75mm Celotex Cavity Wall Insulation Board (1200mm x 450mm) – CW4075

4 customer reviews
Secure your product at this price before the increase.

In Stock
Free Delivery On Orders Over £300 +VAT

Delivery In 2-3 Working Days

Only £49.03 ex VAT £58.84 inc VAT


Get the best prices on Cavity wall boards here! Celotex 75mm Cavity Wall Insulation Board is a quality product made up of a polyisocyanurate (PIR) core with a low emissivity foil lining bonded to each side.


  • Celotex as a brand is renowned for its quality products and reliable services
  • Their high-quality products manufactured are virtually impossible to beat in price!
  • Celotex insulation has better thermal efficiency than many other materials
  • The Celotex brand offers materials to suit a wide range of applications including, pitched roofs, flat roofs, walls, floors, and ceilings.
  • Other Celotex product include Thermaclass, cavity wall boards, and insulation boards

75mm Cavity Wall Board

  • 75mm – Product code CW4075
  • 75mm Cavity Wall Boards is a popular product within the construction industry
  • The cavity boards have a straight edge to ensure boards can be tightly butted together to avoid thermal bridging
  • The 1200mm x 450mm board is designed to be easily fit between wall ties
  • Low emissivity foil facings for improved thermal insulation performance in cavity air spaces
  • This product means you can improve the thermal quality within the internal structure of the building itself
  • Cavity Wall Boards are lightweight making them super easy to handle, cut, and install, this versatile product can be installed within domestic or commercial buildings
  • This board offers an incredible thermal conductivity of just 0.022W/mK – which for those who don’t know, means very small amount of heat can pass through the board, keeping the heat inside your home or office!
  • Whilst staying warm in the winter and cool in the summer, you’re also providing an energy efficient environment that contributes to the reduction of climate change
  • While you think it stops at helping the environment, with less heat escaping, Celotex cavity boards can also save you money on your energy bills
  • These boards can be applied to partial fill masonry walls applications, fitted between wall ties
  • Cavity boards are also available from 40mm up to 100mm to suit every application need
  • All Cavity boards are CFC, HCFC and Formaldehyde Free with zero ozone depletion potential (ODP) and low global warming potential (GWP)


  • Reaction to Fire: Euroclass E according to BS EN 13501-1
  • CE Marked (18.DOPCW4000-01) to BS EN 13165
  • BBA approved – certificate 16/5343
  • Achieves a BRE Green Guide A+ rating
  • Quality Management Standard – ISO 9001:2015

More Information:

  • Product code: CW4075
  • Thickness: 75mm
  • Size: 1200mm x 450mm
  • Materials: Polyisocyanurate (PIR), Foil,
  • Thermal Conductivity: 0.022W/mK
  • R-Value: 2.25 m2.kW

How are Cavity Wall Boards installed?

Step 1:

Fit the wall ties into the inner leaf (blockwork) at 600mm horizontal centres. For solid concrete floors, wall ties should start at either one course of blockwork below the damp proof course depending on the location below the top surface (150mm in the UK, 225mm in Ireland) of the ground floor perimeter insulation upstand. For suspended timber floor wall ties start a minimum of 200mm below the top surface of the ground floor perimeter insulation upstand.

Step 2:

Continue constructing the inner leaf up to the next wall tie course (450mm). The next course of wall ties is positioned at regular horizontal centres. Extra wall ties should be positioned at jambs for all openings. The next course of blockwork should then be installed to secure the ties. After raising each section of the inner leaf and before installing insulation boards, excess mortar should be removed, and mortar droppings cleaned from exposed edges of the insulation boards.

Step 3:

The first row of insulation boards should now be installed – with the foil facing, facing inwards – between the two rows of wall ties, ensure each insulation board is retained tight against the inner leaf and joints are butted. Secure each board at a minimum of three points. Additional ties may be required to satisfy structural requirements or to ensure adequate retention of boards or cut pieces. Apply a self-adhesive breathable tape no less than 100mm wide to all horizontal and vertical board joints. Ensure surfaces are clean and dry and free from dirt.

Step 4:

Next, build the outer leaf (brickwork) to the level of the top of the boards and repeat the process.

If finishing at a gable, insulation boards should be continuing 200mm beyond the height of the top storey ceiling and a cavity tray installed above the insulation.

Frequently Asked Questions –

Will Cavity wall insulation stop damp?
When Cavity wall insulation is installed correctly it has a good chance of reducing the chances of condensation and mould developing. The cavity wall insulation will work by evening the heat levels out within the property and avoiding cold spots that can cause dampness.

How do I know If cavity wall insulation has been installed correctly?
Look out for damp spots or wet patches within your property internally. The start of this can often look like a change in paint texture, paint peeling, or a stain in colour. Moisture droplets can also form on the walls. If you notice any of these signs of dampness, it is recommended that you contact a professional.

If there are no signs of damp on the walls there is a high chance the insulation has been installed correctly and will be long lasting!

What is thermal resistance?
Thermal resistance is the measurement of temperature between two faces and the rate heat flows between the two faces per unit area. Thermal resistance determines the heat insulation property of a textile material. The higher the thermal resistance, the lower is the heat loss. For example, if the material is thicker the rate at which thermal conductivity travels from one side of the material to the other is larger and less heat is lost.

What is an alternative to cavity insulation?
An effective alternative to cavity insulation is loft insulation. By insulating your lofts space, you are preventing warm air from escaping your property. Roof insulation fitted in between the rafters can also be an effective alternative, as the heat rises to the roof the foil facings reflect the heat back down into the property heating from the top down.

I don’t have brick walls; can I insulate them?
If cavity wall insulation is not an option for your property, a great alternative is solid wall insulation. This can be applied by dot and dabbing, or mechanically fixing Celotex insulation boards or Celotex insulated plasterboards onto your internal walls.

What property does cavity wall insulation work best for?
Cavity wall insulation is a great option for detached houses and bungalows. Terraced and semi-detached along with flats receive a certain amount of insulation from the adjoining buildings. The neighbouring building provides a protective layer keeping the heat in and the cold out. Detached houses and bungalows and properties that stand alone are most affected by cold weather and heat can easily escape the walls. Installing cavity wall insulation on these properties will save the most money and provide a more comfortable, temperature-controlled environment.

Does my house have cavity walls?
The best way to find out if your house has cavity walls is to look at the brickwork pattern. If the brickwork displays a brick-bonded pattern showing the length of the bricks as well as the width end it is most probably a solid wall. Brick laid with some bricks turns inwards indicating there is a solid wall of two brick layers completely connected.
If the brickwork displays a brick-bonded pattern showing only the length of the bricks it is most probably a cavity wall. Bricks laid in one continuous pattern indicate there is a single wall, a gap, and then another single wall behind it.

What materials can be used in cavity walls?
There are three materials commonly used in cavity wall insulation: mineral wool, formaldehyde foam, and expanded polystyrene beads. Each of these has its own slight differences and relative advantages and disadvantages. The material used will depend on the method of insulation being applied and the type of building being insulated.

What thickness do I need?
The size/thickness you need will depend on the space being insulated. Thicker insulation is always the best option to achieve the best thermal conductivity possible however a thinned board will also improve the thermal conductivity. This decision is really based on how much space you want to save, and if the board meets the building regulations.

How long does cavity wall insulation last?
When correctly installed cavity wall insulation will last for as long as the building does!

How does water get into cavity holes?
Water can get into cavity holes when wall ties are not installed correctly. If wall ties are angled down, or if to much mortar was used during installation this can lead to water ingress. Another fault can be using metal wall ties as over time the metal ties can begin to corrode and cause cracks in the wall inviting water in. Water caused from the wall ties can more easily be seen as the damp will show through on the internal side of the wall around the tie’s location.

Is it possible to remove cavity wall insulation?
Yes! It is currently possible to extract a range of insulation types, including mineral fibre, expanded polystyrene (beads), and urea formaldehyde. Wool materials are sucked out of the wall using a large vacuum. Rigid insulation is recombed by removing some brick, breaking it up into smaller parts and sucking them out. The high-pressure vacuum machine is used to suck the insulation out of the cavity, and the old insulation is bagged and removed from the property, leaving the cavity completely clear of any old cavity wall insulation.

Additional information

Dimensions1200 × 450 mm




Material Type

Polyisocyanurate (PIR)

Pieces Per Pack


Sales Unit


Unit Coverage


Manufacturers Reference


Thermal Conductivity




Fire Rating

Euroclass E

Edge Type



Low Emissivity Foil

Weight (kg/m2)



2-3 Working Days

4 reviews for 75mm Celotex Cavity Wall Insulation Board (1200mm x 450mm) – CW4075

  1. Pavel

    Highly recommend this insulation product! The delivery was prompt, and the quality is unmatched. The website is user-friendly and informative.

  2. Anton

    Helpful staff

  3. Petey A

    Always easy to use and install.

  4. Connor Leff

    Always use Celotex products with no problems

Add a review

Your email address will not be published. Required fields are marked *

You may also like…