Design

Where you live will largely determine the main task your windows need to perform. For example, in Melbourne around 75% of energy is used to heat homes so the emphasis is placed on glazing that reduces heat loss and maximises desirable solar heat gain from the sun in winter. In Brisbane, around 90% of energy is used for cooling homes, so the emphasis is on reducing heat gain while keeping the air conditioned air cool. If the house remains relatively well sealed, double glazing would also be considered.

In Sydney, glazing is selected to minimise heat flow through the glass while balancing between summer peaks and winter lows.

By choosing performance glazing you can select from a range of products that are tuned to our varied and demanding climates, providing greater comfort and energy efficiency.

 

Temperature

It’s hard for us to feel truly comfortable when we’re too hot or too cold. We have a relatively narrow temperature range where we feel ‘comfortable’ in our homes. Yet even in the most temperate climate there’s a wide temperature range from day to night through the seasons. A poorly designed home can make these temperature cycles even more extreme.

One of the critical issues in designing a comfortable home is to smooth out the temperature peaks and troughs of the natural environment to maintain a more consistent interior temperature. Heat migrates from a hot place to a cold place. We can’t change that. But we can slow it down with insulation.

We also use central heating and air conditioning to make a home more comfortable but they use energy, cost money and creates greenhouse gases.

Better to keep a home at the right temperature through proper insulation. Glass is the only building material that can not only insulate us from temperature extremes, it also allows us to control the passage of light and radiant heat into and out of our homes.

Control the internal temperature range of your home

Good design smooths out the temperature peaks and troughs to create a more comfortable home.

 

Climate Zones

Climate is an important driver of your window requirements. Energy efficient glass is not a single type of glass, but a group of glass technologies that each act in certain ways. Just as there are different climate conditions, there are different glass types most suitable for dealing with these conditions.

It is important that the right solution is selected for the different climate zones across Australia.

The Building Code of Australia (BCA) defines eight climate zones — these are the standard climate conditions against which your house will be assessed for its official energy rating. However, for the simplicity of illustrating how it all works, we will view the Australian climate as three zones Hot, Mixed and Cold.

• Where you live helps to determine your window needs.
• In cooler regions, choose glazing that reduces heat loss and promotes solar heat gain (in winter).
• In warmer regions, choose glazing that reduces heat gain and keeps air conditioned air cool.
• North facing rooms benefit from natural light and free, passive heating (in winter).
• Performance glazing allows greater design flexibility to overcome climate and site limitations.

Climate drives window requirements

There are two main considerations in window functionality.

• Solar Heat Gain (measured by the Solar Heat Gain Coefficient — SHGC), or the heat from the sun gained through windows (remember this can be a bonus in cold climates!).
• Thermal Conductivity (measured by the U or R Value) — this is the insulation value provided by windows — how well it keeps heat or cold in or out.

Climate rules of thumb for window selection

HOT ZONES

Broadly speaking, in hot climates, you will want a very low SHGC, keeping as much of the sun’s heat out as you can. Typically in hot climates, SHGC will be the most important factor to address. Seek low SHGC glazing throughout, but especially for east, west and unshaded windows.

Once radiant heat is under control, then comes U-value. If air conditioning is used, invest in lower conductivity (U-value) windows to keep air conditioned air cool.

COLD ZONES

In cold places insulation (or U-value) will generally be the most important factor — most often, we will want to retain as much of the heat inside our homes as possible.

Broadly speaking we would like to benefit from free solar heat entering our home during the cooler months. Windows with a high SHGC will facilitate this.

MIXED ZONES

This zone combines the principles above — an optimal solution will strike a balance between solar control in the summer and passive heat gain in the winter. Net of other design elements, a mid range SHGC offers a good compromise.

U-value (or insulation) remains important — get the highest U-value you can afford to insulate against temperature spikes and troughs, keeping the energy inside (whether this be energy from heating or from cooling).