Insulation Board

Browse our range of Insulated Plasterboard from Celotex, Kingspan, Ecotherm, Quinntherm or Fibran to name just a few. Use the sidebar to narrow down the options. Whether its XPS, Polystyrene or a rigid foam board, we are here to provide expert advice if necessary. Don't be a stranger, call us on 020 3582 6399 or chat with us Live Chat

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­Insulation Board Buyers Guide

You can use Insulation boards for walls, floors or roofs. 
Rigid insulation board is one of the most effective insulation materials around. 
It is a very good insulator for such a thin material. Other materials such as fiberglass need to be much thicker to give the same level of insulation.

Benefits you get from the insulation

  • Your electricity and or heating bills will be lower and, 
  • Your property will be much warmer and more comfortable.

Materials related to various insulation boards

  • All without taking up as much of your valuable living space as some of the other insulation options.
  • The boards are usually faced with a wide range of materials. Such as paper, bitumen, glass fleece, or plasterboard,but will be most likely faced with aluminium foil.
  • There are a lot of different options out there when it comes to choosing insulation board.

Factors to focus for buying the board

In this expert buying guide on rigid board insulation online, we’ll take you through: 

  • The different insulation board material options, 
  • The different facing options, 
  • The different areas it can be installed

There are more things to consider forbuying insulation board.

Insulation board available in various categories

There are many different types of cheap insulation boards for sale. Some of the more popular types include the following:

PIR insulation board - Great for most applications such as floors, walls, and roofs

Polyisocyanurate, (also referred to as PIR or Polyiso) has 50% better thermal efficiency than Polystyrene. And since it is more mainstream it tends to be cheaper than some of the alternatives. It has several other traits-

  • No harmful materials are produced during the production process. It is really good for the surrounding.  
  • The material is tested for performance and is fire proof. It meets all the current building regulations. 

    Examples of PIR board include Celotex GA4000 andEcotherm Eco-versal

Rigid phenolic insulation. –This is perfect for when high performance and saving space are important. The major features include-

  • Phenolic insulation is rigid foam sandwiched between two flexible layers
  • It is more efficient and has lower U values than the PIR boards for the same level of thickness. 
  • This is particularly significant where space saving is important. 
  • It is popular in highly efficient low energy design such as passive house. It meets the new Building Regulation standards without increasing the thickness.  

The downside is, they are generally more expensive than PIR boards of the same size . 

Examples include the Kingspan Kooltherm range. 

Polystyrene boards

Polystyrene is also known as Styrofoam or Aeroboard.

It's been around a long time and has a wide range of uses.

  • It is one of the cheapest forms of insulation.
  • It comes in two types; extruded (xps) and expanded (eps)
  • They are both made of polystyrene but they have very different performance properties.

The major issue with these boards is that they are flammable. This rules them out as a viable option in a most applications.

Extruded polystyrene (XPS) 

  • Used for specialist applications 
  • XPS is strong when compressed under load.
  • This is perfect for specialist applications like under car parks and commercial floors.

Expanded Polystyrene (EPS) Foam Insulation

  • Used for specialist applications 
  • EPS is a good cheap insulator. It works especially well for basement walls and areas where space isn't at a premium. 

Types of facing options

Some Insulation board comes bonded to a range of different materials. Here are the most common:

Insulated Plasterboard

The perfect solution for internal solid wall upgrades. The plasterboard is bonded directly to the insulation board.

You can install the insulation and plasterboard at the same time. This cuts down on time and labour costs.

Examples include the Celotex PL4000 range. 

Foil faced Insulation

  • Choosing insulation board with a foil facing reflects heat back into the building.  
  • Adding a foil facing to insulation significantly improves the U-value.
  • This enables a thinner insulation to be used to achieve the same U-value. 
  • You can create an effective vapour barrier by taping the seams with insulation board tape.

Glass tissue (external wall) 

  • This is an excellent option for reducing heat loss from your walls if you do not have cavity walls. 
  • It’s a rigid insulation board that is fitted to the exterior walls of your house. It's used behind both render and dry cladding. And it provides excellent thermal performance. 
  • You can give an old house a fresh look by applying external wall insulation to the exterior. It can transform the look of the property.
  • One thing to consider is that it is pricier than EPS insulation. Examples include Kingspan K5 

PIR Plywood Laminate

  • Plywood laminate is insulation board bonded to plywood.
  • It is designed for flat roof systems which will by covered with a waterproofing felt layer.
  • It cuts down on installation time and cost and also reduces the risk of condensation.


Bituminous waterproof facing

  • Insulation board attached to a bitumonus layer for use in warm flat roofs. 
  • It's used under torch-on, bituminous waterproofing systems.
  • Again, it cuts down on installation time and labour costs.

Where do you like to use your insulation board?

Boards for wall

With insulation board you get high u-values using the thinnest amount of insulation. 

This makes the best use of the space you have available. 

You can reduce other construction costs like using smaller fasteners and timber studs.

Solid walls can also be insulated with insulation board. 

On the inside of the solid wall, insulated plasterboard can be used.

And on the outside of the solid wall, insulation board with an external facing render can be used.

It is also more likely to perform well over the entire life of the building. It doesn’t slump or sag over time like glass type insulation can. 

There is no risk of gaps appearing. Which would cause thermal bridging and reduced performance 

The gaps between the boards can be sealed with for even better airtightness and thermal performance.


Boards for fitting to the outer side of the building

There are two types of insulation board that can be attached to the outside of the home; 

  • Expanded polystyrene (EPS)
  • Phenolic.

The expanded polystyrene is the most popular since it is the most cost effective.

Phenolic insulation is best when space is at a premium. You can use less insulation to achieve the required u-value.

Installation technique:

In most cases, homeowners get in a professional to install solid wall insulation. It is not normally considered a DIY job.

This is because the insulating process involves covering the original brickwork. The process transforms the outside of the property and is labour intensive.

The same goes for internal wall insulation, it is advised to get someone who knows what they are doing to install it. 

Boards for pitched roofs

Insulation boards are commonly used in pitched roofs.

It can be used between the rafters, over the rafters and under the rafters depending on the application. 

Insulation board allows you to insulate to the current standards without sacrificing valuable headroom.

Installation technique:

Rigid and cheapest insulationboards can be installed by you in several ways i.e. 

  • Joist level rigid board which is installed right above ceiling
  • Rafter level rigid board that is installed below roof

Determination of rigid board installation is done on the basis of how the roof layout is. The roof layout can be warm or cold – therefore it needs careful evaluation.

At joist level if you are intending to walk on the boards it is best to put a layer of chipboard on the boards. This helps in dividing the weight along the boards and joists for sustainability.

Try to use boards which have a foil coating on one or both sides. This will help reflect heat back into the space you are trying to insulate. 

The foil should be pointing towards you when you use the boards to insulate the rafters. This is done so because the heat should be reflected back in the home. So assure pointing the foiled side towards you while you install it.

Also ensure that when you cut the material, the loft joist/rafter space should tightly fit together.

For this a combination of cutting tools can be used like a fine toothed saw, a rigid board cutter or even a Stanley knife.

You should check on the measurements and get the cutting right at once to ensure there is no wastage of material.

Handle the tools with care and make the right cutting to put together a good board.

Boards for flat roofs

Insulation boards are the most common form of insulation in flat roofs. 

There are a few reasons for its popularity:

  • The boards have good compressive strength and are able to withstand foot traffic. This is an important consideration in modern roofs with single ply construction. With other materials there is the risk of compression which could cause water to pool and the roof to leak.
  • They can meet or exceed the current requirements without needing as much space as other forms of insulation. 
  • Rigid insulation is just easy to work with. It’s light, easy to cut and easy to handle which is important in roof applications.

Installation technique:

Homeowners should hire a professional to look after insulating a flat roof. There is a lot involved to make sure it meets regulations.

Boards for floors

Floor insulation is an area that is often overlooked as an area that can bring significant reductions in energy consumption.

The thermal performance of an uninsulated domestic floor is usually fairly poor. The greatest heat loss through an uninsulated floor is from the edges. But if you look at the complete floor insulation, it offers a range of advantages over the perimeter insulations for the houses.

For the suspended timber floors one can install insulation between the joists. This works best!

Using a fibrous material underneath the netting is not quite practical. It would deteriorate the performance of the board, invite the risk of sagging and affect the performance too.

Installation technique

To insulate a suspended timber floor, you place insulation between the timber joists and under the floorboards. This may or may not be easy, depending on the space below and the difficulty in removing floorboards to get in.

Older floorboards are butted together tightly. 

If there is enough void space underneath it may be possible to install insulation by removing a few floorboards at the side of the room. This would allow access to the void space.

If it's a relatively new floor, i.e. less than thirty years old, the floorboards may be tongue-and-groove board. In this case they will all have to be lifted. 

The latter option will generally be uneconomical unless you need to lift the floor to carry out some other work also.

Board for cavity walls

Cavity wall construction still remains the predominant build method within the UK.

Most modern buildings have two walls. An outer wall and an inner wall and there is a gap in between them to stop the wind and the rain.

If there is nothing between the inner and outer walls the heat will simply radiate through. To stop that from happening you need cavity wall insulation.

When cavity walls were first designed heat retention wasn’t a priority, so the vast majority of all homes weren’t built with adequate insulation. Blow-in insulation is most commonly used to insulate existing cavity walls.

Nowadays in all newly built properties, cavity wall insulation is added as part of the building process. Using insulation board can be a great option for new builds.

With new builds you have two options when it comes to using insulation board in cavity walls:

  • Partial fill cavity wall insulation 

Partial fill cavity wall application is an effective barrier against the rain penetration. It is a well maintained traditional cavity wall that is designed so that the insulation is fixated on the inner leaf to give a clear cavity. Here the door and window openings are closed with cavity closers to safeguard the cold bridging. For instance, the celotex CW 4000 range cavity wall works in exactly same manner.

  • Full fill cavity wall insulation

New innovations in insulation board such as the Celotex CF5000 range allow the full cavity to be insulated with rigid board. The are specifically designed with a rebated edge to eliminate the passage of moisture. This maximises thermal performance without the requirement to widen the cavity. 

Other things to be considered

Buy all essential materials on time

It is important to plan your job correctly. Ask for delivery 2-3 days in advance of when you will need it. This gives you a bit of breathing space in case of unforeseen circumstances.

If you don’t get the delivery on time, you are left with men on site waiting around. This costs time and money. Make sure you plan correctly and go with a supplier who has good on time delivery and good reviews.

If you need accessories make sure you take this into account. We supply all the accessories you might need such as bonding, foil tape, mushroom fixings, knives and saws.

Invest on new insulation rightly- Never buy the “seconds

“Seconds” are the boards that didn’t make it through the manufacturer's quality control process. They are a gamble, some insulation board secondscome with air bubbles the size of your fist but you have no way of knowing just by looking at them. 

That might be ok on a small project like a shed or a dog house but you should definitely avoid it on a new build. Seconds can lead to problems like thermal bridging and condensation spots.

If your building contractor is supplying the insulation then you should check for receipts to make sure you are getting good quality new insulation boards.

Check out the board thickness

Rigid boards are available from 20mm thickness to 200mm. As the thickness of the board increases so does the thermal performance. With an increment in 15mm from the last size, you can choose the one that suits your design the best!

A good benchmark for the level of insulation you should be looking to achieve is 0.21 W/m2K.

However, in order to achieve that standard using the standard insulated dry-lining panels, you would require a panel of the order of 100mm thick. This includes the plasterboard that is bonded to the insulation. This can be an issue in terms of losing space in rooms or in corridors/stairways.

If your walls currently have little or no insulation, you can still significantly reduce heat loss through the walls significantly by internally insulating. In this case wall insulation board is highly essential.

Try to know the u-value

U values are important to understand when it comes to selecting the right insulation board. The lower the U value that is achieved post insulation the better the heat retention in the property. For example when using a typical rigid board of 50mm, it is equivalent to a U value of around 0.4, 100mm is equivalent to 0.25  and 150mm and thicker is a U value of 0.2 or lower.

Reliable place to purchase the rigid boards-

Rigid boards can be bought at your local DIY store or they can be sourced from a specialist supplier online. Whether you are buying the product online or at the store you still need to get the measurements right so you know how much of the stuff you need to buy. You can visit the DIY store and have a look at how the product looks like. When you are happy, you can go back online and buy it as very often this will give you a further saving.

Insulation board features- What benefits do you get?

  • Good Thermal Conduct
  • This helps in saving of the resource and space. For instance there isnt a need of increased studs in timber frame buildings.
  • Stability in Dimension
  • Helps avoid the dangers associated with board slumping or sagging
  • Tight cell structure
  • Helps keep the structure safe from moisture and air movements
  • Lasts longer keeping the installations retain thermal quantities for even 50 years
  • No risk of water piercing
  • Non-hazardous
  • Non-fibrous
  • No personal protective tools required
  • Irritant free


Negative sides of insulation boards

Insulation boards are more expensive than fibreglass. They can be up to ten times more expensive for twice the performance. They are also more easily damaged on site and can break in the wind.

How to cut and fit insulation boards

Now, we have presented you a simple video tutorial to guide you in installing the chosen insulation board. With few steps, you will be able to install it rightly at a place. From the step of cutting to the way of fitting it, we have given you comprehensive guide through the video.

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