Episode 9

Whole of Home, Solar, Tiny Homes and Verification Using Reference Buildings

14 May 2026 · 67 minutes · Part 2 of 2 · Hosted by Brian Haines, Matthew Graham and Andrew Hooper

Summary

The second half of the conversation with building surveyor Sean McDonnell moves from the theory of Regulation 233 into the places it actually bites: Whole of Home on renovations, the three kilowatt solar provision, relocated houses, and the flat-pack dwellings currently being sold as an answer to the housing crisis.

The recurring question is the same one Part 1 kept circling — what is reasonable, and who decides. If a renovation is not touching the hot water service, the heating or the cooling, can discretion apply to Whole of Home the way it applies to the thermal performance? If a roof cannot structurally carry a solar array, or physically fit one, does the requirement still stand?

It ends on the topic Brian has a standing thousand dollar bounty on: verification using a reference building. He argues the pathway produces results that cannot be audited, defended or insured. Sean, who says he has not seen one in years, asks the questions from the other side of the desk.

In this episode

• 0:13Two ways to demonstrate Whole of Home, and why one is easier

• 1:55Can Regulation 233 discretion apply to Whole of Home?

• 4:54Solar on an existing roof: shading, shape and structure

• 6:59Where the practice note already answers the question

• 7:23The assumption buried in the ABCB calculator

• 8:49Why a 4.5 star floor exists, and whether it should

• 12:47How each of them actually does Whole of Home

• 14:54The three kilowatt backstop, and where it came from

• 18:04Should a minimum system size be mandatory at all?

• 21:25Relocated dwellings, and how they are treated

• 24:10Flat-pack pods: what you are actually buying

• 26:04Building permits, siting, footings and livable housing

• 30:04Why a 9.6 square metre dwelling cannot be rated

• 31:33The floor area correction factor, and where it runs out

• 36:42Granny flats and what makes something a dwelling

• 38:53The base configuration is a shell

• 44:02Verification using a reference building

• 47:10What a surveyor can and cannot see in one

• 51:58No auditing, no governing body, no insurance

• 57:57How a performance solution is supposed to be assessed

• 1:03:00JV3 compared, and why transparency differs

Key points

Two Whole of Home pathways, and they are not equivalent

Performance requirements H6P1 and H6P2 are distinct, so you can demonstrate the thermal performance through NatHERS and Whole of Home through the ABCB calculator. The calculator takes fewer inputs — no cooking equipment, no lighting per square metre — and is easier to satisfy. In Victoria, Brian notes, a reasonably sized house can pass with no solar at all, provided it uses gas, which is a diminishing option as gas is phased out.

The assumption inside the calculator

The practice note itself warns that the elemental provisions assume building fabric equivalent to a seven star NatHERS rating, and that using the ABCB calculator will underestimate heating and cooling demand for a building performing below that. This is why the practice note prohibits using the calculator where the real rating is below 4.5 stars. Brian's argument is that a performance solution should be able to bridge that, because a renovation should not be penalised on Whole of Home for the existing fabric it has already been granted discretion on under H6P1.

The same assumption applies in Queensland

A neat observation from the discussion: Queensland dwellings taking the outdoor living area concession sit at six stars with a credit to reach the equivalent of seven, and the ABCB calculator treats them as seven star buildings regardless. The team note the parallel without resolving it.

Discretion probably does extend to Whole of Home

Sean has not had it put to him in practice, because most Whole of Home submissions pass. But his answer is that Regulation 233 is not limited to particular performance requirements — it covers all of them. So where a renovation is not touching the hot water service, the heating or the cooling, there is a reasonable case for discretion, and it would come down to the argument put to the surveyor.

The practice note already lists the solar exemptions

Andrew locates the answer to the solar question in the practice note itself, which names constraints including overshadowing, complex roof shapes, numerous roof penetrations and structural issues. It also references cases where upgrading appliances and installing solar would be a disproportionate increase against the cost of the renovation. So a functional existing hot water service is a legitimate reason not to replace it, and a roof that cannot carry or fit an array is a legitimate constraint.

Nobody knows where three kilowatts came from

The provision that every Victorian renovation should have a minimum three kilowatt system is one none of them can source. Sean's contribution is a lawyerly one worth remembering: the wording is *should* achieve rather than *must*, and in legislation "should" is generally read as guidance rather than obligation. Practically, all three note that three kilowatts is now close to the smallest system anyone installs, with five becoming the norm — though Andrew has seen systems specified as small as 0.3 kilowatts when appliances had not been selected and defaults applied, and Queensland's earlier code required just one kilowatt, which produced a lot of pointless one kilowatt installations.

You cannot mandate something that cannot always work

Andrew's objection to a hard minimum is straightforward: narrow blocks, overshadowing and unsuitable existing roofs mean there are situations where it cannot be delivered, and you should not make mandatory something that is sometimes impossible. Brian's counter is that a mandatory minimum at least gets the equipment installed so panels can be added later. The unresolved tension is the same one running through both episodes — a prescriptive number inside a performance based system.

A relocated house is treated as an alteration

An existing dwelling that is re-erected, moved between allotments or relocated on the same allotment is considered an alteration exceeding the fifty per cent volume trigger, which means Regulation 233 discretion is available, subject to the twenty-five per cent extension restriction. In practice that gives a surveyor discretion over essentially the whole building — which Sean considers necessary, since with an old house the openings are fixed and it may only fit on the block one way.

The flat-pack pods are not dwellings

The team work through the products currently marketed as an answer to the housing shortage and find the base configuration is a non-habitable shell: no foundations, no insulation, no electrical fit-out, no plumbing, no kitchen, no bathroom. Bringing one to full Class 1a compliance would likely cost more than the pod itself. On top of that come site-specific footings, siting and setback compliance, easements, a dedicated access path, a laundry, and livable housing provisions that are difficult to satisfy in a very small footprint.

And a 9.6 square metre dwelling cannot be rated

The energy problem is more fundamental. NatHERS has minimum requirements for zones and conditioning that a pod of that size cannot meet, and the floor area correction factor — which exists so that very large and very small dwellings are not unfairly advantaged or penalised — does not extend down that far. Add floor-to-ceiling glazing, an entry door that must be 820 millimetres clear, and a suspended floor sitting on a pad, and the glass-to-floor and glass-to-wall ratios become impossible. Brian notes his team ran exactly this exercise years ago for a flat-pack company across Australia and found it unachievable in certain climate zones. The team's conclusion is that a prefabricated approach can work well — several companies coordinate the permits, the energy report and the engineering for the client — but that buying a shell off a shelf without that support is fraught.

Verification using a reference building

Sean's perspective is that building surveyors generally like verification methods, because they are prescribed and therefore lower risk to accept than an open-ended performance solution. He has not seen one in years and has not encountered it as a point of discussion among colleagues. Brian's objections are specific: the reports arrive as output with no data, so a surveyor cannot tell whether the reference building complies with the elemental provisions as required; the software is specialised and internationally sourced, so few people can produce or check one; there is no auditing and no governing body, unlike NatHERS accreditation with its audits and consequences; and professional indemnity cover does not extend to it. He has offered a thousand dollars for someone to produce one and prove the data is sound, and has had no takers. Andrew's practical test is simpler: the pathway requires the building to satisfy the elemental provisions first, and he doubts many of these buildings could.

How a performance solution is meant to work

Sean sets out the process, which is worth knowing regardless of the pathway. Any performance solution now requires a performance-based design brief first, setting out the scope, the performance requirements being addressed and the assessment method — comparison to Deemed-to-Satisfy, a verification method, expert judgement, or a combination. All key stakeholders must acknowledge that brief, which gives the surveyor a point at which to say they are not comfortable, or to specify what must be demonstrated, before the work is done. The solution itself must then be approved by the surveyor, who is responsible for it and is not permitted to accept it blindly.

Why JV3 sits differently

The team draw the comparison to JV3 in commercial work, which is a similar modelling exercise but, in their experience, arrives with far more transparency. Sean sees relatively few of them. Andrew's closing point is the one that matters for assessors: a JV3 result cannot be directly compared to a NatHERS assessment, whereas a reference building result can — which is precisely why it is possible to see one producing three or four stars worth of specification and to know something is wrong.

Documents referenced

• Building and Plumbing Commission VictoriaPublisher of the Victorian practice notes, including EE-04, and of Regulation 233 guidance.

• ABCB Whole of Home calculatorThe alternative to running Whole of Home through NatHERS software.

• National Construction CodeAustralian Building Codes Board — the code itself, and the Housing Provisions referenced throughout.

Transcript

Lightly edited for readability. Hesitations and repetition have been removed and technical terms corrected; the substance is unchanged. Part 1 is Episode 8.

0:13One of the things that came up on the NatHERS Assessor Network Facebook page recently was that performance requirements H6P1 and H6P2 are completely distinct from each other, so you can do Whole of Home using the NatHERS software, or using the ABCB Whole of Home calculator. You cannot do an elemental Deemed-to-Satisfy and then use NatHERS for Whole of Home, but you understand what I am getting at. I actually thought everybody knew that, but obviously not.

0:53There are fewer inputs with the ABCB calculator than with the NatHERS method. You do not input things like cooking equipment and lighting per square metre. It is just the appliance efficiency values and what type of hot water, heating and cooling it is. And it is easier to comply with. There are circumstances in Victoria where you can get a reasonable size house to comply with no solar, but you have to use gas — and obviously we are phasing out gas, so that will not last much longer.

1:55So based on those limited inputs, would it be possible to get dispensation under Regulation 233, or would you apply dispensation for Whole of Home completely, if the client was not upgrading any heating unit, cooling unit or hot water system, but was doing something with the cooker or the lighting — which can be captured in NatHERS but not in the ABCB calculator?

2:38It is a good question, and I have not come up against it in practice. Mostly Whole of Home submissions have passed and I have not had many requests for 233 specifically for that. I have had it where there was a very small addition and they were not touching anything, so under twenty-five per cent there is discretion.

3:44If someone is using the ABCB calculator, doing an extension but not touching any of those factors — an existing hot water service only a few years old and functional, no significant change to heating and cooling — there would definitely be scope to say they are not altering the parts of the building that form that calculation. You have to pick your path first, whether you are going down that route or elemental Deemed-to-Satisfy, and then put your argument to us. I am not sure it would be enough to tip you across to using one over the other, but I think there is a case in both scenarios for discretion based on the inputs.

4:54Extending from that, what about solar? You mentioned a fifty year old roof may be incapable of taking the load. How detrimental does that become when it is part of a performance requirement and demonstrated as required for compliance?

5:20There would be cases — the same as you often may not be able to put it on the front of a heritage building that has a planning permit. You can repair that roof, but they do not want solar visible on the front. There would also be cases where a large addition means the new roof would be fine, but they specified a five kilowatt system and the new roof cannot fit that size. So there are practical considerations. But there could also be other options — why not use a superior hot water system instead of relying on the solar for the Whole of Home score. So they might have to look at other areas that are not very efficient.

6:24Again we are coming back to the question of what is reasonable.

6:30There is actually a statement in the practice note that answers that. Constraints for installation of solar photovoltaics including overshadowing, complex roof shapes, numerous roof penetrations or structural issues. So structural issues would form part of that use case for Regulation 233 partial compliance.

6:59It also references appliances, where upgrading appliances and installing solar would be a disproportionate increase against the cost of the renovation. So that is where some appliances may be suitable to remain — it is not reasonable to ask them to replace a functional system.

7:23The other issue with the ABCB calculator is written in the practice note itself: the elemental Deemed-to-Satisfy provisions assume the building fabric achieves thermal performance equivalent to a seven star rating, and doing Whole of Home using the ABCB calculator will underestimate the energy demand for heating and cooling for buildings with thermal performance less than seven stars.

8:02So if you are using the calculator and you have rated the renovated home and it comes out at 4.5 stars, because that is the actual rating the client is going to get, you put that through the calculator and it gives you a compliant score — but the calculator thinks it is a seven star house. There is a disconnect. And I think that is why there is a clause in EE-04 saying you cannot use the ABCB calculator if the true rating is less than 4.5 stars.

8:49My argument would be that we should still be able to put together a performance solution to use the calculator regardless, because you should not be penalised by the existing part of the house. If I am getting dispensation under Regulation 233 for H6P1, why can I not get dispensation for H6P2 as well?

9:25It is a difficult underlying assumption. But it works in Queensland as well, because all those six star houses plus the one star credit for a compliant alfresco go through the calculator assuming a seven star house. It is not an exemption bringing it back to six — it is saying six stars with a credit to reach seven, so it is still loosely assuming seven. But in the formula the calculator uses, it is still assuming seven and not six, so you get a little bonus there too.

10:32So in this case it is a four star house — can my performance solution incorporate that I do not want to be penalised by the existing part, so I can still use the calculator even below 4.5 stars, because I am getting dispensation under Regulation 233? I think there is an argument for that.

10:38An argument to say you could use Regulation 233 where it is available to you. Alternatively, what other calculator is there? We do not really have any tools apart from NatHERS and the ABCB calculator. The question I would have is whether you know how to make adjustments to account for that assumption — is there a formula to say what you should adjust because it is at four and a half instead of seven? You could using the NatHERS software, but you could not using the ABCB one. And I think that is what it is trying to say: the rating is too low, the averages are too far apart, we are going to force you to use NatHERS software to get a score of sixty.

12:03Our Regulation 233 is not limited to only some performance provisions. It does cover all performance requirements.

12:17Some building surveyors are strict on that 4.5 star rule, and it comes back to whether the practice note is a guide or written in law.

12:47If I am reading the room, Brian, you do not use the NatHERS Whole of Home very often. Waste of time. I almost exclusively use the NatHERS Whole of Home, and only on occasion the ABCB calculator. A lot of my work uses software that calculates both, so I can see them side by side. Occasionally I get a green tick for both. Usually both are compliant, but ninety-nine per cent of the time I am using NatHERS.

13:43Maybe it goes back to the nature of the work. I have a lot of clients genuinely interested in achieving not just the sixty but beyond the minimum — a lot of them are happy if they get eighty or ninety, and if they can get to one hundred and zero net carbon then they are pleased. I am able to quantify that and go beyond minimum regulatory compliance, whereas you are trying to come up with the most cost effective and energy efficient solution, which I appreciate.

14:54Leading into my next question: there is also the clause about a minimum backstop of three kilowatts. Theoretically, following the practice note directly, you would never be able to build a renovation or extension in Victoria without a minimum three kilowatt solar system, unless you fall back on the items we just discussed. Why do I have a backstop of three kilowatts? Would my performance solution not be able to have fewer kilowatts, if I still comply with the ABCB calculation and I am applying Regulation 233 across both performance requirements?

16:02If you have done enough Whole of Home using NatHERS you will see it is possible to comply quite easily with smaller houses under three kilowatts and still get a score of sixty. I can see the argument that a house below seven stars may need more solar to comply, but this is a renovation and extension — I should have some form of dispensation. Why am I getting full compliance when I do not need to for H6P1?

16:53Can we agree we should be applying Regulation 233 to that three kilowatt paragraph as well? Where appropriate. The practice note is a guide and does not suit every situation, so we are looking at things like the space on the roof, the budget of the build, and the structural soundness.

17:26I do take note that in general legislation the wording is *should* achieve, not *must*. In legislation, "should" is often taken much more as a guide, as opposed to "must". So I personally would not think the three kilowatts is gospel, because there is a "should" in the practice note.

18:04Would anyone install less than three kilowatts these days? The cost of solar has dropped and dropped, and there are rebates. Three is pretty much a minimum — five is generally the minimum if you are shopping around. Although the old Queensland code required one kilowatt of solar, and there were plenty of people installing exactly one kilowatt. There are volume builders whose standard system is 2.13 kilowatts, because that is four panels at a given wattage. It happens, but it is a pointless exercise.

19:17In a lot of my reports I will say it needs one and a half or two kilowatts minimum, because I need the Whole of Home specifications back on the drawing set for the building permit. By then they have usually sized something more appropriate — three to five kilowatts — so I reflect that back and the score exceeds the minimum of sixty. The smallest I have had was 0.3 of a kilowatt, because they had not decided on any of the appliances so we had to apply all defaults.

20:07Nobody is going to put 0.3 on, but it is a good entry point for solar to be mandatory on all houses — you have all the equipment there, ready to add more panels later. But we have already discussed that not every roof is suitable. Narrow blocks, overshadowing. You cannot make something mandatory that cannot work one hundred per cent of the time. If there are situations where it cannot work, you do not make it mandatory.

21:25The last part of the practice note relates to relocatable homes. An alteration is building work that relates to an existing building. An existing dwelling that is re-erected, moved from one allotment to another, or relocated on the same allotment is considered an alteration to the dwelling exceeding the fifty per cent volume trigger. So the surveyor has discretion to allow partial compliance under Regulation 233, subject to the house not being extended more than twenty-five per cent of the original floor area.

22:21So we are almost back where we started — a relocated house is treated the same way as a renovation and extension. Sounds about right. You would have discretion on essentially the whole building, because you are considered to be altering more than fifty per cent of it, which I think is necessary. If you are relocating a very old house with fixed openings, you are only going to be able to put it on the block one way. There are a lot of things that would be very difficult to force into full compliance.

23:33What if you were transferring it to another block but in a worse orientation? That comes into consideration, but you still have the discretion.

24:10We have a random topic for tonight. What are your thoughts on these flat-pack pods that have been in the media — forty-odd thousand dollars for 9.6 square metres? Are these permanent dwellings? They are not on wheels. How does that work with a building permit?

24:42I do not think the retailer is suggesting they do not need a building permit. They have a plumbing aisle and an electrical aisle, but that does not mean an untrained person can do subsurface plumbing or electrical work. It is not their responsibility to get a building permit — that is the person who buys it. They are just providing a product. Is that product fit for purpose though?

25:20I wonder about the energy reports. It comes with windows. What if my property is one metre from a boundary fence and four metres from a double storey neighbour? That is very different from a block twenty metres away with no overshadowing. How can it be one size fits all with all those on-site deviations?

26:04Obtaining approvals is going to be challenging without knowing the intricate details of their whole system, the footings, the frame, and how they intend the building to be used. There are cases about when a building permit is required — generally to be exempt it needs to be readily movable, and I have heard several people quote that it must be able to be moved within twenty-four hours. They may be exempt from planning in a lot of cases if it is considered a small second dwelling, which has boxes to tick, including being less than sixty square metres. But then there are other requirements: a dedicated access path, which most go to the house for, and you need a report and consent if you do not comply. To be a dwelling it must have a laundry, and it must incorporate the livable housing provisions — which is quite challenging in a tiny area when you look at circulation and access requirements, let alone the energy rating side.

27:41Generally, to get a building permit for one of these you need a building designer or architect to coordinate it, because you need site-specific footings from a structural perspective, and it has to comply with siting regulations, setbacks and setbacks from easements. An important distinction is that a prefabricated outbuilding used as a home office or pool house would be ancillary to the dwelling, not a new dwelling. But if it is a completely separate new dwelling, there is a higher onus — energy requirements and a number of other factors. If it were just a small outbuilding in conjunction with the dwelling, there is arguably Regulation 233 if it is less than twenty-five per cent compared to the existing house.

28:52I do not think the premise of these is outbuildings. Looking at the pictures and the advertisements, they are all cost of living crisis and lack of housing — they are advertising them as little houses, tiny houses. So one would assume they definitely need a building permit. I cannot work out whether they are on a chassis, a timber subfloor, or need a concrete slab, which introduces a whole heap of other issues in Victoria.

29:34My understanding is it is a completely self-enclosed unit, which suggests it has its own floor. So if you were putting it on a concrete pad it would still be a suspended floor. Which means it needs to be insulated under the floor.

30:04We have all rated small dwellings, and generally their glass to floor area ratio is not great — they tend to be extremely hard to rate, especially in certain climate zones. Looking at some of these pictures, they are all floor to ceiling glazing. They look lovely, but I do not think they are going to be triple glazed, and if we cannot do insulated concrete slabs it is going to be tough.

30:43The article referred to NatHERS, which is interesting. NatHERS has a minimum requirement for the zones and the conditioning. Some of these do not look like they could even have three zones. And these are a lot smaller than the tiny homes — the terminology here is pods. It is almost smaller than a tiny home, and the floor area correction factor just taps out. It is definitely not going to go down as far as 9.6 square metres.

31:33What is the floor area correction factor? Effectively it is designed not to bias. It is calibrated at your average house size, so that when you do an assessment, as a house gets larger it goes one way and smaller it goes the other. It is designed to calibrate that. Is a seven star hundred square metre house the same as a seven star five hundred square metre house? The correction factor partly takes that into account. But we are talking about 9.6 square metres of floor area, which is tiny. That is not going to work.

33:38The challenge is the glass to floor ratio, and glass to wall. What can you do? You walk in via a glazed sliding door. You need a door, and it has to be 2,100 high — you are not going to have a 1.2 metre high door. Your minimum entry width is 820 clear now, and the majority of internal doors as well. With this ratio it cannot work with small houses.

34:36This has been tried before. Years ago we did calculations all across Australia for a flat-pack company like this, and it became impossible in certain climate zones to get them to work. I think what is happening is that they are simply not thinking far enough down the track, and there is every potential they will not be able to get a building permit, because they have not thought of every factor.

35:23I would like to see a test case. I would like to see someone put their hand up and say they will give it a crack. But it is an eighty thousand dollar gamble. Although you could get all the plans first and go to an assessor and a building surveyor and ask what the complications are going to be. Due diligence, really. If anybody is watching and has a plan set they can share, we will give it a shot.

36:42A granny flat is not a house on its own lot — you are still reliant on the main house as the primary dwelling. Are they allowed to have kitchens? Once you incorporate a kitchen it potentially meets the definition of a dwelling. Generally you need a kitchen sink with cooking facilities, and a bathroom including a shower or bath. Once you tick those boxes it is potentially a second dwelling. The legislation has changed — dependent person's units used to be on there and had to be demountable, but they have been replaced by the small second dwelling clause. From a planning definition, a bathroom and a kitchen make it a dwelling. Though there are exemptions, because there is a clause about the use of the building — a pool cabana not intended as a dwelling might have a bar with a sink.

38:53This might answer some of our questions. The pods in their base configuration are non-habitable outbuildings. They are shells without foundations, insulation, electrical fit out, plumbing, kitchen or bathroom. So you are getting a cardboard box. The buyer must bring the structure to full Class 1a compliance, and the cost of doing so is likely to exceed the cost of the pod itself.

39:35But it comes back to whether you could even bring it to seven stars, because your window specification is fixed as part of the flat pack. You cannot change the structure.

39:53I am not sure why you go down this road rather than considering the tiny homes already out there that have addressed a lot of these issues. It looks like a cheaper alternative, but for something non-habitable there are already steel sheds, and cheaper.

40:47The moral of the story is that it is possibly fraught with disaster, so be careful and engage the appropriate people before spending sixty, seventy or eighty thousand dollars and not realising you will have to spend that again to get it to comply, if it can comply.

41:19I like the flat pack idea though. It is about prefabrication — the more that is built off site and brought in, the better. There are companies in this space that coordinate everything the client needs: the building permit, the energy report, the engineering, all the permits. That has a lot of value, because for most owners it would be overwhelming to coordinate. And they ensure the designs are done in conjunction with energy raters in the first place, so they are aware of the regulatory requirements. I see that model as much more beneficial to owners than just selling off the shelf.

43:22One of the challenges with small homes is the floor. They are usually on a sled, and it is difficult — it lacks thermal mass and it is hard to get the insulation. It does not have the benefits of an insulated decoupled slab.

44:02Moving on to my favourite topic, and the one with the thousand dollar bounty attached. Sean, what are your thoughts on verification using a reference building?

44:22I might answer a question with a couple of questions. In practice I cannot recall the last one I saw. I see them very minimally. But I am interested in them, because in the structure of the NCC the reference building is a prescribed verification method. As building surveyors we often like seeing a verification, because most performance solutions can be open-ended — there is discretion, they may not be well justified or quantified. We like verification because if you tick all the prescribed boxes it is relatively low risk to accept, and it is generally prepared by someone who is an expert in that field. One example is openings close to a boundary, where a fire engineer bases their report on radiant heat and the rate is prescribed.

46:07So from our side you like seeing verification because it is prescribed and not very open-ended, at least from the outside. I am interested to hear what the issues are.

47:10The first thing that jumps out to me is that it has to comply with elemental before you can even start doing verification. So are they actually complying with all those wall heights and colours to start with?

47:39That was always the issue under NCC 2019 too — one of the requirements was that the reference building has to be the same as the elemental Deemed-to-Satisfy. It was the manipulation of the reference building that was the issue.

48:08There is a whole set of requirements in the specification that, as a building surveyor, you are not going to know one way or another whether they have been complied with, because you are not getting the data. You are not receiving any information about the modelling. Somebody has done it in specialised software, but you do not know what the modelling is. All you get is output on a piece of paper saying complied. You do not know whether that reference building complies with elemental Deemed-to-Satisfy. That is my worry — I could put anything into that data and say it complies, and that does not mean it does.

49:02Does it come back to the fact that NatHERS can be manipulated if you are not doing it correctly, and we do not see the background of how you came up with those results either? Is this an issue within your industry, raised by your accreditation board? And is the software quite complex?

49:30Very much so. There are a few products, very advanced and internationally used, very complicated. I have tried learning it a few times myself and given up, because I have not got the time to dedicate to it.

49:55So there are only limited energy raters who have the expertise or training to do it. And there is no auditing of any of this, so you would not know whether they were competent or capable at all. That is another issue — at least with NatHERS you get audited, not all the time, but you do, and there are consequences if your data is not accurate. There are no consequences here at all. No one would know.

50:27It is not prevalent in Victoria. It is highly prevalent in Western Australia. My understanding was that it would be less prevalent with NCC 2022, but it is creeping back into the market. It is in South Australia and there are energy raters trying to promote it in other states. Obviously we are heavily dependent on a star rating, so I do not think it will make too much traction, but it is there and that is the issue.

51:23Maybe we could invite somebody on as a guest who does do it. I am trying, and I am not getting anywhere. That is the issue. I am willing to pay for somebody to come in and tell us what they do, but you are not going to get it. Push comes to shove, I will share our NatHERS files. I do not care, I am happy for anybody to look at them. But no one is going to share their reference building files.

51:58Is there a reason it is not audited? There is no governing body for it. Anyone can do an elemental Deemed-to-Satisfy report and hand it to you, and if you think it is okay it gets passed. It is the same here. And any energy rater doing it — their professional indemnity insurance is not covering them, so the liability would fall on the certifier or the building surveyor for accepting it.

53:23The history: in 2019 it moved from NatHERS software to requiring internationally recognised simulation software, which NatHERS is not, and you could not use NatHERS software to do one. Before that they were using NatHERS software and doing it as a performance solution, which is how they got around it. With NCC 2022 and the new specification it was meant to be near impossible to comply with — which is why the pathway was going to stop working compared with NatHERS. And yet here we are again.

54:44I would like to see evidence the other way, but I am still waiting. If nobody can audit it, nobody can look at the file, nobody can look at the data — how are we to know otherwise? Based on the preponderance of evidence from previous years we can assume it is not accurate. I think that is fair to say.

55:22I do not do it, but there has been a lot of work I have lost to it. I am surprised, but obviously they managed to deliver a solution to the client that was more cost effective than it would have been under NatHERS.

55:53So to your question, Sean, about how you can be sure we are doing the right thing — we are insured, we are audited, and you get a certificate which gives all that information. You are probably in a more comfortable position that an accredited assessor is doing the right thing.

56:04If I gave you an elemental report that was just a summary sheet saying this is the insulation in the walls and this is the glass, would that be enough, or would you want the breakdown — the wall characteristics, the glazing calculator, the lighting calculator?

56:36It is arguable how they get presented. The majority I see now are NatHERS reports, so I do not see a huge amount of elemental. Obviously it is preferable to see assumptions and wall types, and nominating for this wall type this insulation is needed. But it is open to interpretation how far we are required to go. You would definitely be asking for the glazing calculator and the lighting calculator. Absolutely — they are spreadsheets, they are easy to provide.

57:57What about JV3? That is effectively the same as a reference building for a house. What would you want to see? Any verification is still a performance solution, and any performance solution now needs a performance-based design brief to start with. You are outlining the scope, the performance requirements you are looking at, and how you are assessing it — whether comparison to Deemed-to-Satisfy, a verification method, or expert judgement. You have to get key stakeholders' acknowledgement at that stage, so nobody is jumping the gun. It is also a point where a building surveyor who is not comfortable can say slow down, I am not accepting this, or say we are comfortable but you need to cover these things. Following that acknowledgement they prepare the performance solution, which then also needs to be approved by the building surveyor. There are a few steps, and we do not accept any performance solution blindly — we are not allowed to, and we must review and approve it because we are responsible for it.

1:00:49You get some fairly poor performance solutions where you look at it and think you are missing a lot of key things, and you need to show why this part is suitable. They are prepared by different people with different qualifications, experience and understanding of what a performance solution is.

1:03:00The big difference with JV3 is that it is not comparable in the same way to a NatHERS assessment as a reference building result is. Where we can see a reference building result producing three or four stars — but you would not know until you do the comparison. There is no direct comparison with a JV3 that lets you calculate a megajoule load. The way you would have to analyse a JV3 is the same way you would have to analyse a reference building report, but you do not get the transparency with a reference building that you do with a JV3.

1:03:39And remembering it has to be the equivalent of elemental Deemed-to-Satisfy, or seven stars, first and foremost. That is the issue, because it simply is not. The reason it is often done is that you cannot get it to comply conveniently with the other tools. So you are looking to get out of that box and take a different approach — but if you have a three metre high ceiling in Victoria, they are hard to comply with under elemental. So how are you going to do that and then get it into verification? I would be asking a building surveyor: have you seen the elemental data demonstrating it complied in the first place?

1:04:28Are you aware of the tables in Part 13 where, if there is a cross in it, it simply cannot be done? So that methodology cannot be used, which would rule out the pathway anyway.

1:04:44It is good to hear you are not seeing them. That is a positive. They have not made their way into Victoria, at least for NCC 2022 — especially given you do custom homes more than volume work, where you would expect to see more of it.

1:05:12You probably would. We do a lot of architectural and higher end work, which often leads to more glazing. But it is not an issue I have had to address any time recently. Off the top of my head the last one I saw was seven or eight years ago, maybe longer, and part of that was a change of use from a warehouse to a dwelling with other layers involved. A lot of the architects we work with are conscientious about getting designs to comply, and work with energy raters and other consultants early. We are even finding we are given jobs a lot earlier than we used to, because they want to make sure there are no major issues they have missed. There are so many extra layers now that most parties are involved earlier than they traditionally would have been.

1:06:38Thanks so much for joining us, Sean. It has been enlightening to hear your points of view. Thanks for having me. That wraps up this episode of The Rating Room. Thanks for joining myself, Matthew, Andrew and Sean tonight as we uncovered another corner of the NatHERS world. Your thoughts, comments and questions are important to us, so leave a message on the NatHERS Assessor Network Facebook page or leave a comment below. Until next time, keep rating.