1、Designation: E241 09Standard Guide forLimiting Water-Induced Damage to Buildings1This standard is issued under the fixed designation E241; 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 paren
2、theses indicates the year of last reapproval. Asuperscript epsilon () 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 evaluat
3、ionof 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 safe
4、ty) 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 guide is not intended for direct use in codes andspecifications. It does not attempt t
5、o 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 life
6、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 example,whether failure constitutes a life-safet
7、y hazard), and the judge-ment (that is, tolerance for damage) of the building owner. Forthe reasons stated in this paragraph, prescribing limits ofdamage would require listing many pages of exceptions andqualifiers and is beyond the scope of this guide.1.5 This standard does not purport to address t
8、he safetyconcerns 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:2C168 Terminology Relating to Thermal
9、InsulationC717 Terminology of Building Seals and SealantsC755 Practice for Selection of Water Vapor Retarders forThermal InsulationC1193 Guide for Use of Joint SealantsD1079 Terminology Relating to Roofing and WaterproofingE331 Test Method for Water Penetration of Exterior Win-dows, Skylights, Doors
10、, and Curtain Walls by UniformStatic Air Pressure DifferenceE547 Test Method for Water Penetration of Exterior Win-dows, Skylights, Doors, and Curtain Walls by Cyclic StaticAir Pressure DifferenceE631 Terminology of Building ConstructionsE632 Practice for Developing Accelerated Tests to AidPredictio
11、n of the Service Life of Building Components andMaterialsE1105 Test Method for Field Determination of Water Pen-etration of Installed Exterior Windows, Skylights, Doors,and Curtain Walls, by Uniform or Cyclic Static AirPressure DifferenceE1643 Practice for Selection, Design, Installation, and In-spe
12、ction of Water Vapor Retarders Used in Contact withEarth or Granular Fill Under Concrete SlabsE1677 Specification for an Air Barrier (AB) Material orSystem for Low-Rise Framed Building WallsE1745 Specification for Plastic Water Vapor Retarders Usedin Contact with Soil or Granular Fill under Concrete
13、 SlabsE2112 Practice for Installation of Exterior Windows, Doorsand SkylightsE2136 Guide for Specifying and Evaluating Performance ofSingle Family Attached and Detached DwellingsDurability1This guide is under the jurisdiction of ASTM Committee E06 on Performanceof Buildings and is the direct respons
14、ibility of Subcommittee E06.41 onAir Leakageand Ventilation PerformanceCurrent edition approved Nov. 1, 2009. Published December 2009. Originallyapproved in 1964. Last previous edition approved in 2008 as E241 08. DOI:10.1520/E0241-09.2For referenced ASTM standards, visit the ASTM website, www.astm.
15、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 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 Other D
16、ocuments:ASCE/SEI 2405 Flood Resistant Design and Construc-tion, American Society of Civil Engineers, StructuralEngineering Institute, Reston, VA.ASHRAE Handbook of Fundamentals Chapter 23: Ther-mal and Moisture Control in Insulated AssembliesFundamentals; Chapter 24: Thermal and Moisture Con-trol i
17、n Insulated AssembliesApplications; Chapter 27:Ventilation and Infiltration; Chapter 29: Residential Cool-ing and Heating Load Calculations; Chapter 30: Nonresi-dential Cooling and Heating Load Calculations; Ameri-can Society of Heating Refrigerating, and AirConditioning Engineers; Atlanta, GA, 2005
18、.ASHRAE Standard 62 Ventilation for Acceptable IndoorAir Quality3ASHRAE Technical DataBulletin, Vol 10, No. 3 Recommended Practices for Con-trolling Moisture in Crawl Spaces, American Society ofHeating, Refrigerating and Air Conditioning Engineers,Atlanta, GA, 1994.ASTM MNL 18 Trechsel, H., (ed.), M
19、oisture Control inBuildings, American Society for Testing and Materials,West Conshohocken, PA, 1994.ASTM MNL 40 Trechsel, H., (ed.), Moisture Analysis andCondensation Control in Building Envelopes, AmericanSociety for Testing and Materials, West Conshohocken,PA, 2001.Bateman, R., “Nail-On Windows” I
20、nstallation (2) movement of water vapor by airmovement; and (3) water vapor diffusion by vapor pressuredifferences. These transport mechanisms can deliver moistureinto the building or the building envelope, in which cases it isdesirable that they be controlled. These transport mechanismscan also act
21、 to remove moisture from the building or buildingenvelope, in which cases they may be used to promote drying.5.3.1 In control of moisture delivery to the building orbuilding envelope, the transport mechanisms that have thepotential for moving the greatest amounts of moisture should(where practical)
22、be controlled first. In promotion of drying ofthe building or building envelope, the transport mechanismsthat have the potential for moving the greatest amounts ofmoisture should (where practical) be utilized first.5.4 Building assemblies can become wet in three ways: (1)moisture can enter from the
23、exterior, (2) moisture can enterfrom the interior, or (3) the assembly can start out wet as aresult of using wet building materials or building under wetconditions.E241 0945.4.1 Moisture typically enters building assemblies from theexterior through three mechanisms: (1) liquid flow by gravity,air pr
24、essure, surface tension, momentum, or capillary suction;(2) movement of water vapor by air movement; or (3) watervapor diffusion by vapor pressure differences.5.4.2 Moisture typically enters building assemblies from theinterior through two mechanisms: (1) movement of watervapor by air movement, or (
25、2) water vapor diffusion by vaporpressure differences.5.4.3 Operation of mechanical equipment has not alwaysbeen recognized for its potential influence on moisture transfer.This potential influence should not be overlooked. Mostnotably, air handling equipment can induce a moisture trans-port mechani
26、sm that is capable of moving large amounts ofmoisture, namely movement of water vapor by air movement.Unplanned pressurization or depressurization of buildings orportions of buildings by air handlers can result in substantialmoisture accumulations in the building envelope.5.5 Moisture can typically
27、be removed (dried) to the exte-rior or the interior by three mechanisms: (1) liquid flow bygravity (drainage) or capillary suction, (2) movement of watervapor by air movement (ventilation), or (3) water vapordiffusion by vapor pressure differences.5.5.1 Where condensation of water vapor or water lea
28、ks canoccur, weep paths to drain liquid water to a place where it canbe dissipated are often effective. Converting liquid water tovapor, and dissipating the vapor by air movement may also bepractical.6. Limit States6.1 Identification of conditions that must be avoided inorder to prevent degradation
29、of building components is animportant step in making design or operating decisions. How-ever, precise guidelines for identification of such conditions aregenerally lacking. Rather rough estimates based on empiricalexperience are often used.6.2 Time and temperature are factors that are interrelatedwi
30、th moisture level in the degradation of building components.The moisture/temperature/time combinations that result inmaterial degradation furthermore vary with the type of mate-rial. For example, wood will not decay, even at elevatedmoisture content when its temperature is near or belowfreezing, and
31、 even at temperature conditions conducive todecay, wood can withstand intermittent wettings of shortduration to elevated moisture contents without decay becomingestablished. Conversely, masonry units can generally be ex-pected to withstand elevated moisture conditions at tempera-tures above freezing
32、 for extended time periods (conditionsunder which wood decay might be expected), but sufferdamage if frozen in a saturated condition.6.2.1 Many materials or constructions have threshold watercontents below which deterioration may be slow enough to benegligible for designed life expectancy. As indica
33、ted in 6.1these threshold values are often rather rough estimates. See“Humidity and Building Materials” (Connolly, 1993) forestimates.6.2.2 The concepts of critical moisture content and criticalcumulative exposure time (see 3.5.5) are discussed in Chapter26 of ASTM MNL 18. Although these concepts ar
34、e generallyrecognized by building scientists, organized use of these aslimit states by designers has not yet become a well-recognizedpractice.6.3 Alimit state is frequently based on avoidance of damageto a component as the result of its getting wet.Alimit state mayalso be based on avoidance of damag
35、e to a component as aresult of moisture conditions in an adjacent component. Forexample, limiting moisture-induced dimensional change ofplywood sheathing may be critical to prevent cracking ofstucco cladding.7. Design Evaluation Tools7.1 Means for evaluating the design of building envelopesfrom the
36、perspective of moisture management can be classifiedas follows: (1) conceptual, (2) mathematical using computersimulation models, and (3) mathematical using calculationsthat can be performed without computer software (sometimesreferred to as manual design tools).7.1.1 Conceptual Design EvaluationThi
37、s approach in-volves the following three-step procedure: (1) determine prob-able external and internal environmental loads (determineclimate and interior design conditions), (2) determine thepotential moisture transport mechanisms in each assembly, and(3) select moisture control strategies. This app
38、roach provides aqualitative perception of how a building will perform under theinfluence of all the moisture loads the building is likely to besubjected to. The Moisture Control Handbook (Lstiburek andCarmody, 1991) provides a more comprehensive treatment ofthis approach. Conceptual design evaluatio
39、n can be used toselect a construction for a given climate, as well as to evaluatehow a proposed construction may perform in a given climate.7.1.2 Computer Hygrothermal Analysis SimulationModelsThese models have been developed to quantitativelypredict moisture and temperature conditions within propos
40、edassemblies using boundary conditions representative for theclimate and interior design conditions. As stated in Chapter 6of ASTM MNL 40, the more detailed computer simulationmodels employ finite-element or finite-difference schemes.These models mathematically model moisture and heat transfermechan
41、isms at the inner and outer surfaces of the assembliesand within the assemblies. Some of the models predict mois-ture transfer by air movement and liquid water flow as well asby vapor diffusion. Use of such models requires knowledge ofbuilding physics and of the limitations of the model used. Mostmo
42、dels allow estimates of the duration of a set of temperatureand moisture conditions within assemblies. A discussion ofavailable models is found in Chapter 2 of ASTM MNL 18,inChapter 6 of ASTM MNL 40, and in Chapter 23 of theASHRAE Handbook of Fundamentals.7.1.3 Manual Design ToolsThese are termed “s
43、implifiedhygrothermal analysis method models” in Chapter 6 of AST-M MNL 40 and “simplified hygrothermal design calculationsand analyses” in Chapter 23 of the ASHRAE Handbook of-Fundamentalss. Manual design tools, like computer simulationmodels, provide quantitative estimates of moisture conditionswi
44、thin building envelopes. They only account however formoisture transfer by vapor diffusion. Their focus is on predict-ing the occurrence of sustained condensation within buildingassemblies. The calculations for manual design tools can beE241 095easily performed with a handheld calculator or in a com
45、puterspreadsheet. The traditional design tool used in North Americais a manual design tool and is referred to as the dewpointmethod. An example of the dewpoint method is outlined inAppendix X1.1 of Practice C755. The validity and usefulnessof predictions made with manual design tools have limitation
46、s.Most notably, manual design tools do not provide estimates ofthe time period during which potentially damaging conditionsmay occur. Despite the limitations of manual design tools,some relatively unsophisticated analysis procedures, like dew-point analysis, can be useful for rapidly comparing relat
47、iveperformances of many different proposed constructions. Adiscussion of manual design tools is found in Chapter 11 ofASTM MNL 18 and in Chapter 23 of the ASHRAE Hand-book of Fundamentals.8. Examples of Practices that Enhance Durability8.1 Drainage of Precipitation and Surface Runoff:8.1.1 Surface G
48、radingGround should slope away fromwalls so that precipitation runoff from land areas does not pondnear the foundation.8.1.2 Building External DrainsDischarge from drains atground level should be carried away from the foundation, andshould flow away from it.8.1.3 Below-Grade Drainage SystemsIn some
49、casesbelow-grade drainage systems may be required. In some cases,dissipation of collected water by pumping will be required.Below grade drainage systems are discussed in Chapter 2 ofThe Moisture Control Handbook (Lstiburek and Carmody,1991).8.2 Limiting Intrusion of Precipitation:8.2.1 Precipitation has the potential for delivering excep-tionally large moisture loads to buildings, and is usually thelargest potential moisture source (see Chapter 8 of ASTM-MNL 18). It is imperative that this source be controlled,specifically that precipitation be excluded from the building
