Johns Manville R-38 Unfaced Fiberglass Batt Insulation, 64-sq ft Coverage, 24-in x 48-in, U366SR 38 Unfaced Fiberglass Attic Batt Insulation, 24x48 in High R 38, unfaced fiberglass batts designed for wood framed attics, ceilings, and floors. Precut 24 in x 48 in pieces provide 64 sq ft of coverage per package and install easily between 24 in on center joists for improved energy efficiency and sound control. Key Features: High Thermal Performance: R 38 batts boost energy efficiency and comfort in attics, ceilings, and floors Unfaced Design: No

R-38 Unfaced Fiberglass Attic Batt Insulation, 24x48-in

High R-38, unfaced fiberglass batts designed for wood-framed attics, ceilings, and floors. Precut 24-in x 48-in pieces provide 64 sq ft of coverage per package and install easily between 24-in on-center joists for improved energy efficiency and sound control.

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Key Features:

• High Thermal Performance: R-38 batts boost energy efficiency and comfort in attics, ceilings, and floors
• Unfaced Design: No vapor barrier—ideal for adding over existing insulation where permitted
• Precut Convenience: 24-in x 48-in batts sized for 24-in on-center framing; simple press-in installation
• Durable, Healthy Choice: Formaldehyde-free fiberglass that won’t rot, mildew, or corrode pipes/wiring
• Certified for Indoor Air Quality: GREENGUARD Gold and SCS Recycled Content certified; ENERGY STAR partner

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Specifications Table:

Specification	Details
R-Value	38
Coverage Area	64 sq ft
Dimensions (each batt)	24 in W x 48 in L x 13 in T
Stud/Joist Spacing	24 in on-center
Faced/Unfaced	Unfaced
Insulation Type	Fiberglass
For Use in Attics	Yes
For Use in Ceilings	Yes
For Use in Floors	Yes
For Use in Walls	No
Formaldehyde Free	Yes
Sound Barrier	Yes
Vapor Retardant	No
ENERGY STAR Certified	Yes (program partner)
GREENGUARD Gold Certified	Yes
Framing Type	Wood studs
Length	48 in
Width	24 in
Thickness	13 in
Package Weight	37 lbs
R-Value per Inch	2.923
Package Count	8 pieces
Package Type	Multi-pack
Multi-Pack Quantity	4
Total Package Quantity	32
Warranty	1-year limited
UNSPSC	11162400
Bag Dimensions (L x W x D)	20 x 20 x 50 in

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Frequently Asked Questions (FAQ):

Q: How much area does one package cover?
A: Each package provides 64 square feet of coverage with eight 24-in x 48-in batts.

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Q: Can these batts be installed over existing insulation?
A: Yes. Because they are unfaced (no vapor retarder), they can be added over existing insulation where local codes allow.

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Q: Where can I use this product?
A: It’s designed for attics, ceilings, and floors with 24-in on-center wood framing; not intended for walls or masonry.

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

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Q: What is the thickness of each batt?
A: Each batt is approximately 13 inches thick to achieve R-38.

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Luxurious Warmth, Effortlessly Layered

Imagine a cocooned quiet settling over your home as these plush white batts disappear beneath your attic joists. Their generous 13-inch loft creates a serene, insulated envelope that elevates comfort and hushes the outside world. Pair with crisp, painted ceilings and natural wood finishes to accentuate the calm, controlled environment they enable. This is the invisible foundation of refined, luxurious living—comfort engineered with elegance.

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Upgrade your attic with JM R-38 batts today for immediate comfort, quieter rooms, and long-term energy savings.