R-21 Unfaced Fiberglass Batt Insulation (15 in. x 93 in.)

JM R-21 unfaced fiberglass batts deliver thermal performance and sound control for 2x6 wood-stud cavities. Precut to 93 in. for standard 8 ft. walls, each bag covers 67.81 sq. ft. and can be used in walls, floors, and crawlspaces.

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Key Features:

• Right-Size for 2x6 Framing: 15 in. wide x 5.5 in. thick batts fit 2x6 wood-stud cavities for a secure friction fit
• Unfaced for Flexible Assemblies: No vapor retarder, making it suitable for layering with existing insulation or where a separate vapor control layer is desired
• Energy & Comfort Upgrade: R-21 helps reduce heat transfer to improve overall energy efficiency
• Sound Control: Helps reduce noise transmission through wall, floor, and ceiling assemblies
• Formaldehyde-Free & Durable Fiberglass: Made with resilient glass fibers; designed not to rot or mildew and to remain dimensionally stable in the cavity

Please check the Product Data Sheet Here

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Specifications Table:

Specification	Details
Brand	JM (Johns Manville)
Manufacturer	Johns Manville
Model / Manufacturer Part #	U1321
Insulation Type	Fiberglass batt
Faced or Unfaced	Unfaced
R-Value	R-21
Coverage Area	67.81 sq ft
Batt Width	15 in
Batt Length	93 in (7.75 ft)
Insulation Thickness	5.5 in (5-1/2 in)
Fits Wall Size	2 x 6 wall
Stud Spacing Compatibility	16 in on-center (standard 8 ft wall precut length)
Pieces per Bag	7 pieces
Product Weight	28.6 lb
Bag Size	3.9 ft x 40 in x 15 in
Batt/Roll Size	7.75 ft x 15 in
Insulation Features	Friction fit; sound control/soundproofing
Application Areas	Walls, floors, ceilings, basements, attics, crawlspaces (new construction and remodels)
For Use With	Wood stud framing
Flame Spread Index	<25
Smoke Developed Index	<50
Temperature Rating	850°F
Water Vapor Sorption	<5%
Standards/Certifications	ASTM C665 Type I; ASTM E136; IBC; Energy Star Certified; Greenguard Gold Certified; Indoor Air Quality Certified; NAIMA 16 CFR Part 460; Recycled Content Certified

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Frequently Asked Questions (FAQ):

Q: Is this insulation faced?
A: No—this is unfaced fiberglass batt insulation (no vapor retarder).

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Q: What wall cavity does it fit?
A: It’s sized for 2x6 wood-stud framing with 16 in. on-center spacing (15 in. wide batts).

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Q: How much area does one bag cover?
A: One bag covers 67.81 sq. ft.

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Q: Can I use this in basements, attics, or crawlspaces?
A: Yes—it's listed for use in areas such as attics, basements, ceilings, crawlspaces, floors, and interior/exterior walls (where appropriate for fiberglass batts).

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Q: Do I need special tools to cut it?
A: Batts can be cut to fit using a utility knife and a straightedge; wear appropriate PPE when handling fiberglass.

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Quiet luxury, engineered into the walls

There’s a particular elegance in rooms that feel calm—where temperature holds steady and sound softens at the edges. These R-21 unfaced fiberglass batts tuck cleanly into 2x6 cavities, creating an invisible layer of comfort that lets your finishes shine. Use them as the quiet foundation behind paneling, plaster, or millwork-heavy spaces where acoustics matter as much as aesthetics. It’s the kind of behind-the-scenes upgrade that makes a home feel unmistakably more refined.

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Upgrade your comfort and sound control—choose JM R-21 unfaced batts to efficiently insulate 2x6 wall cavities with reliable coverage per bag.

Warranty

Installation