Spray Foam Insulation

Hard to treat cavities

The challenge, the solution

The Energy Company Obligation (ECO) is a funding mechanism launched in 2013 designed to target the refurbishment of existing housing stock. The objective is to support the Government’s programme of reducing carbon emissions from domestic properties by increasing their energy efficiency.

The Department of Energy and Climate Change (DECC) suggests that the capital value of the remedial work required is in the region of £58 billion. Clearly the programme to refurbish housing presents enormous opportunities for the building industry.

ECO recognises the need to improve the thermal insulation of wall structures and will provide funding for fitting insulation onto solid walls and into hard to treat cavities.

The most recent English House Condition Survey suggested that there are currently around 3.2 million houses in the UK that have hard to treat cavities.

Hard to treat cavities are defined as:

  • Masonry cavities less than 50mm wide
  • Prefabricated concrete construction systems with cavities
  • Metal frame construction systems with cavities
  • Random stone cavities
  • Timber studwork cavity
  • Buildings more than three stories tall
  • Walls exposed to severe wind driven rain

The most cost effective and least disruptive way to treat cavities of this kind is to inject insulation material directly into the existing cavity.

Recognising the potential for this type of refurbishment, BASF developed a version of its WALLTITE® spray foam insulation specifically for injection into existing cavities.

WALLTITE® CV 100 is the injection grade. Applied in liquid form, the WALLTITE® CV 100 takes fractionally longer to expand into its finished closed cell foam, ensuring that all irregularities within the cavity are covered, sealed and insulated.

Injected into the hard to treat cavity, WALLTITE® offers the following advantages to specifier and homeowner:

  • The product bonds permanently to any substrate material, providing additional structural stability to existing cavity wall structures.
  • WALLTITE® will also provide an airtight insulation layer around a house whose fabric has previously allowed significant air leakage.
  • The injection process requires holes of just 12mm diameter to be drilled in the mortar.  No bricks will be damaged and, once repointing has taken place, there will be no sign of the installation.
  • Only BASF approved Foam Master qualified companies can install WALLTITE®.

The results that can be achieved will vary depending on the material used, but calculations based on the use of WALLTITE® CV 100 rigid closed cell foam insulation injected into a 40mm cavity suggest that the U-value of the refurbished wall should be in the region of 0.46W/m2K to 0.56W/m2K depending on the make up of the internal and external walls.


WALLTITE® has undergone various performance tests. Certificates are available on request.

NBS Plus

Additional resources


Below is a short video demonstration on how WALLTITE® works in an uneven cavity


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