20mm Insulation Board

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Get the best price on 20mm insulation board on our website. At insulationboard.co.uk we are the home of PIR insulation boards. 20mm insulation board can be installed within the entire thermal envelope of the building. The 20mm PIR board can be used in a variety of applications. This includes roofs, lofts, floors, walls, as well as timber and steel framed systems within industrial, commercial, and residential buildings.

20mm PIR Board

20mm PIR boards are manufactured from rigid polyisocyanurate (PIR) core, with low emissivity foil facings bonded to each side. Low emissivity foil facing provides improved thermal performance in sealed cavity air spaces, improving the achievable U-value.
The process uses a blowing agent that has zero ODP, which is otherwise known as Zero Ozone Depletion. In addition to this, it also has low global warming potential (GWP).
Most 20mm Insulation boards on our website come in size 2400mm x 1200mm. Coverage for 2400mm x 1200mm PIR boards is 2.88m2. The exception to this rule is for cavity wall boards where the size tends to be 1200mm x 450mm. PIR board has an excellent thermal conductivity of 0.022 W/mK or 0.021 W/mK for Thermaclass The PIR Insulation boards are available in a range of thicknesses and sizes to suit any project.

20mm Insulation Board features

  • 20mm PIR Board is easy to cut and shape
  • Lightweight materials and easy to transport
  • Multi-purpose board designed to fit many applications
  • Good reaction to fire in accordance with EU standards
  • Made from high performing Polyisocyanurate (PIR)
  • Sustainable and energy efficient
  • Squared edge and easily butted together
  • Cost effective and provides long-term energy savings for buildings
  • Features low emissivity foil facings for enhanced performance
  • Reliable and long-lasting product
  • Maintains internal temperatures

20mm Board Applications

There are many different applications for 20mm insulation board. This includes roofs, walls and even floors. The versatility of the 20mm insulation board is a top reason so many people use it. Specifically, PIR 20mm can be used for flat roofs, pitched roofs, solid masonry walls and floors as well as timber framed & steel framed systems. 20mm board is easy to cut and shape as well as install. Furthermore, there are many benefits of 20mm boards. One big benefit is that they can provide long-term energy savings for buildings.

Full application types can be found below

  • Ground Floor – Concrete Slab
  • Ground Floor – Suspended Timber Joist
  • Ground Floor – Beam and Block
  • Ground Floor – Upgrading Existing Concrete Slab
  • External Wall – Timber Frame Internal Linings
  • External Wall – Timber Frame Sheathing
  • External Wall – Between Timber Frame Studs
  • External Wall – Solid Masonry Internal Linings
  • Pitched Roof – Over Timber Rafters
  • Pitched Roof – Sarking
  • Pitched Roof – Below Timber Rafters
  • Pitched Roof – Between Timber Rafters
  • Pitched Roof – Loft insulation – Between and Over Timber Joists
  • Flat Roof – Balconies & Terraces Over Joists
  • Flat Roof – Between Timber Joists
  • Flat Roof – Below Timber Joists

20mm PIR Insulation

20mm Insulation Boards are extremely long-lasting and when installed correctly have a lifespan that often lasts for as long as the building. Potential building hazards such as mould, damp, and rot should be determined before the product is installed.
Installing 20mm PIR boards will create a more temperature-controlled environment that maintains cooler summers and warmer winters. It will also lower energy bills by preventing heat from escaping the property. Furthermore, reducing heat loss will also have positive effects on the environment.

20mm insulation board is lightweight and versatile. This makes the board easy to manoeuvre and install. 20mm insulation boards can be easily cut by using a sharp knife to score one side of the board, snape over a hard edge, and then score the other side. Another way to cut this board is by measuring and marking the board and cutting to shape using a fine-toothed saw.

The low emissivity foil facings of the insulation board reflect heat. The means to heat will remain in specific areas and rooms instead of escaping through the walls and roof. An example of this process is when the heat rises in the property, heating from the bottom up, the insulation in the roof will reflect the heat back down into the building and begin the heating process again from the top down.

Popular brands of 20mm insulation board include Celotex, Kingspan, Recticel and Iko Enertherm.

How are 20mm insulation boards installed?

Consult a building professional before any insulation board installation.

PIR insulation boards can be cut to size and tightly fitted in between rafters and joists with no fixtures or adhesive necessary. The thickness of the board required will depend on the depth of the frame or rafter. Any joining boards should be tightly butted together, and foil tape should be applied to all board joins and edges. Furthermore, the boards can be secured with insulation netting materials or overlayed horizontally with plasterboard or insulation boards. The securing materials should be cut to size and attached to the frame or rafters using the required fixtures and fittings.
There are various ways to install PIR boards. The methods depend on the location of insulation in the property and the purpose of the insulation. Other installation methods include fixings and the dot and dab method.


The product achieves a BRE Green Guide A rating.
Euroclass E Reaction to Fire classification, according to BS EN 13501-1. Products with this level of classification are not provided with a rating for smoke emission.
Quality Management Standard – ISO 9001:2015 and BBA Certified.
CE Marked (18.DOPGA4000-01) to BS EN 13165.

Health and Safety

Protective wear such as face masks, gloves, and goggles is ideal. Cutting insulation board will release dust. Furthermore, ensure you ventilate the relevant space if possible and do not consume food or drinks around the released dust.
Store away from incompatible materials. Store in accordance with local regulations. Keep in a cool, well-ventilated place. Store in a dry place on a flat surface. Do not store them near heat sources or leave them exposed to elevated temperatures. Keep away from flammable and combustible material. Ensure there is no smoking near this product. Do not use a water jet as an extinguisher, as this will spread the fire.