A homeowner wants to reduce the energy transferred from her house to the surroundings.
The Table shows information about four methods she could use.
Table
| Method | Cost to install in £ | Energy saved each year in kWh\text{kWh}kWh |
|---|---|---|
| loft insulation | 450 | 2500 |
| cavity wall insulation | 1200 | 4000 |
| double glazing | 6000 | 1000 |
| draught excluders | 60 | 300 |
Energy costs 12p per kWh.
Explain how each method reduces the rate of energy transfer from the house.
Use calculations to evaluate which method gives the best value for money.
50 exam-style questions on OCR GCSE Physics 7.2 Power and efficiency, covering 7.2.1 Dissipation of energy, 7.2.2 Energy transfers in domestic devices, 7.2.3 Power ratings of domestic appliances, 7.2.4 Efficiency of energy transfers, 7.2.5 Ways to increase efficiency, 7.2.6 Reducing unwanted energy transfers, and 7.2.7 Thermal conductivity and the cooling of buildings. Each one has a worked solution and a mark scheme showing where the marks go.