Abstract
A rig has been designed and constructed to measure the thermal transmittance (U-value) and conductance of test walls 2 m by 2 m in area. The rig is of the guarded hot-box type and is based in principle on details given in the ASTM C 236–66 standard. Special measures have been taken in the design and operation of the rig to improve the accuracy of measurement. The guard system is automatic and controlled from the output of a thermopile on the metering box walls. Fans are used to circulate the air in the metering box and the heat contribution from the fan blades is taken into account in the measurement. Validation tests have been made using a glass fibre panel and the results agree very closely with the calculated thermal transmittance and conductance.
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