Home Insulation Guide

Home Insulation: The Fastest Way to Cut Your Energy Bills

Complete guide to cavity wall, loft, solid wall and floor insulation. Save hundreds per year on heating bills. Free installation under ECO4 scheme for eligible homes.

Free under ECO4/GBIS Save £300-600/year Cut heat loss by 45%
Insulation Types

Four main types of home insulation

Loft Insulation

£590
Average annual saving

Prevents heat rising through roof. Easiest to install DIY. Recommended depth 270mm.

Cavity Wall

£395
Average annual saving

Fills gap in walls built 1930s-1980s. Professional installation only. Quick 1-day job.

Solid Wall

£445
Average annual saving

Internal or external insulation for pre-1930s homes. Higher cost but excellent results.

Floor Insulation

£70
Average annual saving

Suspended floors & solid floors. Prevents heat loss through ground. Often overlooked.

Loft Insulation

The highest-impact, lowest-cost insulation

Loft insulation is the most cost-effective home improvement you can make. Heat rises, and without adequate loft insulation, up to 25% of your home's heat can escape through the roof.

Loft insulation types

  • Blanket insulation: Rolls of glass wool or mineral wool between joists
  • Loose-fill insulation: Granules blown between joists
  • Board insulation: Rigid boards for rooms in roof
  • Natural insulation: Sheep's wool or recycled materials

Recommended loft insulation depth

Current building regulations recommend 270mm depth of mineral wool insulation. Many homes have insufficient insulation:

  • 100mm or less: Definitely needs upgrading
  • 100-200mm: Consider topping up
  • 200mm+: May benefit from topping up to 270mm

DIY vs professional loft insulation

DIY loft insulation costs £200-400 for materials vs £400-600 professionally installed. DIY is feasible if you have easy loft access and no electrical complications. Professional installation is recommended for complex lofts or if claiming government grants.

Loft insulation installation tips

  • Check for air leaks: Seal gaps around pipes and cables first
  • Protect electrics: Ensure cables aren't compressed by insulation
  • Ventilation: Don't block eaves ventilation
  • Loft boards: Install loft boards over insulation for storage
Cavity Wall Insulation

Fill the gap to save hundreds per year

Cavity wall insulation fills the gap between the inner and outer walls of your home with insulating material, preventing heat loss through the walls.

Do I have cavity walls?

Houses built between the 1930s and 1980s typically have cavity walls. Here's how to check:

  • Measure wall thickness: Cavity walls are typically 260-300mm thick
  • Check brickwork pattern: Cavity walls usually show stretcher bond (all bricks laid lengthways)
  • Age of property: Pre-1930s homes usually have solid walls
  • Professional survey: Get an installer to check with a borescope

Cavity wall insulation materials

  • Mineral wool: Most common, blown in as loose fibres
  • Polystyrene beads: Small beads with adhesive binder
  • Foam insulation: Urea formaldehyde foam (less common now)

Installation process

Professional cavity wall insulation takes just 1-2 days:

  • Survey: Check cavity is empty and suitable
  • Drill holes: Small holes drilled in outer wall
  • Inject insulation: Material blown into cavity
  • Fill holes: Holes made good with matching mortar

Is my cavity already filled?

Many homes had cavity wall insulation installed in the 1980s-2000s. Check for small filled holes in the mortar or contact your local authority for records. If you're unsure, an installer can check with a borescope camera.

Cavity wall insulation should last 25+ years and typically pays for itself within 2-5 years through reduced heating bills.

Solid Wall Insulation

Insulating older homes without cavities

Solid wall insulation is for homes built before the 1930s that don't have cavity walls. It's more expensive than cavity insulation but can provide excellent energy savings.

Internal vs external solid wall insulation

Internal solid wall insulation

  • Cost: £5,000-£8,000 for average home
  • Installation: Insulation boards fitted to interior walls
  • Disruption: Requires moving furniture, redecorating
  • Space loss: Reduces room size by 100-150mm
  • Best for: Homes where external appearance must be preserved

External solid wall insulation

  • Cost: £8,000-£15,000 for average home
  • Installation: Insulation applied to exterior walls
  • Disruption: Less internal disruption
  • Benefits: No space loss, can improve appearance
  • Planning: May need planning permission

Solid wall insulation materials

  • Rigid foam boards: High performance, thin profiles
  • Mineral wool batts: Natural materials, good for internal use
  • Natural fibre batts: Sheep's wool, wood fibre
  • Render systems: External insulation with decorative finish

Planning permission for external insulation

External wall insulation may need planning permission, especially for listed buildings or conservation areas. It can also affect boundary distances. Check with your local planning authority before proceeding.

Solid wall insulation is a significant investment but can transform the comfort and energy efficiency of older homes, often saving £400+ per year.

Costs & Savings

Insulation costs and annual savings

Insulation Type Professional Cost DIY Cost Annual Saving Payback Period
Loft Insulation (270mm) £400 - £600 £200 - £400 £590/year 1-2 years
Cavity Wall Insulation £900 - £1,500 Professional only £395/year 2-4 years
Internal Solid Wall £5,000 - £8,000 £2,000 - £3,000 £445/year 5-10 years
External Solid Wall £8,000 - £15,000 Not recommended £445/year 8-15 years
Floor Insulation £800 - £1,500 £300 - £600 £70/year 4-8 years

Savings figures are based on a typical 3-bedroom semi-detached house. Actual savings depend on your home size, current heating costs, and existing insulation levels.

Free insulation under government schemes

  • ECO4: Free insulation for households on qualifying benefits
  • Great British Insulation Scheme: Free cavity wall and loft insulation for council tax bands A-D
  • Local authority schemes: Some councils offer additional support

If you're eligible for free insulation under ECO4 or GBIS, it's definitely worth taking advantage as the payback is immediate.

Insulation and heat pumps

Good insulation is essential if you're considering a heat pump. Heat pumps work most efficiently in well-insulated homes. Many heat pump installers require certain insulation standards before installation.

FAQ

Home insulation questions answered

Common questions about insulation types, costs, installation and government schemes.

Main types include cavity wall insulation, loft insulation, solid wall insulation (internal/external), and floor insulation. Each type suits different property ages and construction methods.
Loft insulation saves up to £590/year. Cavity wall insulation saves £395/year. Solid wall insulation saves £445/year. Floor insulation saves £70/year on average.
Yes, insulation is free under ECO4 for eligible households receiving certain benefits or living in social housing. The Great British Insulation Scheme also provides free insulation for council tax bands A-D.
Homes built 1930s-1980s likely have cavity walls. Check by measuring wall thickness - cavity walls are typically 260-300mm thick. Solid walls (pre-1930s) are usually 220mm thick.
Loft insulation can be DIY installed. Cavity wall and solid wall insulation require professional installation. DIY loft insulation costs £200-400 vs £400-600 professionally installed.
Loft insulation: 1 day. Cavity wall insulation: 1-2 days. Solid wall insulation: 1-2 weeks. External wall insulation may require scaffolding and planning permission.

Check your free insulation eligibility

See if you qualify for free insulation under ECO4 or Great British Insulation Scheme. Enter your postcode to start.