You can’t build ten versions of the same house, live in them for ten years, and then pick the best one.

We’re sitting down with thermal modelling specialist Cameron Munro to talk about why “model early and model often” should be a non-negotiable part of pre-construction, whether you’re chasing Passive House or just trying to build a home that actually feels good to live in.

We explain what modelling is really for (direction, not perfection), how to run “what if” scenarios across glazing, insulation, shading, and floor build-ups, and why the best decisions come from cost-benefit thinking instead of intuition. We also get into the real-world gap between models and lived performance, the risk of not updating models as drawings change, and why overheating is the mistake that bites hardest when you skip the final iteration.

If you want fewer ugly conversations later, this is the episode.

CHAPTER MARKERS

00:00 Introduction

02:08 Modelling As A “What If” Tool

06:31 Where To Spend Your Effort (Heat Loss Breakdown)

09:04 Under-Slab vs Over-Slab: Thermal Bridges And Payback

13:34 Pro Clima Detail Library Shoutout

15:17 “You Don’t Need Triple Glazing In Melbourne” (Context Matters)

17:00 Overheating Risk And Why Passive House Classic Is Safer

18:07 Shading: External Beats Internal

24:24 When To Bring A Modeller In (Concept Stage)

33:25 Why You Must Update The Model As Drawings Change

35:37 Treat Modelling Like Engineering

37:30 Builder Liability And Using A Modeller To Reduce Guesswork

45:14 Keep It Simple: Standard Details And Practical Wins

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Connect with Hamish:

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Connect with Matt:

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Website: www.carlandconstructions.com/

We are, uh, coming from, uh, the Pro Clima Built to Last studio, which is actually

Kye's- Office … office and boardroom.

Um, so we've recorded a few here recently, so thank you to the guys at Wilderness

Build Co. Um, we're continuing our conversation around pre-construction.

Yeah.

And it's probably no secret that Matt and I choose to build of a higher standard

than most other builders, and part of our process is to model early and model…

What, what, what's, what's your little saying?

Model early and model often.

Model early and model often.

So we have the modeling king, Cameron Munro.

Calvin Klein

model.

The Calvin, Calvin Klein.

The Calvin Klein.

We have the Calvin Klein of thermal modeling.

There you go.

We can get AI to for this episode to put Cal- Cameron- Yes

on a Calvin Klein model walking down the catwalk.

Oh.

Um,

we already did that, didn't we?

That's right.

Six pack.

Uh-huh.

Um, so I want you to take your Passive House hat off today,

though, with modeling- Yeah … and not just think about PHPP.

It's be

agnostic around the

modeling.

Yeah.

Yeah.

I think it's the whole idea is to encourage- people, I think sometimes,

I don't know, do they get scared off by Passive House modeling?

And then I think then they get your m- your report and they're

like, "Ah, this is easy."

Well, I think people just get, just on that, people get

scared about Passive House.

The amount of times that I get phone calls, go, "Oh, you know what? We

love the idea of Passive House, but, you know, we just, we just don't

know if we can afford it, or we don't know if we should go that far."

And I'm, I mean, it's a whole other- Yeah … podcast.

So let's m- let's just be code or, or level of finish performance

agnostic, modeling agnostic, and just talk about why modeling's important-

Mm

… regardless of what you're building.

Okay.

So I, I think there's two ways to think about this to start with.

Number one is you can't build 10 versions of the same building, live in them for

10 years, work out which one is best and say, "That's the one I wanna go with."

Okay, well that's the end of the podcast.

Thanks, Cam.

So modeling is a waste of time.

And, and, and so given that you can't build those 10 buildings, live in

them, and work out which one was the best, you've gotta have another way of

doing it, and that's what modeling is.

And I think the way I always try to bang on about modeling is it's a what if.

What if I do this?

What if I do that?

And it tries to provide a balanced quantitative, so numerical basis, to

establish the difference between option A, option B, option C, through to Z. And

when you say option A, it could be like double glazing or triple

glazing, or is that, that's what you mean by option A, option B?

And I

think it'd be cheaper to model things 10 ti- 10 times than

actually build a house 10

times.

Yeah, of course.

Yeah.

And,

and it's almost impossible with a real build building to actually evaluate

how much energy, and, you know, we should say at the outset the particular

sort of modeling we're talking about here is thermal modeling- Yep, yep

of building.

How energy efficient is it?

How comfortable ultimately does it become?

Uh, y- you've got a, it's a v- a very challenging thing to build a building

and measure how much energy it consumes.

That's not as trivial as it may at first appear.

Have you ever done that?

Like, so you've obviously run that many PHPPs.

Have you ever got, like, lives data, put it back in and compared it to the model?

Or what-

Yeah, so I've tried to do that with my place.

Yeah.

Um, so just to jump into that for a second.

Obviously you're trying to benchmark the heating and cooling

energy required that was modeled-

Yeah

… with the heating and cooling energy of the real observed building.

Now, problem number one is the climate file you've used in the

thermal model doesn't necessarily accord with the last 12 months.

Yeah.

You know, was it a hot year, cold year, or et cetera?

Uh, the temperature set points that you've used for your heating

and cooling system may differ.

So, you know, in NatHERS have got different requirements in different rooms

for the minimum and maximum temperatures.

PHPP has its limits as well.

And so you might operate outside of that.

Like from our particular family, we don't particularly like it cold, so

we'll definitely keep to that sort of Passive House 20 degree minimum.

Yeah.

But we allow it to get up to 26, 27 inside in the summer.

Really?

We don't mind that, you know.

Yeah.

Everybody's different, but the modeling doesn't predict that.

And if you allow that cooling or that temperature inside to go up to 26

or 27 degrees, your cooling energy required can drop precipitously,

30 or 40% over what you might have modeled in the thermal modeling if

you set the limit at 25 degrees.

So, the only way you can sort of cleanly understand the differences between your

double and triple glazing, R6 insulation in the ceiling, R8, whatever it may be,

is to try and have a clean data set, which is essentially a thermal model of saying,

"I'm just gonna change this parameter- Yeah … and assess what it's gonna do."

And so, I think a key thing to remember, all models are,

are wrong, some are useful.

And the idea is here that it's gonna predict an outcome, but that's

just a prediction, and it could vary significantly, plus or minus

30% or more on that, depending on the climate and how the- Is,

is that, so is that, is that like the tolerance they say

within the documentation?

Well,

I, I just made- Oh, okay … a number up, but a- as a, as a guide, you know, you

shouldn't be overly prescriptive and says, "My thermal model, NatHERS, EnergyPlus,

PHPP," whatever it is, "said the heating demand for this building is gonna be 15.6

kilowatt hours per square meter per annum.

Uh-oh, I'm at 15.58," you know, is wrong.

Yeah.

Clearly, clearly that's within the tolerance.

You know, a much larger tolerance is, is practically what you're gonna get.

What matters is the directionality.

Am I directionally correct?

So, if my options that I'm trying to evaluate are triple glazing versus

double glazing and increasing my ceiling insulation from R6 to R7 and changing the

HRV from this cheaper unit with lower heat recovery to that one with more, which,

which one has the greatest impact on the thermal performance of my building?

If it's, if it's option, is option A greater than option

B greater than option C?

It doesn't necessarily matter that option A is precisely 25.64% better

than option B. You just need to know that it's roughly 20% to 30% better

So we're looking for bigger ga- the best gains we can find against a pr- project.

So is that what you're saying?

Yeah.

So if we were to have an order on list, do we start with windows?

Would that be, to me, make the most sense?

Well, I, I'm gonna give you the usual, "It depends." Be- because- I'll miss this.

Where's your pro- So

can we, can we actually mark down how many times we get, "It depends", in

this episode?

No, no, no.

Well, you haven't defined the problem adequately, Matt.

Like, like, you know- Yeah, we get our orientation, yeah … where

is, where, where is the building?

How much glazing is it?

What climate are we?

Okay.

Any number of factors.

But, but this is where the model points you in the direction.

So for this particular building, I've run the thermal model.

I've established from that, that 40% of my heat loss in the winter

is coming from the windows.

Okay.

Right.

That tells me straight off the bat that the windows are something I'm probably

gonna have to put a lot of effort and money into to improve the performance-

Well, 40% … of this building.

40%

of your effort goes into it.

Well, well, yeah, and, and everything else might be smaller, 'cause there's

probably 10 things, and so 40% is a larger chunk, and your next one might

be floor slab at 20%, and so on down.

Yeah,

like if it's, that's something at 1%, are you gonna have the conversation about it?

It, it… And that's exactly the point, right?

It's directionality.

Yeah.

Like, tell me where I should put, put all my effort.

So then the other thing- I mean, where, so where should you put your effort?

No, no.

I think the other thing to also think about as well is it, it depends

on the, the- Oh, that's twice.

the thermal, um, performance goals of the project.

If the client's going for passive house and that's an absolute must-have,

then everything becomes relevant.

Well, do we look at this wrong?

Are we, we say c- like we've said, this comfort is a criteria of things.

Is thermal, the word thermal modeling the wrong modeling

term that we should be using?

I like it because it defines exactly what you're doing.

Yeah,

yeah, I know, but like, com- like you could have a thermally efficient building,

but it might not have great air quality.

Well, that, that's a broader discussion.

Uh, y- but yes, that's true.

Uh-

Or it might be noisy or it might have smells like-

Mm.

Like, uh, y-

I think, I think we're com- I think we're, we're think we're mixing a

couple of different things here.

I know, I know, but like that's why I say it's ther- like it is thermal

modeling for energy efficiency.

Mm. A- a- and I suppose, you know, as building designers, take that term

in a broader sense from builders, architects, building designers, you

know, thermal engineers, whatever.

As people influencing the design of buildings, we've got to consider it as

a system and all of those parts come into this, but I think this conversation

specifically is about that building.

Yeah.

Definitely.

Yeah, but like we had that conversation with Jesse Clark, and to be devil's

advocate, he was like, "Why is energy efficiency in the code?

Shouldn't health and safety be in the code? And should it be, should

it be a health and safety modeling?"

Oh, look, I think that's a

whole other conversation.

I know,

I know, but

I'm just- But

yeah.

Yeah.

Uh- Yeah … to me, I find that a very circular discussion- Yeah … and you

end up with the same answer- Yeah.

Mm … which is you need a thermal model of your building.

Yeah.

Yeah.

I don't think anyone disputes that that's what- And it depends Yeah.

Yeah.

It depends.

Yeah.

Yeah, I mean, like, like what I love about, and just to sort of zone in on

a very specific example, I know we, we called you up two days ago and said we've

got 38 screw piles and we're, we're trying to work out whether or not we go under

slab insulation or over slab insulation.

Yeah.

We believe that under slab insulation's gonna be a more cost-effective solution

for the client, 'cause then we'll just lay timber over the top of the slab.

If you then go and put battens down, XPS down or batts down and then put

tim- Chipboard … w- chipboard and then timber on top of that, there's

different- there's much more layers and much more cost to the project.

What we wanted to know was- is 38 thermal bridges underneath

that, or punching through the XPS.

What impact does that have on thermal performance?

And I think you came back and it says 1.1 kilowatt hours or something.

Mm. Now, well, it doesn't really matter what numbers.

But- It's like 8%

of your heating

demand for a passive house

but, but it was, but it was small.

But this is not going for certification.

Yeah.

And one of the dis- things that Cam suggested was, well, we could

increase the size of the XPS another 10 centimeters or something.

10 mil.

10 mil, sorry.

10 mil.

It's not 10 centimeters, 10 mil.

And I'm like, "Well, that's probably over the s- the, the size

of that slab, about four grand."

And is that value to my clients?

Probably not.

They're not going for certification.

How long is it gonna take th- for them to pay back that four grand?

So it's off.

So I guess the point- Yeah … I'm trying to make is that why you should

model is to make these decisions.

Yeah, uh, absolutely.

So I think this is where the…

It's about a cost-benefit analysis.

Yep.

So you guys as builders have a grasp of the cost side of the equation.

Yep.

Okay?

But it's, but there's the other part of it is what's the benefit.

Yep.

So you can tell a client the triple glazing is gonna cost them an extra

10 grand on a job, or increasing the under slab insulation from fif- 50 to 60

mil is gonna cost an extra four grand.

But you don't have a grasp of what the impact on the, on the thermal

performance of the building is going to be with either of those.

Yep.

And nor do I, if I just look at the plans.

The only way that I or you or anyone else can really establish with any

degree of confidence, or at least a sufficient level of confidence,

is to run the thermal model.

Yep.

Put it in the thermal model and do the what if.

What if I dou- triple glaze it?

What if I increase the under slab insulation to 60 mil?

And then you've got a, you've al- almost got a, sort of a fraction.

So you've got a numerator and den- denominator.

You've got the cost.

So you can work out the, the dollars per unit benefit.

Mm. Yeah.

You know, the dollars per kilowatt.

And so you're looking for the least cost way of improving the

performance of your building.

And for a particular building, it might be the triple glazing is the solution.

For another one, it might be the under slab insulation.

Another one, going to 140 wall studs.

Yep.

Any number of, of-

And that's the beauty about it, right?

'Cause you, 'cause everything's kind of done iteratively.

You can test the 140 studs versus the 90 studs.

The R8 versus the R6.

You know, you can test the triple glaze versus the double glaze.

Are we gonna put, uh, shading on these windows, or aren't we

gonna put shading on windows?

And

which windows do you shade?

Exactly.

So on your conversation with, and I might word vomit this out a little

bit, you have the floor and you look at it from a, uh… I don't know

how, what I'm gonna be asking here.

But for example, f- a floor is the only surface we touch.

Like, and comfort perspective, how do you measure the comfort of, like,

making sure that your slab is warmer- Mm

so when you're walking on it, like, do you know what I mean?

Do, uh, do, I, I don't know if

I'm way- Well, this is actually one of the things that you initially said.

You know, um- it's probably gonna perform thermally better if we over-insulate.

Yeah.

But then we actually don't get the benefit of the thermal mass inside.

And I'm like, see all of these things- Mm … we can actually find, I'm not gonna

say we can find the answers to it, but we have a good understanding of the impacts

that these different decisions have.

A-

a- and the model is only part of the problem.

And so to Matt's point about, you know, the floor is the only surface

in a building you continually touch.

Yeah.

And so in the winter, if your feet are cold, you tend to be cold-

Yeah … irrespective of the, of the indoor air temperature.

That comfort factor is important.

But it's not really directly captured in the thermal model.

Mm.

And so this is where the interpretation is required.

And so if I run a model for a particular building, and I find that the cost of

increasing that floor insulation is equivalent to the cost of increasing

the ceiling insulation to achieve a particular, you know, one kilowatt hour

improvement in my heating demand, for example, then I would suggest to the

client we do the floor insulation- Yeah

because you're touching the floor.

Hey,

Mattie, I've been talking to a few people recently, and they're like,

"You know what? You've been building with Pro- Proclima for years. Like,

how do we get to where you are?"

So we all started at level zero at one point, and we got there.

But one of the things that Proclima have on their website is they have a library

of so many details, from wall to roof to subfloor to window assemblies, for

multiple different windows, on how to use their product and install it correctly,

and is one of the, the best resources you can find online to learn how to do this.

And if you're an architect and you're not sure how to draw something, they've

probably got the answer already.

And I think about, you know, 2018, 2019, when we've, we, we

first started getting into this.

We had to trawl through all kinds of different document-

We had to make it

up.

We, well, we had to make it up.

It's all there for

you.

Yeah.

The answers are free now.

And social media's great.

There's so many awesome videos and content out there, but the ultimate

source of truth is the Proclima website.

They have every single detail that you can imagine.

And you know what?

If they don't have it, you can email them and they'll help you solve it.

Damn right.

So use Proclima, proclima.com.au, if you need to reach out to them

How about airtightness?

'Cause you're not touching it, but, like, it- there's two

components to the airtightness.

It's the sound thing, it's one of the best things for sound,

but also no one likes draughts.

But we ha- we kind of don't have a way to quantify it.

No, a- and a lot of these things we don't have a way to quantify.

So I think, you know, the modeling is important becau- within the specific

confines of what it's there to do.

Mm. But you can't just take that as a black book and say, "Right,

the answer is X," because there is a bigger context here, including,

first and foremost at the moment, of course, the cost of construction.

Mm.

And, and so, you know, Hamish's point before, how far do you want to go?

And I think this is the other thing that sort of bugs me sometimes, is when

you hear the statements like, you know, to pick on one, "You don't need triple

glazing in Melbourne." Well, where, where… what's the basis for that claim?

Yeah.

A, a particular project, you know, you know, with a particular

orientation and glazing ratio, dou- double glazing might w- you know,

well achieve Passive House standard.

And I've, you know, done projects where we've got Passive House certification

in Melbourne with double glazing.

I've got

two.

And-

Yeah

… it's absolutely doable.

But for another project where you've got a vast expanse of south-facing

gla- glazing, it might not be.

But- Or, or your, or your brother's house, which faced a train line

and that's a different factor again.

Yeah.

But I think the key part to that is what are you trying to achieve as a client?

You know, do you want the Passive House standard?

And if you do, that sets us, you know, a very well, you know, clearly articulated-

Yeah … s- set of performance criteria which you must achieve.

We know what the goalposts are.

Yeah.

Or you might be saying, "Look, I'm not so fussed about that. I just

want something high performance." You know, that famous phrase-

… haven't got any definition for.

I've defined it multiple times.

You've got a 12, 12-point guide.

It's, it's Pass- it's Passive House cer- certification.

Right, okay.

So you're still hitting the, the numbers.

Yeah, you, you ha- or you've gotta be, I would say, within the low

energy for… low energy range.

Yeah.

My, my, my… Hold on with the conversation.

Yeah, I reckon the Th- I'm gonna say two things.

I'm sorry to interrupt for a second.

I think there's a greater risk for an inexperienced builder to say

they're building a high-performance home if they're saying, "Well,

let's build to PH low energy."

Because PH low energy sort of opens- Yes … the parameters up a little bit more.

And if it's a retrofit, like that's what I mean.

Yeah, but also- That's why I say that … also, like I know, and

probably we all know here, that the, what's the biggest issue here?

It's overheating in summer.

And if all of a sudden we are delivering an on-paper PH low energy home, there's

a real chance that some of those rooms are gonna overheat in summer

and be really uncomfortable, and if the house is not managed right, it's,

you're gonna get a lot of callbacks.

That, to me, is the risk for an inexperienced builder.

PH- Yeah … Passive House Classic's the, in my opinion, the safest route if

you wanna have a very predictable home.

But this is where really understa- I, I'm rambling on here, but- That's all

right, though … this is really in- this is where really understanding

the model and the modeling and the different ways that you can explore

the different outputs of the model becomes so valuable in pre-construction.

Because you can start testing things- Mm … before you've built it.

Y-

yeah,

I- Stress test it, and also put another fucking AC in there, and

if you think the glass is gonna overheat, put a, put a blind on it.

' Cause external shading, I think, is, on most west and north-faced

windows, is just a safe bet.

And

east.

If you're not, if you're not going…

Yeah.

And east.

Yeah, for the morning.

Yeah.

Depending on how big that window is, though.

Yeah.

But I th- I think that, um, like going back to your thing on double,

we don't need triple-glazed wining- windows, you also don't need slab

insulation in some areas in Australia.

Mm.

So like, again, it's-

Just context

is key

e- exactly.

Yeah.

And it's like depending on where you are and it also comes down to it, like again,

to go outside the thermal, uh, modeling.

It's also comfort.

Sound on a triple-glazed window is gonna be a lot better than you are

gonna be with double-glazed, so if you're under a flight path, yeah, you

might want to think of those things.

You do need to just, we're diverging a little, but, uh, do do need to be

a little bit ca- careful with, um, arguing that triple glazing give you a

better acoustic response than double?

Because it- Right … that's not necessarily true.

I,

I know, yeah.

There's a, there's- Yeah … it's only, it's only slightly more,

but there are acoustic glazing.

'Cause people talk Logic House, they've got a decibel chart you can follow.

A-

and you know, you go for the laminated sort of glass- Yes … and there's

the deeper cavities and stuff.

But you can do that with double glazing, too.

You

probably do better single glazing with some, if you had a

proper acoustic glass, if you-

Po- possibly, yeah.

Yeah.

But, you know, uh, yeah.

Uh, I- This started a confusing

conversation

for the- We're going off tangent … for

the listeners, all of it.

Yeah.

Um, but to- It could be

triple, double or single glazed.

Or, or quadruple like this guy that we know that dirty Skylar

out of a triple glass window.

But, but-

Take one guess who that is.

Um, but just to come back to the subject of this conversation, I think

it's, there's so many parameters you can play with in your building-

Yeah … to achieve some arbitrary performance standard that you're after.

And, and you just have no way of intuitively knowing which

is the best way to play it.

And when I see drawings come across my desk often, the architect or

someone has already marked up, you know, 100 mil of XPS insulation

under the slab or some- Yeah

detail.

They've called for something.

And it's like, well, where have they come up with that from?

And, you know, it's an intuitive guess, and it might well

be a very reasonable guess.

I'm not critical of that.

But quite often, when I see that detail and, you know, in the Melbourne

sort of Victorian climates I work with, often that's excessive even to

hit the passive house standard- Mm.

Let alone some lesser standard.

75. You can sometimes go at 50.

And in other cases, you might need that- You need, yeah … 400

or you might need more.

Yeah.

Uh, the only way of establishing whether that is the most cost-effective way to

proceed is to build a model with it-

Mm

… test a bunch of scenarios, and then flip it over to the builder and say, "Hey,

can you just give us a- an idea about the cost of this versus the cost of that?"

And then you do that cost benefit analysis.

How many dollars per unit heating, cooling benefit do I get from this?

And you prioritise them.

Yep.

And you say, "Right, we're gonna pick these off from top to

bottom." That's our number one.

Within that broader thing of, to Matt's point of there's also benefits

from this airtightness component of dust and mo- bugs and whatever,

and acoustics and all the other things that we're trying to achieve.

And the-- I think most people are now designing with a 140 stud, I'd

say is a general, a generalized.

I haven't seen a 90 mil plan for

Oh, I mean, I think we're- Yes … we're, we're in this beautiful

little bubble I'd bubble.

But like, I think- Beautiful little bubble … even within that hers, to get across the

line for seven stars now, if you don't get your orientation right, 140 is an easy

joist.

Actually, do you know what who'd be… And, you know, Sarah, if you're listening

to this, we'll, would love to get you on.

Like, Sarah does argue differently to that.

Like, she's r- achieving really great results.

I know it on her, um, show-

She also designs with the right orientation.

Yeah.

Remember that.

It's very true.

Yeah, true.

Yeah, no.

Like she's not- So this is Sarah from Cooy, you know

Yeah.

She's not- Knows her stuff.

Yeah

… she's not putting all south face windows and- … going north.

I, I look, I think from Sanctum Home's point of view, we're typically gonna

frame with a 140 stud, but you know, if you're listening and think, you know,

and you build this building with a 90 mil stud, it's not terrible, and you,

then you're not getting a, a piece of shit home, 'cause you need context.

We need to understand what the rest

of the- And if, and if you're building in Sydney, uh, you- Exactly.

Yeah … you can build a Passivhaus standard with 90 mil.

Yeah.

But also you could probably go install a R2 batt- an R2 wall.

If you were to give a volume builder a 140 mil wall, probably get more insulation out

of an R2 than an R4 they would install.

Because the installers, they, going back to why we like

Passivhaus, is the verification of- Yeah … it is installed as per-

Yeah

… like the… And that's the problem.

The- Yeah … and that's probably the biggest i- problem

I have with the NatHERS model.

It's never verified or checked.

It's just a tick box before you get to site.

A- a- and this is true, of course, of all thermal models.

Yeah.

We're assuming that insulation has been installed- Yeah … perfectly.

Yeah.

Yeah.

And it's- And no building has ever had the insulation installed perfectly.

Yeah.

Even our buildings, like there are, like, there, you, you would find inefficiencies.

But, and, and, and I think that's probably…

I don't wanna go down that whole verification road, but I think

that's the biggest thing that you would see a big difference of uptake

in the way we build if we included that as some form of checklist.

Oh, great.

Or a stat- even just a simple stat deck that you installed it

as per guide or something like

that.

You do have to have… You do.

You, you, you've gotta sign it.

You absolutely have to sign it.

You're saying, have you built to- Yeah, yeah … the energy-

No, it's have you installed the, the right, this insulation,

is what they'll word it as.

Yeah.

Yeah.

But, so, so typically the things that we will look at in that pre-construction,

like the floor build up, like we have a rough idea that you're

gonna need something in the floor.

It's probably more the site- What I look at first is, like, what matches the site?

Is it a slab or is it subfloor?

Mm-hmm.

Like, that's probably the first thing that I'll look at rather than anything, um,

and then make the decision based on that.

And if we're doing a subfloor, I'll use just the joist size for the insulation.

We'll base our joist size off what insulation we think we need.

So if it's a 140 mil, if we need R4, we'll put a 140 joist.

Typically, we're just using a 190 joist so we can get less bearers and less

footings, and then we can then use an R5, and we get pretty good insulation.

That's been my rough rule of,

um- Just a quick one, um, on, on that, uh, and I guess when someone like Cam

should get involved in the process.

'Cause you, you were talking before about, you know, seeing 100 mil under the slab.

And, like, I see that and I go, "Oh, is this house going for certification?" Yeah.

Because that feels like a certified detail.

At what point should you get involved from, from a, from

a modeling point of view?

So I, I would argue that the modeling is-

Early on.

Yep

And, and following through from that concept design stage.

Mm. Yep.

So you've got your schematic or concept design up.

Yep.

Uh, and you're starting to work out and maybe having those initial

discussions with the builder of, you know, "Is this gonna be on slab or on

suspended timber?" You know, "What's our broad construction methodology?"

Run that first model.

Mm.

You know?

Yeah.

And again, to your earlier point, this is completely agnostic.

It's could be PHPP, it could be NatHERS.

You can run that initial model and get a feel for where the lay of

the land is with this geometry.

Yeah.

And so from my point of view, I don't try and play with the geometry.

I think that's up to the client and the architect to work that out.

Yeah.

I'm just gonna play within the confines of what you've got here, and I might

point out to you, "Look, you're aware that you've got this really chro- crazy

form factor with bits going everywhere and all the south-facing glass.

So we're gonna have to work harder- Mm

and it's gonna cost you more money.

But hey, if that's what you want, fine.

I'll work within that." And then it's to have that conversation with the

architect, client, builder to say, "Well, how are we gonna do this floor?

What are our options?

What are the constraints in which I c- have to work?" Because there are a million

ways that I can tackle the build-up of this geometry that you've given me.

Yeah.

Go whack

100 mil PIR board and you've probably solved your problem.

I c- I could do a million different things, and so I'm just trying

to work… I don't want to test a million different options.

Yeah.

I wanna… You know, and I certainly don't wanna waste my time or everybody else's

time testing options which are not viable.

Mm.

Because there's something about the ground that means you

can't do some particular th- I,

I think the walls is probably the easiest one to work with.

Well, e- even

that- The surface, surface area.

Yeah, perhaps.

A- and we've got our, you know, Aussie build st- Yeah … stud

frame, so is it 90, 140?

I mean, you know, to your point before about 90 mil frame, I've got some Passive

House under construction and complete in Victoria with a to 90 mil frame.

All right.

But, but they have that 45 services batten internally, which is insulated.

Yep.

So in effect, you're get-

And external insulation, or no?

No.

So in effect, you're getting close to your R4 that you get out of a 140

wall.

Yeah.

Interesting, 'cause I've worked- It's pretty remarkable … on most my jobs

I've had to, we've had to add the service cavity in to get it over the line.

Yeah, but I mean, th- uh, I reckon because you're building where you're building,

there's a lot of other site constraints about solar gains- That, that's,

again, it's the design and architecture … and all that kind of stuff.

So, yeah.

So again, uh, classic Cameron Munro term, it depends on so

many other factors and variables.

'Cause that house on a different site might get Passive House like that.

Yeah.

Or it might not have the benefit of being shaded by the house next door.

That's just… That's g- I think the easy low-hanging fruit is shading.

Like, that's something that just should be… And that's probably not a regret

of mine, because I probably didn't need it, but I wish I actually put

it on two or three of those windows.

Well, yeah, I think that's a- So, so for blinds- Yeah … like, uh, the, the

best solution for shading is invariably external, like zipped screen blinds-

Yeah … that drop down, because we can obviously fully retract them in

the winter, so we can get all that- Yeah … lovely winter sun in, and

fully extend them in the summer down.

Uh-

Do internal blinds do anything?

A little bit, but not much.

Okay.

A- and it depends on the, how, how much gla- what the glass is.

Will they

do more in summer or more in winter?

Will they, will they, will they-

Oh, you meant for winter, uh, re- Retention, yeah … retention.

Well, okay, so diff- different thing.

So, so the external zip screen blind I'm talking about- Yeah, yeah

for anyone who doesn't know, you know, it's just like a shade cloth

type of- Yeah … material that lets a little bit of dappled light through

so you can see someone coming through

the window.

They're a bit sexier than shade cloth.

Yeah, I, I, like, I don't reckon you even… It doesn't drop the

light quality at all, almost.

Like- Well, but you-

… they're close to- So you can see someone- Yeah, yeah … coming through it, but

you c- you don't, they're not clear.

Yeah.

They're not transparent.

Uh-

But you've, you've, you've actually got different choices of different

transparencies.

Oh, I reckon the ones I've seen, that I've seen, like, it, it just

looks like it's, I don't know, 6:00 PM a bit, sun's gone down a bit.

That's it.

Y- yeah.

Yeah.

And, and to Hamish's point- Yeah … that you can get them with

different levels- Yeah … of opacity.

Yeah.

So, and, and that's, again, something you can test in the model.

Yeah.

Right?

Mm. So you set up the model, and then you put different, uh, levels

of opacity in to work out what you wanna do in thermally- Yeah

and what's gonna work for your client.

'Cause if your client is expecting that from October through to, uh,

March the blind's gonna be down, we don't some- want something

that makes that room into a cave.

Yeah.

Mm.

And so you probably go for a, a more open, uh, weave.

Um, so those external blinds are f- terrific in the summer.

Then to the point about winter, then you're really talking about,

you know, the, the classic thick pelmets and thick- Mm … curtains

that reduce that heat transfer out.

But once you've got very high performance glazing- Sure … the benefit of that

starts dropping in a proportional sense.

Yeah, okay.

So if you've got single glazing and you can't currently afford to rip

those out and do something better than that, then yes, thick, you know,

curtains will, will help at the margin.

But you're fighting against it because that single glazing

is so dreadful to start with.

Once you've gone for high performance double or triple glazing, then-

Assuming they're also airtight too, or close to airtight windows.

Well,

it,

it's all hel- it all

helps.

Yeah, I know, I know.

It all helps.

Yeah, I just wanna make that clear because, yeah.

Yeah.

A lot, a lot of windows can be pretty tight.

I would be more and more worried about sliding doors.

You know, there's al- there's also the psychological- Yeah, French ones … like

I live in a pretty shitty performing house, and there's a psychological, um,

warmth impact that I get from closing the windows at nighttime, 'cause I

know it's fucking freezing outside.

It's like sh- And I'm, and I might have a fire on inside.

Um…

How do you model that in?

Uh, not all, not all of us can live in a passive house- No … or almost passive

house.

It's, it's so, so, it's actually… I don't know if it's relevant,

but, like, I've never found winter so easy to get through, ever.

Mm. Like, mentally.

Like, I don't feel like I'm… it's an uphill battle every single day.

C-

can I talk this for a second?

So I've worked, the last, last two, two weeks, um- I've woken up with

a headache and a really dry mouth

Maybe you shouldn't have turned on the fire the night before

Well, maybe there's that.

Um, but I'm like, oh, that's right, 'cause all the fucking kids are sleeping

in my bedroom, and the CO2 levels must just be absolutely through the roof.

Yeah.

'Cause as soon as I get out, it's fine.

Go get one of the IKEA models that… Weren't you on Cam's presentation

on the air filter last week?

Yeah.

I, I'd be actually be careful with that CO2 thing.

Uh, there are some studies out there that suggest that sleep quality is

affected by CO2 concentrations, but they're not the most powerful high

quality studies that you'll find, and there's, uh, other studies that suggest

there's no real meaningful impact.

Right.

A- and the most obvious analogy to compare CO2 concentrations is your submarine.

Yep.

Oh, yeah.

Because they've got CO2 scrubbers to manage CO2, but they're still operating

generally 2,000 parts or above.

Really?

Geez.

And, you know- No dice … a submarine, you'd expect you want those

occupants to be pretty on the ball.

And aren't, aren't the, aren't the levels of oxygen in submarines lower,

'cause, 'cause it reduces, like, fire spread and stuff like that?

Possibly.

I mean, it's 20% in the atmosphere.

Wasn't

there a submarine expert on the-

There was.

Yeah

… on, on the pod call- Oh, really?

Yeah, yeah.

Mm-hmm.

The Soviet Union back in the day.

Love to have a conversation off air on that one.

Hey, I'm about to go on a journey with systems, and I'm working

with James from Biztech Guru, who, he was a guest on our podcast.

He was, and I've actually done a lot of work with James in the past, and

it has transformed my business from just being this classic clusterfuck

of a building company to a systems orientated focused business.

And

what is, from understanding, it's all focused on builders, and-

Yep … we're going to be doing a live webinar with him coming up-

Yep … as part of this, and it's gonna be a big introduction to systems

and how it can improve your business.

And you know the beauty about it?

It is gonna be absolutely free.

Yeah.

So keep an eye out for the dates.

Uh, this is gonna be a really incredibly valuable workshop to not miss out on.

Yeah.

So either shoot us a DM, um, check the show notes, but we'll put a link

below here to show you how to sign up.

So- Cheers … make sure you sign up

I, I've never found winter so easy.

Like, I- usually the go-to is I'm going to Europe or I'm getting to

up north just for some nice weather.

Not felt like I needed it at all- Yeah … this, uh, this winter.

Happy days.

And it's, um… And I, and I've, and I've, I've said this before, I

really struggle to talk about it now that why we don't do more of this

model early, model often for everyone because, like, it does change you.

It does change a lot.

It changes your life to a huge, uh… Like, I c- I actually really struggle

to talk about it now, um, because you… I don't think we understand

what comfort is until you've had it.

Mm. And that's one thing that I've really started to understand.

I

don't feel sorry for you, though.

No, no, no.

No, but, but, but it makes me think that, like, I get actually probably more

agitated like, "Why aren't we doing this?"

Oh,

totally.

Like, it probably makes me more like, "Why?"

Yep, no, I

totally- Fr- Like, just the high level of frustration.

So I, um… So you talked about modeling early at concept stage,

but I also wanna talk about the importance of then m- seeing the model

through as the design progresses.

And

that- 'Cause I have, you know, I am the sum of all the times I've fucked up, and,

uh, we did have a project recently where we didn't get the last iteration of the

drawings modeled, and that was by the client's choice, and now we have some

overheating that we've gotta deal with.

So, you know, I hope everybody learns from my mistakes on this, that if

you start with modeling, also carry it through and finish with modeling.

What do you mean by- And this is probably doing- What do you mean by overheating?

Like, what's actually happening?

Uh, there was a few changes to the floor plan upstairs which didn't

capture a change in window size, so now we've got an overheating issue.

Can't you just run your cooler more?

It's a bit more complicated than that.

Yeah,

okay.

But we- we're, we're, we're looking at a few things.

Yeah.

Yeah.

Uh-

So, so when you make that model, you're making a bunch of assumptions based

on the drawings that you have at the time, and probably some inferences

of things which are not stated.

And then hopefully you're documenting those in the report which you're

giving to the builder, client, architect, and they're noting

those and carrying them forward.

Yeah.

Now, invariably, being busy people, we miss some of those caveats or that

bit where you said, "I've assumed you're gonna do this under the slab",

and you go and do something slightly different and it's all, you know.

That clearly changes the assumptions in the model, and therefore the

model results are wrong or different to what has actually been built.

Uh, so yes, I think to, to a large extent, if you are going to, to do

the model early, then you should… You know, the advantage is that you're

probably, your geometry at that point is as 90-something-plus percent fixed.

You're gonna move a few windows, change some window dimensions

perhaps, but that's about it.

Just update the models you go through- Mm. .. the design process, so when

you get to the construction drawing set, you've got some feel for it.

And that's, you know, certainly how I try to work is, builder or someone'll call

up and say, "Hey, we've this, this job.

We're just gonna make that window 500 ml wider.

What's that doing?" And it's, you know, I can't speak to other model

systems 'cause I'm not familiar with them, but certainly in the PHPP, I

just bring it up, change that, run the s- shading on it, pull it across.

You know, within five minutes you can give a guide as to what the impact of

that's going, that change is going to be.

I think we need to look at our energy rating models as the

same we do with our engineering.

Like, we don't just call up, we just don't get a, a beam and change it from a 140

ml- Really good, good point … down to a 90 ml stud, like, beam and assume it's

all gonna be fine, because the building surveyor's gonna check us up on it.

The same should be with modeling.

You just can't go, "We're gonna do this and change this from a window",

and assume it's gonna be fine.

Mm. And I think we've gotta look at it that way, 'cause

there's really no difference.

It's just a different type of engineering.

A- a- and I, I think a lot of the ther- all the thermal details that would go

into the m- the modeling, where NatHERS, PHPP, whatever, ultimately need to end

up on the construction drawing set.

Yep.

So that is the responsibility ultimately of the architect, building

designer- Mm-hmm … draftsperson-

Yep

… to incorporate what the energy modeler has said.

You know, the, the beam size that the structural engineer has called up.

All of that's gotta be on that set.

That's the one s- set of truth- Source

of truth,

yep

which you builders on site are then referring to and going, "Right, it's

calling for 140 studs at 600 centers with R4 insulation. Right, let's go do that."

Yep.

Yep.

No, T, I, I, I Yeah, I totally agree.

I think- And,

and I think if we're talking about, um, why this is important in

pre-construction, and if you think about why we s- why we spend so long in

pre-construction, all about relationship buildings, because, you know, clients

are getting us all on as the experts.

And if we're saying it's performing a certain way, we want def-

definitely wanna make sure that it's performing a certain way.

And the only way to do that is to update the model, check the

model- Yeah … confirm the model.

Know your limitations of what you do.

I know building, I don't know the modeling.

Like, I'm not a data brain in the sense of- Yeah

like I can't just go, "Oh, that now equates to this." And also-

This, this is probably putting my, um, like business hat on.

It's like you kind of also as the builder wanna push the liability to

someone like Cam that can actually model it and give you the answer

rather than go, "Oh, hypothetically this is what I think might work."

Like, even though I know on a general thumb if I do 140 mil is with a

service cavity and triple glazed windows and some, I know, an R 2.5

75 mil XPS slab, I know I'm gonna be pretty close to Passive House.

Mm. But am I?

Yeah.

I, you've got no way of knowing.

And I know I'm

gonna be- Like I've got no way of

knowing

I've got n- I, I know it's gonna be very, very close.

It will make, might need some tweaks, but do I know?

I, I, um, from my point of view, every time I see a set of plans, I look at

them, I go, "Mm, looks like that one's good, got a good chance. That we won't

have to work hard on that one." Yeah.

"That one over there looks a bit harder."

And I keep tripping myself up.

Do you write down like- Keep getting it wrong … a guess and

then see what it comes in at?

Do you have like a- I've, uh- … a game and see?

I haven't done that.

But if I did do it, I'd have a really poor

accuracy, really poor.

Do you know what you do?

You're probably, "I'm getting in really accurate."

And then one time you don't do it, it'll be-

That's really important to sit in just for a second.

Like, s- for someone who actually does it every single day, multiple times

a day, and you can't even look at something and predict it, like, it just

goes to show, I guess the listeners, how important it is just to actually

go through the process of modeling.

You can't- Well, can you predict the lintel size over the window?

Uh, f- sometimes, yeah.

And I'd probably over-engineer it, though.

The exa- yeah, that's what I mean.

Like-

Well, I'll double

two, two

240s.

A- and that's what I see a lot of too, is like, to the point about, oh, you

know, especially for those of us doing the higher performance stuff, you know,

the criticism, oh, you're just adding so much cost to the build and there's,

you know, possibly some truth to that.

But, um, I'm seeing over-engineered insulation levels.

Mm. You know, to our example of the- Yeah … 100 mil XPS.

I'm like, not sure if that's required and, you know, uh, my presumption

might end up being true when I run the model, and then I get to go

back to the client with good news.

"Hey, look, I reckon you can, we can hit Passive House, which

you've told me you want, with only 50 mil of under slab insulation.

And, you know, Joe over here, your builder, says we're gonna be able

to cut four grand out of the job for that." E- everyone's happy.

Yeah.

No one complains about that.

No one complains about that.

But- But they'll complain if you'd go the opposite way around and you

think he needs- Uh, un- un- uh, uh … 50 mil and you needed 75.

And unfortunately, I get those jobs too, where you have to deliver bad news.

But- And I think it's also important on site, one thing, and what Passive

House has taught me, is like, sometimes what is drawn and what you're thinking,

you can have all the conversations, it doesn't work, especially in a retrofit.

So it's always important to call up your CAM, who's done the mon-

go, "Okay, this is what we've got.

This has changed.

What does it change?

Is there an issue that you would see?" And he can quickly maybe plug it in and

go, "No, you're fine." Or like, "Oh, now we've gotta stop and think about this."

Mm. Not… And most of the time it's fine, 'cause you've kind of made an allowance.

But again, once you're on site, that conversation kinda doesn't stop.

No, it, it's, should be colla- you know, we always talk about

collaboration between all parties.

Mm. And of course that we, you know- Mm … always should be talking about that.

Throughout the build, "I'm gonna change this, you know-" Give your thermal

engineer a call and say, "Hey, run this through the model for us quickly.

Tell us where that's l- landing, please." Uh, and, um Something else, so

You don't need traded pine batons, that's what you're gonna say

No, I wasn't gonna say that.

Timber can get wet.

Yeah.

Now we've got him.

Oh, Sam's getting some.

It, it depends.

I, I rec- You know what, I reckon just in, in summary- Yeah … um, I think

the model early, model often is just something that absolutely is a no-brainer.

It should be part of every pre-construction process.

It just should be like engineering.

I know, I know it's your analogy, I'm gonna steal it, is when a

architect has a, on a res code or a town planning guide they've gotta

follow, just follow the modeling.

Yep.

And the other thing I was gonna say is that I, I like to s-

sell it to my clients, that it's, uh, it's an optimization

tool for performance and cost.

Yeah, 100%.

That's right.

' Cause then it's finding out what are… And it's probably gonna lead into

the MEGT Mindful Moment that I've-

Go for

it … that I've written down here.

Keep

ploughing it through.

Um, it's so important in pre-construction, from the very beginning, to understand

the client's motivations for their project from a performance level.

Or what their expectations are.

Well, I guess expectations, s- same kind of thing.

What, what are the parameters that we're working within?

Because if, I know as a business, I know you've probably adopted it

as well, we, we like to try and operate within that PHilo energy.

'Cause I think that there's a lot of breadth as you go up

into that next stage to- Mm

to make a few changes to really optimize the building.

So, you know, if I was gonna give any young, and this is probably, uh, maybe

not so much to apprentices, but to young builders out there, is to really decide

with everybody, the client, designer, thermal modeler, what the parameters

are that they're working within.

Yeah,

okay.

And set that from the beginning.

Is it passive house or is it high performance?

So we talked passive house a lot here, and, uh, because it's very definitive.

If you're in, like, what is a good star we should be rate- like, kidding.

So we should, like the code is minimum seven.

Should we be trying to hit eight, nine, 10?

Well, I, I, I think you're back to the client, aren't you?

Like, if the client just wants the cheapest house they can build,

then you just do seven stars, depending on your state, because

that's the minimum compliance.

If they want really high performance, you push it to some other level.

I

think seven star can still be comfortable, though.

Well, uh, well it, it, again, it comes down, it goes back to how is it installed.

Well- Like, I could probably ins- build a six star house better than

most

people do a seven star.

A, a lot,

a lot of certified passive houses in Victoria are mid seven stars.

Yeah.

Seven point five star.

I've had certified buildings like that have been below eight.

Most of mine are kind of 8 to 8.3.

So we did mine and we changed, I think I was 8.8 and we shifted the air tightness

thing and I'm at nine point something.

Yeah, right.

So you're like, yeah, it like, which isn't taken into account, which

is kind of interesting, so, um-

Just, just to jump back to, I remember now what I was trying to say before.

Yeah, treated pine batten's not needed.

No, I wasn't gonna say that.

Uh, I don't… Like, when I do get those calls from builder, architect,

whatever, "What should I do?" You know?

"Should I do…" I, I can't really answer that question because- There's

a whole bunch of things you could do.

So, uh- Yeah … let's say you've defined your target, and let's say for

argument's sake, it is Passive House.

There are a million ways we can get there.

Yeah.

It is a choose-your-own-adventure.

Yeah.

And so I feel like it's the job of someone like me to give

you a menu, a bunch of options-

Yeah … and say- Your form, your f- your PDF that you send is so

good on the way that does that … I

was actually about to touch on form.

I'm glad you brought it up.

Like, I love how you go, "Here's the baseline, and then here's a few things

that we could do." And you even talk to, "Well, you know, if we do X, Y,

and Zed, you're probably not gonna get a benefit if you go do that." Yeah.

"It's probably not worth the investment." Yeah.

But then you also put a caveat around saying, "Check with your builder."

Yeah.

Uh, because it's not just what I say.

Yep.

And it's not just what the architect says, it's not just what the builder says.

You know?

The cl- it's the client's house or building.

Yeah.

You have a lot of say in this, too, and we've all got to agree, you know,

'cause there's competing interests here.

Uh, and, and so here's where you're at now.

Here's Passive House as your, you know, as, uh, our targets say.

Here's a bunch of ways we can get there.

And in, and I'll do that initial analysis with maybe 10 or 15 different things,

and you'll come back and say, "No, that's impossible. That's impossible."

I didn't know that was impossible.

You tell me.

You

could just go, go put 100, you could go, go put 200 mil of XPS

in a slab and go build me a 190 mil wall and that, we're good.

We got there.

But it's like, is that actually reasonable?

Yeah, yeah.

That's right.

We're try- we're trying to balance all those difficult things we do in

builds, and it's going to be iterative.

So I'll throw out there as a starting point, here's 12 things, and you're

gonna tell me three of those are impossible, those three are like,

those six, maybe we've got to tinker them in this way, and what about

these extra two I've thought of?

And I'll go, "Yeah, great. Right, let's test those in the model."

Yeah.

And then we go back and forth, back and forth, until we've found

the right combination that is going to work for that project.

I, I know my go-to on nearly every project, and again, it

depends, is cavity insulation.

It's like my go-to for the quickest, cheapest, easiest wins, 'cause I

would rather do that, um, than some of the other things, 'cause it's

like, then it's like seven other things and a death by a thousand cuts.

Mm. Uh, I think that's exactly right.

I mean, you g- builders obviously carry so much liability in all these builds.

You've got to have a lot of say- Yeah … in, uh, how a lot of the detailing

works, and so that's got to be fed back up the chain when we have that to and

fro about what about this- That's good

what about that?

Especially our standardized details of window and, uh, wall build-ups and stuff.

If you start to change that, it's where it gets confusing for

communication on site and team.

So just keep, for me, it's keep s- shit simple and work around the simple

shit that you can then just kind of-

I'm, I'm gonna-

Substitute

I'm gonna wrap this up by saying, um, like with everything in preconstruction-

Okay … and we, we throw this word around a lot, like it's a collaborative effort

from your modeling, from your design, for your engineering- Every one … to

the costing like, and I hope that, you know, th- this little series that we're

doing at preconstruction is actually demonstrating how everyone's inputs into

preconstruction is important, but you can't just look at it in isolation either.

No.

You need to look at it all together, so.

Totally.

Thanks for coming on again, Cam.

Thank

you, Cameron.

No worries.

Thank you.