Loft and Cavity Wall Insulation
Around a quarter of heat is lost through the roof and a third through uninsulated walls. These two measures are usually the fastest payback you can get.
Loft insulation
Top up to 270mm of mineral wool for roughly £500 to £1,000, saving around £300 to £400 a year on heating. It is a weekend DIY job or a quick professional install.
Cavity wall insulation
If your home has unfilled cavity walls (built 1920s to 1990s), professional filling costs about £1,000 to £2,000 and saves £400 to £500 a year. A free or subsidised option may exist via ECO4 or the Warm Homes Plan.
Solid walls need a different approach
Older solid-wall homes cannot have cavity fill — they need internal or external insulation, which costs more but still cuts bills substantially.
Do it before the heat source
Insulate the fabric first so any new heat pump or boiler is sized smaller and runs cheaper.
FAQs
- Is loft insulation worth it?
- Yes — it is one of the cheapest measures with payback in a few years.
- How do I know if I have cavity walls?
- Homes built after the 1920s with a uniform brick pattern usually have cavities; a survey or installer can confirm.
- Can I get it free?
- Lower-income households may qualify via ECO4, LA Flex or the Warm Homes Plan.