50mm Insulation

50mm insulation is a relatively thin thermal layer used when space is limited, but heat loss still needs to be reduced. In most cases, it does not replace deep insulation systems.

Instead, it improves performance where thicker products simply will not fit. It boosts comfort and efficiency without major structural changes.

What is 50mm thick insulation?

50mm thick insulation measures 50 millimetres from face to face when installed.

With 50mm insulation, heat transfers more slowly than it would through bare masonry, timber, or metal. The material achieves this by:

• Trapping still air (or gas) inside its structure
• Reducing direct heat-conduction paths through the building fabric

50mm thickness insulation is on the thinner side and relies heavily on the quality of the material, not just depth. High-performance boards can outperform softer products at the same thickness.

This is why thin 50mm insulation is often paired with other layers.

What is 50mm thin insulation used for?

50mm insulation is used where build-ups must stay slim, such as:

• Internal wall linings where room size matters
• Service zones in timber frames
• Upgrades to older buildings with shallow cavities
• Floors or ceilings where levels cannot be raised much

It is also used to reduce thermal bridging when correctly detailed and continuous. Even a thin layer can prevent heat from escaping quickly from cold surfaces.

50mm insulation is not chosen for maximum performance. It is chosen to control heat loss without redesigning the structure.

Types of 50mm insulation thickness

The most widely used 50mm insulation materials are:

EPS Insulation (50mm Expanded Polystyrene)

At 50mm thickness, EPS:

• Offers basic thermal resistance.
• Handles moisture well. It is, however, not vapour-tight, and should be used with a vapour control layer.
• Has good compressive strength for its weight.

EPS relies mainly on trapped air, so its thermal performance per millimetre is lower than that of rigid foams. It is commonly chosen when cost and moisture tolerance are desired over outright efficiency.

Phenolic Insulation

At 50mm insulation depth, phenolic:

• Delivers very high thermal resistance per millimetre
• Performs well where space is limited
• Is commonly used in wall linings and soffits

It insulates effectively per millimetre, with 50mm thickness able to match or exceed the performance of thicker PIR or mineral wool.

PIR (Polyisocyanurate)

At insulation 50mm thick, PIR:

• Provides strong thermal resistance
• Is easy to cut and fit accurately
• Works well in walls, floors, and roofs

PIR is often the default choice because it is robust and easy to handle.

Rock Mineral Wool Insulation

At 50mm thick insulation, mineral wool:

• Offers sound absorption as well as thermal resistance
• Is vapour-permeable
• Offers excellent fire resistance.

Its thermal performance per millimetre is lower than that of rigid boards. But its acoustic and fire performance often makes it the right choice for spaces that require high sound and fire protection.

Additional insulation materials available at 50mm include glass mineral wool, XPS, vacuum insulation panel, and stone wool.