Mineral wool vs Rockwool: which loft insulation is best?
"Mineral wool" and "Rockwool" get used interchangeably, which causes a lot of confusion. Here's what's actually going on, and how to choose.
First, let's clear up the naming. Mineral wool is the broad category. Under it sit glass wool (spun from recycled glass — Knauf and Isover are common) and rock wool (spun from volcanic rock — "Rockwool" is a brand name that became shorthand for the type).
So "mineral wool vs Rockwool" isn't really one-versus-the-other — Rockwool is a mineral wool. The real choice is between glass wool and rock wool.
Glass wool (e.g. Knauf)
- Lighter and softer — easy to handle and lay.
- Cost-effective — usually the better value for lofts.
- Excellent thermal performance — traps heat very well.
For most standard, accessible lofts, quality glass wool like Knauf is the sensible choice — which is why it's what we fit as standard.
Rock wool
- Denser — slightly better at blocking sound.
- Strong fire resistance — very high melting point.
- More robust underfoot — holds shape in trafficked areas.
The honest verdict
For a typical loft floor, the thermal difference between good glass wool and rock wool is small. Glass wool usually wins on value; rock wool edges sound and fire resistance. The bigger factor is always depth and quality of installation.
Not sure which suits your loft? Book a free survey.