1. Natural Sciences Grade 7
Term 3: Energy and Change
Insulation and energy saving

2. Topic 4 Insulation and energy saving
Using insulating materials [part 1]
Natural Sciences - Grade 7

3. Using insulating materials
Materials that are heat insulators:
keep cold items cold;
slow down heat transfer from the surroundings;
keep hot items hot;
slow down heat transfer from the hot item to the
cooler surroundings;
insulated window coverings [awnings; curtains; blinds; etc.].
In summer it is closed [minimize heat gain] to cool the house and block out the sun’s radiation.
In winter it is kept open to allow the sunlight through the house.
Natural Sciences - Grade 7

4. Natural Sciences - Grade 7
Types of insulators
Materials that contain air spaces, are the best insulators.
Examples:
- thatched roof [air is trapped in the spaces
between the grass of the thatch]
- wool
- cork
- straw
- feathers
- grass
- styrofoam
Natural Sciences - Grade 7

5. Insulators are used to reduce heat transfer
Styrofoam
It is made from polystyrene [a type of plastic; plastic is a poor conductor of heat].
It is also used to make
food packaging [picnics;
take-away meals; hot coffee; etc.].
The food in styrofoam boxes can be kept warm / hot.
Natural Sciences - Grade 7

6. Insulators are used to reduce heat transfer
Ceiling insulation
It minimizes heat gain during summer.
It minimizes loss of heat during winter.
It is mostly made from fibreglass strands [air is a poor heat conductor and it becomes trapped between the fibreglass’ strands ; the amount of heat loss/gain is limited; stops conduction and convection from taking place].
Foam can be sprayed in the roof structure above the ceilings.
Blanket insulation can be rolled out above the ceilings.
Natural Sciences - Grade 7

7. Insulators are used to reduce heat transfer
Materials that keep us warm
Woollen clothing prevents the body heat from escaping, e.g. jerseys; woollen hats; gloves; jackets; etc.
Bedding, e.g. blankets; duvets; comforters; etc.
It keeps people warm when it is cold. The air is trapped between the fibres and therefore extra insulation is given.
Thermal jackets worn by Russian, Eskimo and Norwegian people keep them warm in temperatures that are below 0°C.
Natural Sciences - Grade 7

8. Insulators are used to reduce heat transfer
Insulating vacuum flasks and cool boxes
Insulating materials such as plastic and styrofoam are used to make cooler boxes [foam / sponge materials are excellent insulators. They have many air bubbles in the foam. Air is an excellent insulator.
Liquids are kept hot or cold in vacuum flasks. Between the flask and the casing is a vacuum, meaning no air particles.
Natural Sciences - Grade 7

9. Insulators are used to reduce heat transfer
Water pipes
- Cover water pipes with an insulating material to:
prevent water from freezing and water pipes from bursting as well
as preventing water waste.
prevent loss of heat through the metal pipes and reduce electricity waste.
- Water pipes are made from plastic materials [PVC].
Doors
Fill the gaps of fitted doors with foam rubber [weather strips]
to prevent warm air from escaping.
Walls
Build outer walls with a double layer of bricks
[cavity walls - air space reduces heat transfer]. .
Natural Sciences - Grade 7

10. Insulators are used to reduce heat transfer
Traditional / Indigenous homes
Roofs and some walls are made of grass which is a good natural insulator.
The framework is smeared with mud.
Floors are made from cow dung [dries and form a hard, waterproof floor and it is heat insulating].
Rondavels are build with thatched grass roofs [Xhosa]; beehive huts [Zulu].
Natural Sciences - Grade 7