72.5mm Insulation Board

A 72.5mm insulation board is specified when a building needs a noticeable improvement in thermal performance, but there is a limit on the amount of internal space that can be sacrificed.

It is most commonly supplied as an insulated plasterboard system, where insulation and a finished lining are bonded together as a single solid panel.

What is 72.5mm thick insulation board?

A 72.5mm thick insulation board is a panel that combines a rigid insulating core and a plasterboard finish to save time on site. Separate insulation and lining layers are not required since it is factory-made with the board bonded straight to insulation.

In most products, the foam core is rigid PIR (polyisocyanurate) insulation with a thermal conductivity of around 0.022 W/m.K, and the plasterboard layer is about 12.5mm thick. Others use a phenolic core as the insulating material. This means the board provides good resistance to heat transfer.

It is relatively lightweight and easy to handle on site, and can be fixed with dry-lining adhesive or mechanical fixings.

What is 72.5mm insulation thickness board used for?

An insulation 72.5mm board is mainly used where you want good insulation without building up lots of separate layers. It is typically used in:

• Internal face of external solid walls to improve thermal performance
• Drylining and insulating timber frame walls
• Below rafters in pitched roofs (as an internal lining system)
• Stud partitions where improved thermal comfort and a finished lining are required

Because the insulation and plasterboard are combined, you cut down installation time and reduce the risk of gaps forming between insulation and lining layers that might let heat escape.

Types of 72.5mm insulation board

Two main types of 72.5mm insulated plasterboard are available:

72.5mm PIR Insulation (Polyisocyanurate)

 – The most common type. Polyisocyanurate foam provides very good thermal performance per millimetre of thickness, making it efficient at reducing heat loss. These boards are rigid, light, and factory-bonded to plasterboard.

72.5mm Phenolic Insulation Foam Board

– A slightly higher-performance option where the core is phenolic foam. Phenolic can have a lower thermal conductivity and may offer improved fire performance depending on the specific product classification. An example is Kingspan Kooltherm K118, which is especially suited to wall and roof applications.

Both types can be used under rafters, on walls, and on ceilings to deliver insulation plus a finished plasterboard surface.

Benefits of insulation 72.5mm thickness board

Insulation 72.5mm boards offer several benefits:

• Thermal efficiency – Lowers heat loss, making buildings more energy efficient.
• Combined finish – Separate board layer after insulation is not needed.
• Speed – Fixing what is effectively two products in one cuts labour time.
• Easy to handle – Relatively light and easy to cut with standard tools.
• Versatile – Can be used to line walls or below roof rafters in new builds and refurbishments.
• Regulation-friendly – Can contribute towards meeting UK Part L requirements when correctly specified.