1、Designation: E 241 04Standard Guide forLimiting Water-Induced Damage to Buildings1This standard is issued under the fixed designation E 241; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par
2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide concerns building design, construction, com-missioning, operation, and maintenance.1.2 This guide addresses the need for systematic eval
3、uationof factors that can result in moisture-induced damage to abuilding or its components. Although of great potential impor-tance, serviceability issues which are often, but not necessarily,related to physical damage of the building or its components(for example indoor air quality or electrical sa
4、fety) are notdirectly addressed in this guide.1.3 The emphasis of this guide is on low-rise buildings.Portions of this guide, in particular sections 5, 6, and 7, mayalso be applicable to high-rise buildings.1.4 This standard is not intended for direct use in codes andspecifications. It does not atte
5、mpt to prescribe acceptable limitsof damage. Buildings intended for different uses may havedifferent service life expectancies, and expected service livesof different components within a given building often differ.Furthermore, some building owners may be satisfied withsubstantially shorter service
6、life expectancies of buildingcomponents or of the entire building than other buildingowners. Lastly, the level of damage that renders a componentunserviceable may vary with the type of component, the degreeto which failure of the component is critical (for examplewhether failure constitutes a life-s
7、afety hazard), and the judge-ment (i.e. tolerance for damage) of the building owner. For thereasons stated in this paragraph, prescribing limits of damagewould require listing many pages of exceptions and qualifiersand is beyond the scope of this standard.1.5 This standard does not purport to addres
8、s the safetyproblems associated with its use. It is the responsibility of theuser of this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Ther
9、mal Insulating Materi-alsC 717 Terminology of Building Seals and SealantsC 755 Practice for Selection of Vapor Retarders for ThermalInsulationC 1193 Guide for Use of Joint SealantsD 1079 Terminology Relating to Roofing, Waterproofing,and Bituminous MaterialsE 331 Test Method for Water Penetration of
10、 Exterior Win-dows, Skylights, Doors, and Curtain Walls by UniformStatic Air Pressure DifferenceE 547 Test Method for Water Penetration of Exterior Win-dows, Skylights, Doors, and Curtain Walls by Cyclic StaticAir Pressure DifferentialE 631 Terminology of Building ConstructionsE 632 Practice for Dev
11、eloping Accelerated Tests to AidPrediction of the Service Life of Building Components andMaterialsE 1105 Test Method for Field Determination of WaterPenetration of Installed Exterior Windows, Skylights,Doors, and Curtain Walls by Uniform or Cyclic Static AirPressure DifferenceE 1643 Practice for Ins
12、tallation of Water Vapor RetardersUsed in Contact with Earth or Granular Fills and ConcreteSlabsE 1677 Specification for an Air Retarder (AR) Material orSystem for Low-Rise Framed Building WallsE 1745 Specification for Water Vapor Retarders Used inContact with Soil or Granular Fill Under Concrete Sl
13、absE2112 Practice for Installation of Exterior Windows,Doors, and Skylights2.2 Other Documents:ASHRAE Handbook of Fundamentals (1997) Chapter 22:Thermal and moisture control in insulated assemblies -fundamentals. Amer. Soc. of Heating Refrigerating, andAir Conditioning Engineers, Atlanta, GA.1This g
14、uide is under the jurisdiction of ASTM Committee E06 on BuildingConstructions and is the direct responsibility of Subcommittee E06.41 on AirLeakage and Ventilation Performance.Current edition approved April 1, 2004. Published April 2004. Originallyapproved in 1964. Last previous edition approved in
15、2000 as E 241 00.2For 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.1Copyright ASTM International, 100 Barr Harb
16、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ASHRAE Standard 55, Thermal Environmental Conditionsfor Human OccupancyASHRAE Standard 62, Ventilation for Acceptable IndoorAir QualityASHRAE Technical Data Bulletin Vol. 10 Number 3. Rec-ommended Practices for Controlling Moistu
17、re in CrawlSpaces, Amer. Soc. of Heating Refrigerating and AirConditioning Engineers, Atlanta, GA., 1994.Bateman, R. Nail-On Windows: Installation flashings are almost alwaysrequired at such penetrations. Design, installation and mainte-nance of roofs are very important. There is an entire Volume(Vo
18、l 4.04) of the ASTM Annual Book of Standards thatcontains standards concerning roofing and waterproofing.Therefore, a comprehensive treatment of these subjects is notattempted in this standard.8.2.3 Water intrusion through building facades (in low riseconstruction, this primarily means walls) can be
19、 of substantialconsequence. There are two broad strategies for controllingrainwater intrusion into walls: (1) reduce the amount ofrainwater deposited on building walls, and (2) control rainwa-ter that is deposited on building walls.8.2.3.1 Reducing rainwater deposition on wall assemblieshas traditio
20、nally been a function of siting and architecturaldesign. The following measures have historically proven ef-fective: (1) site buildings so they are sheltered from wind-driven rain, (2) provide roof overhangs and gutters or otherpiped roof drainage systems to shelter walls from direct rainexposure or
21、 roof runoff.8.2.3.2 As suggested in 8.2.1, roof runoff is usually anexceptionally large potential water source. In temperate andcold climates, exposure to roof runoff is one of the mostcommon causes of freeze-thaw spalling of masonry claddingE241045systems. Wood and wood-based cladding systems are
22、widelyrecognized as being incapable of performing adequately ifexposed to roof runoff. Among the more common waterintrusion points in walls are the interfaces of walls with roofs,especially with level or nearly-level roofs. Thresholds of doorsthat open to balconies represent one of the most common s
23、itesof serious water intrusion into walls. Serious water intrusion atthese sites can generally be expected unless the balcony surfaceis pitched to drain water away from the wall. For the reasonsstated in this paragraph, it is generally accepted that walls ofbuildings must not be exposed to roof runo
24、ff.8.2.4 Walls are most susceptible to water intrusion at jointsin and penetrations of the exterior cladding system. Jointsbetween the cladding system and windows and doors arelocations susceptible to water leakage. Junctures of walls withlarge horizontal or sloped surfaces (for example roofs, decks
25、 orbalconies) are susceptible to leakage. Therefore, particular careis required at these locations.8.2.5 Strategies for control of rainwater that is deposited onbuilding walls can be broadly categorized as follows: (1)strategies to prevent water penetration of the outermost face ofthe wall system, (
26、2) strategies to dissipate water that penetratesthe outermost face of the wall system. Strategies in these twogeneral categories often are effectively used in combination.Strategies for control of rainwater deposited on building wallsare discussed in Chapter 2 of The Moisture Control Handbook.Furthe
27、r discussion on the subject, as well as recommendationsconcerning design details are found in Nail-On Windows(Bateman, 1995). It is important that the strategy or strategiesselected by the designer be clearly understood by constructioncontractors and those responsible for maintenance of thebuilding.
28、8.2.5.1 Exterior MechanicalsPenetrations of this type (forexample electrical equipment) should be of a type suited forexterior service and be installed with adequate moisture seals.8.2.5.2 FenestrationImportant consideration in selectionof fenestration units (windows and doors) are (1) the ability o
29、fthe units themselves to shed water, and (2) the ability withwhich the units can be integrated into the buildings water-shedding system.A units resistance to water penetration can be identified, inpart, by laboratory tests such as Test Methods E 331 and E 547.Third party certification of a products
30、water resistance ishighly recommended to help identify whether the product isappropriate for its intended application (anticipated in-serviceexposure of the unit to wind and rain).Proper installation and integration of the product with thebuildings water-shedding system are essential. PracticeE2112
31、provides guidance for proper installation and water-shedding system integration for simple fenestration products.For more complex systems (such as mulled units, stacked units,or new designs), pre-construction mock-up testing and fieldtesting early in the building project can be valuable forpurposes
32、of risk reduction and quality assurance. Field testingis especially valuable where water management and integrationdetails are unclear or are not provided. Test Method E 1105outlines a useful field testing technique.Cladding termination accessories, window installation ac-cessories, or site-fabricat
33、ed trim may provide a transitionbetween fenestration units and the surrounding cladding sys-tem. Water penetration can occur at the interfaces betweenthese entities and either the fenestration unit or the surroundingcladding system.Adequate building design and adequate work-manship during constructi
34、on are both essential to reducing thepotential for water intrusion and water-induced damage to thebuilding.Appropriate maintenance of the fenestration product and itsinterfaces with the wall system will help ensure long termdelivery of the desired water penetration resistance. If thewater-shedding c
35、apabilities of a unit are compromised bymechanical damage or deferred maintenance, water intrusioninto the wall can occur.NOTE 3The considerations mentioned previously in this section asapplicable to fenestration units in walls (doors and windows) also apply toskylights. Skylights, which are install
36、ed on roofs, can be expected to havegreater weather exposure than fenestration units in walls.8.2.5.3 Sealant JointsIn contrast to high-rise construc-tion, design of sealant joints in low-rise construction hasgenerally not become a well-developed discipline. Design ofreliable sealant joints can incl
37、ude many factors such as:sealant-substrate compatibility, avoidance of 3-sided adhesion,joint geometry and anticipated movements in joints (seeStandard Guide C 1193). Workmanship, including conditionsunder which sealant joints are installed, is also important.Maintenance of sealant joints must not b
38、e overlooked, sinceanticipated life of sealant joints will almost certainly besubstantially less than design life of the building.8.3 Control of Indoor Humidity8.3.1 From the standpoint of building durability, indoorhumidity control is primarily of concern during winter intemperate or cold climates.
39、 It may also be of concern howeverin air conditioned buildings in hot humid climates, particularlyif the building is designed to dry toward the interior. In mildweather in any climate, humidity control may be of importancefrom the standpoint of preservation of property within thestructure or from th
40、e standpoint of indoor air quality (forexample preventing mold growth that releases spores andmusty odors or inhibiting the propagation of dust mites), butgenerally is not of great concern to durability of the buildingstructure.8.3.2 Indoor humidity can be limited by controlling mois-ture sources or
41、 by removing humidity by air exchange with theexterior or by dehumidification.8.3.3 As indicated in 5.1.1 and 8.3.1, the indoor humidity(RH) level that a given building will tolerate is climate-dependent. ASHRAE 55 recommends that for human comfort,dewpoint temperature of occupied spaces not fall be
42、low 36 F(2 C). Over the dry-bulb temperature range of 6774 F(1923 C) (the approximate temperature range outlined inASHRAE 55 for winter comfort) this corresponds to an indoorRH range of approximately 3225%. In contrast, experienceand computer simulation models suggest that damaging mois-ture accumul
43、ations can be expected in many buildings ofcustomary design in cold climates if winter indoor RH inheated buildings is maintained at levels in excess of 40%.E241046These observations suggest that it is reasonable to expectbuildings of customary design in cold climates to tolerateindoor RH levels abo
44、ve the minimum for human comfort, butnot much above such levels. When higher indoor humiditylevels are necessary or desired in cold climates, the buildingmust be carefully designed, built, and operated to tolerate suchlevels.8.3.4 In most heating climates during cool or cold weather,air exchange wit
45、h the exterior can significantly reduce indoorhumidity (Chapter 15 of ASTM MNL 18 and Chapter 23 ofASHRAE Handbook of Fundamentals). Chapter 23 of theASHRAE Handbook of Fundamentals suggests that at normalrates for residential occupancy and moisture generation and inall but mild humid climates, vent
46、ilation to a level of 0.35 airchanges per hour (as recommended in ASHRAE Standard 62,Ventilation for Acceptable Air Quality) will usually be suffi-cient to prevent excessive indoor humidity. Mechanical dehu-midification is rarely used for indoor humidity control duringcold weather. In mild humid cli
47、mates, air exchange with theexterior may be of limited effectiveness for control of indoorhumidity. In these climates, dehumidification may be moreeffective than ventilation for controlling indoor RH, but asindicated in 8.3.1 is more likely to be deemed necessary forreasons other than that of durabi
48、lity of the building structure.8.3.4.1 In designing for provision of air exchange betweenthe living space and the exterior, energy efficiency and airquality considerations as well as durability considerations areusually important.8.3.4.2 In buildings constructed prior to 1970, air exchangebetween bu
49、ilding interiors and the exterior during winter intemperate and cold climates has occurred primarily by acombination of infiltration (much of which occurred throughfenestration units) and escape of air up chimneys (a combina-tion of air movement through furnaces, draft hoods, andbarometric draft dampers). The effect of chimney draft hasoften been sufficiently great that the buildings have operated ata negative air pressure relative to the exterior, causing airleakage through the building envelope to be predominantlyinfiltrative. Infiltrative air leakage is not capabl
