Reducing Heat loss

Lesson Objectives Students should be able to: identify the main areas heat energy is lost from houses identify methods to reduce this loss calculate payback time evaluate the cost effectiveness of these materials use fractions and percentages when calculating heat loss/cost effectiveness

5 main areas heat if lost from a house In which is the most heat energy lost? In which area is the least heat energy lost? Different houses could have different answers – why? The main area is usually the walls The lowest area is usually the floor This can change from house to house – depends on SIZE of house/ number of windows / age (type of walls or windows) / insulation already fitted.

Amount of heat lost (J/s) How much energy is lost Area Amount of heat lost (J/s) % of total heat losses Insulating materials Highest Walls 2nd highest Roof Windows 2nd lowest Draughts/Door Lowest Floor This house loses the most heat energy from the walls and the least from the floor. Use the numbers below to fill in the table to show the amount of heat lost per second from each area. 180J/s 360J/s 240J/s 120J/s 300J/s You could use watts instead of J/s

Calculating percentages A percentage is the fraction of the total amount out of 100. % = number x 100 total First you need to work out the total energy loss from the house. Total energy loss = 1200 J

The Roof The roof loses 300 J out of 1200 J Write this as a fraction and calculate the decimal Fraction = 300 = ______ 1200 Write this as a percentage? (multiply the decimal by 100%) Roof = 25%

Calculate the % heat loss from each area Percentage = number x 100% 1200 How much energy is lost Area Amount of heat lost (J/s) % of total heat losses Highest Walls 360 2nd highest Roof 300 Windows 240 2nd lowest Draughts 180 Lowest Floor 120 30 25 20 You can highlight the biggest % = most heat loss 15 10 REMEMBER – your answers ALWAYS add to 100%

Amount of heat lost (J/s) Reducing heat loss In pairs, think about different materials people can use reduce heat loss and fill in the final column. How much energy is lost Area Amount of heat lost (J/s) % of total heat losses Insulating materials Highest Walls 360 30 2nd highest Roof 300 25 Windows 240 20 2nd lowest Draughts/ Door 180 15 Lowest Floor 120 10 Foam cavity wall insulation Fibre glass loft insulation Double glazing Draught proofing Carpets with underlay

Practice exam question 1 Energy consultants tell their customers how to save money. They explain how people can reduce energy loss from their homes. This picture shows the percentage energy loss from different parts of a house. Calculate the percentage energy loss through the walls of the house. (b) Suggest the two most effective methods of reducing heat loss for this house. 1 ................................................................................................................... 2 ................................................................................................................... Other areas = 25+10+15+15 = 65% So Walls = 100 – 65 = 35% Foam cavity wall insulation ( walls have the biggest % heat loss) Fibre glass loft insulation (the roof has the next biggest % heat loss)

Reducing energy consumption By reducing heat losses, people can reduce how much energy they use. This means saving money on their energy bills.

Savings from energy losses How long will you live in the house. Some ways of reducing heat loss are very expensive. People need to think about 3 things before they spend money on insulating these areas. Installation Cost Savings from energy losses How long will you live in the house.

Payback time Payback time = Cost of installing savings This is the time in years to get back the money you have spent on insulation from the savings you have made. Payback time = Cost of installing savings

Calculate the payback time for each method. Where is heat lost Cost of energy losses (£) Method Installation cost (£) Payback time (years) roof 250 Fibre glass insulation 300 walls 350 Foam filled cavity wall insulation 1050 windows Double glazing 4500 doors 80 Draught proofing 40 1.2 3 15 0.5 Hint - the savings are made from the energy losses.

Which method would you install first? Draught proofing Draught proofing is the cheapest and has the shortest payback time. But other methods have bigger savings from areas with bigger heat losses.........

Cost effectiveness This compares the TOTAL SAVINGS made over a few years compared to the cost of the insulation. Using the information in the table, work out the profit made after 5 years for: Draught proofing Roof insulation. Hint – don’t forget to take away the cost of the installation

draught proofing Saving = £80 a year = £80 x 5 = £400 Cost = £40 Profit = £400 - £40 = £360

2. fibre glass in the roof Saving = £250 a year = £250 x 5 = £1250 Cost = £300 Profit = £1250 - £300 = £950

Savings from draught proofing = £360 Savings from Fibre glass insulation = £950 So Fibre glass insulation is the most cost effective over 5 years because it makes the biggest profit.

whether or not you will get back your money (payback time) AND So, when answering questions, you need to look at: whether or not you will get back your money (payback time) AND if you do get your money back, how do the total savings over time compare to the cost (profit) PAYBACK TIME & PROFIT