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ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in

ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in

4.7(18 ratings)

Last price we saw

$132.90at Zoro, last seen Nov 7

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Our take on the ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in

ROXUL 40320 is a 1-inch mineral wool board, 48 by 24 inches, with an R-value of about 4 and a density of 8 lb per cubic foot. It is built for high-temperature service and does not absorb moisture, so it suits fire-rated and hot-side assemblies where foam or fiberglass would fail. It is sold as a single board, so a job needs several. Rated 4.7 out of 5 from 18 ratings.

Best forFire-rated wall and ceiling assembliesInsulating around stoves, flues and hot pipesSound damping in interior partitionsJobs needing a moisture-resistant, non-combustible board
Pros
  • Non-combustible mineral wool for high-temperature use
  • Density of 8 lb/cu ft gives a stiff, self-supporting board
  • Does not absorb moisture
  • Cuts with a serrated blade and friction-fits between studs
  • R-4 per inch of thickness
Cons
  • R-4 per inch is lower than foam board of the same thickness
  • Sold as one 48 x 24 in board, so coverage per unit is small
  • Mineral fibers irritate skin and lungs; gloves, sleeves and a mask are needed
  • Heavier and denser than fiberglass batts
  • Dust and crumbs during cutting

ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in prices at every store

  • ZoroCheck price at Zoro

ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in price history

Lowest price we've seen: $132.90 on Nov 7 at Zoro. Tracked across 1 store since Nov 7.

What reviewers say

  • 4.7 / 518 ratings

Buyers rate it highly, at 4.7 out of 5 from 18 ratings, and treat it as a dependable non-combustible board for hot and fire-rated spots. Complaints center on handling: itch, dust and the small coverage of a single board.

What people mention
  • Heat resistancePraisedBuyers use it around stoves, flues and rated assemblies and report it holds up where other insulation would not.
  • HandlingCriticisedOwners say the fibers itch and require gloves, long sleeves and a mask.
  • CuttingMixedIt cuts cleanly with a serrated blade but leaves dust and crumbs behind.
  • R-valueMixedAt about R-4 per inch it insulates less than foam board of the same thickness.
  • MoisturePraisedIt does not absorb water, which buyers value in damp or exterior-adjacent spots.

Specifications

Density
8 lb/cu ft
Thickness
1 in
Moisture Absorption
No
Approx. R Value
4
Length
48 in

Questions and answers

Is ROXUL 40320 safe around a wood stove or flue?
Yes. It is non-combustible mineral wool rated for high-temperature service, which is why buyers use it as a heat shield behind stoves and around flues. Check your stove's clearance requirements and local code before installing.
What R-value does one 1-inch board give?
About R-4. To reach R-13 you need roughly three layers, and each layer adds thickness, so plan the cavity depth before buying.
How many boards do I need for a wall?
Each board covers 8 square feet (48 by 24 inches). A 100-square-foot wall needs about 13 boards for one layer.
Can I cut it with a utility knife?
A serrated blade or insulation knife works better than a plain utility knife on this dense 8 lb board. Cut outdoors or with ventilation, and wear gloves and a mask.
Does it absorb water?
No. The board resists moisture absorption, so it can go in damp locations where fiberglass would sag or mat.
Is it heavier than fiberglass?
Yes. At 8 lb per cubic foot it is much denser than fiberglass batts, so expect a stiffer board that stays in place but is harder to carry.
What do buyers say about the ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in?
Rated 4.7 out of 5 from 18 ratings.

Stores we've priced the ROXUL 40320 Mineral Wool High Temperature Insulation 1 in x 48 in x 24 in at

  • Zoro deals and prices