Insulated plasterboard (also called thermal laminate or PIR-backed board) combines standard plasterboard with a rigid insulation layer. It is one of the most cost-effective ways to improve the thermal performance of solid masonry walls in older properties.
What is Insulated Plasterboard?
Standard plasterboard (12.5mm) is bonded to a layer of rigid polyisocyanurate (PIR) or expanded polystyrene (EPS) insulation. The board is fixed to the wall with adhesive dabs or mechanical fixings, and the plasterboard face is then skimmed to a smooth finish.
How Much Insulation Does It Provide?
A 62.5mm insulated board (12.5mm plasterboard + 50mm PIR) improves the U-value of a solid brick wall from around 2.1 W/m²K to approximately 0.55 W/m²K — significantly better insulation for a relatively modest reduction in room size.
Insulated Plasterboard Costs
| Board thickness | Installed cost per m² |
|---|---|
| 37.5mm (12.5mm board + 25mm PIR) | £25–£40 |
| 62.5mm (12.5mm board + 50mm PIR) | £35–£55 |
| 92.5mm (12.5mm board + 80mm PIR) | £50–£75 |
When is Insulated Plasterboard the Right Choice?
- Solid-wall Victorian or Edwardian properties where cavity wall insulation is not possible
- Rooms where cold external walls cause condensation problems
- Where a small room depth sacrifice (25–80mm per wall) is acceptable
Limitations
Insulated plasterboard reduces room size slightly. For very deep insulation requirements (100mm+), separate batten framing with insulation between may be more practical. The boards must not bridge a damp-proof course — keep the bottom 100mm as standard plasterboard.
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