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4 ways that windows can help you achieve BASIX target

4 ways that windows can help you achieve BASIX targets


The Building Sustainability Index, or BASIX, is a set of requirements set out by our State Government to ensure all NSW residential dwellings are energy and water-efficient.

Their overall goal is to reach a 40% reduction in greenhouse gases, water consumption and the energy used for thermal comfort.

Not a bad idea, right?

A BASIX certificate is required as part of your development application if you are:

  • Building a new home
  • Doing renovations that cost $50,000 or more
  • Installing a pool or spa of more than 40,000 litres.

To receive a BASIX certificate, you’ll need to provide your consent authority (usually your council) with evidence that your development plans meet strict targets in three areas – energy, water and thermal comfort.

BASIX Certificate Pass

You do this by completing an assessment using the online BASIX Tool. It estimates your water and energy consumption, and your thermal comfort levels based on a range of criteria. You’ll be asked to provide information such as the orientation and floor area of your home, the type of insulation and hot water system you are installing, and the size, location and type of windows.

It may sound like a bit of a pain, but BASIX targets are great for the environment and will help you save money in the long run.

On 27 November 2020, several updates were made to BASIX. Energy targets were increased by 10% for houses, and thermal comfort caps were made stricter, so we thought now would be a good time to look at ways to comply with the new requirements.

Here are 4 effective ways to ensure you achieve the new BASIX target increases:

1. Choose the best type of glass

2. Position the right type of windows in the right places

3. Make the most of cross ventilation

4. Work with a reputable supplier.


Comfort Plus Neutral Blue Haze glass - Baxter Homes
Comfort Plus Neutral Blue Haze glass - Baxter Homes.

1. Choose the best type of glass

The glass that you choose for your windows plays an important role in achieving energy and thermal compliance. It lets in natural light and fresh air, and offers views that connect interior living spaces with the outdoors. However, if you use ordinary glass, up to 40% of your home’s heating energy could be lost and up to 87% of its heat could be gained through your windows.

To meet the new BASIX® targets, it helps to understand these three characteristics of glass:

  • Window U-value
  • Window Solar Heat Gain Coefficient (SHGC)
  • Glass Visible Transmittance (Tvis-glass)
WERS U Value diagram

Choose a glass and frame type with a lower U-value. U-value is a measure of the flow of non-solar heat through a window system that includes the frame, glass, seals and any spacers. The lower the U-value, the better a window’s resistance and the better it is at insulating.


WERS Solar Heat Gain diagram

Choose a glass with the right Solar Heat Gain Coefficient value for your home. SHGC or Solar Heat Gain Coefficient indicates how much sunlight comes through your window as heat. It’s expressed as a number between 0 and 1.

Glass with a low SHGC rating reduces the heat inside your home generated by the sun hitting your windows in summer. Glass with a high SHGC will allow in more warmth from the sun in winter.

As you might imagine, installing these windows in the right location is crucial to achieving the desired BASIX requirement. Put them in the wrong place and you may have to crank up the reverse cycle air conditioner.

SHGC can be controlled by the use of Low E or "low emissivity," glass. It has an ultra-thin transparent coating on one surface that reflects the sun's energy (infrared and ultraviolet light) allowing it to act like a sieve. It allows natural light to pass through easily, but restricts the flow of heat, so your windows help retain interior warmth in winter and repel exterior heat in summer.

For example, a large Wideline Fixed Window with Low E glass is just the ticket if you love watching summer sunsets in comfort.

We love the thought of watching the summer sun set in comfort through a large Wideline Fixed Window with Low E glass.

Wideline Windows use a range of energy efficient Low E glass products:

  • Viridian SmartGlass™ for single glazed windows looks like ordinary glass but with a Low E coating that can improve its ability to insulate by up to 39%.
  • Viridian LightBridge™ for double glazed windows can prevent up to 77% of heat loss/gain throughout all seasons. It is constructed of two Low E glass panels separated by a thin layer of non-toxic, inert gas.


WERS Visible Light Transmittance diagram
Images: Your Home

Choose a glass with an acceptable Visible Transmittance. Also known as VT, it is the measure of how much visible light travels through a window into your home. It’s measured on a scale of 0-1 with 0 being the lowest amount of light and 1 being the highest.

VT has nothing to do with your window’s ability to keep heat in or out, so why should we care? Well take a look at this equation: Low VT = too dark inside = lights on = higher energy costs.

It’s not rocket science, if your windows let in more natural light, you won’t have to rely so heavily on electricity to illuminate your home.

On the other hand, letting in lots of light can mean a higher Solar Heat Gain Coefficient – lots of harmful rays, heating up your home, causing furniture to fade and increasing your air conditioning bills. One way around this is to lower your VT and SHGC ratings using glass treatments, like tinting.

Viridian VFloat™ Toned and VFloat™ Supertoned glasses are worth a closer look. Both are tinted with pigment additives that maintain superior clarity while significantly reducing glare and heat from the sun. They’re particularly suited to hotter climates and west-facing windows.


EnergyTech highlight windows

2. Position the right type of windows in the right places

The basic principle of Passive Solar design is to locate windows of the right size and type so that they invite the sunshine in when it’s cold outside and exclude it when it’s hot.

Unfortunately, people incorrectly install windows with the same U-value and SHGC throughout the whole house. Getting your passive solar design right can yield at least half a star more than the ‘one type fits all’ approach.

As a general rule, windows with low U factors (< 0.40) are best for your home. You may need even lower values in extreme heating climates.

In temperate and cool temperate climates like Sydney, Perth, Melbourne, Adelaide and Hobart, position high SHGC windows to the north, northeast or northwest to capture as much sunlight as possible.

Positioning low SHGC windows on the east and west walls of your home can reduce heat in summer, but it also cuts down your warming winter sunlight. It’s a trade-off, where the summer benefits may outweigh the winter issues.

To make the most of passive solar heating in winter, install smaller windows with high SHGC values and low U factors to the south, southeast and southwest.


Cross Ventilation House with sashless windows

3. Make the most of cross ventilation

Cross ventilation is a natural cooling method that relies on air flowing freely from one side of the house to the other. Getting it right, can improve the thermal comfort of your home without increasing your overall energy requirements. The improved energy efficiency will do wonders for your BASIX assessment.

Position small windows in walls facing prevailing winds and large windows on the sheltered side of the house. The idea is that air is sucked in one opening and pushed out the other directly opposite, like a vacuum effect.

Wideline Casement Windows and Louvres are perfect for this as they can be angled to catch the breeze like the sail on a boat and redirect it into your home.

Wideline Double Hung or Sashless windows are another great option because cross ventilation works best when windows exposed to the wind are open at the bottom, and windows on the other wall are open at the top.

Even if you only have one window in your room, you can open both the bottom and the top sashes of a double hung window. Cool air will stream in through the lower opening, while hot air zips out the top. See our blog on Natural Ventilation to learn more.


Wideline Showroom visit window experts

4. Work with a reputable supplier

If you’re doing a new build or a renovation, it’s to your advantage to gain a solid understanding of BASIX. To find out more visit the NSW Government BASIX website.

Remember BASIX levels are a minimum requirement. You can always go beyond the mandatory specifications to future proof your home and make even greater energy cost savings.

The assistance of your designer or architect is essential to achieve a BASIX certificate, but it’s also worth seeking specialist advice from a reputable window supplier who is up to date with current industry standards.

All Wideline windows are BASIX compliant and have been thoroughly tested by a NatHERS-approved Certifier. It’s an independently operated scheme that rates windows and doors for their annual energy impact on a whole house, in any climate of Australia. 


When you’re ready to select your windows and doors, visit one of our NSW Showrooms for advice specific to your situation.

Our expert consultants can review your plans and offer affordable solutions to help you achieve your BASIX certificate. Find a Showroom near you.