Upgrading from single glazing to double or triple glazing can be expensive and can take over 20 years to payback the capital costs when considering the energy saving alone. However, wood or metal windows need repainting every five or seven years, so replacing these with modern composite double or triple glazed windows will have the added benefit of saving maintenance costs. If your classrooms are cold, replacing your windows might be a cheaper alternative to upgrading your heating system.

If you are replacing glazing, ask your contractors about the ‘U’ value of their windows and insist that double glazing should be below 1.4W/m2/K. It may not be worth installing triple glazing (unless for noise insulation) as the additional costs of triple glazing provide little benefit over good quality double glazing.