So we're back with Dr.

Evil here.

In Dr.

Evil's little lair, we've got

Cameron Munroe back, or Dr.

Cameron.

How are you?

G'day guys, I'm all right, thank you.

Now, if anyone is not quite sure

what we're talking about, , Dr.

Evil aka Cameron Munro, triggered a few

people last podcast with his comments

about banning fireplaces and, boy, there

was some people out there that very

strongly disagreed with you, Cameron.

I guess that's the internet, hey Hamish.

all I would say to those that are

perhaps a little bit more moderate

here is to look at the evidence.

we do have the advantage of the internet,

we've got lots of academic papers,

those of us in Australia would be aware

that we've got, some great air quality

researchers that have produced some

really fascinating stuff on the internet.

the impact of particulate

matter on health.

there's a lot out there of evidence,

What's ironic is probably these people

who cracked the chutes at you would

be the same people that would complain

if their neighbour was burning a wood

fire in their backyard and their kids

were breathing it in.

there's that other thing, isn't it?

You know, both those of us here in

Australia and North America and Europe

over the last couple of years have been

exposed to a lot of bushfire smoke.

During their, our respective summers

and we all recognize that wasn't

good, but somehow apparently the, the

smoke from wood fires is, is different

It's only not good when

it doesn't suit them.

Now, before we get too far down

the tangent here, this is all

kind of related to the topic that

we're going to talk about today.

And we're going to be talking about air

tightness in our buildings and proper

ventilation or appropriate ventilation.

Cameron, why firstly would we

make our buildings airtight?

So I would say there are

two reasons for that.

One is energy.

Obviously if you're gonna spend

money uh, heating or cooling and

air mass within your building.

The last thing you want is for that

to rapidly escape because you are

going to have to continually heat

in our heating dominated climates

in southern Australia, that air

that's coming back into the building.

And the second reason is building

durability, which we talked a bit

about last time I was on this idea

that we've got to stop water vapour

that's floating around in the air.

Moving across our assemblies, through

our walls and our roof and potentially

condensing within those spaces.

And so air tightness deals

with both of those aspects.

So where will air get

in through a building?

Where will you typically see this happen?

in Australian buildings, it's

just about everywhere, isn't it?

Really, we're, we're infamously air leaky

in our standard building construction.

Windows and doors are probably

the first obvious place to look.

We all have probably experienced A

windy day and our windows rattling.

Well, that rattling is obviously an

indication of something happening and

you feel that draft coming in around

your windows but skirting boards,

all of our penetrations, plumbing

penetrations, the back of the air

conditioning unit is famous the return

on adducted AC system yeah, Australian

buildings are horrendously leaky.

is air dangerous the sense to durability?

Like, how can air affect the structure?

It's only air.

Yeah, so air itself is obviously fairly

innocuous, and there's occupants of

buildings, and we'll come to this in a

moment when we talk about ventilation,

but air is rather important to us

as human beings, so we need air.

The problem with air and

building durability is that

air carries that water vapour.

And it comes back to this idea of air

transport, so the movement of air across

our assemblies carries this mass of water

vapor within it, and if we allow that

mass of air to cool, then the air can

no longer hold all of that water vapor,

and so it will condense, and when it

condenses, that's what Obviously leads

to mold and rot within our buildings.

So we've got to stop that air

moving throughout construction.

a house needs to breathe

though, doesn't it?

Like, don't we need our house to breathe,

to bring in air from the outside?

That's

Isn't that a famous statement?

How do we irritate those of us in

the high performance building spaces

to say that houses need to breathe?

So houses are inanimate objects.

They don't need to breathe.

They don't need to respirate

to absorb oxygen and then

breathe out carbon dioxide.

But animals need to do that,

and we're a kind of animal.

So we, we need oxygen, of course.

So it's humans.

Occupants of building,

buildings need to breathe.

But buildings themselves, of

course, they don't need to breathe.

So.

Very weird sort of a, a statement.

Where did it come from?

Because at the end of the day,

you think about it, that air comes

through and where you said it

comes through, that's skirting,

and there's carpet in the corner.

So now, that carpet is your

filter, or the insulation.

You can see when you demolish

your house and you see all the

insulation bats are completely black.

Like, that's your filter.

That's what's filtering

the air into your house.

Yeah, I wonder whether part of

the origin of this houses need to

breathe thing is really about vapor

management and this idea that I know

I'm showering and I'm cooking the pasta

and everything and I've got to get

that water vapor out of my building.

I've got to get fresh air in a good idea

that I have a really air leaky building.

Yeah.

Cool.

But to rely on poor building practice,

and that's what we're doing here, is

to say, let's build a garbage building

that is going to cost us buckets to

keep warm in the winter and cool in the

summer, and to deal with this ventilation

part of the problem, providing fresh

air and getting out the stale air

through poor building practice is a very

Odd way of dealing with the problem.

So what you've just been describing

before Cameron with all those leaks

in all those spaces that you've been

talking about before describes most

houses across Australia, I would

argue, or a good, a large proportion

of them, even new homes, by the way.

Obviously myself and Matt and

even yourself have have built

your own high performance home

and you've made that airtight.

But as a human being, as you

said before, we need to breathe.

If I'm making a building airtight,

Won't I not have any oxygen to

breathe inside that building?

Yeah.

It's always the thing, isn't it?

Especially for those of us that

work in the really high performance

end of building, passive house.

The other thing that often you hear

about as well, if your ventilation

system stops working, are you going

to suffocate in your building?

And the answer of course

is absolutely not.

Any building, no matter how airtight is

never that airtight, you know, we can't

be 100 percent airtight in our buildings.

But what, what really does

come into play here is this

separate issue of ventilation.

So really, I think these things have

been poorly brought together and

they just confuse the whole problem.

These questions of airtightness

and ventilation, I think we need to

really separate them and think of them

as two completely distinct issues.

There are relationships there,

but really they are independent.

They're a bit like

peas and

carrots.

kind of maybe that uh, with the

ventilation side, though, what

we're trying to do here is to

create a healthy environment.

We need that supply of fresh air.

And if we ask, you know, any

occupant in a building, do you

want fresh air in a building?

Of course, the answer is

always and a resounding yes.

So how do we ensure that we've

had, have good indoor air quality?

Don't burn your fireplace inside.

So the first wet thing we do

is we deal with source control.

So in source control is making sure

we don't create those problematic

pollutants in the first place.

So we try and avoid things

like wood fires indoors.

We try and avoid things like gas

combustion in our buildings, and that

includes things like gas cooktops.

Uh, We avoid incense inside.

Any number of things to our buildings

usually involving combustion create.

lots of pollutants.

And so if you could don't create

those pollutants in the first

place, then you are doing that.

That's the first step to try

and improve our air quality.

And then in our hierarchy of

controls, we then come to say, well,

there are always going to be some.

pollutants generated in our buildings

and we're going to cook even if we're

cooking on an induction cooktop.

When we cook, it's a burning process.

We're creating pollutants.

So how do we extract those from

the building in a healthy way?

Well, we're in cooking, obviously a range

hood and externally venting range hood

is obviously one good strategy there.

But even beside from that,

you're still generating

pollutants within the building.

We're still breathing in oxygen and

carbon dioxide and all of that needs to

be to be extracted from the building.

So how do we create an indoor

environment where we've got this

constant regulated supply of fresh air

that's sufficient to meet our needs as

human beings, our ability, our need to

breathe, but also our health and our

comfort, because we know if we're in

a building and it feels, might feel

stuffy or stale, then what we'll need

to do usually is open our windows.

There's a huge problem

though with opening windows.

Firstly, obviously,

there's the energy impact.

So in the middle of winter in southern

Australia, you're not really keen to

open your window in the middle of winter,

because you know it's going to get cold.

Conversely, of course, in the middle

of summer, or if you live in a really

humid climate, you're going to get

all the humidity and the heat in.

Then the bigger problem, though, I would

suggest with opening windows, is you

have no regulation, you have no control.

How far do you have to open that window?

How many windows do you have

to open to give you sufficient

airflow, fresh air supply, to

keep that indoor air quality good?

And if you go to bed thinking, well,

it's a bit stuffy in here, I'll open the

window in the bedroom in the evening and

it's windy when you go to sleep, then

you may well be getting adequate airflow.

But what happens at midnight

when the wind dies down?

Then you don't get as

much air in anymore.

And so there's just no real control,

there's no oversight on how much fresh

air you're getting into your building.

But it was two degrees last night,

and as I said, I think I said this

to Hamish on the phone yesterday.

What idiot is opening their windows

and doors to get natural ventilation

when it's two degrees outside?

That just defeats the purpose

of running your heating and

cooling system, doesn't it?

It does, of course, but as home

occupants, what choice do we have?

You're sort of doomed if you do,

doomed if you don't, aren't you?

You know, I know it's all stuffy

and yucky feeling in here, I need to

get some fresh air into my building,

but on the other hand, I'm going

to freeze if I do open that window.

So that's on the that you're

building airtight though.

And Australian homes

typically aren't airtight.

no, I don't think that's true, see,

I think there's a misnomer here.

about saying, well, we don't need

to worry about ventilating our

homes because we build such crappy

buildings anyway, that I'm getting

enough fresh air into my building.

Now, it's true that if it's blowing

a gale outside and there's a big

temperature difference indoor

versus outdoors, you'll get this

convective driven air movement.

And so you'll get a very

high rate of air exchange.

So it will be fresh inside.

But of course, you've got

the energy and therefore the

temperature problem to deal with.

Again, a lot of the time it's not windy.

And so what level of air exchange

are you getting when it's the middle

of winter, as it has been here in

Melbourne the last few days, where

it's also been very, very still?

Then how much fresh air are you

really getting into your building?

You've got no idea.

And what we tend to find when you

actually measure the air quality

within our buildings, is that

actually a lot of the time, even these

really super duper leaky buildings,

have very poor air quality indoors

because we're not getting the level

of air, air movement that we need.

we're not even getting what we

want to in terms of air quality.

Is, is it true to also assume, Cam,

that , in a leaky building, that

some rooms are actually ventilating

or breathing better than others?

so you can measure this.

So as I keep trying to bang on to

anybody who's sort of on the fence about

many of these issues, is measure it.

Measure it in your building.

It's great now that we can get sensors

really cheaply, you know, a few hundred

bucks, sometimes under a hundred bucks,

depending on what it is you're after.

And you can actually monitor the

performance of your particular

home, office, whatever it may be,

and see, see where it's sitting.

and what we find though, is that in

homes, it's the bedrooms, Because

we're spending eight odd hours in

that bedroom, particularly the master

bed, say, where there might be two

occupants in a relatively confined space,

the door may or may not be opened

into the rest of the house.

And even in your relatively new built

Australian home where theoretically

there's been a modest level of attention

applied to air tightness, or in your

1920s, 1910s weather board, you know,

a really, really leaky building, you're

still getting very high levels of carbon

dioxide building up in those master

bedrooms overnight, because you've got

a high density of people in a confined

space over a long period of time.

So, I just want to go

back to airtightness.

How do we define it?

Like, what do we define airtightness as?

So there's a couple of ways

of measuring air tightness.

You can measure it as as an ACH, an

air change rate, which is the volume

of air within that building that

is moved out across the building,

Or in through the building an hour.

So, for example, a typical residential

home in Australia might be somewhere in

the have 5 to 800 cubic meters of air

within that house and so you measure

air change rate is how many of that say

500 cubic meters of air moves in and out

across the building envelope per hour.

And a typical new build house in

Australia at 50 pascals of pressure

difference, which is not a huge pressure

difference in to out, will usually

move around 10 to 15 volumes of air.

So that 5 to 800 cubic meters

of air times 15 will move across

that building envelope every hour.

And that's enormous.

so every hour, all that, heating

and cooling that you've paid for

within that building envelope

is getting sucked out all those

tiny cracks, even in a new build.

So then you're constantly chasing

your tail in trying to keep a nice

balanced, even temperature inside

or a comfortable temperature inside.

That's

15 times per hour, by the way.

so you're feeling the draft by

the window as that air rattles.

You've got the heater running

full blast because that air coming

in is cold and you're heating it

up and then it's escaping out on

the other side of the building.

Now we're going to come back to this

whole air quality thing because you would

say from an air quality perspective, in

theory, assuming the outdoor air is a

good air quality, which we're lucky in

Australia that most of us are, do have

good air quality, it's a good thing.

Yeah, my air quality in my building

in when it's windy outside is great.

The problem is that when it's

calm, I'm not getting that

level of air infiltration.

And so even though that building,

when it's windy, so roughly, you know,

wind of about 30km an hour, which is

not excessively windy, you might get,

say, 10 air changes in that building.

But if it's calm, you might get 0.

5 air changes or less.

So suddenly you've diminished

massively the amount of fresh air

you're getting into the building.

And so now your air

quality is diminished.

And then the other part of

this, of course, is that air

coming in, where's it coming in?

It's coming around the windows,

maybe it's not a big deal.

It's coming in through the wall

somewhere, running through your,

your wall, past all the rat poo and

anything else in the wall, and then

infiltrating into the building.

Is that still fresh air?

Is that clean air?

And then you see when you demolish

a building, you see all that,

like, thick layer of soot and dust.

Like, it is.

It's an inch thick too.

So that is being transported

through the house too, and

that's what you're breathing in.

Is that right?

That's right.

And again, we come back to control.

You've got no way of knowing it might

be fine in a particular building.

In another one, it might be really

problematic and over time it will change.

And so by relying on this natural air

movement across our building envelope,

it's costing us a lot in terms of energy.

It's leading to the deterioration of our

buildings through that moisture buildup,

and it's no, no way guaranteeing us.

a good level of indoor air quality.

So how do we solve it then?

Like, how do we stop that happening?

let's assume it's a new house

then, to make life easier.

Because going down an existing house

is a bit different to a new house.

so there's a couple of

things that we need to do.

Obviously one is air tightness.

So we need to actually

have a strategy in mind.

So this comes back to the initial

design stages of building an air

tightness strategy that says, this is

my layer that is going to act as my

primary air tightness, and I'm going

to ensure the continuity of that layer.

So we're getting, you know, better

in the Australian building industry.

It's sort of thinking a bit about this,

but it all falls apart when we have

all our trades come in and punching

holes through our plasterboard and not

sealing up those penetrations or at

junctions, you know, tricky junctions

where we might have sort of the mid

floor between ground and first floor.

How do we continue the air

tightness through that junction,

those sorts of problems.

So there's that air tightness

side, but then the other

side is the ventilation side.

And in a way I think that's the

more interesting bit and the bit

that most Australians haven't

got their heads around yet.

This idea that maybe I need something

other than just relying on my windows.

to get good air quality.

And that's where we come to things

like mechanical ventilation.

So what's mechanical

ventilation first too?

Can we just define that while we've got

air tightness and mechanical ventilation?

Sorry to jump in Hamish.

Because I know we said we don't put them

together, I just think it's important

that while we're on this we quickly

define the difference between air

tightness and now mechanical ventilation.

Yeah.

So mechanical ventilation is a

way of providing a controlled,

continuous, transparent amount

of air into our buildings.

and so what we're trying to do

here is to say, look, I can't

control the outdoor conditions.

The wind's going to come up and down.

The temperatures are going to change.

I don't necessarily want to

open my windows given particular

climatic conditions at the time.

So mechanical ventilation says I'm going

to set all that aside, but I'm going to

ensure that I provide, you know, 30 cubic

meters an hour of fresh filtered air to

all the living spaces , in this house,

each and every living space in this

house, and continuously provide that.

regardless, irrespective of what

happens the outdoor environment.

And that's where we just create

a sense of stability, because

we need fresh air, regardless of

whether it's windy or not outside.

We can't say, well, this hour was

really nice and fresh air, and

the next hour was terrible air.

And on average, it was all

right, doesn't work like that.

We need to try and create a

continuous supply of fresh air.

And that's what mechanical ventilation

is doing for our buildings.

I'm sitting here just like listening

to Cameron and like forgetting that

I actually have to sit here and not

start asking him some questions.

Cause I always get like spellbound with.

How simply you explain like to

some people might maybe a tricky

topic and I really enjoy, you know,

listening to how you can put it into

terms that most people understand.

So I'm pretty excited that there are

going to be a lot of our listeners

that are going to be listening to this

and maybe if they are on the fence

can start to see what we consider air

tightness and consider, ventilation,

but just talking about the two together.

And I know I've actually asked Joel

Seager in this question before, but

at what air change could we be sitting

there smiling, if anyone can see Cameron

here right now, it's quite amusing.

Um, what should, what, what air change

should we actually be considering?

ventilation, as something that we

should be putting into our homes.

Yeah.

So this is, uh, this

drives me up the wall.

if you read on the interwebs,

you'll easily find reference

to say, you don't need to worry

about mechanical ventilation.

If you're got above five ACH.

And most Australian dwellings

are well above 5 ACH.

So, let's just assume for a

moment that the internet is right.

So, 5 ACH is the threshold.

Now, if you put sensors in your building,

and we often would monitor carbon dioxide

as a proxy for air quality, and we can

talk about whether CO2 is the relative

indicator or not, but if you put a CO2

sensor in your master bedroom at night.

And you're in a conventional home

without mechanical ventilation.

And if it's windy, that CO2 concentration

will probably stay at around a thousand

parts per million or something less.

And the rule of thumb that we use is that

a thousand is our threshold for good air

quality, bearing in mind that outdoors

we're at about 420 parts per million.

so you might be okay on a windy night.

to say that you are utterly

dependent on the outdoor environment.

And if it's not windy, Your CO2 levels

will be much, much higher, and I've

got sensors in lots of buildings,

conventional Australian buildings,

that would indicate in the master

bedroom overnight, it is very common,

particularly in the winter, when

occupants are less likely to want

to open windows, and it can often be

still overnight, we are seeing this

carbon dioxide concentrations well

over 2000 parts per million and often

approaching three to 5000 parts.

So this idea that there is some arbitrary

number, be it below which mechanical

ventilation becomes important and

above which it does not, is a bizarre.

In the first way that it's, it's an

arbitrary threshold, who's to say

it's five and not six and not four.

But more, more critically, I would

argue, every building would benefit

from mechanical ventilation because

it will guarantee the air quality.

Thank you.

Because there is no way we can guarantee

that level of fresh air supply relying

on a natural ventilation strategy.

It just does not

work.

And if you're sitting there

screaming at your pod machine

wondering, then I come back and I

say, well, monitor your building.

Actually put some sensors in

and verify whether what I'm

suggesting to you is correct.

And not just over one or two

nights, but leave it there

over a few weeks to months.

And observe how the carbon dioxide

concentrations will vary greatly

depending on where you are, in

terms of the external climate.

talk about mechanical ventilation, can

we just, you know, A, a ceiling fan

in an, an exhaust in a bathroom or a

tot is that mechanical ventilation,

a ceiling fan is not.

A ceiling fan is just a means of

moving air around within a building.

I should also put like that your air

conditioner, your split system hanging

on the wall is also not ventilation.

Like, there's a huge misunderstanding

about those boxes on the walls.

People seem to think that that

condenser, that fan on the outdoor

side of those units, is somehow

sucking air from outside to inside.

That's not what's happening.

That, that unit on the wall is just

recirculating air that's already

inside, just as a ceiling fan is doing.

So, those units are beneficial, but

they're not providing ventilation.

for ventilation, you've really got to

rely on those opening of the windows,

the cracks in the walls, and the

external environment, or far better,

a mechanical ventilation system.

So, a set of, a fan that

draws in air from outside.

Runs it across a filter and

then distributes that fresh

air to all your living spaces

and then

that'd be a

HRV or ERV essentially.

Well, I almost don't want to use the

phrase HRV or ERV at this point because

we then get on to this other problem

of heat recovery and enthalpy recovery,

which also confuses the situation.

So let's just talk about

ventilation for a moment.

the problem we're trying

to solve is air quality.

So how do we solve air quality?

We've got to provide fresh air.

How do we provide fresh air?

We have a duct and a and a a

motor with a fan that draws in a

constant supply of air from outside.

We run it across a filter, so we pick

up all of the pollens and the dust and

the course material, and then we feed

that fresh air into our living spaces.

And then in an ideal mechanical

ventilation system, it will be balanced.

So we will extract exactly

the same volume or rate of air

that we put into the building.

And that's what these HRVs that

many of us hopefully have now

heard of are usually doing.

They're balance systems.

They're providing exactly the same amount

of fresh air that they're extracting.

But you can do it other ways.

So you can have a, extract only system

like using your bathroom fans and just

relying on the leaky building provide

that makeup air or opening a window.

You can leave your bathroom fan on

24 seven you can add that's an extra

extract only ventilation system

in a conventional Australian home

that will work from an air quality

perspective because you will probably

be drawing in more than enough air.

to, , provide fresh

air into the building.

Now it doesn't work from an energy

or a comfort perspective because in

southern Australia you'll be freezing

to death all winter, but it does

work from an air quality perspective.

Couldn't I just put an air purifier

in my bedroom, or something like that?

So air purifiers, what are they doing?

So it depends on exactly what the

product is, but often they're trying

to remove a lot of the particulate

matter, some of the volatile organics,

but they're not dealing with some

of the viruses, the CO2, et cetera.

So they're not really dealing

with the stuffiness of the

air that you're going to see.

So they're dealing with

part of the problem.

So far better is to take out that air

in the first instance and get it out

of the building and provide fresh air

Is it the vapour in the

air that's the concern?

So the vapor is part of the problem here.

So again, there's a whole host of

things here going on, isn't there?

So we as humans are exfiltrating carbon

dioxide and viruses, you know, if

I've got the flu or COVID or whatever,

and other occupants in my building

are going to breathe that in again.

That's what happens.

And so ideally, we want to

get that out of the building.

We don't want to really recycle our

air because if you look at the carbon

dioxide concentration in your home,

that's really an indication of the

proportion of air that's being recycled.

If it's a high CO2 concentration, that

means you're going to be re breathing

back in air that you've already breathed

out or another occupant of your home.

Building has, has breathed out.

, so what we're trying to do here is

get that constant supply of fresh

air , to deal with air quality

and also in addition to that, and

this is a big part of ventilation

that I think is often missed is,

is deal with all that humidity.

moisture that's built up on

our skin that then evaporates.

But also from all the activities we

do in our buildings like showering and

cooking and so on that creates moisture.

And so we know that when we're showering,

we should use that exhaust fan and

that kind of works well for the 10

minutes that it's on while we're having

a shower and immediately thereafter.

But imagine when you walk out of

that shower space, the shower tiles

are still wet, the towels wet.

And so for the hours afterwards,

that water is going to evaporate.

And where is it going to go?

And in a conventional

building, you just don't know.

It's going to depend on the pressure

differences across the building.

It might well drive back into the master

bedroom, the living space, somewhere,

and then push its way through the walls.

and then condense in those walls.

Whereas if you have a mechanical

ventilation system, what you're

doing then is you're constantly

extracting air 24 7 from those,

those wet spaces like the bathroom.

So as the towel dries out, that water

vapor moves into that bathroom space

and is extracted through the mechanical

ventilation system and is taken outside.

So there's far less chance that

that's going to get into your wall

system and cause condensation.

, that's a huge.

benefit of mechanical ventilation, I

think, that is highly unappreciated.

And it's part of this strategy of

trying to avoid buildings failing due

to water management problems, is to

provide that continuous extraction.

probably, have sort of touched

on this throughout the last, you

know, 30 or 40 minutes, Ken, but.

What issues do we see if that moisture

does get into the wall assembly?

Like what effect can that have on us

as occupants and the building itself?

So as the water vapour that's floating

around that we can't see in that air

mass moves out through our wall, in

a cool dominated climate like, , like

southern Australia, it will cool.

And air that's cold can't hold as much

water vapor within it as air that's warm.

And so as the air cools, the water

vapor and the water molecules coagulate

together, they condense, and you get

water droplets forming within that wall.

And then if you've got, say, a timber

framed wall, or even a steel framed

wall with, paper faced plasterboard,

if that water then obviously gets

onto a cellulosic material, like a

material with a wood basis to it, then

that can lead to, to mould formation.

So, you get mould, And obviously

also ultimately can rot out any

of your timber frame structure.

So it really fundamentally is about

building durability as well as

occupant health, because the last

thing we want is for mold to grow our

buildings, and particularly when it's

hidden away deep within our wall.

So you might have black mold all

throughout your wall, but nothing

that you can see on the interior face.

So it might take you years to

realize what a problem you have

and you

might

be sick for that five or ten years

you might be wondering why you always

got a headache or why you always

got that cough or a bunch of other,

ways that mold illness can show

itself and it, and mold illness is a.

killer that you might not know

about for many, many years

until it's a real problem.

Yeah, absolutely, Amy.

So we've got to do everything

we reasonably can to minimize

the risks of that happening.

And now your air, your house is not air,

the air tightness is a concern and that

air is coming through all those gaps.

That's just taking those mould spores

around the house, is that right?

Is that how it's working because

you're relying on those leaks to,

to transport what we call fresh

air apparently, around the house?

Well, that, that, yeah, that, that, I

suppose the more leaky the building,

the more likely that sort of, um,

material can float around within the

building, but even in an airtight

building, if you have mold forming

on the interior of your construction,

you've probably got a problem,

uh, and you've got to deal with that.

So this comes back to a

hierarchy of controls.

thinking that you've got to

deal with your sources first.

So you've got to minimize the

chance that mold can form.

And, and mold, mold spores are all

around us.

You know, we can't avoid them,

just like we can't avoid water

vapor floating around in the air.

They're part of our nature, but

what we've got to do is try to

minimize the rate of growth of

those mold spores and not provide

an environment conducive to them.

Well,

So, I've got a question here for you.

If you had a chance to sort of

rewrite, rewrite our building

code, what would you do?

What would you change around mechanical

ventilation and air tightness?

So what are the, what are maybe

three things that you could really

implement really quickly to create

great change across industry?

I think the first thing I would

do, to be honest, and last time

you pushed on this, this we, uh,

set the internet on fire, but,

mechanical ventilation should be a

standard part of the building code.

Every building we build.

And forget about this

air tightness argument.

I think we just run down a bit of a

rabbit warren arguing about whether

mechanical ventilation only makes

sense at 5 ACH something else.

I don't care.

the basis of our building codes is

to provide a healthy environment for

occupants, which obviously it is, then

we've got to provide healthy indoor air.

And the only way we can assure a

healthy quality of indoor air is

through mechanical ventilation.

The only way.

And it doesn't matter how

airtight your building is.

That's what you need.

Now, where I think we get muddled

with this whole 5ACH or whatever your

number problem is, is that we get

confused between the role of mechanical

ventilation and heat recovery.

So, we talk about these acronyms, HRV,

MVHR, heat recovery with ventilation.

Mechanical ventilation

with heat recovery.

So, exactly the same thing,

but let's just work with the

HRV acronym for a moment.

It's the V.

It's the ventilation bit

that is why we're doing this.

The heat recovery is almost ancillary.

It's something that we said, well,

we're going to have to take some air

out and provide some fresh air in.

So why don't we just get the heat and

keep the heat as part of it as a bonus?

That's what we're doing with HRV.

We're ventilating buildings,

first and foremost.

The heat recovery bit

is very much a bonus.

It's a win.

So I don't mind, in a way, in our

building code, if we just install

mechanical ventilation and say bugger

it to the heat recovery bit of it.

Now, as it happens, the technology works

that the cost difference of going with

some level of heat recovery is quite

small, particularly compared to the

energy impact of not recovering the heat.

So we might as well do it,

but it's that ventilation role

that's first and foremost.

So we need to ensure we're

ventilating our buildings.

So that's the first thing

I would do in the building

So how about ERV then?

Is that different

depending on the climate?

Because HIV, we retain the heat.

Isn't the ERV taking out excess moisture?

Am I right?

So this gets really difficult.

let's just talk about HRV first.

So heat recovery ventilation.

where do you need that?

Can we just draw a line maybe across

Australia where that is required?

Or we

Yeah, I mean, Because the answer

to these sorts of questions

has got to be, it depends.

and so I don't like these rules of

thumb, but if you're really gonna push

it, then somewhere north of Sydney

to north of Geraldton on the west

coast is probably the line you would

draw, and you would say above that

ERV starts to possibly make sense,

below that HRV probably makes sense.

And you can find exceptions to that

rule, but if that's what you're going

to push for a simple rule of thumb,

that's what it would be.

there's so much of me that wants to

say a whole bunch of other stuff and

go down on other tangents and talk

about our home being an ecosystem, and

we shouldn't just be focusing on air

tightness, we shouldn't just be focusing

on heat recovery or ERV or ventilation,

because we really should be considering

all of it, and there's so much of me

right now that kind of wants to say,

but, but, but, but, but, Thank you.

But as far as ventilation goes, um,

if you're saying, well, let's put a

ventilation in all our homes, right?

Well, you're going to get a big part

of the population saying, well, our

building costs are astronomical as it is.

Why would I go and spend 15, 25, 000

on putting something in here that we

haven't needed for the past 30 years?

how do we drive home to people that these

systems when we're, and then again, I'm

kind of going down another tangent about

performance of thermal comfort of a home.

Like, how do we convince people

that this is a really valuable and

necessary thing in homes if we don't

then consider the thermal comfort of a

home, like try and keep that separate.

Because I know in a

passive house, it is all

encompassing and we're looking

at the building as an ecosystem.

But how do we convince more people

that ventilation is important and it is

actually worth spending that extra money?

So you can't manage

what you don't monitor.

And the problem with all of this,

of course, is that we can't see it.

We can't see the carbon dioxide.

We can't see the particulate matter.

We can't see the VOCs.

So how do we know that

there's even a problem here?

And of course, as you say, Hamish,

most of us have lived in very

ordinary buildings for decades

without any form of mechanical

ventilation and we think it's okay.

And so what I would say to those that are

listening that are maybe dubious about

the merits of things like mechanical

ventilation is to monitor your building.

Spend a couple of hundred bucks, get

a census, stick it in your house, and

see what your house is actually doing.

And that's the way we'll sort of start

to change this at a consumer level, at a

industry level, from us, you know, those

of us working in the industry as well,

to say, well, to recognize that, in fact,

this is not as good as we think it is.

that's the only way we're going to

get this working, I think, from a

ground up or bottom up perspective.

from a top down perspective,

this is where I think, you

know, this cost management thing

and the regulatory frameworks

require a cost benefit analysis.

And so you need to demonstrate

that adding 20 grand to a house

is actually going to benefit.

Now, obviously you can make a very strong

air quality argument, So that's okay.

but does come down to this question of

whether you have a balanced system that

supplies and extracts at the same time,

or you have like an extract only system.

So you can do this as we talked about,

you know, for 50 bucks, just leave your

kitchen range hood extracting and leave

your bathroom extract fan on 24 7.

Hey, you've got a mechanical

ventilation system.

So every house in a way already has this

going.

So that can

work from an air quality point.

to consider here, but, you

know, who wants to leave their

range hood running 24 seven?

Who's going to do that?

No, one's going to do that.

Particularly not an onboard

motor, you know, rattling away.

so it sounds like we need

mechanical ventilation.

really the solution here is a

dedicated mechanical ventilation

system that provides a consistent flow

of air into into your living spaces.

That is silent because if we insist

on installing something into people's

homes, that is going to cost them

a lot in electricity or worse,

probably is going to be noisy.

The first thing they do when

they move into the house is

going to be to turn it off.

and it should be balanced?

an ideal system is a balanced system.

Now, these are a bit more expensive

to be fair, but what we're trying to

do with the balance system is create

a, a consistent flow pathway from

our living spaces to our wet spaces.

So that predominant air

movement is in those directions.

So our wet spaces don't build up

all that water vapor and it floats

back into the rest of the house.

We want it just extracted straight

out of the building and a balanced

system helps you create that.

Controlled flow pathways

through the building.

And it also means you're not drawing

in air through your building envelope

in places you don't know, and you

don't understand, you know, if air

is coming in through my cladding,

through my wall, past all the rat

poo, then in through skirting boards.

I might not actually be doing as good

for my air quality as I thought I

was, whereas with a balanced system,

we're running it across a filter, so

we have that control, that oversight

on what's going on, and therefore

we have much more confidence that

we are actually doing what we

intended to do in the first place,

which is deliver fresh air into our

buildings.

um, the good news for consumers

and people that are listening that,

There are systems and solutions out

there to help solve these problems.

And I know we, the three of us could

probably sit here and talk about

ventilation and air tightness in

buildings and performance ability

to the cows come home, but I kind of

feel like it's almost best to kind

of stop it here and open up another

can of worms in another podcast.

Matt, do you have anything more

to add to today's discussion?

I'm actually just astounded how Cam

has talked so clearly and not once

has gone um or ah the whole time.

And how clearly you speak.

um,

um, thanks.

do you know what my theory is, Matt?

I reckon Cameron is probably always the

smartest person in the room, and he's

had to learn how to communicate to people

like you and I, who aren't as smart as

him, and he's probably had the last 20 or

30 years experience about how to actually

explain to them, I was fortunate enough

to be in the car with Cameron for a

couple of hours, two or three weeks ago.

And I think I even

said this to you, Matt.

and I'm hoping I'm not making you

blush here, but I got out of that car

ride thinking, Oh my God, I feel so

much smarter because I've just sat

here and I've just had the opportunity

just to fire questions at Cam.

And this is actually the reason why

we want Cameron on This podcast is a

regular guest because cam your ability

to explain these sometimes complex topics

in a way that everyone can understand

is awesome And hopefully as a result

more people are going to adopt these

changes in their building So they're

going to be having healthier and more

comfortable and energy efficient homes

I literally have one note here.

It says, I'm so much smarter for this

conversation with Cameron and this

podcast is going into my documents that

I send the client when they reach out to.

me to sort of engage and understand

more about high performance

building or passive house.

It's literally recording will go

in there because you just put it in

such a way that my younger sister

could pick it up and go, yeah, I

understand why it's important now,

but there's people that Hamish and I

were trying to get the message across.

And sometimes we get to get confused and

we may become aggressive or we're just

not, we're not clear, but you just put it

so clear.

And I know anyone that has you on

any project, the project goes so

much better because you're just so

clear at explaining what needs to

be done.

We give Cameron's business a plug then.

Passive analytics.

He's taking on more and more clients.

He's got heaps of time.

Don't have any time.

Thanks, Amy.

we've had a very interesting

internet, connection

day today.

I think myself and Matt, uh,

have had average internet, Cam.

Anyway, thanks very much, Matty.

Good.

to see you, Cam, always great to chat.