Transferring Energy
Heating & Insulating Buildings
Student Name:
Key Definitions
Use the information found here to help you fill in these definitions.
Insulator
A substance which allow thermal energy (also known as ) to move easily
through it is called an insulator. Some common insulators are and .
Conductor
A substance which allows to move easily through it is called a . Most are
good conductors of heat.
U-Value
Read the passage then answer the summary questions:
To Read
Every commonly used building material has a U-Value. A U-Value is a number,
which shows how quickly a material will transfer heat to the surroundings.
A standard window has a U-Value of 5.6 W per m2 per oC. This means that a
window with an area of 1m2 will lose 5.6 J of energy every second, when the
temperature outside is 1oC lower than the inside.
A double glazed window has a U-Value of 2.8. As the U-Value is lower we can
tell that less energy will be lost with the double-glazing, as a window with an
area of 1m2 will lose 2.8 J of energy every second, when the temperature
outside is 1oC lower than the inside.
A higher U-Value means the material transfers heat to the surroundings more
quickly - bad news for insulating a home.
Questions
If there is a temperature difference of 1°C between the inside and the outside,
how much energy will a window with a surface area of 1m2 and a u-value of 3.2
W m-2 °C-1 lose per second (in Joules)?
Would you rather have the walls in your house made with a U-Value of 1.5 W m2
°C-1 or a U-Value of 7.2 W m-2 °C-1? Explain your answer.
Task
Modify the house on the next page to help reduce its power bills as quickly as
possible. Explain what each modification will do to the house in terms of heat
transfer. Use ideas relating to kinetic theory:
Insulators
Conductors
U-Values
Conduction
Convection
Radiation
Particles
If possible, find the u-value of the insulator and estimate how much extra
energy it will keep in the house.
Copy and paste the example, editing the text to cover the modification that you
have researched.
You can find some useful information here, here and here.
Reason:
Double glazing will reduce heat loss from the
house by trapping a layer of air between two
panes of glass. As air is a poor conductor of
thermal energy, this will greatly reduce the
amount of heat lost from the windows.
The U-value of double-glazed windows is: 4.8
The U-value of single-glazed windows is: 2.8