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A discrepancy in polyiso's R-values

Professional Roofing



LTTR; long-term thermal resistance; R-value; polyiso; polyisocyanurate; insulation;

This month, U.S. polyisocyanurate insulation manufacturers begin reporting long-term thermal resistance (LTTR) values based on updated and revised test methods, resulting in lower LTTR values than previous values. Does this change settle a decades-long debate regarding R-values for polyisocyanurate insulation?

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