p2.3 heating and insulating buildings Flashcards
(14 cards)
What is loft insulation and how does it reduce transfer of thermal energy out from the roof ?
Traps air in pockets
Loft insulation materials have lots of small air pockets. Air is a poor conductor of heat, so trapping it reduces conduction of thermal energy.
Reduces convection currents
The insulation prevents warm air from rising up and escaping, which reduces heat loss by convection.
Reflects infrared radiation (optional)
Some types have a reflective foil layer that reflects infrared radiation back into the house, reducing heat loss by radiation.
e.g. fiberglass
What is cavity wall insulation and how does it reduce transfer of thermal energy out from the roof ?
Traps air in the material:
The insulating material contains tiny pockets of air, which reduce heat transfer by conduction because air is a poor conductor.
Prevents convection currents:
Filling the cavity stops air from circulating inside the wall gap, reducing heat transfer by convection.
Slows down radiation (a little):
Some materials can also reflect infrared radiation, though this effect is smaller than in loft insulation.
How is aluminium foil used between a radiator and a wall to reduce heat loss from the house ?
Reflective foil placed behind radiators reflects heat back into the room rather than letting it escape through the walls, making heating more efficient.
Why is insulation important in buildings ?
Reduces heat loss in winter
Keeps warmth inside, so the building stays warmer for longer.
Reduces heat gain in summer
Helps keep the building cool by blocking external heat.
Saves energy
Less heating and cooling is needed, so it lowers energy bills.
Improves comfort
Keeps indoor temperatures stable and more comfortable.
Reduces carbon emissions
Using less energy means less fossil fuel burning, which is better for the environment.
What are double-glazed windows and how do they insulate a house ?
They insulate a house by:
Reducing conduction:
The air or gas in the gap is a poor conductor, so it slows heat transfer.
Reducing convection:
The sealed gap stops air from moving, which prevents convection currents.
Reducing radiation (optional):
Some have a reflective coating that reflects infrared radiation back into the room.
How do thick outer bricks help to insulate a house ?
Greater thickness = more material for heat to pass through
Heat takes longer to travel through thick materials, so heat loss by conduction is reduced.
Bricks have high thermal mass
They absorb and store heat energy during the day and release it slowly, helping to regulate indoor temperature.
Slower heat transfer = better insulation
This keeps the house warmer in winter and cooler in summer.
What are used to heat houses ?
insulator
a material that does not allow thermal energy to pass through it easily.
conductor
a material that allows electrical current (the flow of electric charge) to pass through it easily
3 types of energy transfer
conduction,convection,radiation
what is conduction
conduction is the transfer of thermal energy through the direct contact
what is convection
transfer of thermal energy through the movement of a liquid or gas.
what is radiation
transfer of thermal energy through an electromagnetic wave.
how do solar panels insulate a house
Adding an extra layer to the roof:
This reduces heat transfer by acting as a barrier to heat loss in winter and heat gain in summer.
Reducing direct sunlight on the roof tiles:
This helps keep the roof cooler in hot weather, lowering indoor temperatures.
