Cavity Wall Insulation

What is 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. Cavity Wall Insulation can save you up to 30% on your bills.


  • BBA Approved
  • Prevents condensation
  • Average saving of up to 30% on bills
  • Reduced heat loss in winter and reduced overheating in summer

How we do it

Rockwarm arrange for the insulation of your property to be carried out by their teams of fully trained specialists, approved by certification of both the BBA (British Board of Agreement) and by KNAUF Approved Installers. (NB – we do not sub-contract work)

Holes are drilled into the mortar line of the outer brickwork pattern, approximately 1.4 metres apart.

With semi-detached properties a cavity brush will be placed in the cavity flush to the adjacent property to prevent any spillage of material into the neighbours cavity. The loose wool is then blown into the cavity until it is tightly packed and no gaps are left.

A pressure sensor on the blowing machine cuts off the flow of material when it has reached the correct density in the cavity.

The holes are then re-filled with matching mortar, and the site is thoroughly cleaned after the installation is complete.

What it's made of


Rockwarm has chosen KNAUF – SUPAFIL as its preferred supplier of insulation materials. As one of the market leading insulation product.

A tailor-made product designed to meet individual customer requirements, Supafil is a premium quality, non-combustible, glass mineral wool insulation designed to be blown into existing cavity walls. Supafil Cavity Wall Insulation is a loose, shot free, non-combustible glass mineral wool insulation which requires no mixing on site.

Your property will be regularly visited during the installation by one of our Quality Inspectors. Their role is to assess the quality of the installation at key stages and ensure that Rockwarm’s Health & Safety guidelines and procedures are being followed at all times.

Instant Online Quotations

We are more than happy to answer any of your questions. Installing EWI and render is a big job that requires careful consideration before going ahead. That’s why we are always pleased to advise customers as to the best options for their particular property. If you are looking for a quote, please contact us via the form below to get a quick, free, no obligation response. If you prefer to contact us directly - please call us now on 02476 345554