Science & Technology in Action

5th Edition

The Energy Efficient Building


This lesson describes how domestic energy requirements can be greatly reduced by making better use of solar heating, by using high quality insulation and by exploiting the thermal capacity of internal structures.

Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Over the last few decades there has been a growing public awareness of the need to make more efficient and equitable use of the world’s non-renewable resources – fossil fuels and natural minerals. Carbon dioxide (CO2) is produced when fossil fuels are burned, and so using fossil fuels contributes to the greenhouse effect and climate change. As oil and gas reserves decline and CO2 reduction is demanded, we will need to use energy more efficiently and rely increasingly on renewable energy resources such as biomass, solar, hydroelectric and wind energy.

Energy use in Ireland
Domestic energy accounts for more than a fifth of Ireland’s total energy use. About 60% ofdomestic energy is used for space heating and 24% for heating water. Just 3% is used for cooking and 13% for lighting and for appliances such as washing machines, TVs, etc. While many domestic appliances can be made more energy efficient others are difficult to improve, particularly those that require heat – e.g. tumble dryers, hair dryers and toasters.

Heating and Insulation
By far the best way to save energy in the home is to save on heating. In terms of the fabric of the structure this can be achieved by:

  • Making the house more airtight by preventing draughts.
  • Improving insulation standards.
  • Avoiding large temperature fluctuations by utilisingthermal mass.

Heat is lost from a house by conduction through the floor, walls, windows, doors and roof. The conductive efficiency of such elements is usually expressed in terms of U-values. The external walls of a house typically comprise several layers such asconcrete, insulation and plaster. These resist the flow of heat at different rates. The greater the thermal resistance, the lower/better the U-value. The units are watts per square metreKelvin (W m-2 K).


Quiz questions

  1. About 20% of domestic energy is used for space heating. false
  2. About 20% of domestic energy is used for cooking. false
  3. U-values express the overall conductive efficiency of walls, windows, etc. true
  4. U-value units are watts per kelvin per square metre (W K-1 m-2). true
  5. The thermal mass of concrete in a building helps to stabilise the temperature. true
  6. The higher the U-value, the better the insulation. false
  7. Buildings with the same floor area and the same quality of insulation would be equally energy efficient. false
  8. The thickest layers in a wall have the best insulating effect. false
  9. A BER certificate includes an estimate of the annual CO2 output of a building. true


In its 2012 Sustainability Report, CRH states that it ‘ has progressed and developed in all areas of sustainability and sought to…