1、STD*BSI BS EN 12878-ENGL 2001 Lb24bb9 0902094 814 M BRITISH STANDARD Glass in building - Determination of the a a a. emissivity The European Standard EN 12898:2001 has the status of a British Standard ICs 81.040.20 BS EN 12898:2001 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT L
2、AW STDDBSI BS EN LZq-ENGL 2001 m L24669 0902095 750 m BS EN 12898:2001 Amd. No. Date National foreword Comments This British Standard is the official English language version of EN 12898:2001. The UK participation in its preparation was entrusted by Technical Committee B/520, Glass and glazing in bu
3、ilding, to Subcommittee B/520/4, Properties and glazing methods, which has the responsibility to: - - aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related
4、international and European developments and promulgate them in the UK. - A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document ma
5、y be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British
6、Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. “his British Standard, having been prepared under the direction of the Sector Committee for Building and Cid Engineering, was published under the aut
7、hority of the Standards Committee and comes into effect on 15 April 2001 Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 13 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. O
8、BSI 04-2001 ISBN O 580 37308 8 STD-BSI BS EN L2898-ENGL 2OOL L624b69 0902096 697 m EUROPEAN STANDARD EN 12898 NORME EUROPENNE EUROPISCHE NORM January 2001 ICs 81.040.20 English version Glass in building - Determination of the emissivity Verre dans la construction - Dtermination de Imlssivit Glas im
9、Bauwesen - Bestimmung des Emissionsgrades This European Standard was approved by CEN on 1 January 2001. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
10、Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation und
11、er the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxem
12、bourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMEE FOR STANDARDIZATION COMITE EUROPEEN DE NORMALISATION EUROPAISCHES KOMITEE FUR NORMUNG Management Centre: rue de Stassart, 36 8-1050 Brussels Q 2001 CEN All rights of exploitation in any form and by a
13、ny means reserved worldwide for CEN national Members. Ref. No. EN 12898:2001 E STDeBSI BS EN 32898-ENGL 2001 M 3624bb9 0902097 523 Page 2 EN 12898:2001 Contents Page Foreword 3 1 Scope 4 2 Symbols 4 3 Terms and definitions 4 5 Spectral normal reflectance and transmittance measurements 6 7 Diffuse re
14、flectance measurements . 9 8 Test report 9 Annex A (normative) Tables for determining total normal reflectance and total corrected emissivity 11 Annex B (informative) Procedures to improve the accuracy of spectral normal reflectance measurements . 12 Bibliography . 13 4 Brief outline of the procedur
15、e to determine corrected emissivity 6 6 Calculation of total normal reflectance, corrected emissivity and total normal transmittance . 8 STD-BSI BS EN L2878-ENGL 2003 Lb24bb7 0702078 4bT - Page 3 EN 12898:2001 Foreword This European Standard has been prepared by Technical Committee CENITC 129 “Glass
16、 in building“, the secretariat of which is held by IBN. 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 July 2001, and conflicting national standards shall be withdrawn at the latest by July 2001.
17、 According to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Por
18、tugal, Spain, Sweden, Switzerland and the United Kingdom. STD.BS1 BS EN 12898-ENGL 2001 1b24bb9 0902099 3Tb Page 4 EN 12898:2001 1 Scope This European Standard specifies a procedure for determining the emissivity at room temperature of the surfaces of glass and coated glass. The emissivity is necess
19、ary for taking into account heat transfer by radiation from surfaces at the standard temperature of 283 K in the determination of the U value and of the total solar transmittance of glazing according to l to 5. The procedure, being based on spectrophotometric regular reflectance measurements at near
20、 normal incidence on non-infrared transparent materials, is not applicable to glazing components with at least one of the following characteristics: a) with rough or structured surfaces where the incident radiation is diffusely reflected; b) with curved surfaces where the incident radiation is regul
21、arly reflected at angles unsuitable to c) infrared transparent. However, it may be applied with caution to any glazing component provided its surfaces are flat and non-diffusing (see 3.6) and it is non-infrared transparent (see 3.7). reach the detector while using regular reflectance accessories; 2
22、Symbols b) total normal reflectance at 283 K, n, shall be calculated using the integration procedure specified in clause 6 from the corresponding spectral reflectance values measured according to step a); c) total normal emissivity, En, shall be calculated from the total normal reflectance as specif
23、ied in clause 6; d) the corresponding corrected emissivity, E, shall be determined by multiplying normal emissivity by the ratio, - a reference mirror (free of surface scratches and contamination, see 7, 9 and lo) whose spectral regular reflectance at near normal incidence Rn,st (A) shall be traceab
24、le to a standard material certified by a metrological laboratory; - a specular reflectance accessory consisting of a suitable array of mirrors and a sample support. When the accessory is placed in the sample compartment of the spectrophotometer and the sample (or reference mirror) placed on the samp
25、le support, the instrument beam reaches the detector after being specularly reflected on the surface of the sample (reference mirror) at an angle of incidence I 1 O“. 5.2.2 Measurement The spectral regular reflectance curve of the sample at near normal incidence shall be determined with the relative
26、 method. The following measurements are required to determine the spectral normal reflectance of the sample Rn (4) at each wavelength ;li reported in Table A.l: - E the instrument reading with the sample placed on the sample support of the reflectance accessory; - Est the instrument reading with the
27、 standard replacing the sample; - EO the instrument reading without placing anything on the sample support. At each wavelength 4 the sample reflectance Rn (4) shall be calculated as follows: with Rn,st (4) = spectral normal reflectance of the reference mirror at the wavelength 4. NOTE Metrological l
28、aboratories determine the absolute reflectance by comparing the energy of the beam reflected from the sample to that of the incident beam or with the help of a double reflection accessory called W-W or “Strong-type“ (see 1 O). Commercial versions of such devices exist but their construction is far s
29、hort of the careful layout of the original version. Their accuracy is critically dependent on alignment and beam characteristics (size and divergence) STD-BSI BS EN 12898-ENGL 2001 Lb24bb9 0902103 657 M Page 8 EN 12898:2001 and is difficult to control in conjunction with commercial spectrophotometer
30、s. They should be used only with great caution and under the supervision of a metrological laboratoiy. 5.2.3 Accuracy The accuracy is estimated to be of the order of * 0,02, expressed as absolute uncertainty of regular reflectance (see il). NOTE In annex B information on procedures to improve the me
31、asurement accuracy is given. 5.3 Transmittance measurements Glazing components including at least one glass plate are not infrared transparent and do not request transmittance measurement. For glazing components not including glass or coated glass the spectral regular transmittance curve of the samp
32、le at normal incidence between 5 pm and 50 pm shall be determined with an infrared spectrophotometer by placing it in the sample compartment perpendicularly to the beam. 6 Calculation of total normal reflectance, corrected emissivity and total normal transmittance 6.1 Total normal reflectance Total
33、normal reflectance, Rn, at a temperature of 283 K shall be determined from the spectral reflectance curve by taking the mathematical average of spectral reflectance, n (A), measured at the 30 wavelengths (Ai) given in Table A.l. Such wavelengths are selected at the centre of wavelength intervals for
34、 which the energy of Plancks radiation function for a blackbody at 283 K is constant (see 7). 6.2 Emissivity Total normal emissivity En at 283 K is given by En =l-n (3) NOTE 1 The uncertainty resulting when the measurement range of the spectrometer does not cover the 30 selected wavelengths reported
35、 in Table A.l is discussed in fl. For soda lime glass and coated soda lime glass the corrected emissivity, multiplying normal emissivity by the ratio given in Table A.2. , shall be determined by _- STD.BS1 BS EN 12898-ENGL 2001 1b24bb9 0902104 593 Page 9 EN 12898:2001 NOTE 2 For surfaces other than
36、coated soda lime glass, uncoated soda lime glass, borosilicate glass and glass ceramics the table may be applied with caution, considering that it is not supported by experimental evidence comparable to that obtained for glass (see 6, 8 to 9 and ll to 13). 6.3 Total normal transmittance Where applic
37、able, total normal transmittance at a temperature of 283 K shall be determined from the spectral transmittance curve by taking the mathematical average of spectral transmittance, Tn (A), measured at 30 wavelengths (Ai) given in Table A.l. 7 Diffuse reflectance measurements Diffuse reflectance at 2 p
38、m for near normal incidence irradiation is determined as the difference between hemispherical reflectance and regular reflectance (see l O). NOTE The purpose of this determination is to confirm that a given glazing component consisting of materials other than glass and coated glass is non-diffusing
39、(see 3.6). Glazing components consisting of float glass, coated float glass and laminated float glass have a negligible diffuse reflectance and do not request diffuse reflectance measurements. 8 Test report The test report shall state the following 8.1 Sample identification - sample size (millimetre
40、s) - material(s) of glazing component - thickness of glazing component (millimetres) - type of coating (if any, if known) on the surface being measured - storage, handling and cleaning conditions 8.2 Instrument description - manufacturer and model code of the spectrophotometer - type of spectrophoto
41、meter (single or double beam or FTIR; spectral range; specify if automatic, if - operating conditions during the scan - manufacturer and model of the reflectance accessory and angle of incidence - type of reference mirror and source of calibration interfaced to a computer; if purged with gas) STD.BS
42、I BS EN L2898-ENGL 2001 D Lb24bb9 0902L05 42T Page 10 EN 12898:2001 8.3 Results of the measurements - normal reflectance values at the 30 selected ordinates -total normal reflectance -total normal emissivity - total corrected emissivity - normal transmittance values at the 30 wavelengths, where appl
43、icable - total normal transmittance, where applicable Intermediate values shall be quoted to three decimals in the test report. When normal and corrected emissivities are presented in manufacturers promotional material, the data shall be given to two decimal figures. STD-BSI BS EN L2898-ENGL ZOOL -
44、Lb24bb9 0902306 366 Page 11 EN 12898:2001 Annex A (normative) Tables for determining total normal reflectance and total corrected emissivity Table A.l - 30 selected wavelengths (A) for determining total normal reflectance, n, at 283 K Ordinal number i 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Wavelength(d
45、i) pm 5,5 6,7 784 8,1 896 992 937 10,2 10,7 11,3 11,8 12,4 12,9 133 14,2 Ordinal number i 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Wavelength (di) pm 14,8 15,6 16,3 17,2 18,1 19,2 20,3 21,7 23,3 25,2 27,7 30,9 35,7 43,9 50,0“ 50 pm has been chosen because this wavelength is the limit of most com
46、mercially available spectrophotometers. This approximation has a negligible effect on the accuracy of the calculation. Table A.2 - Factors to compute total corrected emissivity stray light; divergence of the incident beam (potentially causing vignetting of the reflected beam as its path increases, s
47、ee lo). A range of measurement errors typical of Fourier Transform spectrophotometers is described in 14. The wavelength scale can be checked with polystyrene films whose absorption peaks feature minima at known wavelengths. The photometric accuracy can be checked with the help of rotating sectors w
48、hich produce a known transmittance by intercepting a given percentage of the instrument beam or of samples with a known transmittance traceable to a reference material certified by a metrological laboratory (see I 51). 8.3 Reference mirror The reference mirror should have a reflectance as close as p
49、ossible to that of the sample, to limit errors due to non-linearity of the detector (see 1 O). The accuracy of reflectance measurements improves if the reference mirror is carefully stored and handled (see 7, 9 and lo). Some laboratories use as a reference mirror an opaque first surface AI, Ag or Au mirror to which the spectral reflectance suggested by some literature source is attributed. In this case, discrepancies arise due to non-uniform production and storage conditions, non-uniform literature references, insufficient
