Architect's Guide: Meeting NatHERS Heating Loads

Building or renovating a home in Australia? You've probably heard of NatHERS; it’s all about reducing artificial heating and cooling, as heating and cooling represents the majority of the average Australian household's energy use. However, understanding what it actually means and how to meet the requirements can feel quite overwhelming. We're here to break it down so you can understand exactly what NatHERS heating loads are and how they impact your project's success.

What is NatHERS?

NatHERS stands for the Nationwide House Energy Rating Scheme. Think of it as a home's energy report card: the system rates houses on a scale from 0 to 10 stars, measuring how well the home naturally maintains comfortable temperatures without relying heavily on heating and cooling systems. The bottom of the scale, 0 stars, means the building offers no protection from outside temperatures, while the top, 10 stars, rates that the home maintains comfortable temperatures year-round, regardless of the weather outside.

The scheme focuses on thermal performance. It analyses how well a home keeps heat in during winter and out during summer. NatHERS doesn't measure actual electricity bills because that depends on appliances and usage, but it does predict how much energy will be needed for heating and cooling, which typically makes up about 40% of the average Australian household's energy consumption.

As of May 2023, the National Construction Code (NCC) mandates that new homes must achieve a minimum 7-star NatHERS rating (up from 6 stars) and a Whole of Home rating of at least 60 out of 100. These changes mean builders and homeowners need to think more strategically about energy efficiency from the design phase onwards.

How to understand heating loads

When a NatHERS assessor talks about "heating loads," they're referring to how much energy a home needs to stay comfortable during cold weather. This is measured in megajoules per square metre per year (MJ/m²/year). The lower the number, the less energy and money needs to be spent keeping warm, and the higher the number, the more energy and money. The heating load directly influences the star rating, so getting this right is crucial for compliance and long-term comfort.

The NatHERS software calculates these loads by considering:

• Local climate and weather patterns

• House orientation

• The quality of insulation throughout the home

• How airtight the building envelope is

• Window placement, size, and performance

• Internal heat sources such as appliances, lighting, and even body heat from occupants

How to meet Australian building standards

If you're building a new home in Australia, you must comply with the National Construction Code (NCC) energy requirements. This isn't optional; it's mandatory for building approval and occupancy certificates. Your architect or building designer needs to demonstrate compliance through a NatHERS assessment conducted by an accredited assessor from the Australian Building Sustainability Association (ABSA). These professionals use approved software to model a home's thermal performance and make sure it meets both the star rating and heating/cooling load limits for its climate zone.

The process involves:

1. Initial design assessment during the planning phase

2. Design modifications to meet requirements

3. Final certification for building approval

4. Documentation for council submission

It’s important to pay attention to build standards. Always verify the current requirements with your local council or certifying authority before starting a project, as regulations can vary between states and territories and may have been updated since this information was published.

How to improve your heating loads

Are your heating loads too low? Here are some of the best ways to improve it.

Take a look at insulation

Quality insulation in walls, floors, and ceilings is non-negotiable because poorly insulated homes will just let any air in and out. When you have higher R-values, it means better thermal resistance, which directly translates to lower heating and cooling loads. Investing in good insulation pays for itself through reduced energy bills and improved comfort in your home.

Eliminate thermal bridging

Thermal bridges are like energy leaks in your building envelope. They occur when conductive materials like steel studs or window frames create pathways for heat to bypass your insulation. Use thermal breaks and consider advanced framing techniques to minimise these weak points, to keep warm air in and cool air out.

Seal windows and doors tight

A leaky house is an inefficient house. Proper air sealing prevents your heated air from escaping and cold air from sneaking in. This doesn't mean creating an airtight box — you still need controlled ventilation for healthy indoor air quality — but it means properly sealing windows and doors so they work effectively in keeping the right temperature in or out of the space. 

Choose windows wisely

Windows can be your best friend or worst enemy when it comes to thermal performance. When renovating or building a new home, look for windows that have low U-values, an appropriate solar heat gain coefficient (SHGC) for your climate, and quality frame materials with thermal breaks. Strategic placement matters in the home too, because the amount of light let in can affect temperatures. North-facing windows can provide beneficial solar gain in winter, but they need proper shading to prevent overheating in summer.

Consider framing materials

Your choice of frames matters. Timber frames are naturally good insulators, while aluminium frames have excellent durability but conduct heat rapidly unless they include thermal breaks. There are also composite materials which often provide the best thermal performance. Our Miglas AliClad window frames combine the benefits of both timber and aluminium frames to create a window that provides maximum comfort while minimising energy wastage.

How to solve common challenges

Managing energy consumption is not always easy, but there are some aspects you can change to make it better.

Balance light and thermal performance

Bigger windows mean more natural light but also more potential heat loss or gain. High-performance glazing can help, but it comes at a cost, so it’s recommended that you work with your designer to find the sweet spot between natural light, views, and thermal efficiency.

Manage tough climate zones

Building in Australia's colder regions means you’ll face unique challenges, such as limited winter sun, which reduces passive heating opportunities, and higher energy consumption to heat the interior, which makes it harder to achieve those coveted star ratings. To work on this, focus on superior insulation, air sealing, and high-performance windows to compensate.

Retrofit existing homes

Structural limitations on old homes might prevent ideal insulation installation, and full-scale renovation work can be expensive. As a home renovator or builder, it’s important to focus on cost-effective improvements that deliver maximum impact, such as improving windows, adding insulation where possible, and sealing air leaks.

Managing costs without over-engineering

It's tempting to throw expensive solutions at thermal performance challenges, but smart design often beats expensive materials. Work with experienced professionals who understand how to achieve compliance without unnecessary over-engineering so you can save in the long run.

Work effectively with NatHERS assessors for future success

Your relationship with your NatHERS assessor can make or break your project timeline and budget. Here's how to set yourself up for success:

1. Initiate: Engage your assessor during the design phase, not after construction drawings are complete. Early input can save costly design changes later.

2. Communicate: Share your priorities, budget constraints, and any specific requirements upfront. Good assessors can suggest cost-effective solutions that meet your needs.

3. Plan: Rarely does a design meet NatHERS requirements on the first attempt. Build time into your schedule for potential modifications and re-assessments.

4. Ask: Don't hesitate to ask why certain changes are recommended. Understanding the reasoning helps you make informed decisions about your project.

Meeting NatHERS requirements isn't just about ticking regulatory boxes, it's about creating homes that are comfortable, affordable to run, and better for the environment. With energy costs continuing to rise and climate change driving more extreme weather events, building efficiently makes both economic and environmental sense. The upfront investment in better thermal performance typically pays for itself through reduced energy bills, improved comfort, and higher property values. Plus, you'll have the satisfaction of knowing your home is doing its part for Australia's environmental goals.

Build smarter, not harder

Understanding NatHERS heating loads might seem complex, but with the right approach and professional guidance, achieving compliance and creating a comfortable home is possible. The key is starting with good design principles and working with experienced professionals who understand both the regulations and practical solutions. 

At Miglas, we offer comprehensive support to builders, architects and renovators looking to improve the energy ratings of their projects. Whether you're in the early planning stages or working through design challenges, remember that investing in thermal performance is investing in your family's comfort and your property's long-term value. 

Get in touch with us to find out how we can help.