Windows are no longer installed only to increase property value or block unwanted elements. They are integral to the overall building scheme to boost energy efficiency and reach the required 7-star rating. The two most important metrics that help you decide whether your windows are up to the required standard are U-value and Solar Heat Gain Coefficient (SHGC). 

Usually, you’ll find labels for both on the windows. But what exactly do they mean, and how do they affect your building’s energy rating?

To help you, we have created a detailed report on how U-Value and SHGC work and their major differences.

Solar Heat Gain Coefficient (SHGC) 

As the name suggests, the solar heat gain coefficient means how much the windows in the building help you capture sunlight. The higher the SHGC, the more sunlight/heat the window glass allows inside, and the warmer it gets. For instance:

• SHGC 0.8 means 80% of the solar heat enters the building 
• SHGC 0.3 means only 30% of the solar heat can enter the building. 

It is especially useful in improving energy rating in colder climates, as you can warm the home naturally without spending a single dollar. On the other hand, warmer regions are better off using windows with lower SHGC to capture minimum heat. 

U-Value 

U-Value measures the amount of heat that escapes any building element, such as roofs, walls, and the like. It is calculated in watts per square metre degree Celsius (W/m² °C). Since it measures the heat that escapes, a lower U-value means the building is better at utilizing the captured heat. On the contrary, a higher U-value means the building lets captured heat escape and cannot utilize it well enough. 

Key Differences Between SHGC and U-Value 

There are some important differences between SHGC and U-value that every builder must understand to build a more sustainable home. Here’s an overview of these differences: 

1. Performance Goals 

U-value follows a simple rule: lower is always better for insulation. A window with U-1.0 performs twice as well as a window with U-2.0. 

On the other hand, the usage of SHGC depends on the climate. For instance, in hot regions like Darwin, low SHGC is preferable. In cooler areas like Hobart, high SHGC is better for harnessing more sunlight and keeping the building warm. If you are constructing in mixed climatic regions, go for a balanced U-value and SHGC rating for maximum efficiency gains. 

2. Cost 

You pay more for windows with lower U-value, especially if they have argon gas-filled panes and triple glazing. The initial costs are high, but you get excellent long-term returns through less heat escape in colder climates. 

Lower SHGC-rated windows usually have moderate prices and are ideal for warmer climates. That’s because they capture fewer photons and keep the home cool. 

How U-Value and SHGC Work Together 

Although U-Value and SHGC measure different aspects, they are considered together when specifying glazing systems. Optimizing one without the other can lead to an underperforming building. 

For instance, a window with low U-Value but high SHGC might retain internal heat but allow too much external solar heat, which leads to overheating. 

A window with low SHGC but high U-value will let the home lose heat quickly while blocking sunlight. Surely, that’s not an ideal combination in colder climates. 

Balancing both metrics is key. For instance, north-facing windows in Melbourne might need moderate SHGC paired with low U-value to admit winter sun and keep the warmth it provides.

Understanding Australian Climate Zones 

The National Construction Code (NCC) divides Australia into various zones based on climate and temperature. As a result, they have different cooling and heating requirements to meet the national energy standards. Here is how the SHGC and U-Value can work out for some of these zones:

Zone 1 (High Humidity)

• Low SHGC to minimize solar gain 
• Moderate U-value to reduce AC losses 

Zone 3 (Hot and Dry) 

• Moderate SHGC to minimize solar gain 
• Moderate U-value to ensure cooler nights 

Zone 5 (Temperate)

• Moderate SHGC and low U-value are ideal 

Zone 7 (Cool Temperate) 

• High SHGC to capture warmth from the sun 
• Low U-value to retain internal heat 

Quality Energy Performance Assessments With PassivEnergy 

You have seen how SHGC and U-Value change in different Australian regions. It can get quite complicated, but PassivEnergy can handle it for you. Our team of experts has years of experience in design and construction, and we are committed to producing sustainable outcomes. We use advanced software technologies to make the most accurate assessment so you know how your building performs on the energy rating spectrum. 

Whether it is a 7-star energy rating report, BASIX assessment, or sustainable management plan, our team is qualified to do it all. You can trust us for high-quality and high-impact ESD and sustainability reports. 

Talk to us today, and let us help you meet Australian energy requirements most economically.