Insulation By Thickness

Insulation thickness is a simple way to choose insulation based on the depth of the space you need to fill. This allows you to select the most appropriate material or product range to deliver the performance you need for that required depth. That makes it easier to match the insulation to structures and cavities without forcing or compressing it.

What is insulation by thickness?

Insulation by thickness means selecting an insulating material that matches a required depth. The required depth typically depends on the size of timber or steel framing members. It is also determined by UK Building Regulations and target U-values, as well as existing construction constraints that cannot be altered.

To work properly, insulation must fit the space for which it is designed. If it is thinner than the void, heat can escape around it. If fibrous insulation is over-compressed, the trapped air structure is reduced, leading to a drop in performance. So thickness matters just as much as the material itself.

This approach applies to all insulation types. Mineral wool slabs, glass wool rolls, blown fibre, phenolic foam, PIR, EPS, XPS, and aerogel products are all installed to set depths, and so they can be used correctly in different parts of a building.

What are the different insulation thicknesses used for?

Insulation comes in these common depths:

• Very thin insulation (2–10mm) – usually used for surface upgrades. This includes acoustic layers, thermal laminates, pipe wraps, and specialist products like aerogel, where space is extremely tight.
• Thin to mid-range insulation (12–50mm) – common for internal wall linings, under screeds, between battens, and in service voids, to reduce surface condensation and cold-spot formation. High‑performance foams do more at these depths than fibrous materials.
• Mid-range insulation (60–100mm) – widely used in stud walls, timber floors, warm roofs, and solid wall upgrades. Mostly offered in mineral wool (glass or stone), PIR, and phenolic foam. All can perform reliably when correctly specified and installed.
• Thicker insulation (120–200mm) – typically for roofs, lofts, deep floor zones, and high‑performance wall systems. These depths are about slowing heat flow over time, not just stopping drafts. Loose‑fill and quilt products work well here because they fully fill irregular spaces.

What thicknesses of insulation are there?

Insulation Wholesale stocks insulation thicknesses from 2mm right up to 200mm. Manufacturing constraints and performance requirements determine the depth ranges for each material.

Typical available ranges include:

• Ultra‑thin specialist layers – These are mostly 2–10mm.
• Standard board and slab depths – including 20, 25, 30, 40, and 50mm.
• Common structural fills – Usually 60, 70, 75, 80, 90, 100mm.
• Deep‑fill options – Commonly 120, 140, 150, 170, 200mm.

This wide range allows insulation by thickness to work across refurbishments, extensions, and new builds without structural redesign.