Loft Roll vs PIR Insulation – What’s the Difference?

Which insulation is right for your project?

When it comes to insulating a home, most people end up choosing between two of the most common types: loft roll (sometimes called quilt) and PIR insulation boards. They both insulate well — but they’re made differently, installed differently, and work better in different parts of a build.

Here’s a clear breakdown of loft roll vs PIR so you can choose the right one for your project.

What’s the Main Difference?

• Loft roll is a flexible, soft material (usually mineral wool or glass fibre)

• PIR board is a rigid sheet of closed-cell foam (usually foil-faced)

They both slow down heat loss — but the way you use them is different depending on the job.

Loft Roll (Quilt Insulation)

• Best for:

  • Laying between loft joists

  • Large open roof areas

  • Budget-friendly insulation jobs

• Pros:

  • Easy to lay out

  • Great for topping up existing insulation

  • Affordable and widely available

• Cons:

  • Bulkier (you often need 200mm+ to meet regs)

  • Not ideal for walls or tight voids

• Stocked at WGT?
  Yes — we stock Isover loft roll in common sizes

PIR Insulation Board

• Best for:

  • Insulating walls and floors

  • Flat roofs, pitched roofs, and behind plasterboard

  • Jobs where space is tight

• Pros:

  • Higher performance per mm

  • Great for drylining or flooring

  • Lightweight and easy to cut

• Cons:

  • More expensive per m²

  • Needs precise fitting and taping

  • Not ideal for open loft floors

• Stocked at WGT?
  Some PIR boards in stock — others available to order (Celotex, Ecotherm etc.)

Quick Comparison:

Which One Should You Use?

• Use Loft Roll when you’re insulating a large roof space from above (between joists)

• Use PIR Board when space is tight, or you’re insulating behind walls, in roofs, or under floors

Still not sure? Just ask us — bring your measurements and tell us what you're insulating, and we’ll talk you through the right solution.

Wood Green Timber – proper insulation, stocked in North London.