Insulation for Cavity Wall: Benefits, Costs, and How to Get It for Free in 2025

Cavity Wall Insulation Benefits

If you’re looking for ways to make your home warmer and lower your heating bills, insulation for cavity walls is one of the best upgrades you can make in 2025. Many UK homes are still losing valuable heat through uninsulated walls, which means you’re spending more than you need to on energy. 

The good news is you may not have to pay anything to get this done. Thanks to government grants and trusted partners like Free Insulation UK, many people are now getting cavity wall insulation installed completely free of charge.

Let’s take a look at what cavity wall insulation is, why it’s worth doing this year, what it costs, and how you can claim a grant to cover it.

What Is Insulation for Cavity Wall?

Insulation for cavity walls involves filling the gap between the inner and outer walls of your house with insulating material to stop heat from escaping. Homes built in the UK after the 1920s usually have cavity walls, and many of them are still uninsulated.

By sealing that space, you can:

  • Keep more warmth inside during winter 
  • Use your heating less often 
  • Lower your energy bills

This simple upgrade can make a huge difference in how comfortable your home feels.

Why Is Cavity Wall Insulation Worth It in 2025?

With rising energy prices and more support for energy-saving home improvements, cavity wall insulation is more valuable than ever. Here are some of the top reasons to consider it:

  • Save up to £405 per year on heating bills (for a detached home; savings for other property types are lower; see table below)
  • Keep your home warmer in winter and cooler in summer
     
  • Help reduce your carbon footprint
     
  • Improve your EPC rating (Energy Performance Certificate) 
  • Quick installation, usually done in a few hours

Cost of Insulation for Cavity Wall in the UK (2025)

If you’re paying out of pocket, the cost of insulation depends on your property type and size. Here’s a general idea:

Property Type Average Installation Cost Annual Energy Bill Savings
Detached House £4,600 £405
Semi-detached House £2,700 £235–£240
Mid-terrace House £1,500 £140
Detached Bungalow £2,100 £175–£180
Flat/Apartment £1,000 £110

But here’s the exciting part. Many UK homeowners are eligible for full funding through government grants. Free Insulation UK helps match you with these schemes, so you don’t pay a thing.

Find out if you’re eligible FOR FREE CAVITY WALL INSULATION

How to Get Free Insulation for Cavity Wall

You might be wondering how it’s possible to get this for free. There are a few government-supported programs designed to make homes more energy-efficient and reduce fuel poverty.

The Great British Insulation Scheme

This national scheme is designed to help households with lower energy efficiency (EPC ratings D–G and Council Tax Bands A–D in England, or A–E in Scotland/Wales) get free or subsidised insulation, including cavity wall insulation. You don’t always need to be on benefits to qualify, as local councils can set their own criteria. GBIS is available until March 2026.

Energy Company Obligation (ECO4) & ECO4 Flex

ECO4 is a long-running programme that requires energy suppliers to help low-income and vulnerable households improve their homes. 

If you receive certain benefits (like Universal Credit, Jobseeker’s Allowance, or Pension Credit), you could get your insulation fully funded. 

ECO4 Flex allows local councils to recommend households who might not meet the standard criteria but are still at risk of fuel poverty.

Warm Homes Local Authority Grant Scheme

The Warm Homes: Local Grant is a major new scheme delivered by local authorities in England. It offers fully funded energy efficiency upgrades, including cavity wall insulation, to eligible owner-occupiers and private renters (with landlord permission). 

To qualify, your household income needs to be below a set threshold, and your home should have an EPC rating of D to G. Grants can cover up to £15,000 per home for insulation and other improvements. Local councils will reach out to eligible households, or you can check your council’s website for details as the scheme becomes available.

 Even if you’ve been turned down for other schemes, your local Warm Homes programme may be able to help.

Not sure which scheme you qualify for? Free Insulation UK takes care of the hard work. Just fill in a quick form to check your options.

Who Can Apply for These Grants?

You might be eligible for a free insulation grant if:

  • You own your home or rent it privately
  • Your home has an EPC rating of D or lower
  • You receive income-based benefits
  • Your council participates in flexible eligibility schemes
  • You are considered vulnerable to cold weather or fuel poverty

It’s always worth checking, even if you’ve been turned down before. Apply now to find out if you qualify.

Best Materials Used for Cavity Wall Insulation

Cavity wall insulation comes in different materials. The most popular choices in 2025 include:

  • Mineral wool, which is safe, affordable and widely trusted(most common for existing homes)
  • Polystyrene beads, which are great for getting into awkward spaces(also common for retrofits)
  • Foam insulation, ideal for narrow wall cavities
  • Rigid boards, often used in new builds and extensions

Each of these options is designed to last at least 25 years and comes with specific benefits. The material that’s best for your home depends on your wall structure, and Free Insulation UK’s survey team can recommend the right fit.

How Is Insulation for Cavity Wall Installed?

The installation process is quick and non-invasive. Here’s what usually happens:

  1. A trained professional visits your home to check if it’s suitable
  2. Small holes are drilled into the outer brick walls
  3. The insulation material is blown into the cavity using special equipment
  4. The holes are filled and colour-matched to blend in

You won’t need to move any furniture, and nothing needs to be done inside your home. Most installations take just a few hours. Professional installation is essential to avoid issues like damp; always use accredited installers.

Book your free home survey with Free Insulation UK today.

Is My Home Suitable for Cavity Wall Insulation?

You may be eligible for insulation for cavity wall if:

  • Your house was built after 1920

  • Your walls are uninsulated and have a cavity of at least 50mm

  • There are no serious damp or structural issues

  • Your home has brick walls (stone or timber-framed properties might not qualify)

If you’re unsure, we can arrange a free assessment to confirm if your home is ready for the upgrade.

Ready to Apply with Free Insulation UK?

If you’re looking to make your home warmer and more energy-efficient without spending a fortune, now’s the perfect time to act. With insulation for cavity wall available through fully funded grants, you could save hundreds on your energy bills, without paying a penny upfront.

Free Insulation UK makes the process simple. From checking your eligibility to arranging a free home survey, their team takes care of everything so you can sit back and enjoy the benefits.

Don’t wait for your energy bills to climb even higher. See if you qualify for free cavity wall insulation today.