Johns Manville Formaldehyde-free™ FSK-25 thermal and acoustical fiberglass insulation is available in R-Values up to R-30, and is offered in precut batts to fit standard wall cavities. FSK-25 faced batts combine fire resistance with excellent vapor resistance, and can be used in a wide variety of wood frame, engineered wood and steel frame construction applications, including new construction and retrofit. FSK-25 batts are designed with a foil facer that can be left exposed where codes permit.