ASTM C755-2010(2015)e1 Standard Practice for Selection of Water Vapor Retarders for Thermal Insulation《隔热用水蒸气缓凝剂的选择标准实施规程》.pdf
《ASTM C755-2010(2015)e1 Standard Practice for Selection of Water Vapor Retarders for Thermal Insulation《隔热用水蒸气缓凝剂的选择标准实施规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM C755-2010(2015)e1 Standard Practice for Selection of Water Vapor Retarders for Thermal Insulation《隔热用水蒸气缓凝剂的选择标准实施规程》.pdf(12页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: C755 10 (Reapproved 2015)1Standard Practice forSelection of Water Vapor Retarders for Thermal Insulation1This standard is issued under the fixed designation C755; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorially corrected Table 2 in January 2018.1. Scope1.1 This practice outlines factors to be considered, describesdesi
3、gn principles and procedures for water vapor retarderselection, and defines water vapor transmission values appro-priate for established criteria. It is intended for the guidance ofdesign engineers in preparing vapor retarder application speci-fications for control of water vapor flow through therma
4、linsulation. It covers commercial and residential building con-struction and industrial applications in the service temperaturerange from 40 to +150F (40 to +66C). Emphasis is placedon the control of moisture penetration by choice of the mostsuitable components of the system.1.2 The values stated in
5、 inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
6、is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on s
7、tandard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal Insul
8、ationC647 Guide to Properties and Tests of Mastics and CoatingFinishes for Thermal InsulationC921 Practice for Determining the Properties of JacketingMaterials for Thermal InsulationC1136 Specification for Flexible, Low Permeance VaporRetarders for Thermal InsulationE96/E96M Test Methods for Water V
9、apor Transmission ofMaterials3. Terminology3.1 For definitions of terms used in this practice, refer toTerminology C168.4. Significance and Use4.1 Experience has shown that uncontrolled water entry intothermal insulation is the most serious factor causing impairedperformance. Water entry into an ins
10、ulation system may bethrough diffusion of water vapor, air leakage carrying watervapor, and leakage of surface water. Application specificationsfor insulation systems that operate below ambient dew-pointtemperatures should include an adequate vapor retarder sys-tem. This may be separate and distinct
11、 from the insulationsystem or may be an integral part of it. For selection ofadequate retarder systems to control vapor diffusion, it isnecessary to establish acceptable practices and standards.4.2 Vapor Retarder FunctionWater entry into an insula-tion system may be through diffusion of water vapor,
12、 airleakage carrying water vapor, and leakage of surface water.The primary function of a vapor retarder is to control move-ment of diffusing water vapor into or through a permeableinsulation system. The vapor retarder system alone is seldomintended to prevent either entry of surface water or air lea
13、kage,but it may be considered as a second line of defense.4.3 Vapor Retarder PerformanceDesign choice of retard-ers will be affected by thickness of retarder materials, substrateto which applied, the number of joints, available length andwidth of sheet materials, useful life of the system, andinspec
14、tion procedures. Each of these factors will have an effecton the retarder system performance and each must be consid-ered and evaluated by the designer.4.3.1 Although this practice properly places major emphasison selecting the best vapor retarders, it must be recognized that1This practice is under
15、the jurisdiction of ASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.33 on InsulationFinishes and Moisture.Current edition approved Sept. 1, 2015. Published October 2015. Originallyapproved in 1973. Last previous edition approved in 2010 as C755 101. DOI:1
16、0.1520/C0755-10R15E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr
17、Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommen
18、dations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1faulty installation techniques can impair vapor retarder perfor-mance. The effectiveness of installation or application tech-niques in obtaining design water vapor transmission (WVT)performance must be consid
19、ered in the selection of retardermaterials.4.3.2 As an example of the evaluation required, it may beimpractical to specify a lower “as installed” value, becausedifficulties of field application often will preclude “as installed”attainment of the inherent WVT values of the vapor retardermaterials use
20、d. The designer could approach this requirementby selecting a membrane retarder material that has a lowerpermeance manufactured in 5-ft (1.5-m) width or a sheetmaterial 20 ft (6.1 m) wide having a higher permeance. Thesealternatives may be approximately equivalent on an installedbasis since the wide
21、r material has fewer seams and joints.4.3.3 For another example, when selecting mastic or coatingretarder materials, the choice of a product having a permeancevalue somewhat higher than the lowest obtainable might bejustified on the basis of its easier application techniques, thusensuring “as instal
22、led” system attainment of the specifiedpermeance. The permeance of the substrate and its effects onthe application of the retarder material must also be consideredin this case.5. Factors to Be Considered in Choosing Water VaporRetarders5.1 Water Vapor Pressure Difference is the difference in thepres
23、sure exerted on each side of an insulation system orinsulated structure that is due to the temperature and moisturecontent of the air on each side of the insulated system orstructure. This pressure difference determines the direction andmagnitude of the driving force for the diffusion of the waterva
24、por through the insulated system or structure. In general, fora given permeable structure, the greater the water vaporpressure difference, the greater the rate of diffusion. Watervapor pressure differences for specific conditions can becalculated by numerical methods or from psychrometric tablesshow
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