Restrictions in the use of CFC blowing agents and difficulties in esti mating long-term thermal resistance of new gas-filled cellular plastics led to the es tablishment of an expert task group with a mandate to review and improve R-value evaluation techniques
One approach, based on measurement of thermal resistance of thin material layers (scaling factors), was found to be applicable to homogeneous and uniform boards In one case the estimate was confirmed by long-term R-value measurements performed on the actual product Future research to extend application of the technique to non uniform or to faced cellular plastic boards is recommended
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