Today, remarkable new framing and glazing materials have changed the energy performance of windows in a radical way.

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The priority in a mixed climate is to keep heat out of the home, except during a relatively mild winter season, when 'free' solar heat gain and retention of warmth in the house become important. Heat gain or loss takes three forms;

  • radiation,
  • conduction  
  • convection - draughts.

Ideally, mixed climates call for strong solar control on east and west windows, but deliberate use of free sunlight admitted by northerly windows. This means different glazing solutions.

In a mixed climate (temperate), coloured green on the map, the best results are obtained from windows that insulate well (low U-value), admit plenty of free solar energy (high solar heat gain coefficient) on the north during cooler months, but limit solar heat gain from the east and west (low solar heat gain coefficient). Ideally, northerly windows should be protected by correctly sized eaves. This will provide protection from summertime heat and glare while still allowing sun penetration in winter.