Is cavity wall insulation good or bad? First off, what is a cavity wall? These structures consist of two layers or ‘shells’ of brickwork, separated by a gap.
This gap contains nothing but fresh air to improve the thermal qualities of your home. How does this happen? Well, heat transfer does not happen as quickly over air as it does through a solid or damp substance.
The vast majority of new houses today are built with cavity walls as they prove to be twice as efficient as solid walls when it comes to thermal quality.
It makes sense – two walls being twice as efficient as one! A solid wall is exactly that – a solid wall that allows heat to travel through the brickwork, directly to the outside space.
So a cavity wall already features an element that makes it incredibly thermal efficient – why would you bother adding extra insulation? And is cavity wall insulation good or bad? First, let’s talk about the two types…
Insulating the Gap Within the Wall
As it is traditionally known, cavity wall insulation is the process of retrofitting wall insulation material that is injected or blown into the space between the inner and outer shell of your walls.
This fills the gap or the cavity with an extra layer of material that is supposed to reduce the amount of energy lost through your walls.
As this is a retrofit operation, the process is done blindly. Holes are drilled in strategic places within your exterior brickwork, and then hoses are inserted into the holes. The material is then blown into the gap, with the hope that the entire area will be filled.
It is impossible to truly guarantee that every hole and space has been filled, as it is impossible to see through the brickwork. This could create cold spots that significantly reduce the thermal efficiency of this operation.
Even if successful, many experts argue that cavity wall insulation promotes the transfer of moisture between your inner and outer shells, again reducing its thermal efficiency.