Energy Efficiency Explained
Reducing emissions, reducing climate change
To help combat climate change, the Australian Government is implementing national policies to reduce emissions.
These new measures will impact the way we build homes and the materials we choose.
That makes it vital that everyone in the building and construction industry—especially architects, designers and builders— understand how to comply with these changes.
The Role of Windows and Doors in Energy Efficiency
Windows and doors don’t use energy themselves so they’re considered passive products, but by allowing the transfer of energy they severely impact a building’s heating and cooling load.
In fact, regardless of how well a building is insulated, windows are the most vulnerable to energy loss. This means it’s vital to give careful thought to windows and doors during the design and building stages of any project.
How is a window’s energy efficiency measured?
One of the most important ways to reduce a home’s energy consumption is to use the right windows to limit heat gain or loss. There are four main measures for a window’s energy performance, all of which take into account the whole window system (frame, glass seals, spacers, etc.).
Purpose: Provides insulation level.
Application: The lower the U Value, the better it is at insulating energy flow through the window system.
SHGC – Solar Heat Gain Coefficient
Purpose: Controls the passive heat from the sun.
Application: A higher SHGC is desirable in cold climates, where a lower SHGC is better for hot regions.
AI – Air Infiltration
Purpose: AS2047 measures window system’s leakiness.
Tv – Visible Transmittance
Purpose: Provides daylight level.
Application: Rooms with smaller windows need a higher Tv to allow more light, while rooms with bigger windows need a lower Tv to reduce glare.
What affects a window’s energy efficiency?
A window’s U Value and SHGC are affected by the following design factors:
Frame Size (height and depth)
Frame Material Conductivity
This is a material’s ability to conduct energy. The lowest rated is timber and the highest is aluminium, which is 1000 times more conductive than timber.
A window’s U Value, SHGC and AI are affected by the following design factors:
Affect Air Infiltration ONLY, DOES NOT affect U value or SHGC
Even when same framing materials are used, the U value and SHGC will vary depending on the size of the windows. ** NFRC testing sizes are applied to ALL window sizes, despite actual performance changing as sizes and shapes vary.
Choosing the right windows
The NCC requires windows to be rated according to the Australian Fenestration Rating Council’s protocols and procedures.
The standardised ratings mean the performance of different glazed systems can be compared like-for-like.
It’s critical to assess glazing options, including their size, orientation, early in the design process to make sure you choose the right window and glazing system. Increasingly, people are selecting windows that may not help achieve the desired energy outcomes.
Your Trend sales consultant can help you select the Trend products that will allow you to achieve your required rating.