If you have cavities in your walls which are not already filled with insulation then you have a great opportunity to save quite a lot of money. Most household heat is lost through the walls and anything to slow this down helps. The story is similar to loft insulation, you can reduce your energy bill for heating buy up to 25%, but again more realistically 20%. The table below calculates the effect of only insulating your cavities considering several main household fuels and estimates a payback time for the investment. For a larger house cavity wall insulation will cost £ 500 and for the smaller house about £ 350.
| Approx % energy saving | Approx energy saving per year |
Gas |
Electric (Std) | Economy 7 | LPG |
Fuel Oil |
|
| 3 bed house | 20% | 4000 kWh | £ 152 | £ 536 | £ 180 | £ 216 | £ 188 |
| Payback time with cavity wall insulation costing £ 350 (3 bed house) | 2.3 years | 0.7 years | 1.9 years | 1.6 years | 1.9 years | ||
| 5 bed house | 20% | 6000 kWh | £ 228 | £ 804 | £ 270 | £ 324 | £ 282 |
| Payback time with cavity wall insulation costing £ 500 (5 bed house) | 2.2 years | 0.6 years | 1.9 years | 1.5 years | 1.8 years | ||
| Calculations assume the energy required to heat an un-insulated 3 bed house is 20000 kWh and a 5 bed house is 30000kWh. | |||||||
Is it worth doing?
Yes. This measure is on a par with insulating the loft as one of the most effective thing you can do to your house to save money and protect the environment. And like loft insulation there are grants available to many of us to completely pay for the insulation, check for grants from the warm from scheme, energy companies and local authorities and check with your local energy advice centre.
