FSK-25 Faced

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Combining fire resistance with a vapor barrier, Johns Manville FSK-25 batts are designed with a foil facer that can be left exposed where codes permit.

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.

FSK Faced_Batts_Rev_White Background 190x122

Note: Color of product may differ based on the manufacturing location.


Thermally Efficient: Effective resistance to heat transfer, with R-values up to R-30.
Formaldehyde-free: Will not off-gas formaldehyde in the indoor environment.
Sound Control: Reduces sound transmission through exterior and interior walls, floor and ceiling assemblies.
Fire-Resistant: Flame Spread of 25 or less and Smoke Developed of 50 or less. Can be left exposed where building codes permit.
Resilient Inorganic Glass: No rotting, mildew or deterioration. Also noncorrosive to pipes, wiring and metal studs.
Superior Performance: Stable bonded glass fibers will not slump, settle or break down during normal applications.

  ASTM Standards   ASTM C665   Type III, Class A, Category I
  Flame Spread   ASTM E84   ≤ 25
  Smoke Development   ASTM E84   ≤ 50
  Water Vapor Permeance Facing   ASTM E96   0.05 Perms (3 ng/Pa-s-m2)
  Water Vapor Sorption   ASTM C1104   5% or less by weight
  Odor Emission   ASTM C1304   Pass
  Corrosiveness   ASTM 665   Pass
  Fungi Resistance   ASTM C1388   Pass

Data Sheet

FSK-25 Data Sheet




Product Selector Guide

Certifications and Specifications

Fiberglass Batts EDP


Limited Warranty

JM Overview Video

JM Fiberglass Video

Insulating Your Crawl Space Video

Installating in Your Attic Video

Insulating Around Objects Video

Insulating Floors or Ceilings Video

Installing Wall Insulation Video

Available Documents