keeping homes warm Flashcards
how does double glazing work?
double glazing reduces energy loss by conduction. The gap between the pieces of glass is filled with a gas or contains a vacuum.
how does double glazing work using a vacuum or gases?
particles in a gas are far apart. It is very difficult to transfer energy. There are no particles in a vacuum so it is impossible to transfer energy by conduction
how does cavity wall reduce energy loss by conduction and convection?
the air in the foam is a good insulator. So the air cannot move by convection because it is trapped in the foam
insulation blocks with shiny foil on both sides reduce energy transfer by radiation how?
energy from the sun is reflected back to keep the home cool in summer. Energy from the home is reflected back to keep the home warm in winter.
how is energy transferred by conduction?
due to the transfer of kinetic energy between particles
how is energy transferred by convection?
a gas expands when it is heated. This makes it less dense so it rises.
how is energy transferred by radiation?
radiation does not need a material to transfer energy.. Energy can be transferred through a vacuum.
energy transformations can be shown on what?
a sankey diagram
everything that transfers energy will waste what type of energy to its surroundings?
heat
what do you call buildings that loses little energy to the surroundings?
energy efficient
what material is the best conductor?
metal
why are metals the best conductors
because their electrons can leave their atoms and move about as free electrons
how is energy transferred from hot areas of the metal to cooler areas?
by free electrons. The electrons move through the material, colliding with the ions
how do homes lose energy?
through the walls, roof, doors, floors and windows
what is the equation for payback time?
payback time (years) = cost of insulation
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annual saving
