P1.14 heating and insulating buildings

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P1.14 heating and insulating buildings

  1. 1. P1.1.4 Heating andinsulating buildingsevaluate the effectiveness of differenttypes of material used for insulation,including U-values and economic factorsincluding payback time
  2. 2. KEY WORDSEnergyWorkTransferU-valuesPayback timeSpecific heat capacity
  3. 3. One way to reduce the amount of heat that escapes froma house is to insulate it so that the heat energy escapingis reducedWhere is the most heat lost?What can be done to reduce the heat loss?
  4. 4. Important ways of reducing heat loss in a home are:• Loft insulation – this is a thick layer of fibre glass laidacross the loft space. It reduces conduction andconvection.
  5. 5. Important ways of reducing heat loss in a home are:Cavity wall insulation – this is foam squirted betweenthe gaps between bricks. It reduces conduction andconvection.
  6. 6. Important ways of reducing heat loss in a home are:A jacket for the hot water tank this reduces conduction andradiation.
  7. 7. Air is an insulator/ poor conductorConvection stopped foam is an insulator/ poorconductor
  8. 8. Heat is conducted through theglassHeat passes through the glass andair by radiationHeat crosses the gap byconvectionLightX-raysSoundRadio
  9. 9. Cuts down convection currentsAir pockets trap air (from moving)Foam is a poor conductor/ goodinsulatorEvaporation of watertakes energy from the house
  10. 10. convectionconduction
  11. 11. 100 – (15+15+10+25) = 35%Cavity wall insulation and roofinsulation
  12. 12. Payback time – the time taken to recoup theinitial payment - for these is calculated by:Initial cost ÷ annual savingExampleIt costs £250 to install and fit loft insulation in ahouse. It saves £50 a year.How long is the payback time?SolutionUsing: Payback time = Initial cost ÷ annual savingThen £250 ÷ £50 = 5 years.
  13. 13. U-valuesa) U-values measure how effective a material is as an insulator.The U-value shows how fast heat can transfer through a material.The higher the U-value the faster the heat transfer.b) The lower the U-value, the better the material is as an insulator.Good insulators have a low U-value.
  14. 14. 1 – it has the highest U-value
  15. 15. 3 and 4 OR 1 and 2U-values for the 20 mm windows are the same orhigher than those for the 16 mm windowstherefore the 20 mm windows are no more energyefficient than 16 mm windows
  16. 16. c) Solar panels may contain water that is heated by radiation fromthe Sun. This water may then be used to heat buildings or providedomestic hot water.
  17. 17. The specific heat capacity of a substance is the amount of energyrequired to change the temperature of one kilogram of the substance byone degree Celsius.E is energy transferred in joules, Jm is mass in kilograms, kgis temperature change in degrees Celsius, °Cc is specific heat capacity in J / kg °CIt indicates how much energy a substance can store.E = m x c x
  18. 18. ExampleHow much energy is required to heat 3 kg of water from20 °C to 100 °C. The specific heat capacityof water is 4200 J/ kg°C.SolutionUsing E = m x c xSubstitutingm = 3 kgc = 4200 J/ kg°CT = 100-20 = 80 °CGives E = 3 x 4200 x 80= 1008000 J
  19. 19. ExampleHow much energy is required to heat 2 kg of water from10 °C to 110 °C. The specific heat capacityof water is 4200 J/ kg°C.SolutionUsing E = m x c xSubstitutingm = 2 kgc = 4200 J/ kg°CT = 110-10 = 100 °CGives E = 2 x 4200 x 100= 840000 J
  20. 20. Other ways of reducing energy loss includereplacing filament bulbs with low energy light bulbsand LED lighting
  21. 21. Replacing old appliances withenergy efficient onesNewer appliances have anenergy label. More efficientappliances are rated A.Other ways of reducing energy loss include
  22. 22. An advertisement in a shop claims that:‘Replacing an old freezer with a new ‘A’ rated freezer will benefit theenvironment.’Do you agree that replacing the freezer will benefit the environment?YESLess electricity used /energy neededLess fossil fuels burnedLess polluting gasesemittedNOOld freezer must bedisposed ofHazardous chemicals insidefreezer eg CFCsLot of Energy used inproducing new freezer

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