P1.1.4 Heating and Insulating Buildings Flashcards
What are U-values?
U-Values measure how effective a material is as an insulator.
The lower the U-value…
…the better the material is as an insulator.
Explain how solar panels work, as well as the surface colours and textures used.
Solar panels may contain water that is heated by radiation from the sun.
- Solar hot water panels contain water pipes under a black surface.
- Radiation from the sun is absorbed by the black surface to heat the water in the pipes.
- There is a shiny inner surface to keep the absorbed heat in.
Give two uses of the water from solar panels.
This water may be used to:
- heat buildings
- provide domestic hot water.
Give five ways in which you can reduce the amount of heat energy lost in a building.
- Cavity Wall Insulation - foam squirted into the gap between the bricks stops convection current being set up in the gap and radiation across the gap. The insulating foam and the air pockets trapped in it, with air as an insulator, also help to reduce heat loss by conduction.
- Loft Insulation - a thick layer of fibreglass wool laid out across the whole loft floor reduces conduction and radiation into the roof space from the ceiling.
- Draught-Proofing - strips of foam and plastic around doors and windows stop draughts of cold air blowing in, i.e. they reduce heat loss due to convection.
- Hot Water Tank Jacket - lagging such as fibreglass wool reduces conduction and radiation.
- Thick Curtains - big bits of cloth over window to reduce heat loss by conduction and radiation.
Define specific heat capacity.
The specific heat capacity of a substance is the amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius.
What is the formula for specific heat capacity, and it’s units?
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ is the temperature change in degrees Celsius, °C
The materials used in heaters usually have _ _ _ _ specific heat capacities so that they can _ _ _ _ _ _ _ _ _ _ amounts of heat energy.
The materials used in heaters usually have high specific heat capacities so that they can store large amounts of heat energy.
Evaluate the use of water in heaters, mentioning the specific heat capacity.
Water has a really high S.H.C, and is a liquid, making it easy to be pumped around in pipes - ideal for central heating systems in buildings.
Evaluate electric storage heaters, mentioning the specific heat capacity.
Electric storage heaters are designed to store heat energy at night (when electricity is cheaper), and then release it during the day. They store the heat using concrete or bricks which have a high specific heat capacity.
Evaluate the use of oil in heaters, mentioning the specific heat capacity.
Because oil has a specific heat capacity that is lower than water’s, oil heating systems are often not as good as water-based systems. Oil does have a higher boiling point, however, which usually means that oil-filled heaters can safely reach higher temperatures than water-based ones.
