Standard Practice for Determination of Thermal Resistance of Loose-Fill Building Insulation
The thermal resistance, R, of an insulation is used to describe its thermal performance.
The thermal resistance of an insulation is related to the density and thickness of the insulation. It is desirable to obtain test data on thermal resistances at thicknesses and densities related to the end uses of the product.
In normal use, the thickness of these products range from less than 100 mm (4 in.) to greater than 500 mm (20 in.). Installed densities depend upon the product type, the installed thickness, the installation equipment used, the installation techniques, and the geometry of the insulated space.
Loose-fill insulations provide coverage information using densities selected by manufacturers to represent the product settled densities. Generally, it is necessary to know the product thermal performance at a representative density. Some coverage charts utilize multiple densities to show that greater thickness installations usually result in higher installed densities. The use of multiple densities can be detected from the coverage chart by calculating the density for several different thermal resistance levels. (The density for a given thermal resistance can be calculated from the coverage chart by dividing the minimum mass per unit area by the minimum thickness.) If the calculated densities are significantly different at different thermal resistances, the multiple density strategy has been used.
When applicable specifications or codes do not specify the nominal thermal resistance level to be used for comparison purposes, a recommended practice is to use the Rsi (metric) = 3.3 m2K/W (RIP = 19 [h ft2F/Btu]) label density and thickness for that measurement.
If the density for test purposes is not available from the coverage chart, a test density shall be established by use of applicable specifications and codes or, if none apply, agreement between the requesting body and the testing organization.
Generally, thin sections of these materials are not uniform. Thus, the test thickness must be greater than or equal to the product’s representative thickness if the results are to be consistent and typical of use.
Note 1—The representative thickness is specific for each product and is determined by running a series of tests in which the density is held constant but the thickness is increased. The representative thickness is defined here as that thickness above which there is no more than a 2 % change in the resistivity of the product. The representative thickness is a function of product blown density. In general, as the density decreases, the representative thickness increases. Fortunately, most products are designed to be blown over a small range of densities. This limited range yields a range of representative thicknesses between 100 to 200 mm (4 to 8 in.) for most products. To simplify the process for this Practice, the representative thickness for the C 687 tests shall be determined at the midpoint of the blown density range. Once this is accomplished, all thermal testing on this product is conducted at a thickness that is greater or equal to the representative thickness.
For this practice, the minimum test thickness shall be 100 mm (4 in.) or the representative thickness, whichever is larger. If the test is to represent an installation at a lesser thickness, the installed thickness shall be used.
Because of the high cost of construction and operation of large test equipment, it is impractical to test at the higher thicknesses at which products are used. For purposes of this practice, it is acceptable to estimate the thermal resistance at any thickness from the thermal resistivity obtained from tests on the product at the minimum test thickness (see 4.7.1) and at the density expected for the proposed thickness.
In principle, any of the standard methods for the determination of thermal resistance are suitable for loose-fill products. These include Test Methods C 177, C 518, C 1114, and C 1363. Of these test methods, the heat flow meter apparatus, Test Method C 518, is preferred because of its lower cost and shorter testing time.
The thermal resistance of low-density insulations depend upon the direction of heat flow. Unless otherwise specified, tests shall be performed for the maximum heat flow condition, that is, a horizontal specimen with heat flow-up.
Specimens shall be prepared in a manner consistent with the intended installation procedure. Products for pneumatic installation shall be pneumatically applied (blown), and products for pour-in-place installation shall be poured into specimen frames.
Loosefill insulation installed in attic applications will have heat flow up during the winter. At winter design conditions in many areas, the winter design temperature difference will cause convective heat transfer to occur within some loose-fill insulations. The procedure outlined in C 687 is not applicable to that measurement unless a C 1363 test apparatus is used to reproduce the correct boundary conditions. To determine how seasonal differences can affect product performance, use Practice C 1373. Practice C 1373 measures the expected winter thermal performance of loose-fill insulation under simulated winter design temperature conditions and provides specimen requirements necessary for that determination.
1.1 This practice presents a laboratory guide to determine the thermal resistance of loose-fill building insulations at mean temperatures between − 20 and 55°C (−4 to 131°F).
1.2 This practice applies to a wide variety of loose-fill thermal insulation products including fibrous glass, rock/slag wool, or cellulosic fiber materials; granular types including vermiculite and perlite; pelletized products; and any other insulation material installed pneumatically or poured in place. It does not apply to products that change their character after installation either by chemical reaction or the application of binders or adhesives, nor does it consider the effects of structures, containments, facings, or air films.
1.3 Since this practice is designed for reproducible product comparison, it measures the thermal resistance of an insulation material which has been preconditioned to a relatively dry state. Consideration of changes of thermal performance of a hygroscopic insulation by sorption of water is beyond the scope of this practice.
1.4 The sample preparation techniques outlined in this practice do not cover the characterization of loose-fill materials intended for enclosed applications. For those applications, a separate sample preparation technique that simulates the installed condition will be required. However, even for those applications, some other aspects of this practice are applicable.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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