200mm insulation board is used when the job calls for serious thermal performance. It is a practical option for roofs, floors, and some wall build-ups where lower U-values are part of the spec.
A 200mm thermal insulation board is a rigid thermal panel manufactured to a precise 200mm depth, suitable for wall, floor, and roof insulation applications. In the UK, this most commonly means a 200mm PIR insulation board (polyisocyanurate foam) with foil facings bonded to both sides.
It is defined by:
A 200mm PIR board with a declared lambda of 0.022 W/m·K has an R-value of about 9.0 m²K/W.
While PIR is the most common format, other materials are also available in 200mm depth (such as EPS or mineral wool slabs).
Thick 200mm insulation boards are commonly used on:
In ground-bearing concrete slabs, a thick insulation 200mm board may be laid above a damp-proof membrane and below the screed, subject to floor design and damp strategy. PIR boards can be suitable here where sufficient compressive strength is stated, provided loading calculations are correct.
In suspended beam-and-block floors, boards may be specified in beam-and-block floor build-ups, subject to the floor design. Edge insulation is still required to prevent cold bridging.
Because of the depth, you must account for finished floor levels early in the design.
A 200mm insulation thickness board is common in:
For loft projects, a 200mm loft insulation board is sometimes used instead of mineral wool when:
Rigid boards give more insulation per thickness than fibrous insulation, such as mineral wool.
In masonry cavity walls, 200mm is generally too thick for standard cavities unless designed for wide cavities from the outset. Standard cavities are typically 100-150mm.
In timber frame or SIPS-style builds, insulation 200mm thick board can form part of the structural envelope.
In internal wall upgrades, this depth would significantly reduce room size, so it’s usually reserved for major refurbishments rather than light retrofits.
Even at 200mm, products vary by core, facing, and intended use.
These are rigid, foil-faced, and the most common, with high thermal performance. They include products from major UK manufacturers such as Celotex XR4200.
Phenolic foam boards are more expensive and more brittle than PIR. They have slightly lower λ-values (around 0.018–0.020 W/m·K) depending on the product, making them a preferred choice in the green guide. This means they deliver marginally better performance per thickness.
EPS boards are often a lower-cost, higher λ-value (~0.030–0.038 W/m·K) option. To match PIR performance at 200mm, you would usually need thicker EPS, either in singular boards or layered.
Slabs are available in 200mm depth and are mainly used for acoustic or fire performance in walls and roofs, particularly when combined with plasterboard. They have a thermal conductivity of around 0.034–0.037 W/m·K.
Each type has different strengths, fire ratings (Euroclass), moisture resistance, and detailing requirements.
A thick insulation 200mm board offers practical, measurable advantages:
But remember the board alone does not guarantee results; performance depends heavily on airtightness, detailing, and correct installation.
A typical 200mm PIR insulation board has:
For comparison:
Confirm declared values from the specific product’s BBA certificate or manufacturer's technical sheet to know the exact values you are getting.
Order 200mm insulation thickness boards at low wholesale prices, and we’ll quickly deliver them to your UK site or home.
If using a 200mm loft insulation board:
You must also maintain safe access and avoid blocking eaves ventilation unless switching to a warm roof design.
Because boards are thick and rigid, accurate cutting is essential to ensure they fit well and insulate effectively. Poor fit creates thermal bypass (unintended heat flow paths). Always refer to the manufacturer's installation guidance to achieve the best results.
Thermally, a 200mm insulation board is very effective.
A 200mm PIR insulation board, such as the Celotex XR4000 PIR insulation board, in a properly detailed wall can produce very low U-values – often below 0.15W/m²K subject to full wall build-up and detailing.
However, effectiveness depends on:
If gaps, compression, or poor sealing occur, performance drops. But when installed correctly, 200mm provides a high level of resistance to heat loss.
You can buy a 200mm insulation board online from Insulation Wholesale, including options with low-emissivity foil facing. We stock and supply a wide range of 200mm PIR insulation boards from trusted brands, with UK stock available for immediate delivery to your site. Our store offers competitive pricing and clear trade discounts on both single-pack and pallet orders.
200mm XR4200 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
