What Sizes Does Rockwool Insulation Come In and Which Should You Choose?

Get sizing wrong, and your insulation may leave gaps, waste material, or drive up costs.

Rockwool insulation is available in batts, rolls, and boards, with common thicknesses from 25mm to 150mm, widths of 400–600mm, and lengths of 1.2–2.4m. Custom sizes are also available.

If you select the wrong size, you risk losing performance and needing to buy extra materials. I have helped clients save thousands by carefully matching insulation sizes to their projects.

What Are the Standard Thickness Options for Rockwool Insulation?

It’s easy to go too thin or too thick without guidance.

Standard rockwool thicknesses are 25mm, 50mm, 75mm, 100mm, and 150mm. Thicker layers increase thermal resistance and soundproofing but may not fit in shallow cavities.

Let’s compare at a glance:

If you insulate a chemical tank, 100mm or more may be needed for cold loss. Attic retrofits or residential walls may use 50–75mm for adequate comfort. Always check available stud or cavity size before purchase.

I once worked with a team that ordered 25mm batts for a 100mm cavity. They tried to stack four layers but ended up with poor fit and air gaps. Upgrading to the correct size delivered instant energy savings.

What Are the Typical Length and Width Options for Rockwool Insulation?

Getting lengths or widths wrong can waste material and drive up labor time.

Most batts are 400–600mm wide to fit standard stud spacing and come in lengths from 1.2m to 1.35m. Boards for industrial use may measure up to 2.4m.

Let’s break it down:

On a tank installation, I once had to order custom 1.2m x 2.0m boards. The larger size sped up installation, reduced seams, and kept labor costs low.

Are Custom Sizes Available for Special Projects?

Sometimes, standard doesn’t fit. Then what?

Manufacturers like us offer custom sizing for large tanks, curved surfaces, or special frames. You can specify thickness, width, and length—or even semi-circular or wedge shapes for tank shells.

Custom orders take a little longer, but they solve many headaches and reduce long-term risks. For example, curved segments for a German client’s cryo-tank made installation easy and kept thermal loss to a minimum.

Custom sizing is often worth it when insulation is mission-critical, or when cutoffs and scraps waste money.

How Should You Choose the Right Rockwool Size for Your Application?

I always recommend checking these points:

• The cavity or frame size
• Desired R-value
• Installation method
• Quantity needed

Use a measuring tape and double-check against local building codes and energy targets. When in doubt, send us your dimensions. I have built many custom kits for customers to fit odd layouts perfectly, saving them money and stress.

Conclusion

Choosing the right rockwool size means tighter fits, faster installs, and maximum energy savings for your project.