90mm Insulation Board

90mm insulation board is a thick, rigid insulation panel used to reduce heat transfer through the building fabric. This depth of insulation is specified when space allows, and high levels of thermal resistance are needed to meet modern performance targets.

What is 90mm thick insulation board?

A 90mm thick insulation board is a factory-manufactured panel with a fixed depth of insulation material measuring approximately 90mm from front to back. The core is usually a rigid foam insulation that restricts heat transfer through a closed-cell structure.

The board is rigid and does not compress under normal installation loads. This makes it easier to cut, fit tightly, and maintain consistent performance across the whole wall or floor.

What is 90mm insulation board used for?

An insulation thickness 90mm board is used for:

• Internal masonry walls, including solid wall upgrades.
• Framing walls such as timber or steel stud systems.
• External wall systems behind cladding or render, where the product is approved for the system.
• Floors above unheated spaces, when supported by a suitable structural deck.
• Flat roof build-ups and warm roof systems.
• Pitched roofs, fitted between or over rafters.
• Ceilings beneath concrete or timber floors where insulation is fixed below the structure.
• Full fill cavity walls where the product is approved for that use.

Because 90mm is relatively thick, it is rarely used where space is very tight. It suits projects where thermal performance takes priority over saving internal space. 90mm insulation boards are most common in refurbishments, extensions, and higher-spec new builds.

Types of insulation in 90mm thickness board

90mm insulation boards are available in the following types:

EPS insulation (Expanded Polystyrene)

EPS offers steady thermal performance and has good moisture resistance when correctly detailed. It is often used in floors and external wall systems where cost control matters.

Phenolic insulation Foam Board

Phenolic foam offers high thermal resistance relative to its thickness. It is brittle compared to EPS or PIR, so careful handling is advised. It is commonly preferred to deliver strong performance where increasing insulation thickness is not feasible.

PIR Insulation (Polyisocyanurate)

PIR insulation 90mm board is widely used on internal walls, floors, and ceilings. It offers strong thermal efficiency in both residential and commercial buildings. It is typically installed behind a separate plasterboard lining or structural deck, depending on the application.

Benefits of 90mm thick insulation board

Installing a thick 90mm insulation board has several advantages:

• Strong reduction in heat loss.
• Improved internal comfort.
• Reduced heating demand when correctly specified and installed.
• Stable performance that does not sag or slump.
• Predictable results when calculating U-values.

The rigidity of the board helps limit gaps, improving real-world thermal performance.

Why buy 90mm insulation boards from insulation wholesale?

At Insulation Wholesale, we:

• Stock UK-spec insulation products from established manufacturers.
• Offer clear technical advice from experts who understand site conditions.
• Supply full packs and pallet quantities.
• Keep lead times short so work does not stall.

Our team is set up to support both small refurb jobs and larger trade orders.