Lesson 2.4 - Windows and Doors that Keep Heat in

You cannot use fibreglass insulation in windows because windows are made to see through!  Doors can be insulated with material such as fibreglass, but this has to be done when the door is made. 

Read page 115 in your textbook to learn more about some of the ways that windows and doors are made to keep the heat in your house. Then, answer the following questions.

Question 1. How are modern windows constructed to reduce the heat loss from a house? 

Question 2. How are modern doors constructed to reduce the heat loss from a house? 

Question 3. What gas is inserted between the panes of glass in a double-glazed window? 

Question 4. How do you think the gas between the panes of glass reduces heat loss compared to ordinary air? 

Question 5. How can you check to see if air is leaking through cracks around your windows and doors? 

Question 6. How much extra fuel will a furnace have to burn to replace the heat lost through a 1.5 mm crack around one window in your house? 

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. How are modern windows constructed to reduce the heat loss from a house? 

Modern windows are constructed of two or three panes of glass separated by spaces that are filled with air or argon gas.

Question 2. How are modern doors constructed to reduce the heat loss from a house? 

Modern doors are constructed of wood or metal and have the space filled with insulation.  If the door is made of metal there is a break in the metal between the inside and the outside to reduce heat transfer.

Question 3. What gas is inserted between the panes of glass in a double-glazed window? 

Argon gas is inserted between the panes of glass in a double-glazed window.

Question 4. How do you think the gas between the panes of glass reduces heat loss compared to ordinary air? 

This question was not explained in the textbook and that is why it asked you what you think.  Argon gas reduces the heat loss by convection in the same way that ordinary air reduces heat loss.  If it is the same as air, then why use argon?  Argon gas has special properties that reduce heat loss by conduction more than ordinary air.

Question 5. How can you check to see if air is leaking through cracks around your windows and doors? 

Try This on page 115 tells you to use a piece of recording tape tied to a short stick.  Any thin film can be used such as a small piece of plastic wrap or tissue.  The thinner the material used, the more noticeable the movement due to a draft.

Question 6. How much extra fuel will a furnace have to burn to replace the heat lost through a 1.5 mm crack around one window in your house? 

Did You Know? on page 115 tells you that the furnace may burn an extra litre of fuel in one day to replace the heat lost through that one crack around the window.

 


Go to the next page to continue Lesson 2.