1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 15976:2011Flexible sheets forwaterproofing Determination of emissivityBS EN 15976:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN
2、 15976:2011.The UK participation in its preparation was entrusted to TechnicalCommittee B/546, Flexible sheets for waterproofing and watervapour control.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all t
3、he necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 67969 8ICS 91.100.50Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strate
4、gy Committee on 31 May 2011.Amendments issued since publicationDate Text affectedBS EN 15976:2011EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 15976 April 2011 ICS 91.100.50 English Version Flexible sheets for waterproofing - Determination of emissivity Feuilles souples dtanchit - Dterminatio
5、n de lmissivit Abdichtungsbahnen - Bestimmung des Emissionsgrades This European Standard was approved by CEN on 17 March 2011. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard
6、without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any ot
7、her language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic
8、, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NOR
9、MALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15976:2011: EBS EN 15976:2011EN 15976:2011 (E) 2 Contents Page Foreword 31 Scope 42
10、 Normative references 43 Terms and definitions .44 Symbols 45 Principle of low emitting surfaces .56 Hemispherical blackbody radiator .66.1 Principle of hemispherical blackbody radiator .66.2 Description of hemispherical blackbody radiator and of the specimen holder 76.3 Handling procedure of calibr
11、ation standards .86.4 Calculation of the emissivity 96.5 Measurement range of hemispherical blackbody radiator 97 Sampling and preparation of the test specimens 97.1 Sampling .97.2 Dimensions and numbers of specimens .97.3 Preparation of specimens before testing 98 Procedure for measurement of speci
12、mens .99 Expression of the results . 1010 Emissivity after conditioning . 1010.1 Specialities of application related aging 1010.2 Conditioning procedure . 10Bibliography . 11BS EN 15976:2011EN 15976:2011 (E) 3 Foreword This document (EN 15976:2011) has been prepared by Technical Committee CEN/TC 254
13、 “Flexible sheets for waterproofing”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2011, and conflicting national standards shall be withdrawn a
14、t the latest by October 2011. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the n
15、ational standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlan
16、ds, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 15976:2011EN 15976:2011 (E) 4 1 Scope This European Standard specifies the method to determine the emissivity of plastic, rubber and bitumen vapour control layers, underlays for walls
17、and underlays for discontinuous roofing. It also defines a conditioning procedure for these product families in order to quantify the sensitivity of emissivity to humidity and temperature. 2 Normative references The following referenced documents are indispensable for the application of this Europea
18、n Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 13416, Flexible sheets for waterproofing Bitumen, plastic and rubber sheets for roof waterproofing Rules for sampling 3 Terms
19、 and definitions For the purposes of this document, the following terms and definitions apply 3.1 emissivity emissivity of a material (usually written ) is the ratio (proportion) of the energy radiated by a surface relative to the energy radiated by a blackbody at the same temperature. It is a measu
20、re of a materials ability to radiate heat 3.2 blackbody blackbody is a theoretical object that absorbs all electromagnetic radiation that falls on it at all wavelengths. No electromagnetic radiation passes through it and none is reflected NOTE A blackbody is also a perfect emitter with a normal and
21、corrected emissivity of 1. 3.3 TIR Thermal Infrared Radiation principle 4 Symbols For the purposes of this document, the following symbols apply c specific heat capacity is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature
22、interval. the wavelength is the distance between repeating units of a propagation wave of a given frequency. NOTE In this document it is understood the wave length is limited to the infrared light spectrum. BS EN 15976:2011EN 15976:2011 (E) 5 (alpha) represents the absorption coefficient of a surfac
23、e and is the ratio of the radiant energy absorbed by that surface relative to that of a blackbody at the same temperature. (epsilon) emissivity (see above definition of emissivity) (0 1). (rho) reflectivity coefficient is the proportion of the incident electromagnetic radiation reflected from a surf
24、ace or an optical element. (tau) transmission coefficient is the proportion of incident electromagnetic radiation (light) passes through a surface or an optical element. Lemissivity for the low emissive calibration standard. H emissivity for the high emissive calibration standard.U sensor signal of
25、the specimen in Volt. UHsensor signal of the high emissive calibration standard in Volt. ULsensor signal of the low emissive calibration standard in Volt. 5 Principle of low emitting surfaces Flexible sheets for waterproofing with a low emitting surface are commonly referred to as radiant or reflect
26、ive barriers. The principle of a radiant barrier is based on its ability to reflect radiant heat instead of absorbing it. Radiation (radiant heat) is the transmission of electromagnetic rays through space and in this context “radiation” refers only to the energy of infrared rays. At any temperature,
27、 all objects radiate infrared rays, which travel in all directions until they are reflected or absorbed by another object. The heating of objects excites the molecular surface structure, resulting in an emission of infrared radiation from the surface. The radiative flux through a body will satisfy t
28、he conservation-of-energy equation: + + = 1 Radiant barriers are typically rather opaque to infrared radiation, so in a simplified consideration the transmission is negligible: = 0 + = 1 = 1 - BS EN 15976:2011EN 15976:2011 (E) 6 Key 1 Incident energy 3 Absorbed energy 2 Reflected energy 4 Emitted en
29、ergy Figure 1 Energy diagram The amount of emitted radiation is a function of the emissivity factor () of the source surface. At the same nominal wave length the absorption factor () equals the emissivity factor (): = 6 Hemispherical blackbody radiator 6.1 Principle of hemispherical blackbody radiat
30、or The hemispherical radiator (half sphere) in the form of a blackbody uses the thermal infrared radiation principle (TIR-principle). The temperature of the blackbody is set and controlled at 100 (+/- 0,5 C). The hemispherical shape of the radiator is necessary in order to achieve a complete and hom
31、ogenous illumination of the measuring surface allowing even the emissivity of rough and structured surfaces to be measured correctly. Part of the energy reflected and emitted by the sample passes through a small opening in the hemispherical radiator and is focussed onto an infrared sensor by an infr
32、ared lens. The infrared sensor changes the incident thermal radiation into a voltage signal in a broad band and linear manner (the voltage signal is proportional to the reflected thermal energy). At any given temperature of a blackbody, the spectral distribution of the thermal radiation is given by
33、Plancks law. The radiators temperature has been chosen to be 100 ( 0,5 C) so that the corresponding spectrum BS EN 15976:2011EN 15976:2011 (E) 7 has its peak at a wavelength () of ca 8 m and more than 97 % of the radiant energy is in the wavelength range from (2,5 to 40) m. Key 1 Thermopile Ir Senso
34、r 2 Ir lens 3 Sample Figure 2 Hemispherical blackbody radiator 6.2 Description of hemispherical blackbody radiator and of the specimen holder In order to reduce the hemispherical blackbody radiator (in the following also written as apparatus) related errors to a minimum the half sphere should have a
35、 diameter of not smaller than 70 mm. Also the distance of the surface to measure to the apparatus shall be approximately 2 mm. The axis of the infrared sensor and infrared lens assembly shall point at the centre of the specimen and shall be between 70 and 80 to the specimen surface. An adequate elec
36、tronic method to evaluate the measuring signals should be applied. In order to avoid the heat up of the specimen the measuring time should be limited to 3 s maximum. BS EN 15976:2011EN 15976:2011 (E) 8 The specimen holder should have a solid flat front surface with a minimum of 140 mm by 140 mm. The
37、 fixation of the specimen onto the specimen holder should be adapted to the type of material to test. The specimen must be flat and wrinkle-free over the whole surface. Thin materials may be wrapped around the left and the right edges of the specimen holder and then fixed on both sides by magnetic s
38、trips. For thick and stiff materials, fixing should be adapted on case by case basis (clamps, hooks, etc.). The specimen must be maintained parallel to the apparatus during measurement. The distance of 2 mm between specimen and apparatus should be pre-defined by spacers, which should also prevent an
39、y rocking of the specimen. Dimensions in millimetres Figure 3 Hemispherical blackbody radiator and specimen 6.3 Handling procedure of calibration standards Typical calibration standards for low emitting surface should be 0,01 0,94. Calibration standards must be certified by the manufacturer of the a
40、pparatus or by an independent Institute, accompanied by a certificate showing the measured emissivity. The calibration standards must be recertified (or replaced by new certified standards) at least every two years. The calibration standards must be stored in a dark, clean, dust-free and dry environ
41、ment. If the low emissivity calibration standard shows up spots with different brightness, scratches or other visual defects caused by handling, it shall be replaced. BS EN 15976:2011EN 15976:2011 (E) 9 6.4 Calculation of the emissivity Determination of the emissivity () results from comparing the m
42、easuring result of the specimen with the two calibration standards. With the sensor signals (U, UHand UL) and the known emissivity of calibration standards (L and H), the of the specimen is calculated by: 6.5 Measurement range of hemispherical blackbody radiator The measurement range of the apparatu
43、s is limited to values between those of the two calibration standards used thus from emissivity range of 0,02 0,94. 7 Sampling and preparation of the test specimens 7.1 Sampling A sheet sample of an undamaged roll shall be selected in accordance with EN 13416. 7.2 Dimensions and numbers of specimens
44、 A minimum of five specimens should be taken with a regular spacing. The specimen size should be adapted to the size of the specimen holder and to the fixation system of the specimen holder (see 6.2). 7.3 Preparation of specimens before testing The specimens should be kept for a minimum of 2 h at a
45、temperature of 23 2 C and relative humidity of 50 20 %. Special precaution should be taken to ensure that the calibration standards, the specimens and the apparatus are equilibrated in the same standard climatic conditions. Air currents and draughts in the measuring area must be avoided. 8 Procedure
46、 for measurement of specimens The apparatus should be switched on at least 2 h before calibration and beginning measurements. The apparatus should be installed in a fixed position and must not be moved during measurement. The specimen is brought up to the apparatus in a vertical orientation, pressed
47、 firmly against the spacers around the measuring window of the apparatus and the apparatus is activated to begin measurement. In order to avoid that the specimen temperature changes during the measurement, the residence time of the specimen in the measuring position must be reduced to a minimum. Bet
48、ween specimen positioning and start of measurement, not more than 1 s shall pass. If this speed of measurement is not achieved, if the measurement is otherwise interrupted or if the measurement on a specimen is to be repeated, the specimen should be withdrawn from the apparatus for the time it needs
49、 to cool down to laboratory temperature. The higher the emissivity and/or the lower the specific heat capacity ( c) of the material, the longer the specimen will need to cool down to laboratory temperature. In order to reduce measurement variability to a minimum (laboratory, specimen and apparatus related), after a time interval of maximum 1 h, the apparatus shall be recalibrated using the two calibration standards. = H - (H L)
