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3.4 Special Design Considerations

Incorporation of Recycled-Content Materials
GSA is committed to maximizing the use of recycled content materials specified in the construction of federal building projects. Many commonly used products are now available with recycled content including steel, aluminum, concrete, masonry, acoustic tile, paint, carpet, ceramic tile, and insulation.

To support markets for the materials collected in recycling programs, the Resource Conservation and Recovery Act requires agencies to buy recycled-content products designated by EPA. Through the Comprehensive Procurement Guidelines (CPG), EPA designates items that must contain recycled materials when purchased by federal agencies, or government contractors, using appropriated federal funds.

The CPG items listed in table 3-3 are frequently found in buildings. Product specifications and standards that might exclude the use of recovered materials should be revised to allow the use of these items.

Table 3-3 Examples from the CPG List of Designated Products

Building Insulation Thermal insulation made from recovered materials is available in several forms including rolls, loose-fill, and spray foam. Insulation can include a range of recovered materials such as glass, slag, paper fiber, and plastics.

Carpet Recycled-content polyester carpet is available for light- and moderate-wear applications. Recycled fiber polyester carpet is manufactured from PET recovered soda bottles.

Carpet Cushion Carpet cushion, also known as carpet underlay, is padding placed beneath carpet. Carpet cushions made from bonded urethane, jute, synthetic fiber, and rubber can be made from recovered materials.

Cement and Concrete Coal fly ash and ground granulated blast furnace (GGBF) slag are recovered materials that can be used as ingredients in cement or concrete. Coal fly ash is a byproduct of coal burning at electric utility plants. Slag is a byproduct of iron blast furnaces. The slag is ground into granules finer than Portland cement and can be used as an ingredient in concrete. The level of coal fly ash in concrete typically ranges from 15 to 35 percent of total cementitious material, but can reach 70 percent for use in massive walls and girders. The level of GGBF slag usually ranges from 25 to 50 percent.

Reprocessed and Consolidated Latex Paints For Specified Uses Reprocessed paint is postconsumer latex paint that has been sorted by a variety of characteristics including type (i.e., interior or exterior), light and dark colors, and finish (e.g., high-gloss versus flat). Reprocessed paint is available in various colors and is suitable for both interior and exterior applications.

Consolidated paint consists of postconsumer latex paint with similar characteristics (e.g., type, color family, and finish) that is consolidated at the point of collection. Consolidated paint is typically used for exterior applications or as an undercoat.

Structural Fiberboard and Laminated Paperboard Structural fiberboard is a panel made from wood, cane, or paper fibers matted together which is used for sheathing, structural, and insulating purposes. Laminated paperboard is made from one or more plies of craft paper bonded together and is used for decorative, structural, or insulating purposes. Examples of these products include building board, insulating formboard, sheathing, and acoustical and non-acoustical ceiling tile.

Floor Tiles and Patio Blocks Floor tiles for heavy duty or commercial specialty applications can contain up to 100 percent postconsumer rubber. Floor tiles containing 90 to 100 percent recovered plastic are also readily available. Patio blocks made from 90 to 100 percent recovered plastic and 90 to 100 percent postconsumer rubber are used for walkways and trails.

Shower and Restroom Dividers / Partitions Shower and restroom dividers/partitions are made of 20 to 100 percent recovered plastic or steel. They are used to separate individual shower, toilet, and urinal compartments in commercial and institutional facilities.

Signage Signs made from recovered materials are used inside and outside of office buildings and other public places. EPA’s designation pertains to plastic signs used for nonroad applications and covers any associated plastic or steel supports.

Concrete
Because concrete is one of the most widely used building products, incorporation of recycled materials that do not impact strength may make a substantial contribution to the nation’s recycling effort.

The following is a list of specifications for cement and concrete containing recovered materials:

Cement Specifications:

  • ASTM C 595: Standard Specification for Blended Hydraulic Cements.
  • ASTM C 150: Standard Specifications for Portland Cement.

Concrete Specifications:

  • ASTM C 618, “Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete.”
  • ASTM C 311, “Standard Methods of Sampling and Testing Fly Ash and Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete.”
  • ASTM C 311, “Standard Methods of Sampling and Testing Fly Ash and Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete.”
  • ASTM C 989, “Ground Granulated Blast-Furnace Slag for Use in Concrete Mortars.”
  • American Concrete Institute Standard Practice ACI 226.R1. “Ground Granulated Blast-Furnace Slag as a Cementitious Constituent in Concrete.”

Acoustics
The standards in this section have been established to ensure adequate acoustic qualities in federal buildings.

Design Criteria for Building Spaces. Every element of a built space, including its shape, surfaces, furniture, light fixtures, and mechanical systems contribute to its acoustical characteristics. Four key concepts govern the perceived quality of office acoustics.

  • Appropriate levels of speech privacy. Speech privacy refers to the degree to which a conversation cannot be overheard in an adjacent space. Lawyers, doctors, human resources officers, executives and others whose position requires them to discuss sensitive information require confidential speech privacy, that is, a setting where, when a door is closed, the content of a conversation cannot be overheard. Professional staff members whose position requires extended periods of concentration require normal speech privacy, where the content of conversation in adjacent spaces cannot be overheard without making an effort, providing freedom from distraction. Little or no speech privacy is needed for receptionists, clerical staff, and team oriented workgroups where overheard conversation can actually be beneficial.
  • Appropriate levels of background sound. Continuous background sound in offices is mostly generated by heating, ventilation, and air conditioning (HVAC) equipment. In conference spaces, courtrooms and auditoria, it is important that this background sound not interfere with the intelligibility of speech. In enclosed offices, HVAC background sound is an important component in achieving the required level of privacy because it helps to cover up or “mask” speech transmitted between adjacent spaces. In open plan areas, the background sound provided by contemporary HVAC equipment is often not uniform and/or does not have the tonal balance and loudness needed to mask speech transmitted between adjacent cubicles. For this reason, additional electronic background noise or sound masking is often deployed in these areas.
  • Control of intrusive noise, vibration, and reverberation. Office equipment generating noise levels above the background should be located away from primary work areas or should be surrounded by acoustically isolating panels. Noise induced by mechanical equipment should be controlled through vibration isolation devices, appropriate placement of equipment and noise attenuators in ducts. Reverberation and echoes must be controlled in courtrooms, auditoria, conference, team, and training room spaces. Sound absorbing materials are used to help control reflected sound energy and echoes. Particular attention must be paid to rooms with parallel walls (causes "flutter" echoes) and rooms with curved or concave ceilings (leads to acoustical focusing effects).
  • Isolation from exterior noise sources. Buildings located near airports, highways, rail corridors or other sources of significant environmental noise levels must have exterior wall and window assemblies controlling noise intrusions.

Parameters Used in Acoustical Design. The following parameters are used to specify acoustical standards for GSA buildings:

Background Noise. The continuous noise within a space. The loudness of noise is quantified by several assessment schemes, including noise criteria (NC), balanced noise criteria (NC-B) and room criteria (RC) contours. These contours are published in the ASHRAE Handbook of Fundamentals. Lower values are quieter.

Noise Isolation. The amount of noise transmitted through the perimeter boundary elements of a space. Sound transmission class (STC) describes the sound insulating performance of building elements such as walls, windows, and doors when tested in accordance with ASTM E90. Ceiling attenuation class (CAC) quantifies the sound insulating performance of a ceiling assembly spanning across rooms that share a common plenum when tested in accordance with ASTM E1414. Impact insulation class (IIC) describes the impact sound insulating properties of a floor/ceiling assembly when tested in accordance with ASTM E492. Greater STC, CAC or IIC values represent better performance.

Sound Absorption. The amount of sound absorbed by a surface finish. Sound absorption average (SAA) quantifies the efficiency of a material in absorbing sound energy when tested in accordance with ASTM C423 (SAA replaces the earlier noise reduction coefficient or NRC). SAA/NRC is a single number rating between 0 and 1. Greater SAA/NRC values represent a more effective sound absorber. An excessive amount of reflected sound (reverberation) tends to degrade speech communication.

Speech Privacy. This parameter refers to the lack of intelligibility in a space adjacent to the location where a conversation is occurring. Articulation index (AI) quantifies the degree of speech clarity when tested in accordance with ASTM E1130. AI is a single number rating between 0 and 1; lower AI values mean fewer words can be understood, indicating increased privacy.

Design Criteria for Building Spaces. Acceptable acoustics are determined by the use of a space and the requirements of its occupants. It is the responsibility of the design team to meet the following minimum standards governing the acoustical performance of various space usage categories.

Class A1. This category describes critical, noise-sensitive spaces that must provide optimum speech intelligibility—including auditoria, teleconference facilities and courtrooms. The acoustical treatment of these spaces shall be designed by a qualified acoustical consultant or specialist approved by the GSA project manager. The acoustical design should based on an analysis of the user’s needs and a design brief shall be prepared for review by the GSA project manager. Pre-occupancy testing shall verify that the acoustical performance has been achieved. Note: U.S. court facilities must be designed in accordance with Chapter 9 of this document: Design Standards for U.S. Courts Facilities.

Class A2. Enclosed spaces where meetings take place, including conference and training rooms. HVAC background noise shall not exceed NC/RC 30. Supply and return air systems shall be designed to control speech sounds transmitted between spaces. Partitions enclosing Class A2 space shall have a minimum STC of 50 and extend from the floor to the deck above the finished ceiling. Doors to corridors shall be gasketed. Doors or operable partitions dividing spaces into smaller subspaces shall have a minimum STC of 50. A minimum of 25% of wall surfaces and 50% of ceiling surfaces shall
incorporate sound-absorptive materials with a minimum SAA/NRC of 0.75.

Class B1. Enclosed spaces requiring confidential speech privacy, including judicial chambers, medical examination rooms and certain private offices. The acoustical treatment of these spaces shall be designed by a qualified acoustical consultant or specialist approved by the GSA project manager in order to provide a ‘confidential’ level of speech privacy. The design criteria for Class A2 spaces may be substituted in lieu of design assistance by an acoustical consultant.

Class B2. Private offices requiring normal speech privacy. The acoustical treatment of these spaces shall be designed with the assistance of a qualified acoustical consultant or specialist in order to provide a ‘normal’ level of speech privacy. The following design may be substituted in lieu of design assistance by an acoustical consultant:

(1) HVAC-related sound shall not exceed NC/RC 35;
(2) Supply and return air systems shall be designed to control speech sounds transmitted between spaces;
(3) Partitions enclosing Class B2 spaces shall have a minimum STC of 45 and all corner/ceiling/floor connections shall be sealed with acoustical caulk;
(4) Acoustical ceiling shall have a minimum SAA/NRC of 0.65 and a minimum CAC of 35;
(5) HVAC background noise or electronic sound masking shall generate a continuous minimum noise level of NC/RC 30.

Class B3. Open plan and shared offices requiring normal speech privacy. The acoustical treatment of these spaces shall be designed with the assistance of a qualified acoustical consultant or specialist in order to provide a ‘normal’ level of speech privacy. Pre-occupancy testing shall verify that a maximum AI of 0.20 has been achieved.

Class B4. Open plan and shared offices where speech privacy is not required. HVAC background noise shall not exceed NC/RC 40. A minimum of 25% of wall surfaces and 80% of ceiling surfaces shall incorporate sound absorptive materials with a minimum SAA/NRC of 0.75. Wherever possible, carpeted floors shall be used.

Class C. Areas where people assemble and converse, including dining rooms, lunchrooms, lobbies and atria. When located adjacent to Class A or Class B space, partitions enclosing Class C space shall extend from the floor to the deck above the finished ceiling and have a minimum STC of 50. A minimum of 25% of wall surfaces and 80% of ceiling surfaces shall incorporate sound-absorptive materials with a minimum SAA/NRC of 0.65.

Class D1. Occupied space where speech privacy is not a significant consideration, including internal corridors, mailrooms and file rooms. For corridors adjacent to open plan areas, a minimum of 80% of ceiling surfaces shall be treated with sound-absorptive materials having a minimum SAA/NRC of 0.65.Wherever possible, these same corridors shall be carpeted.

Class D2. Support spaces including fire stairs, toilets and locker rooms.Where possible, Class D2 spaces should not be placed adjacent to Class A and Class B spaces. When Class D2 spaces must be located adjacent to Class A or Class B space, partitions enclosing Class D2 space shall have a minimum STC of 50 and extend from the floor to the deck above the finished ceiling.

Class E. Spaces where concentrations of noisy equipment are located, including Automated Data Processing areas, computer equipment facilities, and rooms containing high-speed copiers.Where possible, Class E spaces should not be placed adjacent to Class A and B spaces.When Class E spaces must be located adjacent to Class A or B space, partitions enclosing Class E space shall have a minimum STC of 50 and extend from the floor to the deck above the finished ceiling. A minimum of 25% of wall surfaces and 100% of ceiling surfaces shall be treated with sound-absorptive materials with having a minimum SAA/NRC of 0.55.

Class X. Warehouses, parking garages, kitchens and spaces where noisy operations are performed. Other examples include elevator machine rooms, trash compactor rooms, mechanical and electrical /telecommunications equipment rooms.Where possible, Class X spaces should not be placed adjacent to Class A and B spaces.When Class X spaces must be located adjacent to Class A or B space, partitions and floor/ceilings bounding Class X space shall have a minimum STC/IIC of 60. The bounding partitions shall extend from the floor to the deck above the finished ceiling. Mechanical equipment in Class X spaces shall control vibration transmitted into the building systems. When Class X spaces are continuously or intermittently occupied, wall and/or ceiling surfaces shall be treated with sound absorptive materials to help reduce the risk of hearing damage as prescribed by the Occupational Safety and Health Administration (OSHA).

Acoustical criteria for specific types of spaces are described in Table 3-4. A description of these types of spaces follows.

Emergency Protection
Federal law requires that federal buildings provide protection suitable for emergency shelters within program and budgetary limits. The program will state if shelters are required on a given project. Emergency shelters are not designated building spaces; they are spaces used for other purposes that can serve as shelters in an emergency.

Shelter locations should be identified during the early stage of design. The optimum shelter location is below grade. Basement levels, including underground parking facilities, offer good protection.

Table 3-4 Acoustical Criteria by Type of Space

Class of Space/Typical Uses
 
Maximum NC Maximum Leq Lmax Maximum
Mid-frequency
RT60
Minimum NRC of
absorptive ceiling
materials/minimum %
of ceiling surface
Minimum NRC of
absorptive wall
materials/minimum %
of wall surface1
Minimum STC Performance
Between Adjacent Spaces
Class A, B
space Adjacent
Class C, D, E, F, or X
Adjacent
Class A12
Auditoria, teleconference facilities, courtrooms
20 30 40 1.0 0.8/
50%
0.8/
25%
55 55
Class A2
Meeting rooms
25 35 45 1.0 0.8/
50%3
0.8/
25%
50 50
Class B1
Private offices, confidential speech privacy
30 40 50 N/A N/A 0.8/
25%
50 50
Class B2
Private offices, normal speech privacy
30 40 50 N/A N/A 0.8/
25%
384 384
Class B3
Open plan offices
40 50 60 N/A 0.8/
100%
0.8/
25%
28 384
Class C
Lunchrooms and lobbies
40 50 60 N/A5 0.65/
50%
0.8/
25%
N/A 384
Class D1
Corridors, mail and file rooms
45 55 65 N/A 0.65/
100%6
0.8/
25%
N/A 384
Class D2
Toilets, locker rooms, stairs
45 N/A N/A N/A N/A N/A N/A N/A
Class E
Office equipment rooms
45 N/A N/A N/A 0.65/
100%
0.8/
25%
N/A N/A
Class F
Warehouses and parking
N/A N/A N/A N/A N/A N/A N/A N/A
Class X
Kitchens and bldg. equipment
N/A N/A N/A N/A N/A7 N/A7 N/A N/A
1 These percentages may be reduced or eliminated if the walls are not parallel and/or there are bookcases, louvered doors, or other materials that will diffuse sound. Absorptive materials must be located a minimum of 4 feet above finished floor level. In Class A and B1 spaces, absorptive materials should be located on two adjacent walls, one of which should be the rear wall.
2 These are baseline standards. Criteria for Class A1 spaces must be established by an acoustical consultant or specialist based on an analysis of the user’s needs. Technical documentation of these criteria shall be submitted as part of design documentation, and used to verify performance prior to occupancy of space.
3 65 NRC may be used if it absorptive material covers 100% of ceiling.
4 Satisfied by standard wall: 3 5/8” metal stud, 2” batt insulation, 1 layer 5/8” gypsum board each side, all perimeter connections (corner/ceiling/floor) sealed with acoustical sealant. Walls that terminate at underside of suspended ceiling: ceiling must have a minimum CAC of 35 with 2” batt insulation above or be constructed of gypsum board. Open return air plenum not permitted without acoustical boot.
5 In lobbies where speech will occur, 1.0.
6 Absorptive ceiling materials for Class D1 spaces are required only for corridors adjacent to open plan areas, but are recommended where practical for all corridors and file rooms.
7 Sound absorbing materials as required in occupied spaces to protect employees from hearing damage as prescribed by
OSHA.

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