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BASIX Energy Requirements for Granny Flats

What are the BASIX requirements for Granny Flats? They are to ensure you meet the Governments requirements for sustainability, regarding:

1. Water Commitments (to save water)
2. Thermal Comfort (Regarding insulation)
3. Energy Commitments (Reduce Energy & Improve Safety)

We were not allowed to move past this approval process for our Granny Flat. Not until we purchased a certificate through a company proving our plans met these requirements.

You can only “buy” the assessment for BASIX through a company licenced to issue them.

I went with a company called “Building Sustainability Assessments” in Hamilton, NSW.

The report cost $525 and they weren’t required to come out and see the site, only to see the plans that were drawn.

DON'T PAY A FORTUNE FOR YOUR GRANNY FLAT. Find out how to deal with council and build a granny flat for the lowest cost possible. Learn More.

What is in a BASIX Granny Flat Report?

BASIX stands for “Building Sustainability Index

Once I found about getting this index, my heart sunk a little.

I thought I would have to change things and pay the designer extra money based on what the BASIX report would show.

This index is achieved by giving you a score out of 10. And the result of your score comes from the report.

If your ‘score’ is not high enough, (Like it was for my report) you have to change part(s) of your plans to get a better score to “pass”.

Why I failed my BASIX Report and What I Had to Do About it

I didn’t make up enough points to pass the “Energy Efficiency” part of the Granny Flat.

This effectively meant the plans submitted for BASIX approval, were not up their standard.

And the way to get more ‘points to pass’ was to install fans in the Granny flat and install a “solar electric boosted” hot water tank on the roof.

Just like this one shown:

I had to confirm the installation of a hot water system with a higher energy rating


Once we confirmed we would install a hot water system like this, we passed.

The issue is now we are up for a little more cost than we budgeted for.

Installing one of these will cost us an extra couple of grand plus more hours in plumbing work.

These systems, although more energy efficient, require more plumbing labour to pump the water to the roof and then back to the granny flat itself.

Alas, I had no choice, otherwise we would not be issued the BASIX certificate and building would be halted.

Water Requirements for a Granny Flat

To pass the water requirements section of the report we needed to meet these rules:

1. Install shower-heads with a minimum 3-star rating
2. Install a toilet with a minimum 3-star flush rating
3. Install all taps with a minimum 3-star rating
4. Install a basin (laundry) taps with a minimum 3-star rating
5. Install a rainwater tank to meet certain requirements (below)

To understand which products above meet these ratings, you can use this site here.

As you can see on the website when you select “taps” for example it will show you a list of brands and their ratings:

The website used to find 3+ star energy efficient products


Rain Water Tank Requirements for a Granny Flat

In order to pass the rain water tank requirements for approval I was told:

1. To install a 3000-litre rain water tank (for a 60sqm) Granny Flat.
2. The rain water tank would have to collect all water from the roof run-off.
3. The rainwater tank would have to connect to: all toilets, the cold water of a washing machine and at least one outdoor tap.

Water tank for a granny flat

It is worth shopping around for a water tank as they can be an expensive addition, upwards of $1000 retail.

Thermal Requirements for a Granny Flat

For the thermal and insulation requirements for a granny flat I was issued with this below:

Insulation and thermal requirements I had to meet


This didn’t mean anything to me, but I had my friend in the building industry explain:

“Effectively, it means when it comes to insulating the roof cavity and the walls of the granny flat I would have to use certain products.
Every insulation product has a rating which indicates how well it does at keeping temperatures even.
Such as indicated by the “U Value” of a window or a rating of the fluffy insulation used in the walls.”

This report makes life a little easier, when it comes to buying materials.

You just have to be sure the windows, skylights, plasterboard and insulation meets these ratings.

Just be sure to ask whatever materials you buy meet the ratings in your particular BASIX report.

Energy Efficient Granny Flat Requirements

In order to meet Granny flat energy requirements these commitments must be met:

1. Install an Energy Efficient Hot Water System
2. Use of Cooling Systems such as vents and internal fans
3. Limit the addition of any heating systems
4. Install ventilation (fans) in the kitchen and bathroom
5. Ensure the primary source of lighting are LED’s or Fluorescent lighting
6. The kitchen must have natural lighting through a window and or a skylight
7. All bedrooms and bathroom(s) must have a window installed
8. The fridge must have adequate ventilation as per BASIX requirements
9. The Granny flat must have an outdoor clothesline installed

Luckily, we passed this portion of the BASIX report with ease. And in most cases, everyone will pass this section as well.

Regarding the fridge, as long as you have at least 100mm of space behind the fridge for heat to dissipate you will be fine (just like in a regular house).

And the installation of a clothes lines, just means it limits the use of occupants relying on a clothes dryer.

Clothes dryers are notoriously bad at saving energy.

Why Do You Need a BASIX Certificate for a Granny Flat?

Every new dwelling, whether a primary dwelling or secondary dwelling (Granny flat, home office, pool house etc) requires a BASIX Certificate.

It is the step which needs to be ticked off after submitting your design plans to a private certifier or your local council.

It is to ensure every new dwelling built in Australia is as energy efficient as possible.

An environmental initiative to reduce our carbon footprint on the planet.

Every individual property needs its own BASIX Certificate and it must be accompanied with submissions you make.

No matter if you require a full Development Application (DA) or the lesser; Complying Development Application (CDC).

To find out more about BASIX Requirements use this link here. https://www.planningportal.nsw.gov.au/planning-tools/basix

Energy Rating for Granny Flats

Once our report was completed I was handed back with this rating:

The energy rating I received from the report

5.4 out of 10 doesn’t sound that great, however we just needed over 51% (or 5.1) to pass.

The more energy efficient additions you have added to the plans the better your score will be.

Truthfully, I didn’t want the extra cost of adding an electric boosted solar panel on the roof.

However, this needed to be done in order to raise the score above 5.1.

Once this was added, it went through their computer system to spit out a score which enabled us to pass that section of the report.

And meant we could move on to get approval for our granny flat.

Ideally, you want to be as close to “10/10” as possible, for the planet and relating to a reduction of future energy bills.

Government Rebates Available

Sometimes, it isn’t always the case that you need to spend more money to reach a higher energy rating.

There are always different rebates available from the government.

This site will help you find current rebates depending on the state you live in.

These constantly change based on the political landscape at the time and what initiatives the local or federal government wants to support.

It is worth checking out during different stages of your granny flat build to see what you can save money on.

For instance, I recall years ago, the government was rolling out free roof insulation for any primary or secondary dwelling.

Companies were just door knocking asking if you wanted free insulation installed and all you had to say was “yes”.


Energy efficient granny flats are rated by your BASIX score.

A score given depending on water, thermal and energy scores on any new build.

These ratings are determined by a score given after you pay for a BASIX report through a licenced company.

A commitment by the owner-builder must be made to follow the requirements in a BASIX report in order to be approved to build a granny flat.

If the requirements set out in the report are not met on final inspection of your granny flat, it won’t be approved.

This means bigger problems in the future, such as when it comes time to sell your house. Not to mentioned insurance being void if something happens (such as a dwelling being damaged by fire).

The commitments are not too difficult to meet and there are always ways around meeting them.

Be sure to have a chat with your designer to ensure you do what you can to meet the BASIX requirements and save yourself the headaches down the track.