Johns Manville Formaldehyde-free fiberglass batts offer the greatest thermal performance. They are for use in new or existing attic floor/ceiling applications. Use of a separate vapor barrier may be required. This product helps save energy and provides good sound absorption. Glass fiber will not settle, rot, mildew or deteriorate. Convenient pre-cut batts mean less cutting. This product has been GREENGUARD® certified for superior indoor air quality.