Taking the Guesswork Out of Carpet Performance and Construction Specification
The Performance Standards and Specifications Committee of the Carpet and Rug Institute (CRI) has developed a convenient new tool for specifiers. By referencing appearance-retention ratings, the committee has established carpet-selection guidelines that identify the performance requirements of carpet according to the specific areas of intended use.
To achieve an appearance-retention rating, a carpet undergoes rigorous testing to determine appearance changes produced by foot traffic over defined periods of time. Using a Hexapod or Vetterman Drum, the test mechanically simulates various levels of foot traffic over a carpet sample. After the carpet is tested, appearance changes are assessed and a retention rating value is assigned. CRI’s Appearance Retention Rating Scale does not gauge variable factors such as soiling, staining, maintenance, and installation.
How the new specification guidelines workA moderate-, heavy- or severe-use classification is established for each application based on the level of expected traffic in the specific area. For example, the classification chart designates private offices or conference rooms as moderate use, while corridors or common areas are classified as heavy- or severe-use areas.
The new use-classification system indicates the minimum carpet rating that should be recommended for a particular area. The classification determines the value, expressed on a scale of 1 to 5, that is needed according to CRI’s Appearance Retention Rating Scale. Most carpet specified for use in severe traffic conditions should meet or exceed the Appearance Retention Rating of 4.5 over the short term and 3.5 long term.
Physical construction characteristicsOnce the physical performance requirements for the carpet have been determined, the specification will include the physical construction characteristics such as the type, texture, fiber weight, color, and backing system. Guidelines for each type of construction, with recommended physical requirements, are included in the new document.
Construction specifications should tell the manufacturer in precise terms how the carpet is to be made — including the look, size, weight and manufacturing of raw materials, and processes — without directly stipulating performance needs or end-use requirements.
A construction specification would include the following:
- Construction type (i.e.: tufted, woven, knitted, needlepunched, etc.).
- Construction materials, including fiber, backing and adhesives.
- Construction methods used for yarn manufacturing, fabric formation, coloration techniques, finishing, and treatments.
- Product characteristics, including texture, color/design, size/type, and functional enhancements.
Construction specifications should be used to describe the overall look of a product and not be too detailed as to limit the manufacturer from making a quality product.
Important factors in specifying constructionOne of the most important and often misunderstood factors in a construction specification is density. Density is simply the index of how much yarn is packed into a given volume or area. The larger the density value, the more compact the pile, and the more firm the walking surface will be.
Density can be an important determinant of carpet performance, especially for high-traffic environments. Density is influenced by many factors, such as stitches per inch, yarn thickness, gauge, and tuft height. Specifiers who understand the various factors that affect density have a greater chance of specifying the best carpet performance for a given budget.
There are various methods of stating relative density specification for pile carpet. Average Pile Yarn Density (APYD) is the most common and useful decision tool when used in conjunction with other carpet specifications. APYD is determined by pile weight (specified in finished ounces per square yard), pile thickness or tuft height. Pile thickness and tuft height are laboratory means of determining what is commonly known as “pile height.” Pile height is sometimes measured with a small ruler or “dipstick,” but these measurements are only rough determinations and should not be considered accurate.
Generally, the higher the APYD value, the better the expected carpet performance once other important factors are considered. Average pile yarn density for quality commercial carpet will normally exceed 4,000, while high-demand usage may require an APYD greater than 6,000.
Additional factorsOther factors that affect carpet performance include yarn size and characteristics. Yarn twist and proper heat setting are of utmost importance for cut-pile styles. A low twist, or poorly heat-set yarn in a cut-pile carpet will tend to mat, tangle and appear worn.
Other determinants often written into construction specifications are backing systems, fiber type, spun or continuous filament yarn, and dye method.
Construction specifications can be proprietary. They may identifying a specific carpet by grade, name and manufacturer. An “or equal” specification also could identify a specific grade, listing its construction factors so that other manufacturers can bid for the order competitively. In this case, the usual procedure is to approve “or equals” in advance of the actual bidding. Requirements for performance, density and special needs should be stated.
Performance specifications for custom ordersSpecifying performance for special-order or custom-made carpet — rather than in-stock grades — can create some unanticipated delays. For a custom order, the specifier must allow time for development and testing against performance criteria. The manufacturer must have time to develop the basic construction, and trial samples also must be tested to ensure it performs as expected. The time required for this process may run considerably longer than typical specifying and bidding periods allow.
Government specifications and regulationsWhen specifying carpet for use by a government entity, special requirements may need to be included. As a major user of carpet, the federal government publishes standards regarding carpet performance and use. Two federal agencies that publish carpet specifications and standards are the General Services Administration (GSA) and the U.S. Department of Housing and Urban Development (HUD).
Specifying for good indoor air qualityWhile no federal laws or regulations currently govern Indoor Air Quality (IAQ) in commercial or institutional buildings, the federal government encourages builders, designers and manufacturers to adopt reasonable standards to ensure healthful IAQ.
When specifying carpet and flooring adhesives, CRI suggests that specifiers select a product that bears CRI’s Indoor Air Quality Testing Program label. Under this program, carpet product types are collected from carpet manufacturers and tested quarterly for total volatile organic compound (VOC) content.
Products that do not exceed the established emission levels are allowed to display the label. Using carpet, cushion, and floor covering adhesives with the CRI label assures the specifier and end user that the installation is low-emitting and will have minimal impact on indoor air quality.
The new carpet specification guidelines are available on CRI’s website at www.carpet-rug.com under the Selecting Carpet and Rugs, Commercial Specification link. They may also be obtained by telephoning CRI publications at (800) 882-8846.