Cavity wall insulation is installed in the space between in the inner and outer leaves of both external and party walls in many building types, both in new build and renovated properties. The latter includes numerous UK homes dating back to the 1920s. 

Without adequate insulation, properties will lose more heat – resulting in greater energy use to warm them effectively, and higher bills. 

Discover more about the benefits, products and installation methods of ROCKWOOL cavity insulation today.

Cavity Wall Insulation Products

Why do we need cavity wall insulation?

Fitting insulation for cavity walls is among the quickest and most cost-effective ways to improve energy efficiency. 

An uninsulated cavity will result in increased heat loss during a cold period. In fact, around a third of the heat lost escapes through uninsulated cavity walls1.

Cavity wall insulation acts like a blanket that stops heat escaping. It retains the heat and releases it back into the internal space. The insulation also keeps the home cool in summer, so the property maintains a comfortable indoor temperature and doesn’t overheat.


Key benefits include:

  • Improved energy efficiency
  • Enhanced fire safety
  • Reduced heating and cooling costs
  • Quick and easy installation
  • Long term performance 
  • Durability 

Calculator and savings

The exact cost of installing cavity insulation and the energy savings it can bring will depend on property size and type. 

Stone wool insulation can be installed as partial or full fill, with the thickness of insulation required being determined by building regulations and the specified thermal performance. 

Generally, you should recoup the installation cost within five years, with research suggesting it can save you up to £285 per year on energy bills in the UK.2


Property type

Energy bill savings (per year)

CO² savings (kg/CO² per year)

Detached house



Semi-detached house



Mid terrace










Use the ROCKWOOL U-value calculator to determine the thermal performance of the building’s walls. 

Typical British Home - Masonry Cavity Wall Type
ROCKWOOL cavity wall insulation offers an excellent fit, by taking up irregularities within the wall construction, as well as knitting tightly together at the joints, reducing heat loss that can occur through gaps in the insulation layer. With a proven lifetime of more than 50 years, performance will not deteriorate over time.

Roger Peeters

ROCKWOOL Group Product Manager
To be updated
829.4 KB

Full Fill Cavity Batt Datasheet

Insulation for masonry cavity walls. Cavity datasheet includes applications, performance, installation guidance and product specification text.

To be updated
2.7 MB

HP Partial Fill Cavity Slab Datasheet

Robust, long-lasting protection for masonry cavity walls. HP Partial Fill Cavity Slab datasheet includes applications, performance, design guidance, installation and NBS clauses.

To be updated
2.2 MB

ROCKCLOSE® Datasheet

Minimises thermal bridging at door and window reveals in cavity wall constructions. ROCKCLOSE datasheet includes information on applications, performance, installation guidance and NBS clauses.

Download our guides

Financial Support

Check the Energy Savings Trust website to see whether there are any financial support schemes available for cavity wall insulation.

Building, Energy Efficiency, Thermal Comfort


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