Noadswood Science, 2011

To describe the effectiveness of insulation methods and to understand what an U-Value is

Tuesday, April 11, 2023

Which of the following houses would you expect to have the highest energy bills?

The house on the right has the highest energy bills as it is wasting the most to the surroundings (as shown by the thermal image)

Reducing a homes heat loss saves a huge amount of energy and money – although this can be expensive initially the gains long time outweigh the initial offset…

Loft insulation

Double glazing

Cavity wall insulation

Draft excluders

Underlay and thick carpets

Insulation of pipes

Which insulation method is best and how can you decide this?

Insulation cost / savings ratio is worked out using payback time – the amount of time it takes you to get your money back in savings…

Payback time (years) = cost of insulation (£)

savings per year in fuel costs (£)

Work out the payback time for the following (remember payback time (years) = cost of insulation (£) ÷ savings per year in fuel costs (£)

Method of insulation

Cost (£)Savings per year

(£)Payback time

(years)

Cavity wall insulation

£350 £100 3.5 years

Lost insulation £150 £150 1 year

Double glazing £5000 £200 25 years

Insulation of hot water tank

£60 £15 4 years

Draught-proofing £50 £15 3.4 years

The effectiveness of insulation is measured using u-values – the lower the u-value the more effective the insulating material…

Double Glazing U-Value

Standard 2.8

Low-e Glass 1.8

Low-e Glass & Argon Gas Cavity 1.5

In this example the best double glazing is the low-e glass with argon gas cavity as it has the lowest u-value

The thicker the insulation the lower the u-value…

Look at the table below – plot the results on a suitable graph…

Insulation Thickness

U-Value

60mm 0.46

70mm 0.41

80mm 0.37

90mm 0.34

100mm 0.30

110mm 0.26

120mm 0.23

The data is continuous – requiring a line graph…

Green loans – money saving over time…