ISO INTERNATIONAL STANDARD 10291 First edition 1994-09-15 Glass in building Determination of steady-state U values (thermal transmittance) of multiple glazing Guarded hot plate method Verre dans la construction - Deétermination du coefficient de transmission thermique U, en régime stationnaire des vitrages multiples Méthode de la plaque chaude gardée ISO Reference number ISO 10291:1994(E) ISO 10291:1994(E) Foreword 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 which a technical committee has been established has the right to be and non-governmental, in liaison with ISO, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (lEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International a vote. ISO1994 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. InternationalOrganizationfor Standardization Case Postale 56· CH-1211 Geneve 20· Switzerland Printed in Switzerland ii INTERNATIONAL STANDARD ISO ISO10291:1994(E) Glass in building - Determination of steady-state U values (thermal transmittance) of multiple glazing - Guarded hot plate method Scope IsO 10292:1994, Glass in building — Calculation of 1 steady-state U values (thermal transmittance) of mul- This International Standard specifies a measuring tipleglazing method used to determine the coefficient of thermal transmittance, the U-value, of multiple glazing with General flat and parallel surfaces, including cast and figured 3 rolled glass. Thisinternational Standardmakespossiblethedeter- It applies to multiple glazing with outer panes which mination of the coefficient of thermal transmittance, are not transparent to far-infrared radiation, which is the U-value, in the central area of the multiple glazing the case for normal window glass. However internal Edge effects, due to the thermal bridge through the elements may be far-infrared transparent. spacer of a sealed glazing unit or through the frame are not included. Neither is energy transfer due to solarradiationtaken intoaccount. Thedeterminationof thecoefficientof thermal 2 Normative references transmittance is performed for conditions which will correspond to the average situation for glazing in The following standards contain provisions which, practice. In this way a fair comparison between dif- ferent products becomes possible. through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements Basic equations and units 4 based on this International Standard are encouraged The coefficient of thermal transmittance, the U-value, toinvestigatethepossibilityofapplyingthemostre- cent editions of the standards indicated below. cf glazingcharacterizestheheattransferthroughthe Members of IEC and ISO maintain. registers of cur- central part of the glazing, i.e. without edge effects, rently valid International Standards. and defines the steady-state density of heat transfer per unit of time, per surface area unit and per tem- Is0 8302:1991, Thermal insulation - Determination perature difference between the ambient tempera- of steady-state thermal resistance and related prop- tures on each side. The U-value is given in watts per square metre kelvin [W/(m².K)]. erties- -Guardedhotplateapparatus.