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Cavity Wall Insulation

Cavity Wall Insulation

Cavity wall insulation is a material which is used to reduce heat loss in your home. It works by filling the gap in between the bricks in your walls. This reduces the transfer of heat from within your home to the outside. Over a third of the heat from your home escapes through your outer walls. As a result installing wall insulation can mean substantial savings on energy costs.


Properties in Scotland built before the 1920’s have solid brick or stone walls. If your home was built after this is a good chance it have a cavity in between the bricks of your outer walls. Scottish homes built with solid walls during this period are in a minority. Our surveyors can confirm this by drilling a small hole in your wall and looking inside with specialized equipment..

Your house will usually be suitable for cavity wall insulation if:

  • your external walls are unfilled cavity walls
  • the cavity is at least 50mm wide
  • the masonry is in good condition
  • it was built after the 1920’s

When retrofit cavity wall insulation is installed into a property that is located or built in a way that means it should not have the cavities filled or if the work is undertaken incorrectly, the first and most obvious sign of a problem is almost always internal dampness.

Most homeowners are blissfully unaware if cavity wall insulation hasn’t been installed correctly.  They don’t know if it is over-packed, underfilled, where it has slumped, where areas have been missed, vents have been blocked, or obstructions missed.  This is because even though the energy savings won’t be as advertised, there is no visible sign of any defect. Those that are aware of a problem with the insulation within the walls will almost certainly have been put on notice with the appearance of dampness within their home.


Condensation creates damp conditions which often soak insulation.  We are now getting many calls from people who have had cavity wall insulation – their house is getting colder and colder.  The reason is simple.  Cavity walls were designed to breathe. The original concept of cavity walls was intended to be used in coastal areas where windblown rain was a problem and soaked house walls.  It then became standard construction everywhere.  Rain hits the outside wall, and it is able, because the wall is only single brick, to get through.  It then runs down inside the cavity and exits via the bottom.  Airflow in the cavity keeps things nice and dry.

Remember, dry things don’t conduct heat.  Wet things conduct and lose heat very easily.  If your cavity is then filled – you completely destroy any chance the house has of staying dry.  Water can easily get through the outer leaf, and it soaks the cavity fill.  Condensation from the house also gets through the wall on the inside – and instead of wicking away through the cavity, it finds a nice fluffy mess of waste paper or waste cotton.  It all gets wet.  And it stays wet.  So now, your house has wet walls, and a much greater ability to lose heat through the walls – once upon a time, they were nice and dry.  Now they are wet, so they are colder.


Most cavities should be ‘tied’ with brick ties.  If they stay dry, they don’t rust. The wall remains secure.  Cool…

Now then – you fill the cavity, and it gets wet.  The brick ties get wet and stay wet.  And they rust. So the wall is no longer tied together, and it can bulge or fall.  Not so Cool…

Cavity insulation also makes a lovely environment for little critturs – lots of lovely mice nests, rats, you name it – they love the stuff.  The man from the cavity wall insulation company will tell you it’s treated to stop them.  Rubbish.  Have you ever seen a mouse eat plastic?  They do… I’ve seen them eat their way through bags of building chemicals in our store – and keep eating.  It just doesn’t affect them. There’s virtually nothing that will stop a mouse from eating and making a nest. Cavity walls full of fluffy paper or cotton are a paradise for them.  All of this action also makes the insulation settle.  Some areas will have none; others will have lots.  This makes your walls very prone to being damp or cold in some spots, and not in others – so you start to experience random problems with damp.

Additional Extras
Free Thermal camera survey

Thermal imaging surveys utilise thermal imaging cameras to showcase the surface temperatures around your property in order to identify thermal changes that indicate possible defects that require resolution. Thermographic surveys can identify potential problems long before lasting damage is caused. This is the only non-intrusive way to locate missing insulation and thermal bridges within the fabric of a buildng.
Damp Survey

A Damp Survey is a detailed look into a property which has shown potential damp problems. Damp is a common issue, and if left untreated, can cause some costly damage. Following an external inspection, an internal survey will be carried out, this could be a general inspection, or be restricted to a specific area where a problem is located.

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Renewable Energy

Solar power can help reduce CO2 emissions mainly by being a clean and renewable source of energy. It’s shown that of energy production methods including coal, gas, oil that renewable energy such as PV solar and wind energy have a far lesser carbon footprint. Solar power is not dependent on burning fossil fuels or other products.

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