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Cavity Wall Insulation

Cavity wall insulation is used to reduce heat loss through a cavity wall by filling the air space with material that inhibits heat transfer. This immobilises the air within the cavity (air is still the actual insulator), preventing convection and can substantially reduce space heating costs.

We have always found (and this is supported by many years of testing and design work) that retro fit cavity wall insulation works extremely well when fitted correctly (that is, fully filled to the correct density) in properties that are suitable. However, there are many properties with a cavity wall that are unsuitable for cavity wall insulation. There are various reasons for this but chief among them are that the DPC is too low, the property is exposed to wind blown rain, there are inherent damp issues, the cavity is too narrow, the brickwork is in poor condition, the property has finlock guttering or there is rubble in the cavity. In these instances, we would usually advise against fitting cavity wall insulation. In every case, or experienced surveyors will assess the suitability of your property for cavity wall insulation.

Unfortunately, we see many examples of cavity wall insulation in houses that were unsuitable for one or a combination of the reasons above. We also see damp problems occurring in houses that were suitable for cavity wall insulation but have just been poorly treated by the insulation installers; leaving void areas and unfilled holes that attract damp problems. Technical failures are monitored by the energy companies and recorded as 15-17%.

Important: If you think that cavity wall insulation has been installed incorrectly or that your property displays one of the above characteristics and you have experienced problems (most usually damp problems) please let us know. It may be that the cavity wall insulation needs to be extracted or removed.

You can read more about the potential problems with cavity wall insulation if not done carefully and correctly here.

New Build Cavity Wall Insulation

Most people associate cavity wall insulation with being retro fitted long after the house was originally built and this indeed does account for a large proportion of our work. However, house builders are quickly realising the benefits of new build cavity wall insulation – blowing the cavity internally during the construction process, once the cavity has been closed (e.g once the roof, windows and doors have been fitted). The advantages of insulating the cavity wall this way are significant:

  • It is generally cheaper than PIR board and can achieve the same U-Value
  • It allows brickwork contractors to more efficient build the walls up to height, maintaining a good clear cavity in the process
  • In cases where mineral batts are used, there is no risk of the insulation being soaked by adverse weather during construction or mortar gathering in the centre of the insulation
  • There is no requirement for site storage
  • There is no requirement for waste disposal
  • You eliminate entirely the potential for theft of materials

All our operatives are fully accredited for site work. For a full list of our training and accreditations, please see Our Standards