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 (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 Foam

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

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.

FAQ

Where to buy 50mm thick insulation

You can buy 50mm insulation online from Insulation Wholesale. We stock a wide range of 50mm thick insulation from leading manufacturers, including rigid boards and mineral wool. We offer:

• Clear technical advice
• Consistent UK stock
• Fast delivery options
• Trade pricing

If unsure which 50mm insulation is right for your project, our team will walk you through the best options.

How to cut 50mm insulation

Rigid boards (PIR, phenolic, EPS): Use a fine-tooth saw or insulation knife. Score, snap, then trim cleanly.
Mineral wool: Use a long serrated blade. Compress slightly, cut once, and avoid tearing.

How to install 50mm insulation

50mm insulation often sits behind plasterboard, between studs, or over solid surfaces. The fixing method depends on the substrate used.

Installation must keep the insulation continuous:

1. Fit boards tightly together.
2. Avoid crushing soft materials. Insert them gently, ensuring they fill the whole space.
3. Seal gaps where air could move.
4. Keep insulation dry during install.

How good is 50mm insulation?

50mm insulation is moderately effective, not powerful. It improves comfort and reduces heat loss, but it does not transform a building on its own.

Here’s what 50mm insulation does well:

• Cuts surface heat loss – Cold walls and ceilings lose heat fast. Adding insulation 50mm thick reduces that loss and raises surface temperatures. This reduces cold spots and the risk of condensation.
• Works where space is limited – Thin 50mm insulation fits behind plasterboard and inside shallow frames. It is also ideal for underfloors where thicker materials will not fit.
• Improves efficiency when layered – On its own, it gives a noticeable improvement. Combined with other insulation layers, it becomes much more effective.

However, 50mm insulation thickness has some limits:

• It cannot meet high-performance targets alone – UK standards for new builds and major upgrades often need more than 50mm thickness insulation.
• Material choice matters more at this depth – At insulation 50mm thickness, high-performance rigid boards outperform softer materials by a wide margin.