Heating and insulating buildings

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Reducing rate of energy transfers at home

How we reduce the rate of energy transfer at home and reduce our home heating bills;

  • LOFT INSULATION such as fibreglass reduces the rate of energy transfer through the roof. Fibreglass is a good insulator. The air between the fibres also helps to reduce the rate of energy transfer by conduction
  • CAVITY WALL INSULATION reduces energy loss through the outer walls of the house. The 'cavity' of an outer wall is the space between the two layers of brick that make up the wall. The insulation is pumped into the cavity. It is  better insulator than the air it replaces. It traps air in small pockets, reducing convection currents 
  • ALUMINIUM FOIL between a radiator pannel and the wall reflects radiation away from the wall 
  • DOUBLED-GLAZED WINDOWS have two glass panes with dry air or a vacuum between the panes. Dry air is a good insulator so it reduces the rate of energy transfer by conduction. A vacuum cuts out energy transfer by convection as well 
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U-Values

-We can compare different insulating materials if we know their U-Values

-This is the energy per second that passes through one square metre of material when the temperature difference across it is 1 degree 

-The lower the U-value, the more effective the material is as an insulator 

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Solar heating panels

-A solar heating panel uses solar energy to heat water

-The pannel is usually fitted on roof that faces south, making the most of the Sun's energy

-One type of solar heating panel is:

  • A panel which is a flat box containing liquid-filled copper pipes on a matt black metal plate
  • The pipes are connected to a heat exchanger in a water storage tank in the house 
  • A transparent cover on the top of the panel allows solar radiation through to heat the metal plate. Insulating material under the plate stops energy being transferred through the back of the panel 
  • On a sunny day, the metal plate and the copper pipes in the box become hot
  • Liquid pumped through the pipes is heated when it passes through the pannel 
  • The liquid may be water or a solution containing antifreeze
  • The hot liquid passes through the heat exchanger and transfers energy to the water in the storage tank 
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Payback time

-Solar heating panels save money because no fuel is needed to heat the water 

-But they are expensive to buy and install 

-Suppose you pay £2000 to buy and install a solar pannel and you save £100 each year on your fuel bills. After 20 years you would have saved £2000 

-In other words, the payback time for the solar panel is 20 years. 

-This is the time taken to recover the up-front costs front costs from the savings on fuel bills 

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