1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 675:2011Glass in building Determination of thermaltransmittance (U value) Heatflow meter methodBS EN 675:2011 BRITISH STANDARDNational forewordThis British Standard is the
2、UK implementation of EN 675:2011. Itsupersedes BS EN 675:1998 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee B/520/4, Properties and glazing methods.A list of organizations represented on this committee can beobtained on request to its secretary.This p
3、ublication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 71596 9ICS 81.040.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the
4、 authority of theStandards Policy and Strategy Committee on 30 June 2011.Amendments issued since publicationDate Text affectedBS EN 675:2011EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 675 June 2011 ICS 81.040.20 Supersedes EN 675:1997English Version Glass in building - Determination of ther
5、mal transmittance (U value) - Heat flow meter method Verre dans la construction - Dtermination du coefficient de transmission thermique, U - Mthode du fluxmtre Glas im Bauwesen - Bestimmung des Wrmedurchgangskoeffizienten (U-Wert) - Wrmestrommesser-Verfahren This European Standard was approved by CE
6、N on 12 May 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 without any alteration. Up-to-date lists and bibliographical references concerning such national standards ma
7、y 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 other language made by translation under the responsibility of a CEN member into its own language and notified
8、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, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Lu
9、xembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All r
10、ights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 675:2011: EBS EN 675:2011EN 675:2011 (E) 2 Contents Page Foreword 3Introduction .41 Scope 52 Normative references 53 Terms and definitions .54 Basic formula .65 Brief outline of the measuring
11、procedure .66 Test apparatus .67 Calibration of the test apparatus . 108 Dimensions of the specimens . 109 Preparation of the specimens . 1010 Performance of the measurements. 1111 Evaluation of the results 1111.1 Thermal resistance of the multiple glazing 1111.2 Declared U value . 1111.3 Design U v
12、alue 1212 Expression of results . 1212.1 U values . 1212.2 Thermal resistance . 1212.3 Intermediate values 1213 Test report . 1213.1 Identification of the specimens . 1213.2 Cross section of the specimen 1313.3 Results . 13Bibliography . 14BS EN 675:2011EN 675:2011 (E) 3 Foreword This document (EN 6
13、75:2011) has been prepared by Technical Committee CEN/TC 129 “Glass in building”, the secretariat of which is held by NBN. 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 December 2011, and confli
14、cting national standards shall be withdrawn at the latest by December 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. This docum
15、ent supersedes EN 675:1997. The main change in this edition is that the internal and external heat transfer coefficients have been amended slightly to reflect changes to EN 673. Clarification is also given in the scope that the procedure specified in this European Standard should generally only be c
16、onsidered when the calculation method detailed in EN 673 is inappropriate or unsuitable. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czec
17、h Republic, 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 the United Kingdom. BS EN 675:2011EN 675:2011 (E) 4 Introduction
18、CEN/TC 129/WG 9 “Light and energy transmission, thermal insulation“ prepared a working draft based on the document ISO/DIS 10293 “Glass in building - Determination of steady-state U values (thermal transmittance) of multiple glazing - Heat flow meter method“, document that was prepared by ISO/TC 160
19、, “Glass in building“. This was published in 1997 as EN 675. The document for the calculation of the overall U value of windows, doors and shutters (see 2) gives normative reference to the U value evaluated for the glazing components according to this standard. For the purposes of product comparison
20、, a vertical position of the glazing is specified (see Clause 10). U values evaluated according to the present standard are used for product comparison as well as for other purposes, in particular for predicting: heat loss through glazing; conduction heat gains in summer; condensation on glazing sur
21、faces; the effects of the absorbed solar radiation in determining the solar factor (see 1). Reference should be made to 2, 3, 4 or other European Standards dealing with heat loss calculations for the application of glazing U values determined by this Standard. BS EN 675:2011EN 675:2011 (E) 5 1 Scope
22、 This European Standard specifies a measurement procedure to determine the thermal transmittance of glazing with flat and parallel surfaces. For the purpose of this Standard, structured surfaces may be considered to be flat This European Standard applies to multiple glazing with outer panes which ar
23、e not transparent to far infrared radiation (in the wavelength range 5m to 50m), which is the case for soda lime silicate glass products, borosilicate glass and glass ceramics. Internal elements can be far infrared transparent. The procedure specified in this European Standard determines the U value
24、 (thermal transmittance) in the central area of glazing. The edge effects due to the thermal bridge through the spacer of an insulating glass unit or through the window frame are not included. Energy transfer due to solar radiation is also excluded. The procedure specified in this European Standard
25、should be considered only when the thermal transmittance of the glazing cannot be calculated in accordance with EN 673. The determination of the thermal transmittance is performed for conditions which correspond to the average situation for glazing in practice. NOTE Patterned glass is an example of
26、a glass with a structured surface; 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, the latest edition of the referenced document (including any amendments)
27、applies. EN 673, Glass in building Determination of thermal transmittance (U value) Calculation method EN 12898, Glass in building Determination of the emissivity ISO 8301, Thermal insulation Determination of steady-state thermal resistance and related properties Heat flow meter apparatus ISO 8302,
28、Thermal insulation Determination of steady-state thermal resistance and related properties Guarded hot plate apparatus 3 Terms and definitions For the purposes of this document, the following terms and definitions apply: 3.1 U value parameter of glazing which characterizes the heat transfer through
29、the central part of the glazing, i.e. without edge effects, and states the steady-state density of heat transfer rate per temperature difference between the environmental temperatures on each side. NOTE The U value is given in watts per square metre Kelvin W/(m2K) 3.2 declared value U value obtained
30、 under standardized boundary conditions. NOTE See 11.2. BS EN 675:2011EN 675:2011 (E) 6 4 Basic formula The U value depends on the thermal resistance of the multiple glazing and on the external and internal surface heat transfer coefficients according to the relation: 1U= R +1he+1hi(1) where R is th
31、e thermal resistance of the multiple glazing in square metres Kelvins per Watt ()mKW2heis the external surface heat transfer coefficient in watts per square metre Kelvin ()W/ m K2hi is the internal surface heat transfer coefficient in watts per square metre Kelvin ()W/ m K2According to this standard
32、 the surface to surface thermal resistance is determined by measurements taken using the heat flow meter method. Thereupon the declared U value is determined according to Equation (1) with the values for the internal and external heat transfer coefficients specified in 11.2. The external surface is
33、the surface of the glazing intended to face the outside of the building in use. The internal surface is the surface of the glazing intended to face the inside of the building in use. 5 Brief outline of the measuring procedure The surface to surface thermal resistance of the multiple glazing is deter
34、mined by means of the heat flow meter method laid down in ISO 8301. The recommendations of that standard shall be complied with except for variations contained in this standard and for variations resulting from the special structure of the specimen. Within the present context further requirements ar
35、e necessary, viz. the size of the test specimens and the performance of the measurements are laid down to meet special requirements for measuring multiple glazing (see Clauses 6 to 13). 6 Test apparatus For the measurement of the thermal resistance of the specimen, the single-specimen apparatus with
36、 symmetrical configuration or a double specimen apparatus as shown in Figures 1 and 2 is used. The single-specimen apparatus consists of a heating and a cooling unit between which the specimen or a reference sample for the calibration of the apparatus is sandwiched. The cooling unit has surface dime
37、nsions as large as those of the heating unit. A heat flow meter is positioned in the centre of the hot plate surface and the cold plate surface. These heat flow meters face each other on either sides of the specimen or the reference sample. On each side of the heat flow meters a thin natural or synt
38、hetic foam rubber sheet is placed to ensure sufficient thermal contact. Surface contact is obtained by applying pressure. The foam rubber sheets have the same dimensions as the surface area of the heating unit. BS EN 675:2011EN 675:2011 (E) 7 The double-specimen apparatus consists of a heating unit
39、and two outer cooling units. The heating unit is sandwiched between the specimen to be measured and a control sample. For calibration a reference sample shall be introduced at the position of the specimen. On each side of the reference sample/specimen and the control sample heat flow meters are plac
40、ed. On each side of the heat flow meters a thin foam rubber sheet is placed to ensure sufficient thermal contact. The surface dimensions of all elements and the positioning of the heat flow meters in the central area of the assembly are the same as for the single specimen apparatus. For both apparat
41、us the heating unit shall be of such a size as to completely cover the surface of the reference sample/specimen and in the case of the double apparatus of the control sample. Heat losses from the outer edges of the heat flow meter apparatus shall be restricted by edge insulation or by controlling th
42、e surrounding air temperature or by both. For both apparatus the metering area of the heat flow meters shall have a circular or square shape and a minimum size of 75 cm. Its maximum size shall lie within an area of 50 cm x 50 cm. The metering area shall further be surrounded by a protective zone con
43、sisting of the same material in the same thickness (with a tolerance of 0,1 mm) covering the whole sample area (see Figures 1 and 2). Thermocouples are mounted in pairs. They are positioned to face each other and shall have direct contact to the surfaces of the reference sample/specimen and in the c
44、ase of the double apparatus the control sample. At least three thermocouple positions shall be chosen, one positioned in the centre of the metering area of the heat flow meters and two others diametrically opposite in a distance of 2/3 from the centre of the metering area to its perimeter. Additiona
45、l thermocouples may be arranged in such a way that an optimum cover of the metering area is achieved. Such thermocouples shall have a thickness not exceeding 0,2 mm; the junctions shall be flattened so as not to exceed 0,2 mm and a contact material (e.g. zinc oxide loaded silicon grease or metal tap
46、e) shall be used to insure a good thermal contact between the junction and the specimen. BS EN 675:2011EN 675:2011 (E) 8 Dimensions in millimetres Key metering area of the heat flow meter insulating material protective zone thin foam rubber sheet 1 heating unit 2 specimen 3 cooling unit” Figure 1 Si
47、ngle-specimen apparatus BS EN 675:2011EN 675:2011 (E) 9 Dimensions in millimetres Key metering area of the heat flow meter insulating material protective zone thin foam rubber sheet 1 cooling unit 2 specimen 3 heating unit 4 - control sample 5 cooling unit Figure 2 Double-specimen apparatus BS EN 67
48、5:2011EN 675:2011 (E) 10 7 Calibration of the test apparatus The heat flow meter method is a relative measuring method since the ratio of the thermal resistance of the specimen to that of a reference sample is evaluated. The thermal resistance of the reference sample shall be determined separately i
49、n accordance with ISO 8302 (Guarded hot plate apparatus). As a reference sample a homogeneous, non hygroscopic material with flat and parallel surfaces, with a heat resistance comparable to that of the specimen to be measured shall be used. The heat flow density, , in watts/m2 transferred through the heat flow meter is computed from the voltage V (in volt) generated and the mean temperature Tm(in Kelvin) of the heat flow meter metering area according to the
