Windows and doors let in light and fresh air and also provide the means to look outside to admire your garden or view. They are also a weakness and if they are uninsulated, they will also let in the cold or heat. They are also a major source of heat loss or cooling loss.
The trick is to seal your building envelope with double glazing and adequate wall insulation. When you do this, you will find that the temperature of your home is more consistent. The heating or cooling spreads to the building envelope and stays in your home. Even your pantry and wet areas will be warm in winter and cool in summer. You are also able to utilise the space near your windows and doors as there will not be a draught.
Without this insulation in your windows and doors, you can lose up to 40% of your heating energy and 87% can come into your home. Source: www.yourhome.gov.au
When you are building, it is important to spend some time looking at where you windows are placed, what size they are, do they seal well, are they shaded with eaves? You also need to look at thermal mass to store the sun’s heat and cross flow venitilation across your home. It is worth visiting your block at various times of the day to look at shading from your neighbour or significant trees.