What do the letters show?

Homework Explain how solar panels can be used to heat

buildings and water.

P1 1.6 Heating buildings.

Lesson Objectives

• Explain how solar panels can be used to heat buildings or water.

• Use the idea of payback time.

• Explain what U- values measure

• Evaluate the effectiveness of materials used for insulation.

• Evaluate building design.

Heat loss in the home

You are an advisor for EOn how can you encourage households to reduce fuel bills?

walls 36%

floor 28%

roof 20%

windows 12%

doors 4%

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.

A poorly insulated house loses more energy and so costs more to heat. It also means that more pollution, particularly

Carbon dioxide, is created in order to heat the house.

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

What are the Keywords?

Designing better houses

• There are many government building regulations that specify how buildings should be designed.

• Part of the regulations defines U-Values for roofs, walls and floors. The U-value shows how good a material is a building component is as an insulator.

• THE LOWER THE U-VALUE, THE LESS ENERGY THE MATERIAL TRANSFERS.

The insulating effect of the gap can be improved by removing the air and creating a vacuum.

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.

The problems with double glazing are that it can be expensive and that it is difficult to break in emergencies without a special hammer.

side-view

of double glazing

insulating layer

of air

Conserving energy

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

Conserving energy

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 but, if there is no roof insulation, the warm air continues to rise.

The heat eventually escapes through the roof and is lost due to conduction through the roof tiles.

Reducing heat loss

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 that the radiator is attached to, and so the wall heats up.

This can be a real problem on 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.

This method of insulation is very cheap to install.

Conserving energy

Draught excluders are hairy or spongy strips that can be used to close the gaps around doors and windows.

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.

This is one of the easiest types of heat loss to prevent.

They prevent draughts escaping and so reduce heat loss.

Conserving energy

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

Warm air rises and is carried up towards the windows in a house by convection currents.

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.

Q What are draughts?

True or False?

• Cavity walls reduce the insulation through the wall.• Double glazing reduces conduction through

windows.• Carpets can reduce heat loss through the floor.• Most heat is lost through the floor.• Air is sucked out of the gap in a cavity wall to

create a vacuum.• Curtains help reduce heat loss by convection.

What is the main type of heat transfer prevented by each type of

insulation?Conduction Convection Radiation

Loft insulationDraught excluderCurtainsFoil behind radiatorsCarpetDouble glazingCavity wall insulation

What is the main type of heat transfer prevented by each type of

insulation?Conduction Convection Radiation

Loft insulation Cavity wall insulation Foil behind radiators

Double glazing Curtains

Carpet Draught excluder

Loft insulationDraught excluderCurtainsFoil behind radiatorsCarpetDouble glazingCavity wall insulation