Cavity Wall Insulation Types - Mass Foam Systems

Cavity Wall Insulation Types

Cavity Wall Insulation Types

General Insulation

Whether you’re a fan of the cold season or not, sufficiently heating your home is important. This necessity comes with a bill of its own, and no one is a fan of paying anything more than they should. If left unchecked, the cost of heating your home can seriously derail your financial plans. Cavity wall insulation helps save on those heating bills.

What is a Cavity Wall?

Most UK homes built after the 1920s have cavity walls, which consist of two thin brick walls (skins/leaves) with a gap or cavity in between them. Holding them together are metal wall ties.

The problem is that most of these old houses have empty cavities, which beats the purpose of having the cavity wall in the first place. Most modern houses take full advantage and fill up the spaces with insulating material.

Checking for Existing Insulation

Naturally, you might want some assurance that your home has cavity wall insulation. To confirm, the best course of action would be to ask a professional to perform a borescope inspection. This entails drilling a tiny hole in the wall to check for any insulation. You could also just check with your local building/regulatory authority.

There are other giveaways that may indicate that your home is insulated. If your wall has one-inch filled holes at regular intervals, or if your loft is insulated, then insulation might already be present. It is, however, important to have a professional do the checking for you.


Not every wall is suitable for insulation. The following factors help determine the suitability for filling a cavity wall. They are best discussed with a professional to determine the best course of action.

  • Building material
  • Exposure to wind-driven rain
  • Cavity size
  • Tree or building cover
  • Wall height

Types of Walls

Not all homes have cavity walls. Some walls have no gaps and are referred to as ‘solid’ walls. These have a lot of ‘half-length’ bricks (cross bricks) in the middle of the walls.

Other homes are made of timber, steel-frames, or even pre-fab concrete.

All these homes can be insulated in separate ways. Consult an accredited installer to find the best insulation to go for.

The Importance of Insulation

As already alluded to, insulation can save a lot of your hard-earned money in terms of heating costs. More than half of the heat loss in homes is through the roof and walls. It just makes sense, doesn’t it?

Types of Wall Insulation Materials

Different materials make up different cavity wall insulation types. Some materials are more commonly used than others – and for good reason.

Blown Mineral Fibre/Mineral Wool

This is the most used insulation material for residential homes. It is made up of fibreglass strands that are obtained from heating and spinning igneous rock. It is blown into the wall cavity using compressed air and occupies the entire space.

Blown mineral fibre can be used all over the UK.

Polystyrene Beads (EPS)

Expanded Polystyrene Beads, also known as EPS, is a lightweight, foamed plastic with great insulation capabilities. It comes as either loose or as a sticky resin for the purpose of ensuring that it holds together. The beads or granules are pushed into the cavity using compressed air.

EPS is preferred for narrower spaces compared to mineral wool. This also makes it an ideal solution for insulating homes with solid walls. It traps heat effectively and efficiently as it tends to be gap-free. However, in some cases, polystyrene granules have been known to escape through airbricks.

Advantages of EPS include:

  • A great value for money
  • EPS has lifetime durability when installed properly
  • It is resistant to moisture and humidity
  • It also serves as sound insulation
  • It is easy to install
  • It is lightweight, therefore easy to transport and handle
  • Its thermal insulation is excellent owing to the fact that EPS in 98% air
  • It has two grades. FR-grade (Flame Retardant) is self-extinguishing and non-FR


A great EPS solution is ThermaBead. The ThermaBead bonded bead system comes with two options:

  • Carbon Saver
  • Diamond
cavity wall thermabead solution

With both, you get excellent thermal properties but due to Diamond’s unique shape and additional manufacturing processes, it is the premium choice and gives unbeatable results in terms of improving energy efficiency.

Urea Formaldehyde Foam (Cavity Foam)

Cavity foam is another popular insulating material. The foam requires significantly smaller drill holes than other materials. It is formed within the cavity mixing two chemicals. The foam then expands to fill the cavity.

This material requires experts to install and needs consistent attention.

Urea-formaldehyde was a popular choice but has since been overtaken by Polyurethane foam. It is still a completely viable option, even though some foams are known to degrade over time.

Insulation Types for Solid Walls

Insulating solid walls is not as straightforward as insulating cavity walls. There are two choices for this type of insulation – internal or external insulation.

Internal Wall Insulation

Also known as dry lining, internal insulation is only installed in the rooms of your home. Most people attempt to do this themselves, with mixed results. Getting it done professionally will definitely disrupt your stay, but it offers a greater chance of offsetting any drawbacks of internal solid wall insulation.

With this type of insulation, heat has more avenues of escape as compared to other forms of insulation. The savings, therefore, may not be as significant and it takes longer for the job to pay for itself.

Stud Wall

A stud wall is a wooden or metal frame that is fixed to the wall, before being filled in with mineral wool.

The insulation filling must be at least 12cm and will eat into the available space in the room. It is however strong enough to hold up anything that is fitted onto it. It is a great option for uneven wall surfaces.

Rigid Insulation Boards

These are plasterboards filled with foamed plastic that are fixed directly onto your interior walls. They require level surfaces and take up less space than stud walls (6cm to 10cm).

External Wall Insulation

External wall insulation adds to the thickness of your walls, reducing whatever space the wall is adjacent to. Anything attached to these walls like pipes and gutters is naturally shifted further outward.

This insulation type involves fixing wooden lattices onto walls to hold your insulation material of choice in place. External wall insulation is bound to change the outlook of your home.

External insulation has four layers:

  • The primer to prepare the wall for insulation
  • The insulation layer
  • A glass-fibre mesh to bind to the insulated wall
  • The final, decorative layer

Considerations and Best Practises

As good as you may be and as satisfying as A DIY job may be, it is very important to get trained, qualified, and accredited personnel to install insulation in your home. It is recommended to have a specialist contractor who should provide a Cavity Insulation Agency (CIGA) guarantee.

The guarantee is only valid if the work is done by a qualified professional. Resources you should consult include the aforementioned CIGA, the British Board of Agrément (BBA), and the National Insulation Association (NIA).

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