Phase 2: Design

Low-energy buildings

These activities introduce the environmental reasons behind the need to reduce energy costs in buildings. Students build a picture of how energy is used before using an interactive tool to explore a passive solar design for a low energy building. They follow up by considering how renewable energy sources can further lower a building’s carbon footprint.

  • Use Why do buildings need energy? as a starter. Find out in advance what fuels your establishment uses for heat and, if possible, obtain usage (in kWh) from the facilities manager or caretaker.

Answers: Why do buildings need energy?

Depending on their size and purpose, buildings will use energy for:

  • heating
  • ventilation and air conditioning
  • cooling
  • lighting
  • power for appliances and small equipment
  • power for alarm and security systems
  • lift and escalator operation.

Some buildings will use energy for specific purposes, e.g. factories, swimming pools, commercial kitchens or laboratories.

  • You can set a student homework task to find their energy use at home – see also the links page for carbon footprint calculators.

Interactive – create a low energy building


  • Introduce the idea of a carbon footprint for a building. Elicit that this can be lowered through good design as well as by the actions of the occupiers.

Main activity

  • Use Create a low energy building to explore a low-energy building design. Students make notes of what is happening at each stage.
  • Students use their notes to write a list of steps that explain this low-energy design.
  • Explore the importance of using different materials in each part, so that the building performs as it should – this links design and construction.


  • Selected students present their explanations, or build one on the board using input from students. Discuss suitable materials for each part of the building (see notes).


Easier/Level 1:
May not be suitable for Level 1. Work as a whole class. Build the list on the board as you go along. Students then work in pairs to create their handout – this can be done as a homework activity.

Get students to research existing low-energy designs (see Take it further) and present what they discover. What materials do these buildings use, and why?


Highlight that a key performance feature for any low-energy building is airtightness. When a building is airtight this means that its design and construction ensures that there is no unwanted air movement in and out of the building due to leaks, cracks and draughts. This allows air movement to be controlled by the design and by the building’s environmental systems. Airtightness depends on good design, high quality construction and on the building’s users not creating unwanted draughts.

You can develop this activity into a role-play. Emphasise the need for the building envelope to be airtight, with controlled ventilation. Students can research suitable materials for thermal mass, insulated walls etc. Do the windows on the sunny and shady sides require different construction and properties?

The interactive is a simplified representation of some of the aspects of a passive solar design. The application of passive solar design to a building project involves many considerations. Sometimes the building orientation, coupled with a reduction of southern facing windows is used to limit solar gain into the building. Seasonal performance also needs to be considered.

For example, if there is too much solar gain in the summer the building will overheat inside and be uncomfortable to live or work in. In this case ventilation becomes really important to keep conditions at a comfortable level, and measures need to be taken to reduce solar gain. In the winter, solar gain can be used to help heat the building. Thermal insulation and air tightness then become really important to help prevent loss of the heat energy.

Solar gain to buildings can be controlled by use of shades over windows, (known as ‘brise soleils’), special coatings on the glass that reflect the sun’s energy, and also window blinds. Sun shade louvres and roof vents can be electronically controlled and linked to intelligent building management systems that operate the building’s environmental systems to maintain ideal conditions automatically.

Architects and MEP services engineers use computer software to model a building’s energy performance over the annual seasonal cycle to consider issues such as orientation, solar gain, thermal insulation, ventilation and carbon emissions, in order to obtain the best design solution.

These computer models are also used to demonstrate compliance with the Building Regulations, in terms of energy conservation and carbon emissions.

  • Use Renewable energy sources as a follow-up activity – you can do this quickly within the lesson idea above, if time permits, in a separate session, or as a homework task. Emphasise that choices need to be appropriate for the site and the energy demand.
  • Sustainable use, in Phase 4, provides another ideal follow-up that links these design decisions to the whole life of the building. This looks at how the occupiers of a new building can be encouraged to adopt energy-saving habits.




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Create a low energy building

Drag and drop icons to build your school and see how it uses the suns energy.