STEP 4 - Efficient Appliance Selection.
This section discusses the simple appliance choices that have significant impact on Whole of Home energy use, & pave the way for a Net Zero operational energy outcome for our homes.
As a bonus this section also gives the information you need to achieve a high rating score under the NatHERS 7-star Whole-of-Home pathway in the National Construction Code.
So far, we have focussed on Good Design to achieve 7+star outcomes (STEP 1), and Performance Construction (STEP 3) to be able to meet that energy rating on the ground.
Both these steps are very important for comfort, health, minimising heating/cooling loads, and fulfilling builders' obligations.
BUT HOW MUCH ENERGY HAVE WE SAVED?
If we look at the Australian Average Home Energy Use pie graph, we can see the energy split in the average home.
This pie graph also represents an average carbon emission of ~5 tonnes of CO2 per house per year, as fossil fuels are burnt to provide the power in each wedge.
And for this power the average yearly energy bill is northwards of $2000+ per year.
Passive Solar Design and Performance Construction, looked at so far, minimise the energy needed to heat and cool our homes. Together they minimise energy use in the space conditioning wedge of the pie graph, by making the most of local climate and letting good design do the heavy lifting.
The pie graphs below show the indicative savings for various star ratings compared to the energy use of the average Aussie home. As you can see this really highlights the huge benefit good design and quality construction can have in reducing the energy needs of our homes.
It is worth noting that these graphs are based on the Australian average, and that if you are in cooler southern climates the Space Conditioning wedge will be closer to 60% of the pie, making good design and quality construction even more important in those climates.
However, when you look at the graphs, even at 10 stars, it is obvious that there is a lot of the pie left.
There is still plenty of energy use going on, which means a lot of opportunity to minimise energy use in the other wedges of the pie!
This is where a Whole-of-Home approach and this STEP 4 section come in!
In this section we will be using the pie graph above for the 7-star home, and looking at each energy use wedge, to see what strategies and technologies you can include in your builds to reduce the energy needs of each slice of the pie. You will see that choices for fixed appliances are at least as significant as Good Design and Performance Construction, in creating a modern low energy use home.
Note: While getting an 8, 9, or 10 star outcome is great, don't be discouraged if you 'only' get to 7-stars. With today's efficient technology 7 stars is still sufficient for achieving a Net Zero operational energy outcome. Of course, if you do achieve 8,9, or 10 stars it will make Net Zero easier...
NatHERS WHOLE-OF-HOME IS COMING YOUR WAY IN 2023 (or 2024 in Vic, or 2025 if you are in WA or Tassie) ARE YOU READY?
NatHERS Whole-of-Home (WoH) is more than just a move to a 7-star level thermal assessment. It also focuses on those other wedges of energy use in the average energy use pie graph above. This is the "Whole-of-Home component", and it will drive even more change...
SO, WHAT IS THE NEW REQUIREMENT?
As well as upping the NatHERS requirement to a 7 Star Rating, NCC2022 Performance Requirement H6P2 requires all new homes to use no more that 70% of the energy of a 7-star home with the following appliance set:
- a 3 star Ducted Reverse Cycle Airconditioner (GEMS 2019), and
- a 5 star instantaneous gas hot water system
- a lighting power density of 4 W/m2 serving all internal spaces that are provided with artificial lighting
This is actually a pretty high bar. Especially when you consider GEMS2019 is the new updated star label, and a 3 star is actually 4.5 stars in the old label you are probably more used to seeing (and which is still in circulation).
...And you have to be 30% more efficient than that to pass!
A pass is represented by 60 or above on the Whole of Home scale.
HOW WILL THE NEW RATING WORK?
When doing an energy rating on a set of house plans, assessors enter the energy efficiency of each of the items in the picture above, into the Whole of Home software (apart from "Plug in Appliance" loads, which are generated automatically dependent on house size). The software then simulates a year of living in the home with the star rating, and appliance suite nominated. Any Solar Photovoltaics (PV) & batteries are a benefit, and treated as a credit on your score.
Where a fixed appliance has not been chosen at the time of rating a lower performance "Default" product will be chosen by the assessor under the protocol, so it pays to put efficient selections on the plans for a good rating.
The software then does 2 calculations:
One with your home design at its actual >7star rating, with your nominated appliance set.
And one with your home design dumbed down to exactly 7.0 stars, with the benchmark appliances above.
If the software calculates that your home design with your appliance set is ~30% more efficient than your house at 7 stars with the benchmark products, then the home will score 60 or above and pass.
The upshot of this, is that in many climates you will need high efficiency reverse cycle airconditioning & heat pump hot water or solar HW to pass.
Alternatively, you can have lower performing appliances and make up for it with a sufficiently large Solar PV system.
AND THIS IS NOT AT ALL A BAD THING.
IN FACT, IT WAS THE INTENT!
And it will drive significant energy savings, as you will see in this section.
On top of this,
the very good news is...
If you can pass Whole of Home,
Net Zero is just ONE STEP AWAY...
To achieve a Net Zero operational energy use outcome from this point, is as simple as either adding a PV system, or increasing the size of the one you had to have to pass the new rating.
And the Whole of Home software will be able to calculate the required system size for you! (We will look at this in STEP 5 of the Roadmap).
So, when 7 Star Whole-of-Home lands in your State, it's worth checking with the assessor what else you would have to do to achieve a Net Zero outcome?
It may not be very much…
Hot Tip: The Australian Building Codes Board has released a beta version Whole of Home calculation tool for DtS Elemental Pathway compliance. If you want to see what appliance combinations are likely to be required in your climate download the Whole of Home Calculator here.
Note, this version does not integrate the thermal model, like the NatHERS software tools do, so you can't input the reduced heating/cooling load benefit of achieving the higher 8,9, or 10 stars. But it does give an indication of what appliance selection will be required for a 7-star rated home to pass in your area.
The first wedge we will consider is Space Condtioning.
As we have seen, good design combined with performance construction reduces space conditioning needs, as reflected by the star rating and the pie graphs above. Unless you have achieved a 10 star design there will still be mechanical heating and cooling required. Even if you achieve 10 stars, unless you are in a very benign climate, when conditions stray outside the data set of the simulation, you will likely need space conditioning to remain comfortable.
If you want to provide the remaining heating and cooling needs with minimal energy use, the technology of choice is heat-pump space conditioning.
Recent improvements in heat pumps have changed everything, and heat pumps are one of the technologies that make the Net Zero all-electric home possible.
Reverse Cycle Air-conditioning, or "split systems", as they are commonly known, are a type of heat pump with a head unit inside the house, and a compressor outside the house.
They are like the LEDs of the heating & cooling world; much more efficient than the old aircons, that were the bane of the sustainability movement in the past.
To put their efficiency in perspective, while the most efficient a gas heater can ever possibly be is 100%, the best Reverse Cycle A/c are around 500%.
They can get these crazy high efficiencies because they are not actually making heat or cool, but just shifting heat from the outside to the inside (heating), or the inside to the outside (cooling).
A Reverse Cycle A/c that is 500% efficient is said to have a Coefficient of Performance (COP) of 5. That is, for every 1kW hour of energy they use to run the compressor, they shift 5kWhr of heat! For cooling mode, they have another number called an Energy Efficiency Ratio (EER), which is usually pretty similar to the COP.
Look for systems that have a COP/EER of 3.5+. You will find this information sitting as a line item of the Specifications for the model.
Looking at the pie graph in the picture above, a house with efficient heat pump space conditioning could make the heating and cooling required in a 7-star build, with ~1/3 the energy of conventional plant.
This not only saves energy, running costs and carbon emissions, but will also set you on course for a good score on NatHERS Whole of Home.
Even though they don't change the temperature of the air, fans can provide up to a 3 degree cooling effect as they blow air across the skin (& moisture is evaporated). This can be all the cooling needed to stay comfortable in all but the hottest conditions for most climates.
Hot Tip: Fans can also be used help to de-stratify the air in the room, and to spread the heating or cooling of the airconditioner, minimising the number of A/c units needed in a home. They are also beneficial to the star rating thermal model, especially for climates where cooling is a priority for much of the year. So for some easy points, and comfort to boot, consider installing some fans!
ENERGY EFFICIENT HEATING & COOLING
Sub-Heading Navigation:
Heating/Cooling heat pump options
How to size Space Conditioning Units
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations
SO, WHAT OPTIONS DO YOU HAVE WHEN LOOKING FOR HEAT PUMP SPACE CONDITIONING?
While Single Split system reverse cycle airconditioners tend to be the most efficient, there are also:
Of these, ducted airconditioning tends to be the least efficient, suffering as it does from the inefficiencies of running air ducts around the house and through attic spaces and subfloors.
If going this route, make sure you choose highly insulative ductwork (Eg. R2.0) to reduce heat loss to the attic space or subfloor, and spend time sealing the vent/plaster connection if you are using the internal plaster as a tightness membrane.
Don't like blown air?
The newest models include sensors that direct air flows away from people in heating mode.
Alternatively, heat pump hydronic units are now also available, though they only do heating, not cooling.
Look out for models with a COP>4.
ENERGY EFFICIENT HEATING & COOLING
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Heating/Cooling heat pump options (Current)
How to size Space Conditioning Units
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations
SO, ONCE YOU HAVE DECIDED YOU WANT TO USE REVERSE CYCLE SPACE CONDITIONING, HOW DO YOU SIZE UP WHAT KILOWATT CAPACITY YOU NEED?
HOW DO YOU KNOW WHAT SIZE TO PUT IN?
There are 3 methods:
1.
If you are like most builders you will get a quote, or get an installer out, and the conversation will go something like…
“What do you reckon?”
“Yeah, well, we’ll do a 2.5 in here”
“And a 3.5 in this room”
“And this big open space - better put in a 7”
Sound familiar?
2.
Well now you can work it out yourself.
Fairair, is back New and Improved!
You enter in the dimensions of the room, choose the closest construction type to your job for wall, floor, & roof, and input window sizes/type.
And bam. It gives you an aircon size.
You will need to do it for each room you want to condition, and do the process for both heating and cooling, then choose the bigger of the 2 capacities recommended when specifying the kilowatt (kW) capacity of the unit you need for the space.
This is useful for double checking the installer's recommendations.
Not that you should discount the advice of an experienced installer, but at least this gives you a bit of knowledge to start a conversation where discrepancies exist.
3.
The third method to sizing heating/cooling kW capacity needed for a room is to ask the thermal assessor. The NatHERS software does calculate peak heating and cooling loads expected for each room of the home, but it is hidden deep in the output file of the calculation engine, and as yet not brought to the fore by software providers. Many assessors know where to look however, and for those that don't here are the instructions! Feel free to share them with your assessor.
To contact an assessor, try the Design Matters National Thermal Performance Assessor Lookup, for an assessor near you.
You don’t want to put in more than you need.
But, more importantly, you don’t want things undersized either.
These 3 techniques help you hit the right mark.
Note: These heating / cooling loads can be used to help size up ANY space conditioning plant, not just airconditioning and hydronics.
ENERGY EFFICIENT HEATING & COOLING
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Heating/Cooling heat pump options
How to size Space Conditioning Units (Current)
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations
WHILE REVERSE CYCLE AIRCONDITIONING IS THE MOST EFFICIENT FORM OF HEATING & COOLING, THERE IS A FAIR RANGE OF PERFORMANCE ON THE MARKET. THIS BEGS THE QUESTION; HOW DO YOU CHOOSE AN EFFICIENT SYSTEM FROM AN INEFFICIENT ONE?
You can of course ask a trusted supplier and specifically ask them to quote/recommend the most efficient systems to meet peak heating & cooling loads in the different rooms of the home.
(Or ask your thermal performance assessor as they get more experienced running Whole of Home simulations.)
But if you don’t have a trusted supplier, or just want to see what is best out there, head to the Greenhouse & Energy Minimum Standards Regulator (GEMS) website and check the ‘Airconditioners’ database. GEMS run the whole appliance star rating sticker system, so rated models on the market should be there.
Here’s how to use the database:
1) Go to https://reg.energyrating.gov.au/comparator/product_types/
2) Choose 'Airconditioners' to go to the database
3) Select search parameters. E.g. Single Split, Reverse Cycle, Both heating & cooling, 2-3kW output range. Then press search.
In the database you will see the old star ratings on the right of the table (still current but being phased out by 2025) and the newer Seasonal Energy Efficiency Ratings (SEER), which now break the ratings into Cold, Hot, and Mixed Climate Zones. These SEER ratings are a more accurate representation of the performance of the unit in your climate. Where SEER ratings exist use those.
4) Determine your climate zone - either Cold, Hot or Mixed.
If you are not sure, look at the map in "What is a Zerl?" below. If still unsure go HERE, click on "Airconditioners", then type your postcode in the box and press "Go".
5) Depending on your climate and whether heating or cooling predominates over the year, click on your climate zone under either SEER Heating Star Rating, or SEER Cooling Star Rating to rank models by efficiency.
6) You will see the most efficient models and manufacturers on the left of the table, which you can then check out for feature specification and get quotes on.
DONE.
HOT TIP 1: Unfortunately, SEER stars and the old stars use different scales and can’t be compared, with SEER stars being harder (a 3 star today is a 4 1/2 star in the old stickers). So, make sure you are comparing apples to apples if comparing difference star rating sticker types in a store.
HOT TIP 2: GEMS have brought out a new less clunky interface at https://calculator.energyrating.gov.au/
Click on "Airconditioners", fill in the postcode of your climate, and it will automatically give results in SEER stars for your climate. Unfortunately the site will only rank by Cooling Stars, which is not ideal if you are in a heating climate. However you can do a proxy filter, by upping the heating star slider preference until only the units with the higher heating stars are listed.
ALSO, if you want to use a reverse cycle Ducted system, this site allows you to sort by "Ducted" which the older database above does not, so would be the better site to use in that case.
AND the other good feature of this site is that it gives 10 year running costs, so you can see the savings as you choose more efficient options!
Below shows an example of the new star rating label using the SEER label.
Just to be more confusing, they call it a ZERL, a Zoned Energy Rating Label.
It is pretty useful though in helping you choose the best unit for your climate, and it also gives the decibel reading, which is important to know if placing units near bedrooms or boundaries.
HOT TIP: This new rating label also shows operational decibel levels in the left hand corner. The lower number the better, with anything under 50 being classed as a low intensity sound, and 30 decibels being a whisper.
Lastly, if you are recommended a system, or are comparing models in a quote, it's always worth checking the Specifications. Here's an example of the Daikin AliraX.
You can see that it conveniently has ZERL Stars for the different capacity units. The 3 numbers are for Hot/Average/Cold climates in that order.
It also has EER's and COP's that can be easier to relate to.
Remember, the higher the number the better. As mentioned above, a COP of 5 means for every 1 kilowatt hour (kWh) of energy used, the machine transfers 5 kWh of heat. In cooling mode they use the acronym EER (Energy efficiency Ratio) instead to describe the efficiency, but it works exactly the same way as COP.
Lastly, when checking system specs also check the refrigerant. In this case R32.
We explain why this is important in the very next section.
So, now you can size, compare, and specify, the most energy efficient space conditioning for you your projects.
This will not only make your clients happy when they see their bills, but also give you a higher score when you do your next NatHERS Whole of Home rating!
ENERGY EFFICIENT HEATING & COOLING
Sub-Heading Navigation:
Heating/Cooling heat pump options
How to size Space Conditioning Units
How to Choose Efficient Airconditioning (Current)
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations
Modern heat pump hot water and air-conditioning are game changing technologies for all electric low carbon buildings. In fact, along with Photovoltaics (& Good Design), they are the technology that enable the Carbon Zero outcome. However, what most people don't realise is the refrigerants they use to do their heat shifting are much worse for global warming than CO2 if they get released.
Refrigerant gasses are all given a GWP number. This stands for Global Warming Potential.
CO2 has a Global Warming Potential of 1.
Some of the newer airconditioners use the relatively benign R32 gas, which has a GWP of 675. That is, it's 675 times worse than CO2! But this is nothing compared to the more common R410a refrigerant which has a GWP of 2090!!
What does this all mean?
Most aircons will have around 1kg of refrigerant. If at end of life the refrigerant is not professionally collected, it will almost certainly leak to the atmosphere. For most airconditioners that's going to be equivalent to releasing over 2 tonnes of CO2!
Therefore, when doing a demolition or replacing an aircon, it is vitally important to hire an aircon plumber for professional decommissioning of the old system.
Don't just rip it out and put it on the skip!
That could undo a large chunk of the energy efficient goodness the machine has achieved over its life…
Hot Tip: For Airconditioners the most benign refrigerant to look out for R-32.
ENERGY EFFICIENT HEATING & COOLING
Sub-Heading Navigation:
Heating/Cooling heat pump options
How to size Space Conditioning Units
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential (Current)
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations
NatHERS WHOLE OF HOME REQUIRES THAT THE SPECIFICATIONS OF MAJOR FIXED APPLIANCES ARE CORRECTLY ENTERED INTO NatHERS SOFTWARE. BUT WHAT INFORMATION IS REQUIRED?
The process of an energy rating can often be tediously bogged down when the relavant information is not on the plans. In which case the assessor either uses default assumptions, or has to spend time contacting clients and explaining what information they need. With NatHERS Whole of Home the potential for missing information regarding the specifics of chosen fixed appliances is greatly increased. This will mean either a potentially longer back and forth email correspondence between client and assessor, or worse yet, assessor will just assume low efficiency defaults, which in the case of Whole of Home lead to a fail.
To make the rating process quick and seamless,without lots of back and forward requests for information between assessor and designer/client, download & fill out a blank version of the following template blocks and add them to your plans so that the assessor has all the information they need at their fingertips when conducting the rating. Here's an example of what they look like filled in with data ready for the assessor to enter.
If you get together the right information from the start, not only are you likely to source more efficient appliances, but the rating process will be that much quicker.
And as the old adage goes...Time IS Money!
ENERGY EFFICIENT HEATING & COOLING
Sub-Heading Navigation:
Heating/Cooling heat pump options
How to size Space Conditioning Units
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating (Current)
Airconditioner Installation considerations
NON-DUCTED REVERSE CYCLE AIR-CONDITIONERS ARE THE MOST EFFICIENT HEATING AND COOLING RIGHT? WELL, DEPENDS…
If you get a poor install maybe not!
Big holes behind units are not uncommon.
Big holes mean the installer doesn’t really have to measure too precisely.
Big holes make the unit easier to fit off.
Big holes allow plent of play making centring of wall unit easy.
And the head unit hides the hole.
What’s the problem?
The ‘problem’ is that these units are usually on external walls.
The problem is cold air will leak in during winter directly behind the wall unit, which is trying to provide energy efficient warm air.
The problem is hot air will leak in during the summer directly behind the wall unit, which is trying to provide energy efficient cool air.
The problem is it makes for a leaky house, and really undermines the selection of these efficient space conditioning units in the first place.
And the problem is, this happens all too often…
SOLUTION:
Let your installer know you MUST have a tight install.
That means:
Not that hard to do.
Hot Tip: And when installed correctly, non-ducted reverse cycle air-conditioning remains the most efficient space heating/cooling option on the market.
ENERGY EFFICIENT HEATING & COOLING
Sub-Heading Navigation:
Heating/Cooling heat pump options
How to size Space Conditioning Units
How to Choose Efficient Airconditioning
Refrigerants & Global Warming Potential
Aircondioner Details to put on Plans for NatHERS Rating
Airconditioner Installation considerations (Current)
WITH HOT WATER THERE ARE 2 MAIN STRATEGIES TO REDUCING THE ENERGY USED.
1) Minimise the Hot Water you need through water efficient fixture selection.
2) Choose an energy efficient water heater.
Let's look at each of these in turn, as they both have a big effect on energy consumption...
Sub-Heading Navigation:
Choose Energy Efficient Hot Water Systems
Specifying Efficient Hot Water
Hot Water System Details to put on Plans for NatHERS Rating
The first step to reducing the Water Heating energy use in the average home, is to reduce the amount of hot water used in the first place!
This is pretty easy to do.
Almost 1/2 the hot water use in the house goes to the shower, and ~1/3 to the washing machine.
By choosing 4-star WELS (Water Efficiency Labelling Scheme) showerheads and a 4- or 5-star WELS washing machine you will save nearly 30% of the energy on the Hot Water wedge, simply by having less hot water to make!
If you go to www.waterrating.gov.au you can search the database for rated products to help you choose. Rank by WELS stars and you will get a list of product models you can then check out.
It's also useful to check sites like Choice, or ask at the My Efficient Electric Home page on Facebook for good reviews. The last thing you want to do is put in an efficient shower that doesn’t satisfy, or a washing machine that doesn’t clean well.
Replacing inferior products is certainly not sustainable!
For washing machines, front loaders are usually well rated.
If you go to https://calculator.energyrating.gov.au/Washer.aspx you will find a database which can be ranked by efficiency. This will give you brands and models to start on you product search.
Such choices are a good start on minimsing the hot water energy wedge, but there’s still a lot we can do...
Note: Energy savings through water efficiency are not currently included under NatHERS Whole of Home, but will have a big effect in practice. So, specifying water efficient showerheads & washing machines should see the house perform better than expected. Or, alternatively, can give a builder a little bit of margin in operational performance, in case of minor shortfalls elsewhere...
Sub-Heading Navigation:
Minimise Hot Water Needs (Current)
Choose Energy Efficient Hot Water Systems
Specifying Efficient Hot Water
Hot Water System Details to put on Plans for NatHERS Rating
NOW THAT YOU HAVE MINIMISED HOT WATER NEEDS, WHAT IS THE NEXT STEP TO MINIMISE THE REMAINING HOT WATER ENERGY USE?
SURPRISE! Yes, it’s heat pumps again. This time for Hot Water.
As I said, heat pumps are game-changers.
In the case of hot water, they are of course, only set on the heating cycle.
3 things to look for:
1) What is the COP of the unit?
The best units have COP’s of 4+
2) What is the Global Warming Potential (GWP) of the refrigerant gas?
Some refrigerants can be thousands of times worse than CO2 as a global warming gas, if/when they leak from the unit at end of life. See above.
Choose R744(CO2) with a GWP of 1, where you can. Some hot water heat pumps use it. (Note the most benign refrigerant for airconditioners at the moment is R-32).
3) Choose heat pumps that can be set to heat water during the day, when your PV system (which we will look at in STEP 5), is putting out more power than you can use.
Assuming you get a heat pump hot water with a COP of at least 3, you can expect to make the hot water needed for the average house with about 1/3 the energy in the hot water wedge.
Another huge saving in operational power requirements!
What about Solar Hot Water (SHW)? In many climates SHW is still a fantastic option, with good units providing >75% of hot water from sunlight contribution during the year. However, SHW boosters are either gas or resistive electric, and where a lot of boosting is required, this can use a fair bit of energy in the winter months. They also take up space on the roof which may be needed for PV, and tend to cost more than heat pumps. Quality Solar Hot Water however should definitely still be considered in areas with a high number of sun hours over the year.
If you do use SHW, limit lengths of flow and return lines and make sure to get the most insulated versions you can, especially where pipes run externally.
Sub-Heading Navigation:
Choose Energy Efficient Hot Water Systems (Current)
Specifying Efficient Hot Water
Hot Water System Details to put on Plans for NatHERS Rating
WITH ALMOST ¼ OF HOUSEHOLD ENERGY GOING TO HOT WATER, YOU WANT TO GET THE HOT WATER SYSTEM RIGHT. HOW DO YOU CHOOSE AN EFFICIENT SYSTEM FROM A NON-EFFICIENT ONE?
Firstly, as already mentioned, if you want efficient hot water there’s really only 2 broad types of hot water to look at:
Both these types save around 2/3 of the energy compared to conventional hot water systems, and both can be considered to run on solar energy from sunlight.
Makes sense for Solar Hot Water, but how does that work for Heat Pumps?
Well, while solar hot water (SHW) gets it’s heat from the sun warming up panels; heat pumps get their heat from sunlight warming the air. And with -273 degrees centigrade being absolute zero, there is always heat in the air, even on a cold night, courtesy of the sun.
Heat pumps then use expansion and compression of refrigerant in a piped loop, to ‘shift’ that heat from the outdoor air, into the hot water tank. They can be thought of a bit like a sponge, soaking up heat, then squeezing it out into the water tank, heating the water within. So, while not as direct perhaps as SHW, they can still be considered ‘solar’ in this sense.
But let's get back to the question.
How do you choose an efficient system?
Well, for solar you could look for % yearly solar contribution in the product literature, and for heat pumps look for the coefficient of performance (COP) – the higher the better. But often this information is not available from the manufacturer.
So instead, check the STC REGISTER!
STC’s are Small-scale Transferable Certificates, which are given by the government to systems depending on efficiency, for rebate purposes. The more efficient, the more STC’s a system generates. You can use this to compare system efficiencies.
STEPS:
THAT’S IT.
Efficient hot water, lower bills, happier planet!
Check it out.
Hot Tip: Hot Water Units with high STCs (Solar & Heat Pump) are the products of choice if you want to do very well on your next NatHERS Whole of Home rating!
Sub-Heading Navigation:
Choose Energy Efficient Hot Water Systems
Specifying Efficient Hot Water (Current)
Hot Water System Details to put on Plans for NatHERS Rating
OF ALL THE CHOICES YOU MAKE WHEN BUILDING A HOME, THE SELECTION OF THE HOT WATER SYSTEM IS PERHAPS THE ONE WHERE A SINGLE DECISION HAS THE MOST IMPACT ON FUTURE RUNNING COSTS AND CARBON EMISSIONS.
The difference between the energy efficiency of hot water systems currently on the market is wide, and a poor choice can literally mean hundreds of dollars extra in running costs every year. Costs and emissions that don't need to be…
That is why NatHERS has included Hot Water as one of the fixed appliances now covered under the 2022 NCC Whole of Home provisions. And of all the fixed appliances, Hot Water is the most important to specify wisely if you want a high score on your House Energy Rating. We saw how choose wisely in the previous section above.
Once you have chosen an efficient hot water system, what information do you need to put on plans to ensure the assessor has all the information they need for a smooth rating process?
The SBA have made the answer easy, by creating a ready to go template, with instructions, for you to download. 😊
NOTE: As a bonus, if clients want to choose other hot water options (not recommended...), this template can also be used for the other hot water options currently included under NatHERS. Just delete the lines in the table that you are not using before adding to plans.
And that's it.
Hot Water, and one of the most important choices to get right...
DONE!
Sub-Heading Navigation:
Choose Energy Efficient Hot Water Systems
Specifying Efficient Hot Water
Hot Water System Details to put on Plans for NatHERS Rating (Current)
LIGHTING ENERGY ON THE HOME ENERGY USE PIE IS A RELATIVELY SMALL WEDGE, BUT...
...it is a relatively easy one to make some gains on!
The average home the pie graph is based on will still have a few incandescent or halogen lights kicking around, so there is a little bit of saving compared to the average, just by going 100% LEDs.
And probably most new homes are going full LED anyway.
So, full LED’s – job done!
NOT QUITE.
What this wedge doesn’t consider are penetrations lighting causes through the plaster.
In standard construction our plaster is the tightness membrane!
So, if you don’t want uncontrolled air leakage, and want your home to perform to the house energy rating, it is important to minimise the number & size of holes in the plaster. (See Design for Tightness, Roadmap Step 1)
The NatHERS rating does assume some air leakage, dependent on what the assessor enters.
But only to a point...
Hot Tip: Remember, under the Whole of Home protocol, the NatHERS Benchmark house uses 4W/m2 for lighting. With LED's and Pendant lights it is reasonably to use less energy per m2. This means there are some potential easy points to gain during a NatHERS Whole of Home energy assessmet if you include a lighing schedule on your plans showing <4W/m2 on average for lighting intensity.
Sub-Heading Navigation:
Choose Pendants, LEDs, & IC-4 Downlights
Lighting Table to put on Plans for NatHERS Rating
WARM AIR WANTS TO RISE, SO CEILINGS ARE THE MOST IMPORTANT SURFACE TO GET TIGHT AND WELL INSULATED! THUS, THE LESS HOLES YOU CUT IN IT THE BETTER...
Compared to downlights, pendant lights not only require fewer fixtures to light the same area (meaning fewer plaster penetrations), but the penetrations only need to be the size of a wire, and the insulation over can remain complete and undisturbed. A reasonably tight outcome can therefore be achieved as long as you make sure that the electrical wire is forward of any insulation and fixed in position prior to plaster stage. This will save the damage and dislodgement of hunting for wires later!
If you must have downlights, surface mounted versions also only require a wire-sized hole, and once again allow insulation to be undisturbed above, so are generally preferable over recessed versions. They do however still suffer from the fact you need more of them. Which means more labour and more expense and more wire-sized holes in the ceiling plaster...
If you must use recessed downlights, choose downlights that are clearly marked with the IC-4 rating stamp showing insulation can run over as in the picture below. AND make sure that you instruct the electrician to NOT PULL OUT insulation above.
Otherwise, HABIT may take over and ceiling insulation will become SWISS CHEESE...
Remember...
5% of holes = 50% reduction in thermal performance!
And,
Warm moist air wants to rise.
And,
Holes allow moisture transport into your ceiling cavity.
Which you really want to try and minimise.
Choose Pendants.
Hot Tip: Better yet, consider wall mounted up-lights for your lighting. No penetrations to the ceiling at all!
Hot Tip 2: Consider a Passivhaus approach and install an internal ceiling membrane and drop the plaster ceiling to introduce a services cavity. Then you can have downlights and anything else you want, and the wires, pipes and ductwork don't impact the insulation or the tightness!\
Sub-Heading Navigation:
Choose Pendants, LEDs, & IC-4 Downlights (Current)
Lighting Table to put on Plans for NatHERS Rating
WANT SOME EASY POINTS WHEN YOU DO A NatHERS WHOLE OF HOME RATING? OF COURSE YOU DO! HERE’S HOW…
While lighting is only a small energy user in the overall energy usage of the average home, it’s an easy one to get some handy points when you do a Whole of Home rating.
As discussed above, NCC2022 Performance Requirement H6P2 now requires all new homes in VIC, Qld, & ACT (other states to follow in 2025), to use no more than 70% of the energy of a benchmark home with the following appliance set:
• 3 star Ducted Reverse Cycle space conditioning
• 5 star instantaneous gas hot water
• 4W/m2 of lighting density
We have already looked at how to choose & notate Space Conditioning & Hot Water on plans.
Let's now look at lighting...
To achieve less than 4W/m2 of lighting density there are 2 main strategies:
1. Use LED's
LED's are common place now and very energy efficient.
To choose globes the conservative rule of thumb is 1W is ~100 lumens. For general lighting (bedrooms, living areas, etc) allow about 100-150 lumens per square meter. For work areas (studies, kitchen benchtops, etc) 200-300 lumens per square meter is more suitable.
2. Use pendant lighting over downlights
As noted already, pendant lights generally spread their light much better than downlights, (and allow standard construction to be tighter), with the rule of thumb being you can replace 4 downlights with 1 pendant; albeit upping the LED globe by a few watts to compensate.
You come out significantly ahead of the benchmark 4W/m2 taking this strategy over a whole home, with lighting densities of around 2W/m2 easily achievable.
This is an easy credit to get on your rating.
BUT,
You won't get it if you don't prove it to the assessor!
How do you show it on the plans?
Very helpfully, the Australian Building Codes Board (ABCB) have provided a VERY USEFUL EXCEL TEMPLATE.
It's called the NCC 2022 Volume Two lighting calculator.
All you have to do is,
Download it.
Fill it in.
Put it on your plans.
And the assessor will take the number and use it in the rating.
Easy points! 😉
Sub-Heading Navigation:
Choose Pendants, LEDs, & IC-4 Downlights
Lighting Table to put on Plans for NatHERS Rating (Current)
WHY CHOOSE INDUCTION?
Induction cooking is 55% more efficient than gas. This is mainly because much of the gas heat goes around the sides of pots & pans, whereas induction energy is directed into the pot itself.
Cooking however is not a major energy user in the home. And there are ovens and microwaves and other kitchen appliances that also contribute to the energy used in the cooking wedge of the average Home Energy Use pie graph, so the energy savings from choosing induction aren’t all that large...
But the cost savings can be!
As we strive for energy efficiency, the cooktop is often the last hold-out gas appliance standing in the way of the all-electric home.
If an induction cooktop is chosen, you can also then abolish the gas meter and save the ~$300/yr gas connection charge – every year for the life of the house!
If you do, you will find you only have one energy bill, which makes it a lot easier to work out how much energy the house actually uses. No more trying to convert mega joules to kilowatt hours!
And you remove the health risks of carbon monoxide, nitrogen dioxide & formaldehyde emissions associated with gas burning, & bemoaned by the Asthma foundation!
For those concerned that induction cooking won’t be as good as gas, we recently did an online poll, and the feedback among users was overwhelmingly positive, with none saying they wanted to go back to gas.
In many ways this one sleek appliance is the path to the all-electric future...
Note: Network power providers set maximum power supply levels for each phase of their electrical infrastructure in the street. Electricians are required by code to add up the electrical loads in the home and apply a formula to check they are not going beyond the maximum single-phase capacity dictated by the Network provider. With multiple airconditioners, induction cooktops and heat pump hot water units, the number of electrical fixed appliances in the all-electric home are increased. Depending on the number and amperage of the fixed appliances within the home and the limits imposed by the network area, 3 phase supply and a corresponding 3 phase meter may be required. It is important to find this out early, as there can be cost implications.
3 phase does have benefits for car charging speed and also increases feed in solar limits, so if a 3-phase upgrade is required, it can be considered a future proofing benefit to the all-electric home.
Sub-Heading Navigation:
Sidebar: Why Future Homes will Tend All-Electric
Induction Installation Considerations
Oven & Cooktop Details to put on Plans for NatHERS Rating
YOU MAY BE WONDERING, WHAT ABOUT GAS? WHY IS ELECTRICITY THE SUSTAINABLE PATH?
Well, look at the graph.
AUSTRALIA’S GRIDS ARE GREENING, AND PROJECTED TO GREEN MORE!
What you are looking at is the graph of the carbon intensity in kg of CO2-e per kilowatt hour, of the state electricity grids across Australia.
And as you can see, as coal plants have shutdown over the last decade, to be replaced by wind, and solar (including rooftop solar), the carbon intensity is starting to drop in a meaningful way. Even carbon profligate Victoria is heading back to the fold.
If the Department of Industry, Science, Energy, and Resources (DISER) is correct in their predictions, the carbon impacts from Operational Energy in our homes will fall markedly over the next decade as grids decarbonise!
This is great news for Australia, and the Built Environment, and all those with ALL ELECTRIC HOMES. Your homes will become greener over time!
But what about those connected to gas?
Well, as a fossil fuel, it is very hard to reduce the CO2 impacts of burning gas. There is talk of mixing in green hydrogen at around 15%, but really, given that its already cost effective to go all electric, it doesn't seem to make much business sense – at least not in time.
So, all the more reason to go all-electric sooner rather than later.
And all the more reason to start thinking about the embodied carbon in our homes, where the figures are not looking as rosy...
(For more on this see Roadmap STEP 2, Low Impact Material Selection)
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Sidebar: Why Future Homes will Tend All-Electric (Current)
Induction Installation Considerations
Oven & Cooktop Details to put on Plans for NatHERS Rating
While induction cooking and going all-electric does allow you to save running what can be expensive copper/gas lines, it is important to check the amperage required for induction cooktop power supply and make sure you communicate that to the electrician, as different models require different power levels. And different power levels require different cable thicknesses.
So, work it out by Roughin Stage.
Once the plaster is on it is expensive to rectify if you got the cable wrong.
Also be aware, if you do go all electric, you may be required to install a 3-phase power supply to the property. This will cost extra and should be confirmed early on with your electrician.
Going 3 phase does however give significant benefit in allowable PV system size and future car charging speeds.
We will look at in the STEP 5 of the Roadmap, when we discuss Allowing for Future Car Charging.
Sub-Heading Navigation:
Sidebar: Why Future Homes will Tend All-Electric
Induction Installation Considerations (Current)
Oven & Cooktop Details to put on Plans for NatHERS Rating
Cooking specification is another new requirement included in the NCC 2022 NatHERS Whole of Home energy calculation, and while not a large energy user in the average home, there are still some possible points to be gained on the rating. The choice however is not as straight forward as you might think...
When doing a NatHERS Whole of Home rating assessors now need to enter data about the choice of Oven & Cooktop.
The choices are Gas or Electric for the oven, with the extra option of Induction for the cooktop.
As mentioned above, Induction cooking has the following benefits. It:
Which in turn
HOWEVER,
In many Australian States the greening of the grid still has a long way to go. And while induction is more energy efficient than gas, the cost & carbon intensity of the gas supply vs. electricity supply is still in gas's favour in many places.
As a consequence, depending on your location, there are often currently no carbon savings, or rating improvements from choosing induction cooktops over gas.
Of course, if you are making greenpower from your solar panels when you are cooking, or include batteries, an induction cooktop & electric oven does become a very green option.
And as grids continue to green over the next 10-15 years, Induction cooktops & electric ovens are predicted to become the greenest options in all locations...
Whatever you choose, you will need to specify it on the plans for the assessment.
The SBA makes this easy with our new SBA Cooking Appliance Template below.
Download it.
Follow the instructions.
And use it on your plans,
for a seamless assessment process…
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Sidebar: Why Future Homes will Tend All-Electric
Induction Installation Considerations
Oven & Cooktop Details to put on Plans for NatHERS Rating (Currrent)
WE HAVE ARRIVED AT THE LAST WEDGE ON THE AUSTRALIAN AVERAGE HOME ENERGY USE PIE GRAPH.
AND ITS A BIG ONE.
Plug-In Appliances.
¼ of the pie, representing ~1.25 tonnes CO2, and ~$500+ in running costs annually.
And once again, there’s a fair bit of saving to be made.
How easy it is to make those savings will of course depend on whether you are involved in Appliance specification. Most of the time, plug in appliances are left up to the owner.
In either case however, there is a lot you can do to facilitate an energy efficient outcome.
Let's start by looking at the easy case where you are in control of specification.
If you are in charge of specification, then the solution is easy.
Simply buy white goods with the higher stars!
Each extra appliance star reduces the energy consumption of the previous star by ~20%
You don’t necessarily need to buy the best, just keep within a star or 2 of the best.
By following this strategy, you can save about 30% of the energy use in the Appliance wedge, just through white goods alone!
2 great websites to check before going shopping are:
- They run the star scheme and you can search the product directories and rank models by star efficiency.
- Choice do product testing and reviews. You want to specify something that works. The least environmental thing you can do is buy a lemon, which needs early replacement, and creates warranty headaches.
AND LOOK AT WHAT WE HAVE DONE TO THE PIE GRAPH!
We have eaten around 2/3 of it, firstly by good design & construction, and secondly by efficient appliance choices. And what have we given up?
NOTHING!
Just pollution & ongoing costs...
The last step is Going Positive, which we shall look at in STEP 5, Energy Generation & Offsetting
BUT,
What can you do to minimise energy usage in this wedge if clients are supplying plug-in appliances?
In that case a little bit of communication can do wonders to facilitate efficient appliances choices by owners...
Sub-Heading Navigation:
Facilitating Efficient Appliance Choices
Pool & Spa Pump Details to put on Plans for NatHERS Rating
So, your designer has come up with a 7 star+ house design.
Good start.
Your team has built it diligently, and you’ve installed efficient reverse cycle space conditioning, heat pump hot water, LEDs and induction cooking.
Great job!
You’ve guaranteed a low-bills, low CO2 impact home!
OR MAYBE NOT…
If the owners come back from their shopping with energy guzzling white goods & plug-in appliances, it’s not going to reflect well on you when they get their bill!
To give the owners a little more information on where they should focus, you could do worse than show the owners this graph below:
Look at the right side of the pie graph.
What it shows is that approximately half of plug-in appliance energy use goes to 5 items (ignoring the pool if they have one).
In order of energy use they are:
These appliances are very often supplied new buy owners moving into their new home.
Suggest to owners that they might want to buy versions with higher stars if they are getting new items.
If they aim 4-5 stars or higher for most products, they will make considerable inroads on their energy usage.
That’s money in their pocket for the life of the appliance.
Less CO2 for the environment.
And better performance for the home, which reflects positively on you.
The slides below demonstrate this variation in running costs.
This information comes from the Greenhouse Energy Minimum Standards (GEMS) website calculator
(https://calculator.energyrating.gov.au/)
And they are worthwhile showing owners, as the savings for them can be considerable!
Literally thousands can be saved over the lifetime of the appliances!
Calculations shown below are based on best-in-class versus worst-in-class, and average daily usage over a 10-year operating life.
Owners can also potentially use the calculator to compare models with their own estimated daily usage & tariff rates, to get a more accurate accounting if required. They can even put in cost price to work out overall savings.
But the point is, client choices REALLY DO COUNT in how the home PERFORMS ON THE GROUND.
And if you want happy clients, with low bills, who rave about how cheap the home you made for them is to run, this is important information to pass on.
Hot Tip: You can help the owners with their choice and formalize this process a little more by creating a list of recommended fixed appliances for the owner's considerations. (See SBA Tool: Builders Appliance Recommendation Template below.)
Hot Tip 2: As you can see in the slides above each extra star saves between 15 - 30% on the running costs of the previous star. As a Rule of Thumb, let owners know each star represents a saving of ~20% on the star before.
Also Note: As a benchmarking tool, NatHERS Whole of Home just assumes an average appliance load for the house dependent on floor size. Ie. the bigger the house, the more people are likely to live in it and the more things are likely to be plugged in over time. So, efficient plug-in appliances won't affect the official rating.
However, in practice, if owners do choose higher than average efficiency appliances, the house should use less energy than the NatHERS model suggest, reflecting even better on you as the builder or designer, and giving another little buffer against any slight shortfalls in perfection elsewhere...
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Facilitating Efficient Appliance Choices (Current)
Pool & Spa Pump Details to put on Plans for NatHERS Rating
AFTER SPACE CONDITIONING & HOT WATER, WHAT APPLIANCE USES THE MOST ENERGY IN THE HOME?
If there's a pool, especially if a big one, it could be the pump.
As can be seen from the pie graph above, pool pumps can have a big impact on home energy use.
So if your project is having a pool, AND you want an energy efficient outcome, choosing an efficient pool pump over an inefficient one is vital.
And it makes a big difference, as can be seen in the comparison below...
Over $2,500 saving is predicted on 10 year pump running costs, by choosing best in class.
That also works out to a saving of over 9 tonnes in CO2 emissions!!
And that's with a small 750W (1hp) pump!
Bigger pools need bigger pumps, with emissions & costs easily twice that for an inefficient pump in a large domestic pool.
So THIS CHOICE MATTERS.
Which is why Pool (& Spa) Pumps are now also included in the NatHERS Whole of Home scheme.
HOW DO YOU CHOOSE AN EFFICIENT PUMP?
Done.
Hot Tip: Pool & Spa Pumps come in 3 types:
• A single speed pump
• A dual speed pump, or
• A multi/variable speed pump
Of these multi speed tend to be the most efficient, with dual speed more efficient than single speed.
Sub-Heading Navigation:
Facilitating Efficient Appliance Choices
Pools (Current)
Pool & Spa Pump Details to put on Plans for NatHERS Rating
AND HOW DO YOU COMMUNICATE THE RIGHT INFORMATION ON YOUR PLANS FOR THE ENERGY ASSESSMENT?
Easy.
Download the free SBA Pool & Spa Pump Template
On it you will find instructions.
Fill it out...
... & put on your plans for a speedy assessment.😉
Hot Tip 1: Having a pool in your NatHERS assessment will almost certainly require the installation of Solar PV to pass the H6P2 NCC provision.
When doing your NatHERS assessment, ask the assessor how big a PV system you would need to put on to achieve a Net Zero outcome when including the pool energy use. You may find the cost of increasing the system size - and putting the pool pump on a daytime timer - will turn out less than the 10 year running cost of the pump.
Cheaper and greener.
Win-win.
Hot Tip 2: Pool heating is NOT CURRENTLY included in NatHERS, (though likely coming...). But Pool Heating can use A LOT of energy. If planning a heated pool, MAKE SURE you get the most efficient system the price point can afford.
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Facilitating Efficient Appliance Choices
Pool Pump Details to put on Plans for NatHERS Rating (Current)
Where clients are responsible for plug-in appliance selection, you can help them with their selection process, and increase the chances of energy efficient selection, by using the SBA Builders Appliance Recommendation Template.
Click on the below document to download.
It comes with an accompanying information letter that includes much of the information above, and useful links to help clients understand the issues and choose efficient appliances.
Feel free to use it and adapt it as you see fit.
And let us know when you find any great energy efficient appliances!
The Net Zero Homes builders' course is a partnership between Design Matters National and the SA Gov, and was created by the author of this website (Jeremy Spencer - Positive Footprints), so covers much the same ground.
If you like listening rather than reading, this course will be for you. The good news is that all 5 modules are completely FREE at the moment under a funding grant to professionals in the industy.
Highly recommended - register while funding lasts at
https://www.solar.vic.gov.au/net-zero-homes-skills-training
Though we suggest watching the videos in order, Module 4 Part 1&2, deals with the topics discussed in this step most closely.
This webinar by Builders Declare also covers Efficient Appliance Selection with a question period at the end.
Description
Whether it's a well executed Passive Solar build, or Passivhaus construction, or just a well built home*. Design and build quality are not enough to achieve a Carbon Zero outcome. Not even close. The Technology you put in the home must be a focus too. Join Jeremy Spencer - Director, Builder and Energy Assessor for Positive Footprints Sustainable Design & Construct - to find out what you need to know to complete the job of a Net Zero outcome. This is a practical talk for Builders, Architects, and anyone wanting to know how to achieve a Net Carbon Zero home, so you can start designing, building, & living the low carbon future, today.
* See Jeremy's talk, "What makes & What breaks, a High Performance Home", where build quality is covered, on the Builders Declare Youtube page.
To Size Airconditioner capacity
To search for Airconditioner efficiency
https://reg.energyrating.gov.au/comparator/product_types/
(Choose Airconditioning)
To lookup system efficiency of Solar Hot Water & Heat Pumps on the STC Calculator
REC Registry: https://www.rec-registry.gov.au/rec-registry/app/calculators/swh-stc-calculator
Information sheet for clients on the benefit of choosing appliances with high stars
To look for efficient appliances (Washers, Driers, Computer Monitors, Dishwashers, Fridges, TVs, & Pool Pumps)
https://reg.energyrating.gov.au/comparator/product_types/
(Choose Appropriate White Good from the list and use the table to rank by preferences & efficiency)
Appliance running costs calculator to compare costs of different models
https://www.energyrating.gov.au/calculator
Appliance reviews
Current Rebates in your State
