ISO 21129-2007 Hygrothermal performance of building materials and products - Determination of water-vapour transmission properties - Box method《建筑材料和产品的温湿性能 水蒸汽.pdf

1、 Reference number ISO 21129:2007(E) ISO 2007INTERNATIONAL STANDARD ISO 21129 First edition 2007-07-15 Hygrothermal performance of building materials and products Determination of water-vapour transmission properties Box method Performance hydrothermique des matriaux et produits pour le btiment Dterm

2、ination des proprits de transmission de la vapeur deau Mthode de box ISO 21129:2007(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licen

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7、and ii ISO 2007 All rights reservedISO 21129:2007(E) ISO 2007 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Terms, definitions, symbols and units . 1 4 Principle. 2 5 Apparatus 2 6 Test specimen . 4 7 Procedure 4 8 Calculation and expressio

8、n of results 5 9 Measurement accuracy 5 10 Test report . 6 Annex A (normative) Conversion of water-vapour pressure. 7 Annex B (normative) Method for calculating the water vapour surface resistance 8 Annex C (informative) Double-box method . 9 Bibliography . 11 ISO 21129:2007(E) iv ISO 2007 All right

9、s reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for

10、 which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on a

11、ll matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are

12、 circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held re

13、sponsible for identifying any or all such patent rights. ISO 21129 was prepared by Technical Committee ISO/TC 163, Thermal performance and energy use in the built environment, Subcommittee SC 1, Test and measurement methods. ISO 21129:2007(E) ISO 2007 All rights reserved v Introduction The general p

14、rinciples are applicable to all hygroscopic and non hygroscopic building materials and products. It is required to search for hygrothermal performance and thermal performance of building materials in order to solve the condensation phenomenon of building walls and to establish the condensation-preve

15、ntive measures. In the box method, a specimen is fixed to a measurement box. The mass of saturated salt solutions contained in two pans hanging on the two side boxes of a specimen is measured. The amount of water vapour penetrating through a specimen is calculated from change of the mass of the satu

16、rated salt solutions in the two pans. In a cup method, the mass of the saturated salt solution is measured together with that of the specimen; however, in the box method, it is not necessary to measure the mass of the specimen. The reason that the box method is more accurate than the cup method is t

17、hat there are thick materials and/or heavy materials in building materials or products. If the principle of the box method is applied, it is possible to measure the water-vapour transmission properties of not only materials but also some building products with good accuracy. INTERNATIONAL STANDARD I

18、SO 21129:2007(E) ISO 2007 All rights reserved 1 Hygrothermal performance of building materials and products Determination of water-vapour transmission properties Box method 1 Scope This International Standard specifies a box method for determining the water-vapour permeability of building materials.

19、 The box method is used primarily to measure the water-vapour permeance of materials that have low water-vapour resistance, in which the influence of the surface-humidity transmission-resistance cannot be ignored. NOTE Materials with low water-vapour resistance includes those with no greater than 1,

20、8 10 9 m 2 s Pa/kg of resistance water vapour permeability coefficient of 5,5 10 8 kg/(m 2 s Pa or above). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, t

21、he latest edition of the referenced document (including any amendments) applies. ISO 9346, Hygrothermal performance of buildings and building materials Mass transfer Physical quantities and definitions 3 Terms, definitions, symbols and units 3.1 Terms and definitions For the purposes of this documen

22、t, the definitions given in ISO 9346 and the following apply. 3.1.1 density of water vapour flow rate mass of water vapour transferred through per unit area per unit time under specified conditions of temperature, humidity and thickness 3.1.2 water vapour permeance density of water vapour flow rate

23、divided by the water vapour pressure difference between the two surfaces of the specimen 3.1.3 water vapour conductivity water vapour permeance per unit thickness 3.1.4 water vapour resistance reciprocal of water vapour permeance 3.1.5 water vapour permeability product of the water vapour permeance

24、and the thickness of a homogeneous specimen ISO 21129:2007(E) 2 ISO 2007 All rights reserved3.2 Symbols and units Symbol Quantity Unit W pWater-vapour permeance of specimen kg/(m 2 sPa) Z pWater-vapour resistance of specimen m 2 sPa/kg G Water-vapour flow rate through specimen kg/h A Area of specime

25、n m 2P Water-vapour pressure in box or room Pa Relative humidity 1/ Water-vapour surfaces resistance m 2 sPa/kg Surface coefficient of water-vapour transfer kg/(m 2 sPa) pWater-vapour permeability of specimen kg/(msPa) d Thickness of specimen m Subscripts: High High water vapour pressure side. Low L

26、ow water vapour pressure side. See References 1 to 5 for further details. 4 Principle Install a box (called the water-vapour-permeability test box) for measuring the amount of permeated water vapour in a room maintained at a constant temperature and humidity. To create a difference in water vapour p

27、ressure, i.e., a difference in humidity, between the two sides of the specimen, attach the test box to one face (opening) and then place a high- or low-density aqueous salt solution into the box and maintain the box at a constant humidity. During this time, water vapour flows from the box to the roo

28、m or from the room to the box by permeating the specimen. The amount of vapour flow can be determined by measuring the change in mass of the dish containing the aqueous salt solution by taking measurements at constant intervals using a scale (electronic balance); see Figure 1. In this way, the total

29、 water-vapour resistance, including the surface- transmission-resistance of the material, can be calculated by measuring the vapour-pressure difference on both sides of the specimen at a steady state and a constant water-vapour permeance. The water-vapour resistance of the material can be calculated

30、 by subtracting the surface-humidity transmission-resistance on both sides of the specimen, obtained according to Annex B, from the total water vapour resistance. 5 Apparatus NOTE See Figure 1. 5.1 Room, in which the temperature can be freely set within a range of 10 C to 30 C to an accuracy of at l

31、east 0,5 C and the relative humidity of the room can be freely set within a range of (30 3) % to (90 3) %. 5.2 Water-vapour permeability test box, having the standard dimensions of 600 mm 600 mm 600 mm. The measuring box should be made of material such as metal, glass or hard plastic that is imperme

32、able to water vapour and, under the measurement criteria, it should be resistant to corrosion (anti-moisture material). The box joint shall be properly sealed to prevent water-vapour leakage. The box shall be constructed to provide sufficient strength for usage. The part connected to the sample inst

33、allation frame at the opening (flange) shall be made of anti-moisture rubber packing or other material to enable air tightness. ISO 21129:2007(E) ISO 2007 All rights reserved 3 5.3 Mixing fan, capable of blowing air along the surface of the specimen as uniformly as possible. Average velocity of the

34、air movement at a distance of 50 mm from the surface shall be adjusted to be 0,5 m/s. 5.4 Saturated-aqueous-salt solution dish, having an area at least equal to the area of the specimen. The dish shall be resistant to corrosion from the salt solution and be of a construction to enable mass measureme

35、nt by a balance. 5.5 Balance, capable of weighing the pan with a precision of 10 mg. 5.6 Specimen installation frame, made of non-distorting, anti-moisture material. It shall be constructed with an opening in the centre where the specimen can be placed, and enable secure air-tight attachment of the

36、frame to the flange of the water-vapour test box. The opening dimensions shall be 300 mm 300 mm. It shall have a flange-type shape to keep in thick specimens and have gaps to enable the sealing of small surface holes in the specimen. 5.7 Thermometers, two, capable of measuring the air temperature on

37、 both sides of the specimen to an accuracy of 0,1 C. 5.8 Hygrometers, two, capable of measuring the relative humidity of both sides of the specimen to an accuracy of 2 %. Key 1 specimen 7 mixing fan 2 measuring box 8 thermometer and hygrometer 3 frame for specimen 9 sealant 4 suspended weighing pan

38、10 rubber gasket 5 balance 11 rubber plug 6 room at constant temperature and humidity 12 clamp Figure 1 Test apparatus ISO 21129:2007(E) 4 ISO 2007 All rights reserved6 Test specimen 6.1 Size and thickness of specimen The standard size of the test specimen shall be 300 mm 300 mm. The thickness shall

39、 be the thickness of the product. If the thickness of homogenous material exceeds 100 mm, it may be thinly sliced. 6.2 Preconditioning of test specimen Before testing, the test specimen shall be stored at (23 5) C, (50 10) % relative humidity for a period long enough to stabilize its mass. Here, con

40、stant mass refers to a change in weight over three consecutive days of no greater than 5 %. 7 Procedure 7.1 Set-up of saturated aqueous salt solution dish Saturated aqueous salt solution preparation and humidity difference setting Select an aqueous saturated salt solution from Table 1 and set the hu

41、midity in a temperature-controlled room so that the humidity difference is 20 % to 40 %. Dissolve the salt crystals in distilled water and pour the salt solution into the pan to a depth of 10 mm to 20 mm. Further details of suitable salts can be found in ISO 12571:2000, Annexes A and B. It is necess

42、ary to assure that enough crystal remain in the solution until measurement is finished. Table 1 Aqueous solution Aqueous solution Relative humidity % KNO 394 NaCl 75 Mg(NO 3 ) 253 MgCl 233 LiCl 11 NOTE Temperature is 23 C. 7.2 Installation of specimen Mask the edge of the specimen with aluminium foi

43、l using epoxy resin adhesive. Attach the specimen to the specimen installation frame and seal the joint part. At this time, sealant shall not run onto the surface of the specimen because it is necessary that the specimen area be equal to the permeance area. The installation frame shall be airtight u

44、sing rubber packing and a clamp at the opening of the measuring box. 7.3 Calibration of the measuring box The amount of water-vapour leakage from the measuring box is calibrated beforehand as a characteristic of the measurement device. Calibration shall be made at every temperature and humidity acco

45、rding to the procedure of 7.4 by installing a metal plate in the frame. The leakage of water vapour is the mass change of a pan per hour. ISO 21129:2007(E) ISO 2007 All rights reserved 5 7.4 Measuring the permeated water vapour amount Measure the mass of the aqueous solution dish at appropriate time

46、 intervals. The time interval shall be determined so that a change in the mass of the specimen due to water-vapour permeance is within a range of 0,02 g to 2 g. Continue the measurements at the appropriate intervals, for at least five points in succession, until the change in mass (increase or decre

47、ase) at five consecutive points is constant to within 5 %. The amount of permeated water-vapour is calculated by adjusting the amount of water-vapour leaking from the test box in which the mass increase (or decrease) in permeated water-vapour amount per hour was corrected by the calibration as descr

48、ibed in 7.3. The amount of change in permeated water vapour can be the linear slope of the change in mass of at least five points calculated by the least square method. 7.5 Measuring of temperature and humidity The temperature and relative humidity within the box or the conditioned room shall be rec

49、orded continuously during weighing of the mass. Water-vapour pressures can be derived from the air temperature and relative humidity; see Annex A. 7.6 Measurement of surface-humidity transmission-resistance The surface-humidity transmission-resistance on both sides of the specimen shall be pre-determined as described in Annex B. 8 Calculation and expression of results The water-vapour flow rate is determined by a least-squares method from the measurement