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A thermogram shows the distribution of heat over the surface of a house. It highlights where heat is being lost.

The white, yellow and red areas are the warmest, so these are the worst insulated parts of the house.

The blue and green areas are the coolest, so these are the best insulated parts of the house.

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walls 36%

floor 28%

roof 20%

windows 12%

doors 4%

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The insulating effect of the gap can be improved by removing the air and creating a vacuum. Therefore reduced heat loss by convection.

A lot of heat energy can be lost through windows.

Double glazing adds an extra pane of glass. The air trapped between the two panes acts as an insulator and reduces heat loss by conduction.

side-view

of double glazing

insulating layer

of air

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The air trapped in the cavity acts as an insulator and reduces any heat loss due to conduction through the bricks.

Most outside walls have an empty space between the two layers of bricks called a cavity.

Heat loss can also occur due to convection within the cavity. Plastic foam insulation can be pumped into the cavity to prevent this.

convection currents

in the cavity

foam insulationprevents

convection currents

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The air warmed by radiators (and other heaters) is carried around a house by convection currents.

heat loss

loft insulation

Loft insulation contains trapped air and so forms an insulating layer between the loft and the rest of the house. This helps to reduce heat loss through the roof.

The house becomes heated

If there is no roof insulation, the warm air continues to rise. Then it is lost through conduction through the roof tiles.

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Heat loss from a radiator can be reduced by placing shiny foil between the wall and the radiator.

A radiator produces infrared radiation.

Some of this heat energy is absorbed by the wall and so the wall heats up.

This means that outside walls, where the heat energy absorbed by the wall can escape from the house.

The foil prevents heat radiation from reaching the wall by reflecting it back into the room.

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A draught is the movement of air due to a convection current.

A lot of heat energy can be lost from a house due to draughts escaping through gaps under doors and around windows.

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A draught is the movement of air due to a convection current.

Fitting curtains and closing them can prevent draughts leaving a house and so reduce heat loss.

This heat energy can escape through gaps around windows that are uncovered.

In addition, curtains are opaque and so radiated heat does not pass through them.

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How can you reduce heat transfers from a house?

A* Explain the three main of methods in details including information about temperature gradients.

A Explain the methods of heat transfer using a particle and wave models.

B Explain the methods used to minimise heat transfer.

C Describe the methods used to reduce heat transfer.

D Describe four ways that heat can be transferred from the house and how these can be reduced.

E Describe three ways that heat can be transferred from the house and how these can be reduced.

F Describe two ways that heat can be transferred from the house and how these can be reduced.

G Describe one way that heat can be transferred from the house and how this can be reduced.

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Are you now able to….

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.