Johns Manville PEBS Unfaced Filler Blanket Formaldehyde-Free™ insulation offers an R-Value of up to R-49, with sound control and fire resistance for roofs and walls. PEBS is an economical, general-purpose fiberglass designed as filler material for use in both new construction and retrofits of pre-engineered metal buildings. It's easy to cut with a utility knife and the blanket can be friction-fit easily in standard pre-engineered metal framing.