Heat energy is lost from buildings through their roofs, windows, walls, floors and through gaps around windows and doors. However, there are ways that these losses can be reduced.
Heat escape routes
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 through those parts.
Thermogram of a house showing areas of heat loss
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.
Ways to reduce heat loss
There are several different ways to reduce heat loss:
Simple ways to reduce heat loss include 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. If the double glazing has a vacuum there will be no conduction or convection. If the double glazing is made with air between the glass then convection is minimised because there is little room for the air to move. Air is a poor conductor so there will be very little heat loss by conduction.
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. Insulating materials are bad conductors and so this 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.