What do the letters show?

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What do the letters show?
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Homework Explain how solar panels can be used
to heat buildings and water.
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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.

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Heat loss in the home
You are an advisor for EOn how can you encourage
households to reduce fuel bills?
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roof 20
windows 12
walls 36
doors 4
floor 28
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What are the Keywords?
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.
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.
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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.

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Conserving energy
A lot of heat energy can be lost through windows.
insulating layer of air
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
The insulating effect of the gap can be improved
by removing the air and creating a vacuum.
The problems with double glazing are that it can
be expensive and that it is difficult to break in
emergencies without a special hammer.
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Conserving energy
Most outside walls have an empty space between
the two layers of bricks called a cavity.
convection currents in the cavity
The air trapped in the cavity acts as an
insulator and reduces any heat loss due to
conduction through the bricks.
foam insulation prevents convection currents
Heat loss can also occur due to convection within
the cavity. Plastic foam insulation can be pumped
into the cavity to prevent this.
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Reducing heat loss
heat loss
The air warmed by radiators (and other heaters)
is carried around a house by convection currents.
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.
loft insulation
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Conserving energy
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.
Heat loss from a radiator can be reduced by
placing shiny foil between the wall and the
radiator.
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.
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Conserving energy
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.
Draught excluders are hairy or spongy strips that
can be used to close the gaps around doors and
windows.
They prevent draughts escaping and so reduce heat
loss.
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Q What are draughts?
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.
This heat energy can escape through gaps around
windows that are uncovered.
Fitting curtains and closing them can prevent
draughts leaving a house and so reduce heat loss.
In addition, curtains are opaque and so radiated
heat does not pass through them.
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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.

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What is the main type of heat transfer prevented
by each type of insulation?
Conduction Convection Radiation


Loft insulation Draught excluder Curtains Foil
behind radiators Carpet Double glazing Cavity
wall insulation
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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 insulation Draught excluder Curtains Foil
behind radiators Carpet Double glazing Cavity
wall insulation