Glass Insulation

Glass Insulation

Glass is typically not only the single greatest source of heat gain, but also the greatest contributor to heat loss in a house. A single sheet of glass can conduct over 10 times more heat than the same area of insulated wall.


Fortunately, with the now widespread use of ‘Insulating Glazing Units’ (IGUs), most commonly standard double glazing, heat loss through glass can be substantially reduced. However, performance of an IGU is determined by both the glass and the frame of the window – heat loss through standard double glazing can be significantly reduced by using better frames. More information about the relative benefits of various glazing and frame options is provided in Chapter Two.It is useful to understand that the insulation of the house and
its windows is much more important than the heating effect of the sun shining through the windows. The major driver of heating requirement for a house is cold outside temperatures the varying sunshine levels around the country make very little difference to the heating required. For example, Nelson receives much more sunshine per year than Wellington but its houses must be insulated to a higher level than those in Wellington to maintain the same annual heating energy use because of the colder winter temperatures.