Exposing a specimen to conditions of one-directional environmental cycling can increase its moisture content until a decrease in material properties occurs (at a specific number of cycles). Such a test could be inappropriate due to the number of cycles required to cause a decrease in material properties since product performance issues often arise only after many years of exposure. The use of a preconditioning procedure is not intended to duplicate expected field performance. Rather the purpose is to increase the moisture content of test materials prior to subjecting to them to environmental cycling.
The most important aspect of the preconditioning procedure is non-uniform moisture distribution in the specimen. The heat flow is one directional causing moisture flow towards the cold side resulting in zones of dry material on the warm side and high moisture content on the cold side. (Whether the high moisture content zone is located right at the cold surface of the specimen or at some distance from this surface depends upon temperature oscillation and ability of the cold surface to dry outwards). Because the preconditioning procedure involves thermal gradient, this preconditioning procedure results in a distribution of moisture content that may occur under field exposure conditions. However, the resulting moisture content may differ significantly from that which may be demonstrated in typical product applications.
The preconditioning results in accumulation of moisture in the thermal insulation resulting from the simultaneous exposure to a difference in temperature and water vapor pressure. This test method is not intended to duplicate field exposure. It is intended to provide comparative ratings. As excessive accumulation of moisture in a construction system may adversely affect its performance, the designer should consider the potential for moisture accumulation and the possible effects of this moisture on the system performance.
1.1 This test method is applicable to preformed or field manufactured thermal insulation products, such as board stock foams, rigid fibrous and composite materials manufactured with or without protective facings. See Note 0 This test method is not applicable to high temperature, reflective or loose fill insulation.
Note 0If the product is manufactured with a facer, test product with facer in place.
1.2 This test method involves two stages: preconditioning and environmental cycling. During the first stage, 25 mm (1 in.) thick specimens are used to separate two environments. Each of these environments has a constant but different temperature and humidity level. During the environmental cycling stage, specimens also divide two environments namely constant room temperature/humidity on one side and cycling temperature/ambient relative humidity on the other side.
1.3 This test method measures the ability of the product to maintain thermal performance and critical physical attributes after being subjected to standardized exposure conditions. A comparison is made between material properties for reference specimens stored in the laboratory for the test period and specimens subjected to the two-stage test method. To eliminate the effect of moisture from the comparison, the material properties of the latter test specimens are determined after they have been dried to constant weight. The average value determined for each of the two sets of specimens is used for comparison.
1.4 Different properties can be measured to assess the effect of environmental factors on thermal insulation. This test method requires that thermal resistance be determined based upon an average for three specimens measured after completing the test. Secondary elements of this test method include visual observations such as cracking, delamination or other surface defects, as well as the change in moisture content after each of the two stages of exposur......
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