Week 11: Chapter 10- Indoor Environmental Quality: Acoustic and Indoor Air

 Chapter 10

Indoor Environmental Quality: Acoustics and Indoor Air 

In Chapter 10 we learned how to locate open offices for minimal sound transmission and be able to meet client needs for speech privacy and discuss the impacts of LEED on acoustics and indoor air quality. We also learned to Describe the importance of good indoor air quality to the health, safety, and welfare of building occupants, how to specify sustainable materials that support good indoor air quality and  identify acoustical needs in space and how to accomplish acoustic separation goals

According to the Center for Disease Control, “Indoor Environmental Quality (IEQ) refers to the quality of a buildings environment in relation to the health and wellbeing of those who occupy the space within it.” It includes acoustics, air quality lighting, and other interior factors. This chapter addresses indoor air quality and acoustics as lighting has been addressed in a previous chapter. Although many of these topics have been addressed in previous chapters, this chapter will address the specifics of acoustics and indoor air quality each as well as their impact on the health, safety, and welfare of building inhabitants and their relationship to sustainability.

Acoustics

• Acoustics is the study of sound. How sound moves through a space is a function of the shape of the space and the materials and finishes used within it. Unwanted sound is called noise.
•  It is the responsibility of the interior designer to anticipate possible sources of noise and to design spaces that control this potential noise. Privacy is a specific need within interior spaces that can only be provided when sound is blocked from one space into the next.
• Sound is generated in pressure oscillations that produce waves and can be measured in hertz (Hz). A receiver, such as an ear, receives the pressure and then the sound is heard. The range of detectable sound to humans is between 20 and 20,000 Hz. Frequencies below 20 Hz are called infrasonic and above 20,000 Hz are called ultrasonic.
• Similar to light, sound travels in waves and is, therefore, subject to certain phenomena. Sound waves can be refracted, reflected, diffracted, and diffused. Reflection refers to the return of sound from a surface. As with light waves, a reflected sound wave is mirrored back into the space. 
• Similar to light waves, sound waves can be bent when traveling through a medium, which changes the speed of the sound. Temperature changes can cause this change in speed. Diffraction refers to a sound waves capability to bend around a barrier or through an opening. 
• Diffusion of a sound wave occurs when the wave encounters an uneven surface and produces a random sound distribution.
• In an interior space, walls, floors, and ceilings are detailed to reduce sound transmission to adjacent spaces. Absorbent surfaces help to reduce noise within a space.
• Sound pressure is measured in decibels (dBA). The limit of human comfort is about 110 to 120 decibels. Values higher than this can cause permanent damage to the ear. The Occupational Safety and Health Administration (OSHA) requires that hearing protection be used when the noise level reaches 85 decibels. Further, a sustained 80 decibels over an 8-hour day can lead to permanent hearing loss.

Principles of Sound: Control

Unwanted sound waves can be absorbed. Absorption describes the process by which a sound energy is converted into heat. Part of the sound moving through a partition will be absorbed by the partition. All materials absorb some sound. Typical materials will also be rated with a noise-reduction coefficient (NRC). Based on ASTM Standard C423, NRC is the arithmetic average of a material’s absorption coefficient at 250, 500, 1000, and 2000 hertz (Hz). This is the average of the Sound Absorption Coefficient or SAC values. The SAC refers to how much a material can absorb sound on a scale of 0-1. With a value of 0 no sound is absorbed and with 1 all sound is absorbed (thus both are theoretical). Examples of NRC coefficients range from 0.00 to 0.35 that are considered reflective materials to 0.35-1.0 that are absorptive. Table 10.2 shows some typical NRC values for interior materials. It should be noted that NRC values are only valid between 250 and 2000 Hz.

Insulation is commonly used to absorb sound. Like NRC, all material assemblies have a sound-transmission class (STC). In accordance with ASTM E413, the STC refers to the capability of a material to absorb sound and takes into account the entire frequency spectrum and the associated transmission loss (TL) to provide a single number that describes sound transmission for typical human hearing. This single rating takes all frequencies into account and has no unit of measurement. Table 10.3 displays some wall-construction STC ratings.

Sound waves can also be bent. Redirection refers to purposely directing sound waves into a new direction. This is desirable in a room where uniform hearing is desired from all locations, such as a lecture hall or classroom.

Reverberation Time

Reverberation describes the sound that is built up in a room over time (echo). This sound can actually begin to distort what is heard if it builds up too much. Reverberation can be controlled and different reverberation times (RT) are preferred for different facility types. Reverberation time is extremely important when designing auditoriums, classrooms, lecture halls, music rooms, and performance facilities.

Principles of Room Design

The primary goal of acoustical design within most spaces is to achieve some level of speech privacy for the occupants. Table 10.4 shows typical sound privacy ranges and the required STC values between spaces.

Partitions

Sound waves travel with little difficulty directly through wall studs from one room to another. Breaking the path of travel of the sound wave can prevent this transmission of sound. Staggered wall studs will help prevent this direct transfer.

Room Volumes

Generally speaking, the designer should keep the room volume low when low reverberation times are desired. For example, in music performance halls and other spaces that need higher reverberation times, larger spatial volumes are desirable. In order to avoid unexpected sound problems, avoid concave forms that tend to focus sound waves to one point while defocusing others. Avoid reflective surfaces near the rear walls of an auditorium or theater and use them near the stage to enhance the performers’ ability to hear one another.

Privacy

The open-office configuration poses a variety of acoustical challenges with regard to both noise and privacy. Noise-reduction methods include controlling noise at the source, in its path or at the receiving end. Open-office acoustical partitions can also be used to reduce unwanted sound between workstations. These systems work best when proper layout is combined with sound-masking white noise and acoustical ceiling tiles. To effectively block unwanted voice transmission, partitions need to be at least five feet high. A six-foot high partition provides a higher sense of privacy, whereas a partition lower than four feet in height cannot prevent sound travel from one cubicle to the next.

Acoustical Partitions (Open Office)

One of the biggest challenges a designer must face is how to control the acoustics in an open-office environment. Several systems furniture manufacturers produce a variety of products to assist with this type of design. The layout of the actual workstations is left to the designer; this determines if the acoustical panels will function effectively.

Acoustical Insulation in Partitions

Of particular importance in an office environment is the sound separation of human resources spaces and conference rooms, where personal information could be revealed and confidential conversations may take place. These rooms can be easily sound- insulated using a variety of techniques, including full-height partitions extended to the underside of the structural deck above, acoustical ceilings, and walls with insulation.

Acoustical Ceilings

Acoustical ceiling tiles are rated using a Ceiling Attenuation Class (CAC). The ceiling is often a primary surface used to control noise and sound transmission within a space.

Medical Facilities

Health Insurance Portability and Accountability Act (HIPAA) privacy requirements demand that personal medical information be protected. As a result, hospitals have had to institute new methods for patient check-in and release within the medical environment. Sound-separation for these areas can be achieved through the use of dividers at the check-in desk or through separate check-in rooms.

Noise

Studies show that unwanted noise can lead to a variety of health problems. According to a recent article in Environmental Health Perspectives (EHP) about the results of a report from the National Institute of Public Health in the Netherlands, which looked at 500 studies of the health effects from noise exposure, "Noise exposure can lead to small increases in blood pressure readings and possibly even increases in cardiovascular disease prevalence. . . .” The article goes on to associate noise with the following physiological effects: hearing loss, myocardial infraction, hypertension, ischemic heart disease, angina pectoris, and other maladies. (Weinhold, 2002, 151) A May 1998 EHP article listed some of the chronic effects of environmental noise: waking during the night, bad mood next day (depressed and irritable), ischemic heart disease, psychiatric disorders, annoyance, and poor performance by students with learning disabilities or who used English as a second language (EHP, May 1998, 222).

Passchier-Vermeer and Passchier explain that exposure to noise causes health risks. These risks can include hearing loss, annoyance, heart disease, sleep disturbance, and decreased performance. They suggest that irreversible cognitive impairment in children makes this an important subject for future research. (EHP, March 2000, 123)

Sound-separation

Interior materials have different sound-absorption qualities. Generally, carpeting, acoustical ceiling tiles, and textiles are the most absorbent finishes. From a sustainability point of view, all interior materials should be chosen with regard to their life-cycle properties rather than by performance alone. Many developments in both the carpet and textile industries have made the use of sustainable materials much easier. Several manufacturers will also take the products back after their useful life.

Diffusion in Rooms: Sound-transmission Coefficient (STC)

Different types of spaces need different levels of acoustical control.

Different partition types can achieve these differing acoustical separations. Figures 10.13 through 10.15 show examples of three wall sections composed of sustainable materials that meet STC requirements ranging from 45 to 55.

Special Circumstances

Mechanical systems and heavy equipment are two sources of noise in a building. The noise produced by air ducts can be reduced through proper insulation of the ductwork instead of the use of an open plenum return above the ceiling. Equipment noise can be reduced through a combination of sound insulation between the equipment and other spaces as well as through the use of vibration-dampening materials.

Acoustics and Sustainable Design

Recent post-occupancy assessments have examined whether LEED-certified buildings and other buildings claiming to be “green” are meeting user needs. In an article for Architectural Record, “Looking Back and Moving Forward,” author Joann Gonchar (AIA) reveals that one area of frequent dissatisfaction to building users with their new green buildings relates to acoustics. Specifically, in an effort to make natural light available to all occupants, partitions were lowered and acoustical privacy was lost. Thus, when designing for natural light, other strategies besides simply lowering partition heights must be explored to maintain occupant satisfaction levels in other areas. Although the article did not explore these other options, some solutions might include a central light source from a light well, the use of light shelves to bring natural light further into the space, and locating open offices near the perimeter of the building.

In his article “Acoustic Design for Green Buildings” for the Environmental Design and Construction Magazine, Kenneth Roy proposes a solution for acoustical design in green buildings. Specifically, he addresses the new trend for exposed wide-open plans. For this type of space, he recommends acoustical clouds and canopies over specific areas to address noise and privacy issues. Acoustical clouds are flat and come in sizes up to 14 feet by 14 feet, whereas canopies are smaller and curved. Roy also recommends that credits be included in the LEED Rating Systems for acoustical control that would help avoid these problems in future green buildings.

An Approach to Green Acoustics

According to the Whole Building Design guidelines for sustainable acoustics, an integrated design approach should be used to achieve both sustainability goals and acoustical needs. An integrated approach starts with the initial selection of the site. For some building types such as office buildings and educational facilities, the building needs to be located away from high noise areas such as highways, train tracks, airports, and other high-noise-generating sources. If site selection is not possible, noise can be combated using sound control measures, avoiding through wall air-conditioning units, and orienting spaces requiring more quiet away from the noise source. Further recommendations include using an acoustical ceiling with a noise criteria rating (NC) of 0.75, using 60-inch-high partitions, avoiding light fixtures directly over partitions and locating copiers in a separate space. The Noise Criteria (NC) define appropriate maximum levels of noise for specific spaces. Having ducted air returns (instead of an open plenum) and walls that extend to the underside of the structural deck with insulated cavities to raise the STC also assists in making for quieter spaces. To prevent sound transfer from one space to the adjacent one, avoid placing doors next to one another or directly across from each other.

Acoustical solutions can include acoustical ceiling tiles, carpeting and insulation made of recycled content. Several companies also recycle these materials at the end of their life.

The International Green Construction Code 2018

Chapter 8 of the IGCC addresses Indoor Environmental Quality including Acoustical Control. The IGCC addresses acoustical control with regard to the building envelop and interior spaces, including interior background noise requirements.

Indoor Air Quality (IAQ)

Humans spend 90 percent of their life inside of a building. It has been shown that indoor air can contain two to five times more pollutants than outside air. New construction can have as much as 1000 times the acceptable level of indoor pollutants. As air recirculates in a building, the level of pollutants increases. The quality of the air inside of a building (indoor air quality, or IAQ) is impacted by several factors: the HVAC system, access to natural ventilation, the interior materials, the interior furniture, fixtures, and equipment and moisture within a building. Indoor pollutants consist of undesirable substances that make their way into the air supply. These include volatile organic compounds (VOCs) released by indoor products (also known as off-gassing), biological contaminants, minerals, radiation, metals, and water vapor that can lead to mold spores. Proper mechanical design and ventilation are critical to providing fresh air within a space. Although the interior designer does not design the HVAC system, he/she is responsible for interior finishes, fixtures, furnishings, and equipment, and can thus greatly impact the quality of the indoor air quality.

Indoor environmental quality (IEQ) volatile organic compounds may be released into the air by a variety of typical interior furnishings and finishes including new furniture, carpeting and paint. In addition to VOCs, there are several other possible sources of indoor air pollution within a building. These include copy machines, asbestos, cleaners, pesticides, stoves/chimneys/fireplaces, and carbon monoxide that may enter the indoor environment through the use of improperly ventilated appliances including water heaters, furnaces, dryers, and stoves. Mold, radon, and cigarette smoke also add pollution to the indoor environment.

Radon is invisible, tasteless, and odorless, and according to Kerr may be killing as many as 20,000 Americans per year (Kerr, 1988). A by-product of supernovas, or stellar explosions, radon exists in the ground. It is a by-product of radium, and results from uranium decay. Radon is released from the ground and is often found in basements and crawl spaces. The gas tends to concentrate. In high concentrations, it has been linked with lung cancer.

Many indoor materials release odors into the environment in a process known as off-gassing. Some of these may be toxic. These VOCs can be carcinogenic to human beings, thus endangering the health and welfare of the building’s occupants. Building- related illness (BRI) is caused by an accumulation of these indoor pollutants and contributes to sick building syndrome (SBS). BRI can lead to nose, throat, and eye irritation; headaches; nausea; kidney and nervous system damage; and immune system suppression.

ASHRAE (American Society of Heating and Air Conditioning Engineers) Standard 62.1-2010 defines good indoor air quality as “Air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80 percent or more) of people exposed do no express dissatisfaction.” Unfortunately, 90 percent of US chemicals are exempt from federal review and thus cannot be considered known toxins although some might be carcinogenic. Further, 95 percent of materials from manufacturers are considered proprietary and the nature of the chemicals is not public information

Sick Building Syndrome (SBS)

According to researcher Jan A. Stolwijk, “the sick building syndrome (SBS) is defined as the occurrence of an excessive number of complaints by the occupants of a building” (Environmental Health Perspectives, Volume 95, 1991, 99). Among these complaints are a variety of physical discomforts including: nausea, lethargy, dizziness, inability to concentrate, irritation of eyes and throat, and odors. Another term for this type of building condition is tight building syndrome. Biological contaminants found in such buildings include mold and bacteria, whereas chemical toxins include VOCs associated with cleaning materials, furniture, and building materials. Tobacco smoke is another source of irritation in the indoor environment.

Building-related Illness (BRI)

Generally, a small percentage of building occupants experience building-related illnesses. Those with pre-existing conditions are particularly at risk.

Legionnaire's Disease

Perhaps the best-known example of BRI is Legionnaires disease. This disease is associated with buildings that are air-conditioned. When legionella bacteria are allowed to grow within cooling ponds of air-conditioning systems, they can easily be transmitted to building occupants through air ducts. Thus, it is important to drain and treat the cooling pond in addition to regularly maintaining the cleanliness of the ductwork and filters.

Effects

As mentioned earlier in this chapter, poor indoor air quality can lead to a variety of physical symptoms ranging from mild to severe reactions. These include irritation of eyes and throat, dizziness, fatigue, and asthma.

Treatment

The most efficient method of treatment is to remove the source of the contaminants. Improved ventilation and the use of air cleaners and/or air purifiers will also reduce the effect of VOCs.

Selections Criteria

Selecting interior materials and furnishings for good IAQ and sustainability requires that a holistic approach be taken including the use of LEED criteria, VOC content or emissions, life-cycle assessment and the embodied energy of materials.

Life-cycle Assessment

The life-cycle assessment of a material involves looking at all aspects of the life cycle: material extraction, where it is made, transportation costs, how long it lasts, and what happens when it is no longer usable. A complete cradle-to-grave analysis will make it easier to assess the real sustainability of a product.

The embodied energy of a material takes many of these factors into consideration. This is the amount of energy used to create a material from extraction, through production and installation and eventually disposal.

VOC Limits

As a result of LEED and other sustainable design initiatives, the use of materials with VOCs has been rapidly diminishing and is now tracked by manufacturers as well as regulated.

The control of emissions and indoor air quality is an important part of the design, construction and operations and maintenance phases. During construction, material selections and proper ventilation must be addressed to include the healthiest sustainable products possible--preferably those that hold a third-party certification such as Green Seal or Cradle to Cradle. During construction, MERV (minimum efficiency reporting value) 8 ventilation filters should be used and must be replaced following a building flush-out and the completion of the construction phase. A MERV 8 filter has an efficiency of 70 percent at removing particles between 3 and 10 microns in size. A building flush-out requires a building to be opened and aired out prior to occupation.

As a standard part of operations and maintenance, all housekeeping staff must be trained on proper green cleaning of sustainable materials and there should be a set of green procurement guidelines for the building. Periodic indoor air-quality testing then ensures that the building air quality remains healthy for occupants.

The 2018 International Green Construction Code also set VOC limits for adhesives, coatings, ceiling and wall materials. 

Natural Ventilation

While for many years the need for naturally ventilated spaces took a secondary role to safety concerns in building design, the 2012 International Green Construction Code now calls for a minimum amount of natural ventilation in interior spaces. Areas open to the outdoors must include operable windows that equal 4 percent of the total floor space. For example, if the room is 200 square feet, eight square feet of operable window must be provided. Spaces adjoining these must have a total of 8 percent or at least 25 square feet of operable window. Figure 10.17 demonstrates this.

A sustainable indoor air environment has minimal pollutants, controlled microbial and fungal organisms, managed dust accumulations, and good ventilation.

Blogging Assignment

The COVID-19 pandemic has had a mixed impact on indoor air quality, especially when it comes to Sick Building Syndrome (SBS). On the positive side, the focus on preventing the spread of the virus led to improvements in ventilation systems, like better air filtration and the use of HEPA filters, which helped improve air quality in some places. On the downside, with many offices closed and people working from home, HVAC systems weren't always properly maintained, and that lack of airflow could make indoor air worse in some buildings. Plus, the increased use of cleaning products and PPE created more indoor pollutants, which could trigger or worsen SBS symptoms for some people.

https://www.sciencedirect.com/science/article/abs/pii/S0360132322009398