150mm Insulation

150mm insulation is a high-performance build depth specified when heat control is a design priority.

At this level, insulation becomes part of how the building performs day-to-day, rather than a marginal upgrade to meet calculated targets.

This is the thickness preferred when a structure is expected to retain heat steadily under sustained cold conditions.

What is 150mm thick insulation?

150mm thick insulation means the material measures 150 millimetres when installed correctly, without compression. That depth enhances thermal performance by increasing the resistance to heat transfer.

At 150mm insulation thickness, performance comes from:

• Material structure, which disrupts heat flow through the construction.
• Air pockets within the insulation reduce conductive and convective heat transfer.

Different products achieve thermal performance through different mechanisms, but increased thickness is the common factor that improves performance.

What is 150mm insulation thickness used for?

Insulation 150mm is used where high levels of thermal control are required, such as:

• External walls designed for low heat loss
• Roofs targeting modern efficiency standards
• Floors above cold spaces or the ground

This thickness is common in builds that aim to comfortably meet Part L, rather than merely achieving minimum compliance.

What types of 150mm insulation are there?

150mm insulation thick products are available in several types. They include:

• Mineral wool slabs or batts – These have dense fibres that trap air effectively. They offer sound control and provide inherent fire resistance. Often used in timber frames and partitions.
• Glass wool – Light and springy, designed to friction-fit between joists or studs. Easier to handle, but it relies on correct fitting.
• Rigid PIR boards – High thermal resistance for their thickness. Often preferred to achieve lower U-values within a given build-up.
• Phenolic boards – Even higher thermal performance than PIR. Often used to meet strict thermal targets.

Some systems layer thinner boards or rolls to achieve a full 150 insulation depth while reducing gaps.

Benefits of 150mm insulation

Using 150mm insulation provides:

• Lower heat loss across large surfaces.
• More stable indoor temperatures.
• Reduced heating demand over time.
• Better comfort on walls, floors, and ceilings.