Cavity wall insulation
Around a third of the heat in an uninsulated home escapes through the walls. Most GB homes built after the 1920s tend to have cavity walls (two walls with a gap in between) so this insulation method saves residents both energy and money.
At the start of a project, properties are assessed by our retrofit surveyors and independently inspected by the Installation Assurance Authority (IAA) to ensure no pre-existing damp or mould issues need to be addressed before installation.
To install cavity wall insulation, our trained, certified teams:
- Drill small holes at regular intervals around the outside wall
- Blow insulation (mineral fibre or polystyrene beads) into the cavity
- Fill the holes in the brickwork
It generally takes around two hours to insulate an average house with easily accessible walls, and the insulation has a 25-year guarantee, backed by the IAA.
External wall insulation
Insulating external solid walls (found in most UK properties built pre-1920s) is an effective way to cut heating costs and improve home comfort.
To install external wall insulation, our trained, certified teams:
- Begin by assessing the property’s suitability
- Complete enabling work such as moving downpipes and gutters, making changes to rooflines and moving other fixtures
- Attach a thermal layer to existing external walls
- Cover it with a coloured render or decorative finish to protect from wind and rain
- Restore any fittings that were removed
Installing external wall insulation takes around 7–10 days, using scaffolding so our installation team can access walls easily and safely.
Internal wall insulation
Fitting insulation to the inside walls of solid wall properties creates a thermal barrier which significantly reduces heat loss, and can also improve the soundproofing performance of the external walls. Homes built pre-1920s are more likely to have solid walls and thus be suitable for internal wall insulation.
To install internal wall insulation, our trained, certified teams:
- Do a technical survey using our retrofit assessors to check property suitability
- Extend electrical sockets and remove radiators/skirting boards
- Build a stud wall filled with insulation material (such as mineral wool fibre) on to all internal walls
- Add a vapour barrier then plasterboard, ready for decoration
Case Study: Installing insulation at scale under Connected for Warmth
Between March 2023 and November 2025, through the award-winning Connected for Warmth scheme, Agility installed insulation in thousands of eligible homes across England and Wales.
Supported by the National Grid energy efficiency fund, this programme successfully helped reduce carbon emissions, tackle fuel poverty and improve residents’ comfort.
We deliver Warm Homes funding
Agility helps social housing providers, local councils and housing associations to access grant funding including the Warm Homes: Local Grant, Warm Homes: Social Housing Fund and Great British Insulation scheme (GBIS) to support the installation of home energy efficiency improvements – including solar PV, solar batteries, wall insulation, roof insulation and air source heat pumps (ASHP).
Many grants are open to a wide range of households, with some being means-tested (on income or benefits received) while others can be accessed regardless of financial circumstances. Eligibility may depend on factors such as property type, energy performance and postcode.
Discover other energy efficiency measures we install.
