Because polyisocyanurate insulation manufacturers recently
changed how they determine and report thermal-resistance properties
for their products, there now is an additional set of R-values
being associated with polyisocyanurate insulation products. This
has caused some confusion in the marketplace, and I will attempt to
explain and clarify the situation.
On Jan. 1, polyisocyanurate insulation manufacturers began to
use the long-term thermal resistance (LTTR) method for determining
and reporting thermal-resistance properties of permeable-faced
polyisocyanurate insulation products. (For additional information,
see "An end
to a debate?" November 2002 issue.)
Previously, polyisocyanurate insulation manufacturers typically
tested and reported R-values for their products using PIMA 101,
"Roof Insulation Specimen Conditioning Procedure" (previously
RIC/TIMA 281-1), which is a six-month conditioning procedure
for...
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