Keeping homes warm
You should be able to describe how heat energy is lost from buildings and to explain how these losses can be reduced.
Take a look at this thermogram of a house. The roof and windows are the hottest, showing that most heat is lost from the house that way.
Heat energy is transferred from homes by conduction through the walls, floor, roof and windows. It is also transferred from homes by convection. 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.
There are some simple ways to reduce heat loss, including fitting carpets, curtains and draught excluders. It is even possible to fit reflective foil in the walls or on them.
Heat loss through windows can be reduced by using double glazing. These special windows have air or a vacuum between two panes of glass. Air is a poor conductor of heat, while a vacuum can only transfer heat energy by radiation.
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.
You may wish to view this BBC News item (2006) about energy efficiency in homes.
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