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Science

Heat transfer and efficiency

Reducing heat loss

You should be able to describe how heat energy is lost from buildings and to explain how these losses can be reduced.

Heat escape routes

Take a look at this image showing heat loss from a house.

red shows where most heat is lost - through the windows and roof

Most household heat is lost through the windows and roof

Heat is lost:

  • through the roof
  • through windows
  • through gaps around the door
  • through the walls
  • through the floor

Heat energy is transferred from homes by conduction [conduction: The transfer of heat energy through a material - without the material itself moving. ] through the walls, floor, roof and windows. It is also transferred from homes by convection [convection: The transfer of heat energy through a moving liquid or gas. ]. For example, cold air can enter the house through gaps in doors and windows, and convection currents can transfer heat energy in the loft to the roof tiles. Heat energy also leaves the house by radiation through the walls, roof and windows.

Ways to reduce heat loss

There are some simple ways to reduce heat loss, including fitting carpets, curtains and draught excluders.

Heat loss through windows can be reduced using double glazing. The gap between the two panes of glass is filled with air. Heat loss through conduction is reduced, as air is a poor conductor of heat. Heat transfer by convection currents is also reduced by making the gap is very narrow.

Watch

You may wish to view this BBC News item from 2006 about energy efficiency in homes.

Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall, which reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.

Heat loss through the roof can be reduced by laying loft insulation. This works in a similar way to cavity wall insulation.

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