Nov 2022

How to achieve a 7 star energy rating and more

How to work with an energy rater and get a 7 star energy rating

Image of sunshine coming through a window and the edge of a lounge chair, with the text How to achieve a 7 star energy rating... and beyond.

“Most people only get the [energy] rating done after all the major design decisions have been made or are locked in. This is a missed opportunity… an experienced and knowledgeable energy assessor should be able to provide advice on design improvements and changes that can save many thousands of dollars on the final cost of the build.”

—Sid Thoo, Sanctuary Magazine

How do you achieve a 7 star energy rating, or more? If you want the best energy rating for a house, be it 7 stars or more, the best time to engage your energy assessor is at the start of your design process. This helps ensure that the principles needed to increase your home’s energy rating are included right from the start. It also avoids costly changes at the building approval stage. 

House energy rating goals

If you’re asking about how to get to 7 stars, why not 8 stars? Have you thought about aiming for a house that has zero energy bills, or needs no fossil fuels to power it?

The first thing you need to do is set some goals around what you want to achieve and what you want from your home. In addition to a 7 star energy rating, we recommend aiming for:

  • Zero energy bills
  • Comfortable temperatures inside year-round
  • Climate resilience
  • Zero fossil-fuel power
  • Healthy home with great air-quality

These might seem like a lot, but actually a solid process and the same key design levers will get you to all of these goals. And even more importantly, building a house is one of the biggest financial and material decisions that many of us will make. We want you to build something that is no-regrets, and that will help your family and the planet not just for a decade, but for lifetimes to come.

How to achieve a 7 star energy rating, and more

When someone engages us, these are the stages we work through to get the best results. We tailor this process depending on the goals of the client, and the experience of their design team with building energy-efficiently. 

1. Concept development: design advice for 7 stars

When your plans are rough, it’s a great time to get a review and ensure the fundamentals of good solar passive design are present. You might have sketches from an architect or rough plans from a builder at this stage. This is also helpful when you’re thinking about where to place your house on your block, and what direction different rooms will face.

Our insight:

If you want to reach 7 stars energy rating and above easily, and without expensive building upgrades, you need to have the basic design fundamentals right.

Getting good advice at this stage is especially important when you’re new to solar passive design and thermal performance principles, or you want to improve your knowledge. It will help you get the design right before you get too attached to a particular layout; while there is flexibility to make large changes. If you’re a homeowner who is self-managing a project, no matter how big or small, we would still recommend a design review at this stage.

In terms of design, we recommend focusing on a few key elements:

  • Form complexity. How complicated is your floor layout? Is it a straightforward rectangle, or a more complex series of shapes with lots of exterior walls, such as a courtyard house? Generally, the more complex the form, the poorer the house will rate in terms of energy efficiency, as more exterior walls create more heat loss.
  • Are the living areas well-oriented with lots of solar access? In colder climates, including Canberra, Melbourne, southern & central NSW, and Hobart, all living areas should have access to northern sun. The more, the better. North-facing windows allow sun in to warm a house during winter, and generally can be naturally shaded by eaves in summer.
  • Glazing ratios. Although windows allow beautiful light and connection, they’re also the weakest point of a building. The more windows you have, the worse your house will perform thermally. Obviously, there is a sweet spot here – we want a light-filled house that is also comfortable.

An experienced assessor will be able to give you a rough estimate of the star rating, and help you make decisions about the changes and trade-offs in each of these criteria – before you go through the expensive and time-consuming approvals process.

We can’t emphasise how important it is to have your solar access and glazing performing well, if you want to get to 7 stars or higher. 

2. Design development: fine tuning your building details for 7 stars

‘Design development’ is the stage when your plans are reasonably firm and your architect or designer is starting to make detailed drawings. There’s still an opportunity here to move or resize a few windows, but it’s unlikely that you’ll want to make large layout changes…  partly due to the expense of redrawing plans, and also because you might be quite attached to your design!

At this stage, we are looking at the building fabric and choosing windows. We recommend:

  • Prioritising the weakest-performing areas of the house to improve efficiency gains. This includes addressing air-leakage (see our intro article on airleakage). Although the energy rating software does not consider air-leakage in star ratings, it has a huge impact on the real comfort of a home. We use an energy efficiency dashboard to help our clients identify the biggest areas for improving their energy efficiency. The biggest improvements in comfort and energy use are generally always the same: air-leakage, and windows.
  • Reviewing all windows to ensure maximum performance. A good rule of thumb is at least 30{79051017feef4f5ff944d10cc916092b24ee4afe247e0d33115042d116ff4652} of your windows should face North. Another great rule from one of our favourite design books is “two points of light in every room”. Windows are like the engine of the car, except they’re doing the job of warming or cooling your house for total comfort. We want to ensure that all your windows are working for a high rating design, and not against you.
  • If we didn’t complete a concept review (step 1), we’d review those elements at this stage too: form complexity, windows to floor ratio, and ensuring there is plenty of northern-facing glass into living areas.
  • Reviewing building details:
    • What wall construction will you have, and what’s the maximum insulation?
    • What floor construction will you have, and what’s the maximum insulation?
    • What air-tightness measures will you use?

As high-performance houses are fairly new in Australia (although not in Europe and America), we will often recommend cost-effective tweaks to Australian standard building construction.

3. Energy efficiency rating: finally we get to the (hopefully) 7 star energy rating!

This is the stage you may be more familiar with: the mandatory part of the process where you get a star rating for your house. If you’ve got the basic design ratios right and well-specified insulation and windows, this step should be straightforward.

Depending on the state you live in, you will need a minimum of 6 or 7 stars energy efficiency rating for your building approval. Each state and territory is adopting the move to 7 stars energy rating at different times, see our summary for details on your state.

Your energy rating is done under the NaTHERS (Nationwide House Energy Rating Scheme) framework, which is an Australia-wide system that measures how energy efficient a building is. The maximum rating you can get is 10 stars – although this is harder to reach in colder climates such as Canberra, southern NSW and Victoria.

We find that when people finally get to this stage, there isn’t as much opportunity for real game-changing energy efficiency improvements. Plans are usually already approved and people are keen to get building. You can get stuck here. If your design has missed some basic solar passive design principles, you may have to make significant upgrades to your windows or building details to reach the minimum of 6 or 7 stars.

This is why we recommend people engage a thermal performance assessor early in the design process (steps 1 or 2). You will save money and have a more comfortable and healthy house to live in.

4. But wait, there’s more… design your energy systems: solar power, heating, cooling, and smart electronics

After you receive an energy rating, you can use the information to understand how much energy your house needs to run. You can also start to think about how to heat and cool your home.

If you achieve an 8-star energy rating or above, you probably won’t need a significant amount of mechanical heating and cooling at all. But it can be good to have something to get you through extremes such as cold snaps or heat waves, which will unfortunately become more common over the life of your home.

You can use the data from your energy rating to:

  • size your solar system,
  • size your heating and cooling systems,
  • plan for a
  • decide on including a battery and even for planning your off-grid energy system (with a few caveats!).

How to achieve a 7 star energy rating with Powerhaus

We do house energy efficiency rating differently. Our client’s have access to Australia’s first energy efficiency home design app with live data at your fingertips, so you can make changes on the fly and see how each decision integrates with your whole home energy plan and budget.

Using our energy efficiency home design app at concept stage, and into design development, ensures you work through key design ratios and building specifications, to get the highest rating design possible.

If you want to know how to get to 7 stars energy rating and more, chat with our friendly team about working together.