Insulation Savings Calculator
Calculate how much you'll save by adding loft insulation, wall insulation, or pipe insulation to your home.
Estimated property area: 160 m²
Estimated roof area: 96 m²
Total Investment
£17328.00
for all improvements
Annual Savings
£1899.20
per year
Payback Period
9.1
years
Heat Loss Reduction
Typical UK home loses 25% through loft, 33% through walls, 15% through floor, 10% through windows
Recommended Improvements (Priority Order)
Loft Insulation
25% heat lossUpgrade from 0mm to 270mm
Cost
£480.00
Annual Saving
£240.00
Payback
2.0 yrs
ROI
50%
Cavity Wall Insulation
33% heat lossFill cavity walls with mineral or foam insulation
Cost
£2288.00
Annual Saving
£499.20
Payback
4.6 yrs
ROI
22%
Solid Wall Insulation
35% heat lossInternal insulation boards (reduces room size) or External insulation with render (maintains room size)
Internal: £4160, External: £7280
Cost
£4160.00
Annual Saving
£728.00
Payback
5.7 yrs
ROI
18%
Ground Floor Insulation
15% heat lossInsulate suspended floor or concrete slab
Cost
£2400.00
Annual Saving
£192.00
Payback
12.5 yrs
ROI
8%
Double Glazing Upgrade
10% heat lossReplace single with modern double glazing
Cost
£8000.00
Annual Saving
£240.00
Payback
33.3 yrs
ROI
3%
Quick Wins (payback under 5 years)
- ✓Loft Insulation
£480.00 investment, £240.00 annual saving - ✓Cavity Wall Insulation
£2288.00 investment, £499.20 annual saving
Long-term Investments (5-15 years)
- ▪Solid Wall Insulation
£4160.00 investment, £728.00 annual saving - ▪Ground Floor Insulation
£2400.00 investment, £192.00 annual saving
Insulation Types Explained
Loft Insulation
Laying insulation material (mineral wool, cellulose, sheep's wool) between joists. Easiest to install, biggest impact.
- Saves 25% heat loss (largest source)
- Recommended depth: 270mm
- DIY possible for some properties
- Cost: £2-5 per m²
Cavity Wall Insulation
Filling the gap between inner and outer brick layers with foam, mineral wool, or beads. Permanent and unobtrusive.
- Saves 33% heat loss
- Only works on cavity walls (post-1920)
- Professional installation required
- Cost: £10-15 per m²
Solid Wall Insulation
For properties with solid brick walls. Internal boards or external render. More complex and expensive.
- Saves 35% heat loss
- Internal: reduces room space
- External: maintains room size, more visible
- Cost: £20-35 per m²
Ground Floor Insulation
For suspended floors, adds rigid insulation boards below joists. For concrete slabs, internal rigid boards.
- Saves 15% heat loss
- Often overlooked but worthwhile
- Access required from below (hard in flats)
- Cost: £8-15 per m²
💡 Installation Tips
- Always use MCS-accredited or trusted installers
- Request a survey first to identify suitable insulation types
- Check for damp or condensation issues before insulating
- Ensure adequate ventilation after insulation work
- Many installers offer phased payments to spread costs
- Check local authority grants before starting work
- Ask about warranty periods (typically 25+ years for cavity fill)
- Combine improvements for better results and grant eligibility
Where the Heat Actually Escapes
In an uninsulated UK home, roughly 25 percent of heat loss is through the roof, 35 percent through the walls, 15 percent through the floor and 25 percent through draughts and windows. That order matters because it tells you what to insulate first. Loft insulation is the cheapest fix (around £5 per square metre installed) and addresses the biggest single loss path other than walls. The calculator estimates roof area at 60 percent of internal floor area, which is roughly accurate for most semis.
A typical 3-bed semi (160 sq m floor area, 96 sq m roof area in the calculator) with no loft insulation saves around £240 a year by going to 270 mm. That is a payback of about 2 years on the £480 install cost. Going from 100 mm to 270 mm only saves around £100 a year, with a 6-year payback - still worthwhile, but less dramatic. The diminishing returns above 270 mm are why building regulations stop there.
Walls Are the Bigger Prize and the Bigger Cost
Cavity wall insulation (for houses built between 1920 and 1990 with cavity construction) costs about £400 to £700 installed and saves £200 to £350 a year. Payback is around 2 to 3 years and the rating gain is often equal to loft insulation. Solid wall insulation, for older houses, is far more expensive: external wall insulation is £8,000 to £15,000 for a semi, internal is £5,000 to £8,000, but saves £400 to £600 a year and transforms thermal comfort.
The calculator ranks measures by payback so the obvious wins surface first. Insulation matters more than heat-pump efficiency in older homes; spending £8,000 on a heat pump in a draughty 1930s semi often saves less than spending £4,000 on the fabric first. For the heating system side, [Boiler vs Heat Pump Calculator](/boiler-vs-heat-pump-calculator) compares running costs once the envelope is sorted.
Frequently Asked Questions
How much can I save with loft insulation?
A typical UK semi with no existing loft insulation saves around £250 a year by upgrading to 270 mm. The work costs about £500 and pays back in 2 years. Going from 100 mm to 270 mm saves around £100 a year for a £300 cost (3-year payback).
Is cavity wall insulation worth it?
Almost always. Cavity wall insulation typically costs £400 to £700 for a semi-detached house and saves £200 to £350 per year, paying back in 2 to 3 years. The exception is cavity walls already filled (check by drilling a small inspection hole) or homes in very exposed coastal locations where damp risk is higher.
What is the difference between internal and external solid wall insulation?
Internal goes inside, reducing room size by 50 to 100 mm per wall and disrupting living for weeks. External goes outside, keeps room size, doesn't disrupt living, but requires planning permission in some areas and changes the look of the property. External costs roughly double the internal price.
Can I get a grant for insulation?
ECO4 grants (formerly ECO Help to Heat) cover insulation for low-income households or those on certain benefits. The Great British Insulation Scheme (GBIS) covers homes in EPC bands D-G in council tax bands A-D in England and A-E in Scotland and Wales. Both are administered through energy suppliers.
Related Tools
EPC Improvement Checker
See which home improvements will boost your EPC rating. Compare the cost versus increase in property value.
Boiler vs Heat Pump Calculator
Compare running costs of a traditional gas boiler versus a heat pump. See the long-term financial impact.
Double Glazing Payback Calculator
Find out if upgrading to triple glazing or replacing single glazing with double glazing will pay for itself.