Johns Manville R-38 Attic Unfaced Fiberglass Batt Insulation, 63.33-sq ft Coverage (23.75-in W x 48-in L) - U1348S

Regular price $146.11

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R-38 Unfaced Fiberglass Batt Insulation for Attics

Formaledehyde-free fiberglass batts deliver R-38 thermal performance for attics and cathedral ceilings. Pre-cut 48-in lengths fit 24-in on-center framing and provide 63.33 sq ft of coverage per pack.


Key Features:

  • High R-Value Performance: R-38 insulation boosts energy efficiency and comfort
  • Unfaced Design: No vapor barrier—ideal for adding over existing insulation
  • Pre-Cut Convenience: 48-in batts sized for 23.75-in width cavities with 24-in stud spacing
  • Durable Fiberglass: Will not rot, mildew, or corrode pipes, wiring, or metal studs
  • Low Emissions Certifications: GREENGUARD Gold and SCS Recycled Content certified

Specifications Table:

Specification Details
Coverage Area (Sq. Feet) 63.33
Length (Inches) 48
Width (Inches) 23.75
Thickness (Inches) 12
Faced/Unfaced Unfaced
Framing Type Wood studs
Insulation Type Fiberglass
Maximum R-Value 38
R-Value per Inch 3.1667
Stud Spacing (Inches) 24
For Use in Attics Yes
For Use in Ceilings Yes
For Use in Walls No
For Use in Floors No
For Use in Basements No
For Use in Crawlspaces No
For Use in Doors No
For Use in Duct No
For Use in Electrical No
For Use in Garage Doors No
For Use in Masonry No
For Use in Plumbing No
For Use in Vents No
For Use in Windows No
Formaldehyde Free Yes
Sound Barrier Yes
Vapor Retardant No
ENERGY STAR Certified Yes
GREENGUARD Gold Certified Yes
Warranty 1-year limited
Bag Dimensions (L x W x D) 24.3 x 20 x 50
Package Weight (lbs.) 45.68
Package Type Multi-pack
Package Count 8
Multi-Pack Quantity 4
Total Package Quantity 32
UNSPSC 11162400

Frequently Asked Questions (FAQ):

Q: How much area does one pack cover?
A: Each pack provides 63.33 square feet of coverage.


Q: Can I install this over existing insulation?
A: Yes, the unfaced batts can be laid over existing attic insulation where a vapor barrier is not needed.


Q: What framing spacing is this sized for?
A: These batts are designed for 24-in on-center framing with a 23.75-in cavity width.


Q: Is the product formaldehyde-free?
A: Yes, it is formaldehyde-free and GREENGUARD Gold certified for indoor air quality.


Q: Where can it be used?
A: Primarily for attics and cathedral ceilings; not intended for walls or crawlspaces.


Quiet, Cozy Attics with Effortless Elegance

This R-38 batt brings a serene hush and steady comfort to upper levels, wrapping your home in a clean, minimalist layer. The slim profile is tailored for cathedral ceilings, creating a refined envelope without bulk. Pair it with soft, natural finishes—think pale woods and matte paints—to amplify its calm energy efficiency. Consider it a foundational luxury: invisible, indispensable, and beautifully effective.


Upgrade your attic with R-38 performance and start saving on energy costs today.

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