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Content archived on 2024-04-19

Construction, characterisation and application of calibration panels for U-value measurement of glazed assemblies


Draft CEN standards prEN 12412 -1 and prEN1098 and an ISO draft standard, ISO/CD 12567 specify procedures for carrying out thermal transmission (U-value) measurements on window systems and insulated glazing units. The method requires laboratories to carry out hot-box measurements on at least two glazed calibration panels of known thermal conductance. Although the accuracy of the U-values obtained using these procedures will depend critically on the precision to which the calibration panel conductance can be calculated and on how stable the panels are, no guidelines are given as to how these panels should be made. This project set out to establish the basis of a technical supplement to the standards that will specify how the panels should be designed and constructed.

The objective of the project was to:
establish a precise method for the construction, characterisation and application of glazed calibrated reference panels for hot-box use.
validate the chosen design and construction procedure by carrying out the calibration measurements and using the calibration data to derive U-values as specified in the draft standards.
The agreement between the five laboratories' measurements of thermal conductivity of the insulation material used in the core, indicated that a measurement uncertainty of (4 % can be assumed.
The agreement between the five laboratories' measurements of overall panel thickness indicated that a measurement uncertainty of (2% can be assumed.
The fabrication method specified was shown to produce reliable and robust glazed calibration panels whose thermal conductance could be calculated to approximately (6%.
The U-value measurements made using the data from the calibration panels and the CEN procedures have shown that the data from these panels enabled measurement uncertainties of about (7% to be attained.
A number of suggested improvements to the measurement standards have been made. Guidelines for the construction and use of the panels have been transmitted to CEN TC 129 and CEN TC 89.
The project involved five laboratories, from different countries, fabricating the calibration panels. This involved choosing a suitable design; selecting the correct materials, adhesives etc.; measuring the thermal conductivity of the insulation material; measuring the average thickness of the glazed calibration panels and choosing a fabrication procedure that could easily be reproduced in different laboratories. Each laboratory then carried out the hot-box measurements specified in the standards The laboratories then passed each of their panels to a different partner who measured the U-value as specified in the standards, using the data from their own calibration panels. One of the panels was measured by all the participants as a check.


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Queens Road 33
United Kingdom

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Participants (4)