Practical insultation

1. Warm air in the home rises

2. Energy is transferred through the ceiling by conduction

3. Air in the loft is warmed by the top of the ceiling and is trapped by loft insulation

4. Both sides of the ceiling are at the same temperature so no energy is transferred.

5.Without loft insulation, the warm air in the loft can move by convection and heat the roof tiles

6. Energy is transferred to the outside by conduction

Double glazing reduces energy loss by conduction.

The gap between the 2 pieces of glass is filled with a gas (argon) or contains a vacuum.

Particles in a gas are far apart so it's very difficult to transfer energy. 

There are no particles in a vacuum so its impossible to transfer energy by conduction.

Cavity wall insulation reduces energy loss by conduction and convcetion:

The air in the foam is a good insulator

Therefore, the air cannot move by convection because it trapped in the foam.

Insulation blocks, used to make new homes, have shiny foil on both sides to reduce energy transfer by radiation:

Energy from the Sun is reflected back to keep the home cool in summer

Energy from the home is reflected back to keep the home warm in winter.