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Cavity wall insulation

Reducing heat loss from the home will help to keep a house warmer at a lower cost. also cavity wall insulation is a specialist job and can only be carried out by an approved company also the insulation materials themselves and their installation are also subject to registered by authorised body. The System we use is CWI18 White wool under 15/5257 approved. 

The first thing you need to find out is what sort of walls you have. there are two main types of wall construction to be found in houses in the UK , Solid walls or cavity walls:

  • A cavity wall is made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block.
  • A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone.

If your house is a steel-frame or timber-framed building, or is made from Pre-fabricated concrete different rules apply for insulation and we  can not help with this  so you may need a specialist company to insulate a non-standard wall. 

You can easily identify a cavity wall by the pattern produced by the brickwork, which is known as stretcher bond, where are the bricks are running in the same direction as one another – there are no ‘half bricks’. This is obviously harder to do if your walls are cladded or painted and in this case you might need to call in a professional (although sometimes you can see original brickwork in the loft space). In addition cavity walls tend to be over 250mm in width, with more recent cavity walls closer to 300mm. If you can see lots of half bricks in your wall, you have a solid wall with no cavity, so unfortunately cavity wall insulation is a no-go.

The gap between the two walls is the cavity. Filling that gap with insulating material can be very effective in reducing heat loss from your home and cutting the cost of your energy bills. Savings of as much as £250 per year for the average detached home are possible, (According to the Energy Savings Trust)

Cavity wall insulation is not always suitable

-If your property is exposed to driving rain. Installing cavity wall insulation in this instance can actually create damp issues on the inside of the property, since the cavity can now no longer drain the water.

- The cavity must be at least 50mm wide to be considered for filling. 

- If the cavity has mortar or other materials blocking it, the blockages should be cleared before the cavity filled. 

- The external wall must be in good condition. if there are already damp issues of the property, these need to be sorted before insulation is installed, otherwise the insulation could compound the damp issue.

- If the cavity wall cannot easily be accessed by the installation team (and their equipment), then you might also need to look at another insulation solution.


Cavity wall insulation can cost anywhere between £600 – 1500 (depend on the size of the property).


-       Reduces heat loss

-       Reduces your heating bills

-       Keeps your house warmer in the winter and cooler in the summer

-       Competitive prices

-       Improves the comfort of your home

-       25 years guarantee certificate

-       Helps to protect the environment

How much you can save

England, Scotland and Wales



Semi detached

Mid terrace



Fuel bill savings (£/year)






Typical installation cost






Payback time

5 Years or fewer

Carbon dioxide savings (kgCO2/year)

 1,100 kg

 660 kg

 430 kg

 450 kg

 360 kg

These are estimated figures based on insulating a gas-heated home. The average installed cost is unsubsidised*.



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