Description
Johns Manville R-38 Kraft-Faced: The Replacement-Job Standard
When an attic has been cleared of old, rodent-damaged or compacted insulation, the new layer goes directly on the ceiling drywall. That’s where a kraft-faced batt belongs: the paper facing acts as a vapor retarder toward the living space, and the batt fills the joist bays to R-38. Johns Manville’s Formaldehyde-free™ fiberglass has been a staple of that work for years.
Specifications
| Brand | Johns Manville |
|---|---|
| R-value | R-38 |
| Material | Formaldehyde-free™ fiberglass |
| Facing | Kraft paper (vapor retarder) |
| Thickness | About 12″ |
| Common bag sizes | 16″ x 48″ ≈ 42.7–48 sq ft; 24″ x 48″ ≈ 72 sq ft |
| Applications | Attic floors, ceilings |
| Sold by | Bag — confirm width when ordering |
Where to Use It — and Where Not To
- Use it on a bare attic floor or new construction ceiling, paper facing down toward the heated space.
- Use it after insulation removal and attic cleaning, as the first layer.
- Don’t use it on top of existing insulation — a second vapor retarder can trap moisture. Use an unfaced batt such as Knauf EcoBatt R-38 instead.
- Don’t leave the facing exposed — kraft paper is combustible.
How Many Bags?
Divide the attic floor area by the coverage printed on the bag and add about 5%. For a 1,200 sq ft attic with 16″ bags at about 42.7 sq ft, that’s about 30 bags; with 24″ bags at about 72 sq ft, about 18 bags. Call 800-778-3765 and we’ll confirm the count.
Why Replace Instead of Adding On Top?
In many Los Angeles and Orange County attics, the old insulation is compacted, stained or contaminated by rodents. Adding new batts over it hides the problem rather than fixing it. Removing the old material, sanitizing, rodent-proofing and then installing fresh kraft-faced R-38 gives you the full rated R-value and a clean attic.
Buy It or Have It Installed
Order Johns Manville R-38 for your own project, or have our licensed team (CSLB #1139733) do the complete removal and replacement. We serve Los Angeles, the San Fernando Valley, Orange County, the Inland Empire and Las Vegas. See all R-38 fiberglass batts or request a free estimate.
Johns Manville R-38 FAQ
- Which way does the kraft facing go in an attic?
- Down, toward the living space below. The facing is a vapor retarder and belongs on the warm-in-winter side of the insulation.
- Can I use kraft-faced R-38 over old insulation?
- No. Use unfaced batts for any layer that goes over existing insulation, so moisture isn’t trapped between layers.
- Is Johns Manville insulation formaldehyde-free?
- Yes. Johns Manville markets its residential fiberglass batts as Formaldehyde-free™.
