What does R15 mean and where does this batt go?

R15 is the insulation's thermal resistance. This 24x47 batt is sized for 2x6 wall and floor cavities, typically exterior walls.

Is this one batt or a pack?

The listing is for the RXCB3523 batt at 24 inches by 47 inches. Check the store listing for pack quantity before ordering, since coverage depends on how many batts you buy.

Can I use it in a 2x4 wall?

No. R15 mineral wool is made for 2x6 framing; compressing it into a 2x4 cavity lowers its R-value.

How does it compare with fiberglass batts?

It costs more but is non-combustible, handles moisture better and blocks more sound. Fiberglass is cheaper and lighter.

Do I need special tools to install it?

A serrated insulation knife or handsaw, gloves, safety glasses and a dust mask are enough. No stapling is needed for a friction fit.

When is the price lowest?

Building material prices move with seasonal demand, often easing in winter. The best new price was $80.42 at Cowls Building Supply as of November 7, 2026.