Unit 1: Keeping Homes Warm Flashcards
How does double glazing reduce energy loss?
It reduces energy loss by conduction. The gap between the two pieces of glass is filled with a gas or contains a vacuum.
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 loft insulation reduce energy loss?
It reduces energy loss by conduction and convection.
Warm air in the home rises. Energy is transferred through the ceiling by conduction. Air in the loft us warmed by the top of the ceiling and is trapped in the loft insulation. Both sides of the curling are at the same temperature so no energy is transferred. Without lost insulation the warm are in the loft can move by convection and heat the room tiles. Energy is transferred to the outside by conduction.
How does cavity wall insulation reduce energy loss?
It reduces loss by conduction and convection currents.
The air in the foam is a good insulator.
The air cannot move by convection because it is trapped in the foam.
What do insulation blocks used to build new homes have?
They have shiny foil on both sides to reduce energy transfer by radiation.
Energy from the sun is reflected back to keep the home cool in the summer.
Energy from the home us reflected back to keep the home warm in the winter.
What ways can energy be transferred?
Conduction
Convection
Radiation
How can energy be transferred conduction?
Due to the transfer of kinetic energy between particles.
How can energy be transferred by convection?
A gas expands when it’s been heated. This makes it less dense so it rises. The unit of density is kg/m3 or g/cm3
What is the equation for density?
Density = mass / volume
How can energy be transferred by radiation?
It does not need a material to transfer energy. Energy can be transferred through a vacuum .
What is the efficiency equation?
Efficiency = Useful energy output (x100%) / Total energy input.
How can energy transformations be shown?
Can be shown by Sankey diagram.
Where is energy lost?
Energy from the source (home) is lost to the sink (environment).
What is the payback equation?
Payback time = cost of insulation / annual saving
How is energy wasted?
Everything that transfers energy will waste some of the energy as heat to the surroundings.
What is the advantage of a well insulated building?
Little energy will be lost to its surroundings making it more energy efficient.
