If your house has a roof space, then it probably has insulation in it. That insulation is a thick layer of fibre glass. It's actually the air in between the fibreglass that makes it a good insulator.
Air is a very bad conductor. Hardly any heat energy can conduct through the trapped air in the fibreglass.
If air is so good why doesn't it work on its own?
Well, the air can convect the heat energy away from the house if it is able to move. If the air is trapped in small spaces between the fibres in the fibreglass it can't move so it doesn't convect the heat energy.
Many insulators work because they contain trapped air.
There are two real reasons for reducing heat losses from a home:
- Saving energy means that less energy needs to be produced, so there will be less damage to the environment. (Think about the pollution from a coal-fired power station.)
- Saving energy means using less energy so it costs less to heat the house. It can cost hundreds of pounds a year to heat a family house!
Obviously it also costs money to install (put in) insulators and other energy-saving devices. The payback time is how long it takes for the savings to cover the cost of installation.
Each method has to stop either conduction, convection, radiation, or any combination of them.
See if you can identify how each method of insulation saves energy in the home, by dragging the coloured boxes into the correct place:
Of course you can do other things: Use low energy light bulbs, turndown heating thermostats, and fit draught excluders, for example.