Insulation Slabs

What are Insulation Slabs?

Insulation slabs, sometimes called “batts”, are pre-formed panels of thermal insulation designed to slot neatly between studs, joists, or rafters (or to overlay a surface) and create a continuous, uniform thermal barrier.

These batts occupy a sweet spot in building-envelope design: they are rigid enough to maintain declared performance, yet versatile enough to suit a spectrum of applications, climates and regulatory contexts.

Most insulation slabs are manufactured from two principal forms of mineral wool:

• Stone Wool: Produced by melting and spinning natural basalt rock and recycled slag into fine fibres. It is highly regarded for its density, exceptional fire resistance (due to a high melting point exceeding 1000C), superior acoustic absorption, and effective thermal performance.
• Glass Wool: Glass wool starts in the furnace, not the quarry: waste glass blends with sand, is liquefied, and then flung into filaments that cool into a springy mat. The result is an easy-going insulator that keeps rooms warmer and quieter.

Applications

Insulation slabs are versatile enough to go into walls, roofs, or floors, suiting a wide range of build-ups and performance requirements.

Internal Partition Walls

• These walls often carry insulation to improve both sound separation and temperature stability between rooms. 
• Slabs are trimmed as needed and slotted between the vertical studs, timber or metal, before the wall is finished with plasterboard. This added layer can also contribute to fire safety, particularly in larger homes or shared buildings.

External Timber and Steel Frame Walls

• In framed external walls, insulation slabs play a key role in cutting down heat loss and dampening sound. 
• They’re set between the studs and usually work alongside components like sheathing boards and vapour control layers. 
• Together, these elements help the wall meet required energy standards while keeping the interior quiet and comfortable.

Pitched Roofs (Between Rafters)

• Slabs fitted between roof rafters provide insulation for loft rooms and attic conversions. They’re usually installed in layers, depending on the target thermal performance. 
• A breathable membrane is often used on the cold side, with a vapour barrier or plasterboard on the warm side to finish the detail.

Floors (Between Joists or in Floating Floor Systems)

• Mineral wool slabs in floors help with both heat retention and sound control. 
• Between joists, the insulation is held in place with battens or netting. In floating floors, denser slabs can be laid directly beneath the top layer, supporting loads while adding acoustic and thermal benefits.

Suspended Ceilings

• Slabs can be dropped into the ceiling grid to absorb sound from above and reduce noise levels in the room below. 
• Ideal for places like classrooms, open-plan offices, libraries, or any room where speech needs to carry without a distracting hum.

Masonry Cavity Walls (Partial Fill)

• Some slabs are designed specifically for partial-fill cavity walls. These sit against the inner masonry leaf and leave a small air gap, which helps drain moisture while still cutting down heat loss through the wall. 
• The slabs are often treated to repel water, keeping the insulation layer dry and effective over time.

Regulations & Standards

• Energy: Approved Document L (England) sets limiting U-values of 0.16 (W/m²K) for roofs, 0.26 for new walls, and 0.18 for renovated walls and floors.
• Fire: Reaction-to-fire is classified under BS EN 13501-1; mineral-wool slabs routinely achieve A1/A2-s1,d0.
• Acoustics: Sound absorption is tested to EN ISO 354; separating-wall performance is verified to ISO 10140 / BS EN ISO 140-3.