earliest stages and changing it could have major cost implications. On the other hand, the finish floor hardness is often decided based on aesthetic considerations; changing the finished floor may or may not be an option.

Decoupling can be addressed on the floor side or on the ceiling side. On the floor side, a resiliently supported massive layer (a floating floor) is used to provide isolation. Floated floors can range from a separately poured concrete slab that rests on resilient isolators to a thin underlayment underneath the finished floor. The required scale of the decoupling depends on the amount of isolation needed.

One can also introduce decoupling on the ceiling side by installing a resiliently suspended ceiling. Again, depending on the application, this can range from hanging multiple layers of gypsum board on a network of spring hangers to attaching the gypsum board using resilient channels. (In best cases, decoupling is introduced both at the floor and at the ceiling.)

In either case, it is best to begin with a stiff structure. When faced with an existing structure that lacks stiffness, it is typically necessary to add structural members (e.g. more beams) or increase mass (e.g. pour more concrete).

Wood-frame construction is fairly limp to begin with, so addressing the stiffness can make a large difference on the effectiveness of the sound isolation. At least 25 mm (1 in.) of gypsum concrete in wood-frame constructions goes a long way to stiffen the structure and add mass. Steel and concrete buildings tend to be stiffer, but sometimes even they require additional steel framing or concrete to provide adequate impact isolation.

Quantifying sound isolation
Various metrics put forward in the following ASTM standards are used to quantify the sound transmission between spaces and assign a single-number rating to the airborne sound transmission or the impact sound transmission:

  • 
field: ASTM E336, Standard Test Method for Measurement of Airborne Sound Attenuation Between Rooms in Buildings;
  • 
laboratory: ASTM E90, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements;
  • 
field: ASTM E1007, Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures; and Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine.

Airborne sound transmission is typically quantified using the sound transmission class (STC), which is a laboratory rating that cannot be measured in the field. Field equivalents include apparent STC (ASTC) and noise insulation class (NIC). The major difference between the two field ratings is ASTC is normalized to account for the room acoustics in the particular measurement scenario.

Using ASTC, the performance of two different constructions, in two different locations, with different source and receiver room types, can be compared. ASTC is a test that would be used to measure compliance to a design standard. NIC, on the other hand, does not normalize for the room conditions—as such, it better represents what the occupants actually experience rather than simply how the partition is performing.

In all cases (i.e. STC, ASTC, and NIC), higher values indicate better sound isolation.

Impact sound transmission has an analogous set of metrics:

  • 
impact insulation class (IIC), the lab rating;
  • 
apparent IIC (AIIC), the normalized field measurement used to determine compliance; and
  • 
impact sound reduction (ISR), the non-normalized field measurement that correlates well to occupant experience.

Again, higher values indicate better sound isolation.

Physically, a partition’s sound isolation depends on the frequency of the sound. In most cases, partitions tend to isolate higher frequency sound better than low frequencies. Unfortunately, the single-number metrics all combine this frequency-dependent behavior into a single numerical rating. This means the ratings alone may not fully describe the performance.

For example, the two tests shown in Figures 2a and 2b have the same IIC rating, but very different properties of impact sound isolation across frequency. The first fits the AIIC 54 curve closely, whereas the second shows deficiencies at low frequencies and good performance at mid- and high-frequencies. With the floor-ceiling construction associated with 2b, one would be able to hear a 13.5-kg (30-lb) toddler jumping up and down, but not the click of his mother’s high heels.

Figure 2

Acoustic_Acentech_Figure 2 (2)

Impact insulation class (IIC) test data for two different constructions.

A change in STC or IIC of one or two points is not an appreciable difference in sound isolation. However, a change of five points is significant, and a change of 10 points typically corresponds to a largely significant difference—on the order of a doubling or halving of the perceived loudness of the intruding sound.

Code requirements/guidelines
Many states have adopted the International Building Code (IBC) into their state building code requirements. This calls for a minimum STC 50 laboratory rating, or 45 if measured in the field. Similarly, impact sound isolation requirements are IIC 50 or 45 if measured in the field.

It is important to understand these code requirements do not necessarily equate to occupant satisfaction, and certainly do not indicate inaudibility. Higher values are recommended for more sensitive applications. Figure 3 shows a summary of various sound isolation guidelines commonly referenced in the industry.

Figure 3

Acoustic_Acentech_Table 1 (2)

Comparison of sound isolation guidelines.

Ground-borne vibration and sound from rail lines
Multi-family residential structures are typically found in densely populated urban areas. Many of these urban areas also have extensive public transportation systems, some of which incorporate underground rail lines. Anyone who has visited New York City, Chicago, or Boston has likely encountered the characteristic low frequency rumble from a passing subway train.

Interestingly, vibration is actually the mechanism responsible for the rumble sound. Micro-forces due to imperfections at the wheel-rail interface produce vibration that travels through the soil to nearby buildings. Once inside the building, the vibrations cause the walls, floors, and ceiling to vibrate and radiate sound much like giant loudspeakers. It is this radiated sound people hear when the train passes. With the exception of air vents and other openings, the acoustic sound produced by the train in the tunnel is effectively trapped inside the tunnel.

If the vibration is sufficiently severe, people may feel it, but more often than not, the vibrations cannot be felt even though the resulting sound can still be heard. Since the vibration is propagated through the soil, the resulting sound and vibration inside the building are commonly referred to as ground-borne. Surface rail systems also produce ground-borne sound and vibration, although this is often masked by the direct airborne sound from the passing train.

The Federal Transit Administration (FTA) provides guidelines for acceptable levels of ground-borne vibration and sound in residential settings where people normally sleep. While these levels strictly apply to new transit projects near existing communities, they also can be used as a reasonable guideline for a new residential structure near an existing rail line. Unfortunately, FTA does not specifically say what the effects will be if its limits are exceeded.

More insight into this aspect is available from the TCRP D-12 study. The D-12 project studied the relationship between ground-borne vibration and sound and community annoyance and provided a method to estimate the likelihood of annoyance based on the vibration or sound exposure level.

Like airborne sound, mitigation of ground-borne sound and vibration can be conceptualized in terms of the source, path, and receiver. In addition to effective maintenance of the track and rolling stock, source mitigation treatments usually involve a resilient track support. Such supports come in many varied forms, but the basic concept involves the placement of a resilient element (rubber, neoprene or even steel spring) between the rail and the tunnel floor. Figure 4 is one example of a resilient track fastener that is located between the rail and the wood tie. Resilient track supports can be very effective at reducing vibration, however, they also require the direct involvement of the transit agency, whose cooperation can be challenging to secure.

Figure 4

Acoustic_Acentech_GBV_Fig4

Resilient track fastener. Photos courtesy Acentech

Path mitigation has limited effectiveness for ground-borne vibration. Trenches are often proposed as a mitigation option, but in addition to being of limited practicality in an urban setting, their effectiveness is modest at best.

Mitigation at the receiver is a viable option, particularly for new construction. Buildings have a natural vibration attenuation of one or two decibels per floor as one moves up away from the source. There is also distance attenuation as one moves farther from the rail line. Designers can take advantage of this by locating the most sensitive receivers on upper floors, saving the lowest levels for less-sensitive uses such as parking, mechanical, and retail.

More active steps can also be taken to reduce the amount of vibration entering the building at the foundation. Base isolation systems are used to support the building resiliently. Base isolation is typically done at the column base (Figure 5), although continuous pads under mat foundations can also be employed. The isolation performance of the isolation is specified based on the source levels (train) and the design goals for the living spaces. Vibration reductions associated with a base isolation system are comparable to what would be expected from a track isolation system.

Figure 5

edited

A look at the base isolation pad.

Mitigation is also possible within the building on a room-by-room basis. ‘Room-within-a-room’ construction using a floated floor and resiliently supported walls and ceiling can be effective provided constructability challenges such as differential floor heights can be addressed.

Conclusion
Sound and vibration isolation comes down to mass, stiffness, and de-coupling. In multi-family buildings, it is necessary to consider wall constructions, floor/ceiling assemblies, and environmental noise and vibration sources with these factors in mind. It is sometimes said good fences make good neighbors. In a multi-family building, good building constructions can make for good neighbors, too.

Sound Isolation Pitfalls
Acoustic_Acentech_Figure 3

Beam parallel to wall partition. Image courtesy Acentech

1. Some ‘resilient channels’ are not really resilient. Two-legged resilient channels do not provide a meaningful acoustical benefit.
2. Shear panels in wood-frame construction can be tricky. When a resilient channel/clip is applied between a shear panel and a finish layer of gypsum board, it creates a narrow airspace at the resilient element. This narrow airspace of entrapped air is actually quite stiff, preventing the resilient element from flexing. When introducing resiliency, the resilient element should look into as deep an air space as possible.
3. Resilient elements are often pinned in place. This occurs commonly at ceiling perimeters – a resiliently suspended ceiling might be anchored to the walls at the perimeter with a rigid wall angle; this pins the ceiling in place, limiting efficacy of the resilient hangers.
4. Some conditions are difficult to seal. For example, the structural beam running parallel to the partition in the photo at left makes it difficult to get the beam with a caulk gun to adequately seal the partition, exposing the partition to sound isolation problems.

Alicia Larsen is a consultant in acoustics at Acentech, a multi-disciplinary acoustics, audiovisual systems design, and vibration consulting firm. Her special interests include sound and vibration isolation for mixed-use buildings, community noise issues, and acoustical measurement and analysis. Larsen has presented her graduate and consulting work at the Acoustical Society of America (ASA) and Institute of Noise Control Engineering (INCE) national conferences, and chaired ASA’s Greater Boston Chapter. She can be reached at alarsen@acentech.com.

Benjamin Markham, LEED AP, is the director of architectural acoustics at Acentech, and an acoustician involved in projects concerned with performance spaces and other commercial, residential, and civic facilities. He also teaches classes in architectural acoustics at Massachusetts Institute of Technology (MIT) and Cornell University. Markham can be contacted via e-mail at bmarkham@acentech.com.

Jeffrey A. Zapfe, PhD, is Acentech’s president. His expertise is in the area of vibration, structural dynamics, vibration sensitive facilities and equipment, and vibration isolation. Zapfe’s work includes the analysis of structures at the design stage as well as the measurement, analysis, and mitigation of vibration in completed buildings. He can be reached at jzapfe@acentech.com.

Hospital Quiet Zone

hospital_Opener

Photo © iStockphoto.com/babyblueut

by Niklas Moeller
Conversations and the cacophony emanating from telephones, alarms, televisions, carts, doors, medical, and mechanical equipment ensure noise is ever-present in U.S. hospitals. Various economic incentives, regulatory measures, and design guidelines have been developed over the past decade to encourage hospitals to address this problem.

It is important for those involved in the planning and construction of these facilities to understand these initiatives, as well as how to help hospital administrators achieve their acoustic goals.

One of the most powerful measures is the value-based purchasing program (VBP) enacted by the Centers for Medicare and Medicaid Services (CMS). It provides monetary incentive to improve patient outcomes by penalizing poorly performing hospitals, while rewarding those that do better. At its outset, it was funded by a one percent withholding of Medicare. In 2014, that figure began rising by 0.25 percent annually and will reach its currently planned cap of two percent by 2017.

The VBP program is rooted in a total performance score for each hospital calculated from clinical quality assessments (70 percent) and patient satisfaction scores (30 percent). The latter is based on the results of the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) survey. Failure to submit these surveys to CMS results in a two percent withholding 
of Medicare.

The HCAHPS (pronounced ‘h-caps’) survey is given to a random sample of patients between 48 hours and six weeks after discharge, and is used to gain insight into perspectives on the quality of their hospital stay. It includes 18 questions, grouped under eight topics. Hospitals earn points for achieving a certain performance level relative to other hospitals, for improving their performance over previous periods, and for consistency across all eight categories.

The section pertaining to the hospital environment includes a question relating to noise that asks, “During this hospital stay, how often was the area around your room quiet at night?” The patient can respond: never, sometimes, usually, or always. Since 2007—when collecting and submitting the survey became mandatory—noise has consistently been the worst-rated factor nationwide. As such, this problem has the greatest potential to impact hospital funding by dragging down consistency scores as well as patients’ overall rating of their stay. It may also affect a hospital’s competitiveness because the public can review each facility’s results online.

hospital_Image_1

The Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) survey includes a question regarding the quietness of the patient’s room at night. Since 2007, it has been the poorest-rated factor nationwide, dragging down consistency scores. Photo © iStockphoto.com/francisblack

Patient comfort and outcomes
It is worth noting the HCAHPS survey focuses on the quietness of the patient’s room at night. Though noise is not responsible for all sleep disruptions, its contribution is significant.

Researchers have found the sick and the elderly are the most likely to have their sleep disturbed by noise, and people never completely habituate themselves to night-time noise. Noise reduces both the quantity and quality of sleep through delayed onset, shifts to lighter stages, motility (i.e. tossing and turning), and awakenings, which weaken the immune system and impede the body’s ability to generate new cells. It can also lead to problems during the day, such as agitation and delirium.

However, a growing body of medical studies show noise also causes problems during the day. As illness can increase sensitivity to environmental stressors, noise can create anxiety, driving up nursing calls as well as pain medication requests. In fact, side effects such as elevated blood pressure, quickened heart rate, and increased metabolism have led some researchers to conclude noise may even slow recovery rates and length hospital stays.

Additionally, patients are not the only ones affected. Though one might think staff can become conditioned to noise over time, no one is able to fully tune out these disturbances because senses are designed to detect such changes in the environment. Both the American Hospital Association (AHA) and the Institute for Safe Medical Practices (ISMP) recommend that medical error prevention programs take noise into consideration, given it can impact caregivers’ concentration, stress levels, and fatigue.

HIPAA and speech privacy
Speech privacy is yet another acoustic concern in hospitals. Conversations occur at administrative stations, and in hallways and semi-private rooms. Often, areas used for the input and retrieval of both medical and financial information are located near waiting areas.

Patients know if they can overhear conversations occurring in adjacent areas, others can hear them as well, making them uncomfortable and less likely to discuss private matters with their caregiver. They also have a fundamental right to auditory privacy, which has been officially recognized in a set of federal regulations developed by the U.S. Department of Health and Human Services (HHS).

Introduced in 1996, the Health Insurance Portability and Accountability Act (HIPAA) primarily deals with the use of protected health information (PHI) and of any individually identifiable health information, as well as its storage, and sharing in electronic systems. However, a small but essential part of the HIPAA pertains to oral communication, because to exclude conversations would essentially allow for private information to be inappropriately shared if it was done verbally.

HIPAA requires healthcare entities take “reasonable safeguards”—including administrative, technical, and physical measures—to ensure speech privacy during both in-person and telephone conversations with patients and between employees. Compliance was required by healthcare-related facilities and other organizations working with PHI as of April 14, 2003. There are stated penalties for non-compliance, but HHS has elected to address speech privacy issues on a complaint basis to date, and few monetary penalties have been issued. However, a hospital must be able to demonstrate it has investigated acoustics, researched possible solutions, and implemented economically viable ones.

hospital_Image_2

Health Insurance Portability and Accountability Act (HIPAA) requires hospitals to take ‘reasonable safeguards’ to protect patients’ privacy during in-person and telephone conversations. Photo © iStockphoto.com/Squaredpixels

Improving acoustics using the ABCs
If one focuses on the types of noise created by building occupants and small medical equipment rather than structure-borne or mechanical sources, there are three key ways to improve noise control and speech privacy in hospitals: absorbing, blocking, and covering. None of these methods can achieve the desired goals on its own; rather, they must be used in combination. The further challenge in hospitals is to apply them in such a way so as not to compromise cleanliness or staff’s ability to easily access patients and interact with one another.

Using absorptive materials
Hospitals often have hard finishes, causing noises to echo, overlap, linger, and travel great distances. Adding absorptive materials still meeting the criteria for sterility and washability will reduce the energy and, therefore, the volume of noise reflected off their surfaces back into the space.

Since the ceiling is usually the largest unbroken surface in a facility, a good absorptive tile helps lessen the distance over which noises and conversations can be heard. In fact, a Swedish study determined cardiac patients in rooms with absorptive ceiling tiles were less likely to be readmitted than those in traditional rooms.

Ceiling absorption is often rated using noise reduction coefficient (NRC), which ranges from 0 to 1 (i.e. 0 to 100 percent absorption). Articulation class (AC) and ceiling attenuation class (CAC) are two additional ratings to consider. AC is the measure of the tile’s ability to absorb noise reflected off the ceiling into neighboring spaces in open-plan areas in the frequencies important for speech privacy. CAC indicates the tile’s value as a barrier to airborne sound transmission between adjacent closed offices, which is less relevant in hospitals where deck-to-deck construction is typically used. An appropriate tile should be specified and consistent coverage ensured throughout the building.

The ceiling’s absorptive power is affected by the type of lighting system used. From an acoustic perspective, the best lighting is an indirect system because it helps to maintain the coverage of the acoustical tile across the entire ceiling. A system incorporating a minimum number of fixtures while still meeting the lighting requirements should be specified.

Hanging absorptive wall panels may be needed in some situations. They are most effective when applied to large vertical surfaces and reflective locations, such as corridors. Acoustic wall panels are available featuring photographs or artwork.

Soft flooring can be used to lessen footfall and other ‘traffic’ noise. The challenge for hospitals is to implement it in a manner that does not compromise sanitation or hamper the movement of patients and equipment. Some have purchased motorized beds and use modular carpet tiles so individual sections can be removed for easier cleaning.

hospital_Image_6

A sound masking system’s loudspeakers are typically installed in a grid-like pattern above the suspended ceiling. They distribute a comfortable sound similar to softly blowing air, covering up noise and conversation. Image courtesy K.R. Moeller Associates Ltd.

Implementing blocking strategies
When introduced to blocking, most people immediately think of walls, but a well-planned layout can also be used to minimize direct (i.e. line of sight) transmission of sound to and from neighboring spaces. For example, high-activity areas and noisy machines such as icemakers should be located in spaces well-separated from patient rooms. Doors facing each other across hallways should be offset. It is also helpful to rethink traditional aspects of the hospital landscape. For instance, nursing stations can be decentralized in order to prevent large groups from talking near patient rooms.

However, caution needs to be taken when applying blocking strategies, because caregivers must to be able to readily monitor and access patients. When one blocks out noise, the line of sight is also affected.

The most common blocking tactic is to construct deck-to-deck walls. The aim is to completely seal the room, but wall performance is sensitive to any gaps. Basically, if light can pass through, so can sound, and often well enough to substantially reduce the wall’s impact.

Of course, an open door is a private room’s biggest Achilles’ heel and some hospitals are re-e

valuating the open-door policy in an attempt to address this weakness. However, even when the door is closed, sound can transmit through HVAC components, openings under doors, and even back-to-back electrical switches and outlets. Any penetrations must be properly treated and managed during design, construction, maintenance, and renovation to ensure the wall’s integrity.

Covering noise with sound masking
When a closed room fails to provide speech privacy and control noise, some argue it is due to poor design or construction. While there is some truth to this position, it erroneously assumes the correct approach is to rely solely on physical isolation.

In fact, both blocking and absorption only address part of the acoustic equation. These strategies are needed to reduce volume peaks, the distance over which sounds travel, and the length of time they last. They also decrease a facility’s overall background sound level. The lower level makes remaining noises more noticeable and disruptive to occupants. It also allows them to clearly overhear conversations, even those occurring at a distance or in another room.

edited1

Patients and/or caregivers can be given control over the masking volume in patient rooms. Rotary switches or programmable keypads can be installed for this purpose. Some systems also provide room control apps or integration with third-party controllers. Images courtesy K.R. Moeller Associates Ltd.

Providing a higher and more consistent background sound level is accomplished by installing a sound masking system. This technology basically consists of a series of loudspeakers integrated in a grid-like pattern above the ceiling, as well as a method of controlling their zoning and output. The loudspeakers distribute a comfortable sound, similar to softly blowing air.

Adding more sound to a space may run contrary to most people’s understanding of how to control noise, but the premise behind masking is simple: any noises below the new background sound level are covered up, while the impact of those above it is lessened because the degree of change between the baseline and any volume peaks is smaller.

Sound masking’s ability to reduce the quantity and severity of volume changes also makes it an effective method of improving sleeping conditions. In fact, in a 2005 study of intensive care unit (ICU) patients, quality of sleep improved by nearly 43 percent when sound masking was used.

Masking also entirely covers conversations or reduces intelligibility, improving privacy. However, this effect requires some distance and, therefore, masking does not prevent staff and patients from communicating with one another.

There are several design considerations worth noting when procuring this type of system for a hospital. For example, these environments are often highly fragmented, increasing emphasis on the requirement for numerous masking control zones.

Additionally, because opening the ceiling has the potential to spread contaminants into the occupied space below, the system should provide localized adjustment of all output settings and paging zones from a location below the ceiling (e.g. a control panel or computer). One does not want to have to put a containment system in place when changes need to be made to settings.

A networked-decentralized sound masking design will provide the required small zones (i.e. one to three loudspeakers), while allowing hospitals to make adjustments without reopening the ceiling or incurring significant disruption to their operations. It will also allow patients and staff to adjust the masking levels according to individual needs, as described 
in the 2014 Facility Guidelines Institute (FGI) Guidelines for Hospitals and Outpatient Facilities. In this way, the system will not only improve comfort, but also increase patients’ sense of control over their environmental conditions, raising satisfaction levels and HCAHPS scores.

hospital_Image_10

The majority of the acoustical burden has to be borne by the facility’s physical design; however, efforts to control noise and protect speech privacy should continue through behavioral policies aimed at both staff and visitors. Photo © iStockphoto.com/Spotmatik

Reducing noise through policy
While most of the acoustical burden must be borne by the facility’s design as outlined in 
this article, efforts to control noise should not stop there. Once the hospital is occupied, administrators should continue to identify and subsequently reduce or eliminate unnecessary sources. For example:

  • 
lower the telephone’s ringer volume;
  • 
dim the lights in the evening to encourage quiet;
  • 
fix or replace faulty equipment, such as squeaky carts and creaking doors;
  • 
provide training on how to handle loud vocalization by patients;
  • 
purchase quieter equipment, such as hand-towel dispensers and door hardware;
  • 
limit or eliminate overhead paging by equipping staff with personal devices; and
  • 
use visual indicators for low-priority or advisory alarms, rather than audible signals.

Some hospitals have even formed committees tasked with raising caregivers’ and visitors’ awareness of noise and enforcing behavioral policies related to its reduction. Anti-noise posters are often topped with clever acronyms, such as Silent Hospitals Help Healing (SHHH) and Help Us Support Healing (HUSH) or the time-honored, ‘Hospital Quiet Zone.’ Policies for caregivers include:

  • 
respond to alarms promptly;
  • 
change IV bags before alarms sound;
  • 
restock supplies during the evening rather than at night;
  • 
talk only to listeners in close proximity, not from a distance;
  • 
use hushed, rather than normal, speaking tones whenever possible;
  • 
ask patients to employ headsets and turn off unwatched television sets; and
  • 
designate ‘quiet time’ during which no routine checks are made unless medically necessary.

In addition to the aforementioned design strategies, they may also:

  • 
implement waiting lines at a specified distance;
  • 
post signs reminding both staff and patients to consider their voice level; and
  • 
locate staff telephones away from areas where conversations may be overheard.

The hospital should also designate an individual who will document speech privacy practices (as required by HIPAA), provide privacy awareness training for employees, and act as the contact for complaints.

Conclusion
People will always create noise as they go about their day in a busy, round-the-clock healthcare facility. By considering acoustics during the hospital’s planning and construction, one can help administrators meet regulatory requirements, relieve some of the environmental stress from caregivers, and—above all—create more comfortable places in which patients can recuperate.

Niklas Moeller is the vice president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network sound masking system. He also writes about acoustics at soundmaskingblog.com. Moeller can be reached at nmoeller@logison.com.

 

Unique noise control standards developed for mixed-use project

The LegoLand Discovery Center in Assembly Row was designed by Darlow Christ Architects. The development also includes residential, office, and retail space. Photos © Bruce T. Martin

The LegoLand Discovery Center in Assembly Row was designed by Darlow Christ Architects. The development also includes residential, office, and retail space. Photos © Bruce T. Martin

An acoustics consulting firm, Acentech, developed project-specific noise control guidelines for Assembly Row—a new mixed-use waterfront development near Boston.

Located on a 18-ha (45-acre) previously underdeveloped site on the Mystic River in Somerville, Massachusetts,  Assembly Row’s master plan was conceived and coordinated by developer Federal Realty Investment Trust (FRT). It retained Acentech early in the project to address the complex issue of noise control as it related to the mix of uses within four blocks. The acoustic design addressed noise and acoustic issues in buildings and tenant spaces.

Assembly Row’s first phase, includes:
● 450 residential apartments;
● a 12-screen movie complex;
● LegoLand Discovery Center;
● restaurants;
● outlet retail stores;
● 9290 m2 (100,000 sf) of office space; and
● a 2.4-ha (6-acre) waterfront park.

Succinct and prescriptive noise-emission standards were developed and included in the design and technical manual governing tenant fit-outs. These standards included specific design criteria for noise emissions from rooftop or outdoor mechanical equipment, and noise transmission from ground-level retail to residences above. Similar standards were also applied to base building designs throughout the development. These standards were intended to ensure compliance with the municipal noise code, and serve to reasonably protect the various properties from each other’s noise emissions.

“Assembly Row is a new neighborhood designed to foster a 24/7 lifestyle,” said FRT’s Brian Spencer. “Less than 10 minutes from Boston, it is the first neighborhood of its kind in the country, offering outlet retail alongside entertainment and eateries, with apartments and office space above, fostering a true neighborhood feel.”

Consultants worked with architects and developers of specific buildings and tenant fit-outs to design acoustically favorable spaces and comply with the development’s noise emissions standards. The 12-screen movie complex, located above the LegoLand Discovery Center in Assembly Row’s Block 3, presented a unique design challenge.

Acoustic consultants worked to ensure each theater within the movie complex would be protected from noise produced by activities at LegoLand, other building tenants, and mechanical equipment. The resulting design includes floating concrete slabs under every screening room, with certain walls and other features supported from the roof structure above. Through careful coordination with the architecture and building structure, these and other design features ensure the screening rooms are not disturbed by activities in surrounding spaces, and likewise, the cinema’s neighbors are not disturbed by movie noise.

Another challenge was protecting residential tenants in the upper floors of the development from the noise produced by rooftop mechanical equipment serving restaurant and retail facilities on the ground floor. Planning for judicious placement of visual/acoustical screening around rooftop equipment helped reduce noise impacts from HVAC systems on residents of adjacent buildings. Even within buildings—with both commercial and residential spaces—the careful location and vibration isolation of mechanical equipment has helped reduce noise impacts.

Sound Thoughts on Door and Frame Assemblies: Exploring differences between STC and STL ratings

All images courtesy MegaMet Industries

All images courtesy MegaMet Industries

by Edward Wall Jr. and Allan C. Ashachik

When sound control acoustic door assemblies are selected, the usual way is to specify a sound transmission coefficient (STC) rating in accordance with established standards. Derived from testing at a series of frequencies within the range of human hearing, STC is a single number assigned to a door assembly that rates its effectiveness at blocking sound transmission. This sounds simple and logical, just like hourly ratings on fire doors, but the situation is far more complicated.

The challenge with having a catch-all solution in the form of specifying the ‘right’ STC comes down to the range of sound. For example, if a project concerns a high school band’s practice room, the noise that needs to be reduced comes from instruments ranging from the low-frequency (pitch) of a bass drum to the high pitch of woodwinds or chimes. For this application, STC would be appropriate since sounds from many frequencies all need to be blocked or reduced.

However, selecting the right door for a mechanical equipment room at the same school is quite different. Low pitch and constant machinery noise needs to be filtered out. Using the STC rating system for this opening could be much more expensive than necessary to be effective. Fortunately, there is another metric more suited to these situations—sound transmission loss (STL).

The STC rating is actually derived from an average of STL performances. Since STC relies on testing data that establishes the reductions at each individual frequency, the data can be used to determine the STL needed at a specific frequency or frequency range without additional testing.

Setting the stage
This article is not intended as a lengthy discussion of all aspects of sound control, designs, gaskets, or installation. Rather, it seeks to clarify some misconceptions about STC and suggest using alternate values and standards when specifying acoustic door and window assemblies for a particular sound control purpose or requirement.CS_October2014.indd

The authors believe STL is the definitive method of specifying acoustic assemblies, and better accomplishes what the sound-deadening qualities are to be required for a specific opening. On a practical level, this means the building owner gets what he or she really needs, often for less money. To make this argument clear, six myths must be examined.

Myth 1: “An STC rating in accordance with ASTM E90 is all that needs to be specified.”
It is important the reader be a least somewhat familiar with some of the ASTM standards applicable to lab testing and rating of sound control assemblies.

To that end, ASTM E90, Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements, describes the test chamber, testing method, frequencies to be reported, and other lab requirements. However, it does not contain the method of establishing the rating. A second standard like ASTM E413, Classification for Rating Sound Insulation, or ASTM E1332, Standard Classification for Rating Outdoor-Indoor Sound Attenuation, needs to be included.

ASTM E413 is used to define the 16 frequencies at which sound transmission losses in decibels are measured. It also establishes the sound insulation contour values of those frequencies and the sound transmission loss values for each corresponding frequency. From this, a reference contour can be created to which actual test data can be graphed and compared. Interestingly, the profile of this reference contour remains constant for all graphs and is shifted up or down on the graph to obtain a single STC rating (Figure 1).

ASTM E1332 is used to calculate an outdoor/indoor transmission class (OITC) and covers a range from 80 to 4000 Hz. This standard has an extended lower range of frequencies for which the results are calculated rather than graphed. The additional frequencies are intended to measure STL in decibels for outdoor to indoor sound exposure resulting in a different OITC rating. The calculations generally result in a somewhat lower single rating than does ASTM E413 for STC.

In order to convey the purpose of this article, two fictitious ASTM E90 test results—derived from two different examples—are shown in Figure 2. The columns listed show the 16 STL numbers achieved at each frequency of the ASTM E413 test. Ratings are at random and do not necessarily represent a specific door assembly or manufacturer—however, these sample numbers are not unusual.

Sample 1 would be typical of a less-expensive door assembly with an STC of about 40 while Sample 2 would represent an assembly costing two to four times as much with an STC of over 48. As the image illustrates, depending on the frequency of sound, one can save the client a lot of money by specifying the less-expensive door.

CS_October2014.inddCS_October2014.indd

 

 

 

 

 

 

 

 

 

 

Myth 2: “A higher STC rating is always better, regardless of cost. Therefore, one should always specify an STC rating higher than what the client needs—just to be safe.”
To understand how those STL values relate to real-world conditions, the reference charts of common volume sources and approximate frequencies are provided as examples in Figure 3. Simplistically, to reduce the volume from a busy office with mostly male employees to that of a private office, the assembly should be capable of at least an STL of 40 at a middle frequency range. The lower cost Sample 1 would be sufficient in lieu of the more costly Sample 2 usually specified.

To reduce the noise from a bass drum or low-frequency vibrations, the maximum STL should be concentrated in the corresponding frequency range. Here, Sample 2 would be the better choice. Other noise sources should be evaluated accordingly and the correct door assembly chosen to meet the best STL at a certain frequency range. At higher-frequency ranges, Samples 1 and 2 are not really much different in performance, but substantially different in cost.

Neither ASTM E413 nor ASTM E1332 establishes an STC (OITC) value of the ‘perfect’ acoustic door assembly. To evaluate test results to a single number, they must be compared to this contour. The key to this comparison is referred to as the ‘deficiency’—any measured sound transmission loss (STL) variation below the contour. The STL measurements above are not considered variations. Unless otherwise noted, ASTM E413 limits these deficiencies to a maximum total of 32, and a maximum of eight at any single frequency.

For projects like this IMAX movie theater in Brimingham, Alabama (or the Nashville Sympohny on page 96) choosing a door with the proper acoustical ratings is critical.For projects like this IMAX movie theater in Brimingham, Alabama (or the Nashville Sympohny on page 96) choosing a door with the proper acoustical ratings is critical.

For projects like this IMAX movie theater in Brimingham, Alabama choosing a door with the proper acoustical ratings is critical.

Acoustical doors are available in a wide range of sizes for a wide range of applications, such as this Georgian power plant.

Acoustical doors are available in a wide range of sizes for a wide range of applications, such as this Georgian power plant.

Myth 3: “STC is a single number completely reliable to describe performance.”
Unlike fire door assemblies rated based on a certain time and temperature curve, the method of calculating STC by test data and deficiencies from a sliding reference contour can result in different ratings. The test lab will generally use the most advantageous graph in the test report. This will be the one with the highest STC or OITC rating that falls within the parameters of the deficiencies. This rating, however, may not be the one with the lowest total of deficiencies or the one closest to the reference contour. With that in mind, one can see STC expressed as a ‘single’ number does not necessarily mean it is the ‘only’ number available.

The five graphs in Figure 4 show how the STL remains constant while the reference contour is shifted up or down to determine STC. It is important to remember the STC is the point at which the reference contour (not the STL contour) intersects at 500 Hz. This means even though the STL at frequencies is identical in the five graphs, the sample could have multiple STC ratings depending on the variation parameters. For example, the maximum STC (complying with ASTM E413) of the assembly is 43 (with 30 deficiencies) in the graph in Figure 4a. If an STC of 44 is attempted—as shown in Figure 4b—the result is a failure at 42 deficiencies and nine deficiencies at 160 Hz.

The highest STC values with the lowest total deficiencies are:

  • STC 42, with 21 deficiencies as in Figure 4c;
  • STC 41, with 14 deficiencies as in Figure 4d; or
  • STC 40, with eight deficiencies as in Figure 4e.

STC ratings below 40 result in a lower number of deficiencies when the sound transmission coefficient is the only determining factor. This should demonstrate the rating method has far less reliability than what is associated with fire door ratings where the time and temperature curve is more consistent.

STCDoors_Figure 4a-4e

A: In this two contour chart, the cyan is STC 43 with 30 deficiencies, while the dark blue represents STL 41—both are at 500 Hz, as are all of the other Figure 4 graphs. B: Cyan is STC 44 with 42 deficiencies, and dark blue is STL 41. C: Cyan reprents STC 42 with 21 deficiencies, and dark blue remains as STL 41. D: The cyan line plots STC 41 with 14 deficiencies; dark blue is STL 41. E: Cyan is STC 40 with eight deficiencies; dark blue is STL 41.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Myth 4: “It is fine to continue putting STC-rated door assemblies in Section 08 10 00.”
Under MasterFormat, Sections 08 11 13–Hollow Metal Doors and Frames, 08 12 13–Hollow Metal Frames, and 08 13 13–Hollow Metal Doors, are intended to describe common applications of swinging hollow metal (e.g. steel) doors and frames. Not all manufacturers capable of fabricating hollow metal doors and frames are also capable of fabricating acoustic door assemblies, especially those over STC 35. They may also not have the up-to-date testing data and technology to fabricate such specialized products. This could lead to a litany of exclusions or qualifications at bid time; difficult to manage and compare for any distributor or general contractor.

The correct section to specify acoustic door assemblies is 08 34 73–Sound Control Door Assemblies, as this incorporates the latest in acoustic door assembly standards (e.g. American National Standards Institute/ National Association of Architectural Metal Manufacturers Hollow Metal Manufacturers Association [ANSI/NAAMM HMMA] 865, Metal Doors and Frames) that describe qualifications, details, and requirements for this specialized product. This ensures the project benefits from the expertise of manufacturers who are familiar with sound control and have conducted a sufficient number of tests in various configurations.

Myth 5: “STC-rated assemblies can do everything other doors can do.”
In order to perform the specialized performance functions required of STC-rated assemblies, the internal construction of doors must be of sufficient mass or innovative design. In some cases, this may conflict with other performance requirements such as fire ratings, universal accessibility, security, life safety, or wind loads.

Documents such as the aforementioned HMMA 865—or HMMA 850, Fire-rated Hollow Metal Doors and Frames, and Steel Door Institute (SDI) 128, Guidelines for Acoustical Performance of Standard Steel Doors and Frames—contain design or other information useful in determining which performance functions are the most important to the project. For example, an STC-rated door assembly also required to have a 1 ½-hour fire rating might be located in an area where a 20-minute fire rating suffices. An STC-rated door assembly where the entire project is also specified as meeting accessibility needs may be in a critical sound-control room where the accessibility is not the main function.

Qualified manufacturers of these specialized products should be well-equipped to discuss and resolve such conflicts so the specifier can decide which is the most critical to the individual opening.

The windows and door for this West Point recording studio needed to meet certain sound requirements.

The windows and door for this West Point recording studio needed to meet certain sound requirements.

West Point University Recording Studio STC Windows

 

 

 

 

 

 

 

 

 

 

Myth 6: “The STC of the installed opening will have the same STC as the lab test.”
Documents like HMMA 865 and SDI 128 quite clearly dispute this myth. When tested in a lab according to ASTM E90, the instrumentation, room size, calibrations, ambient conditioning, humidity, or other factors—in addition to the installation of the test samples—must be controlled within established parameters. Pre-test inspections and adjustments are common. Such stringent controls are not feasible at the project site.

Although there are accepted standards for ‘field testing’ of STC, the results of such tests could be five to 10 points less than the lab-tested STC.

Conclusion
To be clear, this article does not intend to propose totally replacing the historic STC rating method. It does, however, introduce the option of specifying acoustic assemblies by using a sound transmission loss method at a certain frequency or range of frequencies for special situations. It is important to remember—unlike the STC rating method, the STL lab-tested data does not change.

Edward Wall Jr. is the president of MegaMet Industries, located in Birmingham, Alabama. He was nominated to the technical committee and then the executive committee of (NAAMM’s) Hollow Metal (HMMA) division. Wall is now closing in on two decades of manufacturing hollow metal and developing specialty door products. He can be reached at ewalljr@megametusa.com.

Allan C. Ashachik is an independent consultant, providing services to steel door and frame manufacturers. Since entering the industry as a pencil and T-square detailer in 1968, he has been involved in all aspects relating to steel doors and frames from detailing to final quality assurance in acoustic, windstorm, detention, and fire-protective applications. Ashachik is the 2006 recipient of the A. P. Wherry Award, issued by the Steel Door Institute (SDI) to recognize individuals who have made outstanding contributions to the progress of standard steel doors. He can be reached via e-mail at aashachik@neo.rr.com.

New Arkansas Music Pavilion Opens on a Good Note

This photo shows a view of the Arkansas Music Pavilion at night. The polytetrafluoroethylene (PTFE) cone structures come to life with lighting, while at the same time protect concert attendees. Photos courtesy Birdair

This photo shows a view of the Arkansas Music Pavilion at night. The polytetrafluoroethylene (PTFE) cone structures come to life with lighting, while at the same time protects concert attendees. Photos courtesy Birdair

by Doug Radcliffe

Walton Arts Center (WAC) purchased the Arkansas Music Pavilion (AMP) in February 2011 with the goal of expanding the venue to serve a broader and more diverse audience. The AMP operated at the Washington County Fairgrounds after moving from the Northwest Arkansas (NWA) Mall in 2012. However, after seeing a 200 percent increase in ticket sales in 2012, it was clear a permanent site was required to meet the region’s growing need for arts and entertainment. Further, the lack of a roof meant numerous event cancellations due to weather.

In 2013, the Walton Arts Center council approved plans to build a mid-sized, permanent outdoor amphitheater to attract headlining artists and bigger audiences to Northwest Arkansas. As part of a multi-campus expansion in the region, the new Pinnacle Hills venue serves as a major stop for touring concerts in the mid-south.

The new location, in the city of Rogers, has everything WAC was looking for in a permanent venue, including proximity to a major freeway, multiple access points, ample parking, and a supporting infrastructure. This improvement, as well as the 519-m2 (5590-sf) stage, upgraded technical capacities, an artist lounge, and production offices, is expected to attract bigger acts to the venue. The new AMP will also draw in larger crowds with its seating capacity of more than 6000 people, parking, upgraded concessions, and air-conditioned restrooms.

A look up at the three PTFE cone structures supported by steel.

A look up at the three PTFE cone structures supported by steel.

An orchestrated effort
Architecture firm CORE, Tatum-Smith Engineers, general contract consultant David Swain, and Crossland Construction worked to complete this project. A tent-like, weather-resistant covering for the stage was specified. The three-cone and four-inverted-cone-shaped structure is made of a fabric polytetrafluoroethylene (PTFE) fiberglass membrane, with steel supports. PTFE coats a woven fiberglass to form a durable, weather-resistant membrane.

Raising the roof
The AMP’s three-cone shaped structure creates an open, inviting space. PTFE fiberglass membranes can be used to construct roofs, façades, freestanding buildings, skylights, or accent enclosures.

Fabric roof forms are curved between supporting elements in a manner reflective of the flow of tension forces within the membrane. With the exception of air-supported structures, these curvatures are anticlastic in nature. The curving forms of fabric roofs have dramatic appeal. Another attractive feature of tensioned fabric structures is the enormous range of spanning capability. The aesthetic features and the long-span ability of fabric are particularly appropriate for entertainment facilities like the AMP.

Fabric structures are not only visually appealing, but also environmentally responsible and economically competitive. PTFE fiberglass membrane is Energy Star and Cool Roof Rating Council (CRRC)-certified. PTFE fiberglass membranes reflect as much as 73 percent of the sun’s energy, and certain grades of PTFE membrane can absorb 14 percent of the sun’s energy while allowing 13 percent of natural daylight and seven percent of re-radiated energy (solar heat) to transmit through.

The lightweight membrane also provides a cost-effective solution requiring less structural steel to support the roof or façade, enabling long spans of column-free space. Additionally, the tensile membrane offers building owners reduced construction costs and maintenance costs compared to traditional building materials.

DCRDoug Radcliffe has more than 28 years’ experience in steel, glass, and membrane manufacturing, project management, engineering, and construction business. During his career, he has been an integral member of design-build teams for high-profile construction projects of all sizes. Radcliffe is a tensile architectural systems expert at Birdair. He can be reached at sales@birdair.com.