Q:  What effect does the facing have on the NRC of a product?

A:  The use of facings on products that are typically left exposed (board products) can reduce the NRC value of the material. Gas permeable facings such as the non woven material used with Johns Manville's Insul-SHIELD® Black provide performance equivalent to unfaced products. Impermeable facings such as FSK PSK and vinyl facings reflect high frequency sound reducing the ability for fiber glass insulation to absorb sound.