Windows and Home Energy Efficiency

What is energy efficiency?

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Energy efficiency in Australian buildings is measured using a 6 star rating. The rating, updated in the 2010 Building Code of Australia (BCA), measures the amount of energy lost from a building through its skin - windows, walls and roof - over the course of a year. The rating takes into account the location and climate of the building. This means that a building with energy rating 5 in Tasmania will lose a different amount of energy to a building in Brisbane with the same energy rating.

In other words, the energy rating of your home is based on the amount of heating or cooling required to keep a regular temperature inside.

Is your home energy efficient?

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An individual Australian home generates approximately 7 tonnes of greenhouse gas emissions annually. Of a home’s total energy consumption, approximately 40% is used on heating and cooling - more than any other area. This number can be greatly decreased in a well designed home, that uses less heating and cooling, and more renewable energy sources.
To find out more information about energy efficiency in your home, visit Australia’s Guide to Environmentally Sustainable Homes.

By law all new homes and homes with major renovations must be built with a 6 star energy rating. This rating applies to the entire building, not individual rooms or elements such as windows or walls. For full product information, visit our FAQS page.

What makes a house energy efficient?

There are a range of factors that contribute to a home’s energy rating:

  • North facing windows and glass doors
  • Wall and ceiling insulation
  • Natural ventilation
  • Provide shade
  • Energy efficient glazing

Summer-&-Winter

North facing windows and doors

In the winter months, when the sun sits low in the sky, having north facing windows and doors provides passive heating and light to your home. Because the windows and doors face the sun, it can enter your home, heating up the floor, walls and glass on the windows - saving you on heating bills.

In the summertime, the sun sits too high in the sky for its rays to enter through the windows. This means your home is kept naturally cooler without direct sunlight.

Wall and ceiling insulation

Proper wall and ceiling insulation keep your home at a constant temperature inside, blocking the elements out. In summer, it prevents hot air from entering through the walls, and retains the cool air inside. In winter, it stops the warm air inside from escaping, and blocks the cold air outside. This ultimately saves you money on heating and cooling.

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Natural ventilation

A cool evening breeze and natural air flow can flush out hot air built up inside your home during the middle of a hot summer’s day. Whether you have the freedom to design a new build or renovation, maximising open living areas and air flow, or are working with an existing design, you can make improvements. Good ventilation is key. You can achieve this by installing opening windows and doors that provide cross-ventilation. If your ceiling height allows, install high opening windows that can let hot air escape at night.

Provide sufficient shade

To make north facing windows and doors as efficient as possible, there needs to be adequate shade. Whether outdoor blinds, eaves, verandahs, pergolas - whatever you choose, effective shade can block up to 90% of the sun’s direct heat. To be as energy efficient as possible, shade needs to allow for sunlight to enter in winter, but still block out the higher sunshine in summer.

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Energy-Efficiency

Energy efficient glazing

Windows and glass doors have long been considered an energy drain in buildings. Thanks to modern technology, smart glass is now designed to prevent heat from flowing through your glass panes. Depending on the climate and orientation of your home, you may need single, double or thermal glazing.

Choose your window and door styles

How glass works

Windows make up approximately 8% of the skin area of the average residential home, but account for some 90% of heat gain from the sunshine. In comparison to well-insulated walls and ceiling, windows are an energy drain - heat escapes through thin glass in the winter; and leaks inside during the summer months.

There are two ways temperature is able to flow through glass:

Solar heat gain

Solar heat gain is the heat created inside your home caused by direct sunlight hitting a glass window. In summertime, you want as little solar heat gain as possible to keep your home cool. But in winter, more solar heat gain gives you a warmer house with lower energy bills.

Factors that contribute to solar heat gain include:

  • Position and orientation of windows
  • Type of glazing on windows - single, double or thermal
  • Shading or lack-of protecting the window - patio, verandah or outdoor blinds

Glass-Heating-Up

Heat-Escaping

Heat flow through glass - thermal conductivity

When there is a difference in temperature between the outside and inside, heat naturally flows through the weakest points in the skin of your home - often the windows and doors. Heat flow happens in summer when warm air moves to the inside of your home through your windows. In winter, it happens when warm air leaks from the inside out. The greater the temperature difference between outside and in, the greater the heat flow becomes.

Heat flow is much greater through single glazed, clear glass windows - often found in older homes and buildings. Low-E smart glass, double and thermal glazing are all more energy efficient, saving you money on heating and cooling costs. The type of glazing best suited to your home will depend on your climate, orientation, exposure to the elements and budget.

Smart glass

Single glazing no longer needs to be the energy drain it once was. Low emissivity (Low E) SmartGlass is an innovative product made by Viridian Glass that carries with it improved insulation performance, making it both energy efficient and budget friendly. In the past, toned glass has been used to reduce the amount of heat gain caused by sunlight. The downside of this is it also limits the amount of natural light entering your home; and its darker colour can cause the glass heat up quickly, heat which is then transferred inside through the glass.

Low E Glass allows all of the natural light in from the sun, yet reflects glare and a large amount of UV rays and heat back out towards its source. All in a single pane of glass. SmartGlass is an ideal energy efficient solution for homes in climates where double or thermal glazing may not be necessary. SmartGlass can also be used in double and thermal glazing applications for an even high level of energy efficiency.

  • Up to 39% better insulation performance than traditional single glazing
  • Allows natural light to enter the home
  • Limits the amount of UV rays
  • Limits the amount of heat gain
  • Reduces glare

Double glazing

Double glazing is when two panes of glass are installed with an air gap between them in the window frame. This air gap creates an insulation barrier between the inside and outside, reducing heat flow and thermal conductivity. Double glazing greatly increases a home's energy efficiency, and reduces the energy required for heating and cooling. Because the inside pane of glass is kept closer to room temperature, the occurrence of condensation is also greatly reduced.

The most effective double glazing uses SmartGlass panes, combining the Low E reflective film with the added insulation of an air gap. Double glazing units can sometimes be retrofitted to your existing window frames, however can dramatically alter the facade of your home. At Southside Aluminium Windows, we can replace your existing windows with new aluminium frames and pre-made double glazing units that make no change to the facade.

Learn more about Double Glazing here


Thermal glazing

Thermal glazing, which uses a special combination of Low E glass, double glazing and a thermoset foam, offers up to 68% improved insulation than standard single glazing. Thermal glazing reduces the heat conduction between inside and outside, without reducing natural light from the sun.

Thermal glazing can be built in three different ways. Either with metal spacing between the two panes of glass, a thermoplastic spacer, or a thermostat foam spacer. The most energy efficient thermal glazing is made with the thermostat structural foam spacer. This glazing unit allows for expansion and contraction, UV resistance and has a temperature resistance between -51 degrees celsius and 127 degrees celsius.

Learn more about Thermal Glazing here


Why should I get energy efficient glass?

When building or renovating your home, would you consider not installing insulation? Probably not.

The Australian Bureau of Statistics found in 2011 that 69% of houses had insulation. Around 51% of households considered energy ratings when purchasing appliances; and 75% did when purchasing air conditioners.

So why wouldn't you consider energy efficiency when purchasing and installing windows?


Benefits of energy efficient windows

  • Maximise the energy efficiency of your home
  • Up to 68% improved insulation in your windows
  • Save money on heating and cooling
  • Increase natural light
  • Minimise cold draughts inside
  • Reduce condensation on windows

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