cosy by the fire after having an insulated wall coating

Cavity wall insulation, is it good or bad for my house?

Cavity wall insulation is defined as the injection of an insulating material (usually recycled cardboard, rockwool or polystyrene balls) which fill the cavity (the space between the inner and outer walls) of a house and provide a thermal barrier.

There are tremendous benefits to this system, although there are critics of it too and we look at both sides of the argument here and we suggest viable alternatives to having cavity wall insulation.

In general cavity wall insulation is fitted for a reason; i.e. to cure the symptoms of cold walls and wind chill.

This also has a positive effect on lowering heating bills, however there are some drawbacks too, AND there are alternative ways to insulate your home.

Cavity Wall Insulation, is it a good idea?

Cavity wall insulation is a method if creating a thermal barrier in a house, however it can cause more harm than good and can transmit damp into the house by forming a bridge between the inner and outer leaf of the wall.

The three main types of Cavity wall insulation.


1. A popular and widely used insulation product is made from mineral wool insulation, and is known as Rockwool and is made from stone wool – a blend of naturally occurring volcanic diabase rock.

2. Polystyrene balls. These tiny balls are injected into holes in the wall with a special pump, usually mounted within the teams lorry. (NOTE, NEVER PAINT AGAIN does NOT offer this system)

3. Insulating foam. This is the less commonly used option and is often made from either polyurethane or formaldehyde foam, which must comply with BS:5618  and BS5617

Good or bad?

On the face of it, insulating a cavity wall seems a good idea, however not everyone agrees….

Houses with cavity walls were built to keep out rain driven by the wind, however if the cavity, the gap between each “leaf” of the walls, is filled, there is, some would say, a risk that moisture will then have a way of bridging the cavity and entering the house.

This can cause DAMP where previously it did not exist.

Another problem can be the “wall ties“, the metal rods inside the cavity which help to hold each side the wall together; they can rust when cavity wall insulation is injected, and in the worst case, can cause the outer leaf to fail and come tumbling down into the street or worse.

Of course the cavity wall industry denies this.

And from our viewpoint, it also leaves scar marks across the wall where the team have installed the insulation, meaning that you now have to have the exterior of the house painted with a thick durable paint to hide the blemishes!

house with cavity wall insulation scars

How is suitability for cavity wall installation ascertained?

An authorised contractor will survey the house to determine whether cavity wall insulation is suitable and would commonly look at the following factors.

The exposure of the walls of the house to driving rain, the condition of the masonry joints or “pointing” of the masonry outer leaf, the type of insulation material required and finally, the masonry material itself is considered.

Alternatives to cavity wall insulation.

If filling the cavity walls of your home is not something you feel you would benefit from, then there are other alternatives available, from NEVER PAINT AGAIN.

Exterior spray applied wall coatings

These value for money external wall coatings help in reducing wind chill and curing damp.

All of which can make a house very cold if not treated. Not only does this high performance external wall covering system cure wind chill and cold walls, it also stops damp, and does NOT need repainting for up to 20 years!

Exterior thermal render

This system is an addition to our already popular coloured render and has thermal insulating mesh built into the walls before application of the final aesthetic coat of render.

This amazing system has excellent thermal properties and is suitable for most houses.

Solid wall insulation

Solid wall insulation obviously does not apply for cavity walls and therefore is not suitable, but if your home was built before 1920, chances are it will not have a cavity so that form of thermal insulation isn’t any good.

Exterior retro fitted insulation from NEVER PAINT AGAIN is by the far the best way to insulate a house without cavity walls.

External wall insulation is a layer of material, sometimes boards or sometimes insulated render, applied to the external walls of the house.

applying thermal insulated blocks
2. Applying and fixing the insulation

This can also take the form of cladding, or brick slips, insulated boards which, when fitted to the house, makes it look like the property has a brand new brick wall.

So what’s the answer to insulate my house?

So as you can see cavity wall insulation has its pro’s and cons but overall, if done correctly, big savings can be had on heating, and in some areas of the UK insulation GRANTS and other financial help is also available.

It is worth remembering that GRANTS paid to homeowners for cavity wall insulation are paid for BY TAKING HIGHER TAXES off everyone!!

However, cavity wall insulation can actually cause more problems than it can cure, but if you choose one of our exterior wall coatings, insulation or render systems, you will have the same benefits and MUCH more!

This also includes the fact that we guarantee your house will look amazing, usually in only a few days, and you will get all the thermal benefits of installed cavity walls insulation and much more besides.

We are exterior wall coating contractors and, as such, we offer to remedy walls that have been damaged by cavity wall insulation and our sales line is for SALES ENQUIRIES ONLY please.

Thank you

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