#6 - Blower Door Testing & The Future of Aussie Homes with Sean Maxwell

Jess Kismet (00:00)

Hello, and welcome to this episode of the Building Scyology Poddie My name is Jess Kismet, and I'm going to be your host. And today joining me is Sean Maxwell. Sean Maxwell is the ATTMA Scheme Manager for Australia and New Zealand. Sean has just ticked over 20 years of blower testing experience and building science experience. He's a New York ex-pat. And after moving to Australia for love, he has taken on the Australian building industry.

and is leading the charge for forward movement and adoption of air tightness testing as a way to improve our buildings, commercial and residential. Our industry is full of really passionate people and Sean is right up there as the leader of Australia's growing community of building science professionals. He is endlessly generous with his time and knowledge and shares this with designers, builders and project teams through training and tireless industry advocacy.

His biggest contributions to date include improving the air tightness regulations in the Green Star framework for the commercial space and requiring air tightness to be considered during the design phase and not just tacked on the end. And most recently, the publication of the document called the Air Infiltration of New Dwellings in Australia, published by the CSIRO. We'll talk about both of those things more during our conversation.

So now without further ado, welcome Sean to The Building Sciology Poddie

Sean Maxwell (01:20)

Hello, nice to be here.

Jess Kismet (01:22)

Thanks for joining me. So in the intro, I mentioned that you're the ATTMA Scheme Manager. Can you tell us what ATTMA stands for and what it is? Where it's sort of a bit of a backstory and how you became involved with them.

Sean Maxwell (01:36)

Sure. Well, first I gotta say, you mentioned that I moved here for love. Well, that's true, but I gotta tell you, I'm glad to talk to you, Jess, because my wife does not actually like talking about blower door testing all day long. So it's good to talk to somebody. So this is great. Thanks for having me. I really, really appreciate it.

Jess Kismet (01:54)

You know we can talk about it underwater.

Sean Maxwell (01:57)

Yes,

So, I moved to Australia from the US, so I had been doing testing for Energy Star homes when I first started and then through energy conservation programs in New York. And when I moved to Australia, I was looking for other people doing testing. And really, it was pretty, pretty lonely here. was like crickets. 2015.

Jess Kismet (02:21)

So when did you move here? What year?

Okay, so I met you not long after that. I met you in about 2018. So you hadn't been here all that long. So Sean, for the listener, Sean actually trained me and certified me for ATTMA test back in 2018. Yeah, I know when I was, I know I was writing the intro and I was like, was it seven years ago? So I look back at my photos and I was like, yeah, it really was seven years ago. It really was. Yeah. Anyway, sorry. Carry on.

Sean Maxwell (02:28)

Yeah, yeah. Right.

Yeah, was a while ago. Yeah, you were one of the early ones.

It really was that long ago. You've been at this game for a long time.

Well, so when I first moved here, it was like looking for anybody doing this. Hello? Hello? Anyone? And I was also, I really got into building codes and trying to get something into the building code in the New York state building code. And to do that, we were compiling a database of blower door tests. so,

I came here and I was looking to do the same thing, like let's build a database so we can make the argument that this is a good idea. so going around asking people in the government if we could get some money to build a database. And then as I was searching for database, on the web it came up, ATTMA had this database called ATTMA Lodgement. And so I asked, can I join you guys? And sure.

So I was the first one in the Southern hemisphere to join ATTMA and they gave us access to this database. So ATTMA is the air tightness testing and measurement association. And that's really, there are people who really, really care and are focused on air tightness testing as a discipline and as a regulatory tool. And I'd say their killer app is ATTMA lodgement their database. So the...

Thing about blower door testing is, yes, you can use a blower door as a qualitative testing tool. Like you can find leaks with it, walk around, feel with your hands where the leaks are. But edits, it's also a pretty effective quantitative test. So it lends itself actually to analysis. This data that we get, you can upload to the ATTMA Lodgement database. It scrapes the data from the test file and then spits out analysis of your results.

consistent as the data? Does it follow the laws of physics? I mean, is it realistic? It flags things that look suspicious and it's getting more and more, there's more and more levels of quality control. So that's really how I got really into it was I thought, wow, this is cool. This is going to enable us to get some regulatory change.

Jess Kismet (05:07)

I bet Barry was, Barry Cope is the scheme manager in the UK. So ATTMA actually originates from the UK, right? So you contacted Barry Cope in the UK. I bet he was stoked to hear from you.

Sean Maxwell (05:14)

Yes.

Yeah, yeah, and he was stoked to come down here and spread the gospel.

Jess Kismet (05:23)

Yeah, yeah, sure. So for those who don't know what a blower testing is door an air tightness test is, could you please give us a quick overview of what happens on a blower test day and why it's used?

Sean Maxwell (05:36)

Sure, it was simply named a blower door because it's a blower, fan in a door. So it's a temporary rig that you put up in the front door of a house, for example, and it pushes air in door sucks air out of the house and then air has to come in door flow out to replace that. And you can measure how much air you're pulling out and what the pressure is that it develops. And then you can write those numbers down. And now this test has been done around the world.

definitely around the world millions of times. And so you get a pretty good idea of how a building overall is going to behave with a blower door test. It's pretty simple. You put a fan in the door and you suck the air out and you try to see how well does it hold onto the air? How well does it keep the outside out and the inside in? It's pretty simple test. And there's a lot of things that it sort of glosses over, like doesn't tell you whether the leaks are high door low, doesn't tell you.

how much it's going to leak exactly during any particular weather. But it gives you a pretty simple way of evaluating house to house, apartment to apartment, building to building. Let's have a fair basis of comparison. So that's why it's pretty cool. Simple but effective.

Jess Kismet (06:54)

And why do we use them? What's the purpose of a blow it door test?

Sean Maxwell (06:58)

Well, it's from ATTMA's point of view and my focus really is first, it's a quality control tool. So like I said, it's a very simple way of assessing overall build quality, but that's really, it's at its most basic and its most glorious. It's a simple quality control tool. Like how well do you keep the outside out? So very simple.

Jess Kismet (07:23)

Yep. And, cause if you've got, you know, unnecessary leaks in your, in your walls and your roof, then you're losing a lot of air that you are conditioning, right? So you've got your air conditioner pumping. It's 35 degrees outside. Let's say you're in Adelaide where I am and it's a hot summer's day and you are conditioning your air. And as soon as you turn your air conditioner off, all of that conditioned air, it's going out of all of the gaps and cracks. And so that's why we want to know, we want to be able to quantify what, what

Sean Maxwell (07:47)

Sure.

Jess Kismet (07:52)

the airtightness value of any building envelope is so that we can and then discover where those leaks are so we can seal them up,

Sean Maxwell (07:59)

Yeah, and I'd say even more than quantifying. Well, like quantifying, like knowing what the number is. Basically, the basic thing is less is better. So there's no good argument for having more air leaks through your wall assemblies door your ceiling assemblies door your floor assemblies. It's not a good thing. It's not a good way to dry out your building. Not, not really. We're not saying that you should seal the house up and that you can't open your windows. Absolutely.

The cool thing about when you control the things that you can control, airflow through the building envelope, the outside of your house, you then have better control of how the air is flowing in and out. So when you open your windows, actually, you can control which way the air goes. If you have a more airtight bathroom, you can use it to suck the air out of the bathroom when you're using a shower.

Ventilation systems become more effective when you can't control what you can't contain, one, Maxim.

Jess Kismet (09:07)

Yeah, yeah. So if you've got like, I mean, I've blower door tested a ton of houses in Adelaide, like older houses, where we literally moved the dishwasher away, like it was a house that was actually being renovated, thankfully. But this we moved the dishwasher away from its its like location. And underneath the dishwasher was a hole, like I've got a photo of it, the hole is like, yay, big. And it was just a timber floor, timber subfloor. And there was just air and dust.

and bugs and who knows what else coming up into the house through this gigantic gap that no one knew was there because it was covered over by the dishwasher. It was gross.

Sean Maxwell (09:42)

Oh, it's crazy. Like it's

pretty simple argument to make to a homeowner. Look, we can seal up the paths for the bugs to come in door the rodents to come in. That's what really we're doing. It's like, it's a pretty simple thing. We say like, let's seal up the places where the bugs come in. People are like, oh yeah, please do.

Jess Kismet (09:52)

Yeah, I actually.

Yeah, I feel like that's a more compelling argument than energy efficiency. Just keep the cockroaches and the spiders out please. And the ants. Yeah, for sure. And I know there's significant misconception around building airtight because the first thing people who don't know anything about airtightness say to me is, won't we suffocate? And you mentioned before opening up windows. So of course you can open up.

Sean Maxwell (10:06)

Yeah.

Sure. Yep.

Jess Kismet (10:26)

windows and doors in an airtight home. But let's talk about the motto, the build tight, ventilate right. That's our sort of the thing that we say. What can you say about that?

Sean Maxwell (10:36)

Yeah, sure, sure. That's one of them.

Well, it's not possible to build too airtight. Think about the International Space Station. It's actually being decommissioned soon because it leaks. One of the reasons is that it leaks too much air and it's too difficult to find where this air is leaking out and they need to keep it super airtight to keep the people inside alive. Airtightness keeping people alive. Same thing with submarines. They can be underwater.

for months at a time in a completely airtight vessel. So the problem isn't that the building envelope, the submarine door the International Space Station is too tight. Yes, people need ventilation to breathe. In those cases, they need to get rid of the carbon dioxide and other pollutants so that people can stay alive. But no house is ever going to be that airtight.

I don't mean to, I like to say, you know, if you, if things are stuffy, of course you can open a window. You always can open a window. And I think people get afraid that they're going to feel stuffy door that they, house might be mouldy And often the problem with the mould that we see in Australia is not so much, is not only related to air tightness. People are building more airtight.

but it's also that they're not at the same time providing ventilation to dilute interior moisture and they're not doing other things about thermal bridging that are going to get rid of cold spots where condensation happens. we are, I should say that building more airtight does increase, one, part of the risk equation. It creates more, more risk. and so you need to do other smart things. You can't.

A house is a system. You can't alter one thing in the envelope like air tightness without paying attention to the other things like thermal bridging and vapour control. So it's a system and once you start messing with those things you need to make sure they're all balanced. So build tight and ventilate right is a simple way to put that.

Jess Kismet (12:55)

Yep, yep. And a lot of Australian homes will ventilate using their windows and doors. There's this, you know, the whole indoor outdoor lifestyle is very popular, entertaining, breezes, hearing the birds, all of that kind of thing. What are the other options for ventilating a home?

Sean Maxwell (13:12)

Well, actually, I think what you just mentioned, birds and things, fresh air, that's great. The outdoor lifestyle is great. When the weather's great, please open up your doors and windows and enjoy that breeze. But one thing I think we don't talk about enough is that air tightness lends itself to comfort in so many ways. So not just drafts. Also,

it's quieter when you can seal off the leaks from the outside, you hear less noise. One of the favorite demonstrations of this concept was Chris Nunn in his passive house, North of Sydney. He shows, well, just next door there's construction going on and people building something. opens on a video, he opened the door in here, big trucks and excavators outside. And then he closes the window and then

just totally silent. It's so cool. And if you just tell people, look, we're going to help you build a house that's more, it's quieter and you have fresh air. It's the air is clean and quiet. Think of your house as a sanctuary. And isn't that a lovely selling point? I mean, this is, this is what we're talking about. actually talked about controlling these flows of moisture, sound, drafts, cold bugs.

Get control of that and really make your house into a place that you actually like being.

Jess Kismet (14:44)

For sure. was doing a test yesterday for a soon to be certified passive house and it's on a main road and I experienced the same thing. know, shut the door to start the fan and it was just quiet. And I'm someone, I have a particular like sensitivity to, I'm like sensory about noise. It's a thing for me in particular. yeah, I just, the peace. And as you say, that word sanctuary, that

Sean Maxwell (14:56)

Yeah.

Yep.

Jess Kismet (15:13)

That's how I felt in this house. It was like, just that breath of like, just like that.

Sean Maxwell (15:21)

Yeah, it's, it

is actually think as a selling point for this to say, you know what? Wouldn't you like a good night's sleep? I would. I would.

Jess Kismet (15:29)

Yeah,

yeah. And yeah, I mean, we talk about air tightness in terms of energy efficiency and all those things that you mentioned, but acoustics is actually, insulation is not the only way to control acoustics. Airflow.

Sean Maxwell (15:43)

yeah, no actually, yeah, for sure. So Barry

Cope in UK, the director of ATTMA in the UK, his real passion in life is acoustics. So he's a lower door testing expert, but he's also an acoustics expert. So he knows how closely those are linked.

Jess Kismet (15:54)

Yeah, right.

Yeah, right. I didn't know that. Speaking of Barry, we'll just go back a few steps because we were talking about ATTMA before and we'll go slightly towards the regulations for a minute. So blow-in-or testing is not currently mandatory in Australia. Where are the places? So it's in the building code. It's in the National Construction Code 2022 as an optional way to verify the airtightness of any building.

Sean Maxwell (16:03)

Hmm.

Mm-hmm.

Jess Kismet (16:30)

So that's in the commercial code and the residential code. Where are the countries in Australia? Where are the countries in the world that blower door testing is currently mandatory? I know it is in the UK because Barry's all over that.

Sean Maxwell (16:45)

Yeah. So the UK is, they have really embraced it. It's now required that a hundred percent of buildings, including a hundred percent of apartments. If you have 500 apartment building, you're going to test 500 times. So that's, that's, that's one end of the spectrum. And another is where it's incentivised. so it's incentivised here in Australia. it's optional in the building code.

Jess Kismet (17:00)

Wow.

Sean Maxwell (17:14)

And there are programs like Green Star from the Green Building Council that incentivise their tennis testing and Passive House is a voluntary standard. So that's the other end of the spectrum. But other countries like the US, some states in the US have adopted versions of the IECC, the International Energy Conservation Code, and that has testing, but it's only an option. mean, it's not, sorry.

Some states like the state that I moved from New York, it's mandatory there and it's mandatory in Massachusetts and it's mandatory in many other states. But the US, there's 50 different states and 50 different governments. So it's a patchwork of different versions of the energy code. And they're all at some level, some stage of adoption of testing.

Jess Kismet (18:11)

Is it more like weighted towards the coldest states?

Sean Maxwell (18:15)

Not exactly. Florida is not cold at all and that has blower door testing. Lots of parts of Texas have testing as required. So not at all. mean, California testing is very common in California as well.

Jess Kismet (18:25)

Yeah. Okay.

Okay,

cool, interesting.

So yeah, going back, Barry told me a story about the UK where they literally have like, you can't get hand over unless you get a compliant blower door test. And he told me a story about literally moving vans in the driveway, but the blow-door test fails and therefore the homeowners aren't allowed to move in. They have to wait. Isn't that crazy?

Sean Maxwell (18:55)

It's crazy that they let that argument go to that length before they finally stopped people. But yeah, they're serious about it. And they're serious about it in the US as well, the states that have it. So the ultimate authority is the code official. Most US states, they don't have private inspectors like they do here in Australia. It's employed by the state. each municipality...

Jess Kismet (19:03)

No.

Sean Maxwell (19:25)

door county would have a code official that you have to show your paperwork to and they give you a certificate of occupancy. You don't get that certificate of occupancy unless you've satisfied all the requirements and blower door testing in some cases is one of them. So, yeah.

Jess Kismet (19:40)

I wonder if we'll ever see that here. It's on everyone's mind.

Sean Maxwell (19:47)

I don't know. I don't want it to be painful, because it doesn't have to be. the number one thing, like I keep saying, I want the motto of Atma in Australia and New Zealand to be, do something useful. Do something that actually makes a difference to someone's built outcome, to someone's life. We're not just trying to burn money here. We're trying to make the building actually better.

Jess Kismet (19:50)

Yeah. Yeah.

Mm-hmm.

Sean Maxwell (20:16)

A lot of buildings get zero.

objective assessment of build quality. think of all the things that we even something as serious as fire proof, um, fireproofing. So in apartments, the inspection for fireproofing is visual. You think about this is something serious, right? Like we want to make sure that the penetrations between apartments are well sealed. We've got so many examples of people complaining about, they're complaining about smells from smells and noise from their neighbours.

And when the blower door tester goes there and uses a fog machine on this apartment and they go to the next apartment where they are complaining of the smells coming from, they see smoke pouring from the walls and the light fixtures and things. why is it, what's going on there? If you look behind the cabinets in the bathroom, there's just no plasterboard back there. Like they just didn't do it because they thought, well, you're to put the cabinets there and no one's ever going to see that. we're all good. But.

like these are really, really big holes that if there were a fire in one apartment, they could really cause a problem, a real life safety issue in the next department. So the, the fire inspections, which are visual and subjective about whether something's good enough, it's not good enough for us. And we could do a lot better by doing some simple objective tests with a blower door and say, it has to be sealed at least this much. And then just draw a line.

Jess Kismet (21:45)

Absolutely,

absolutely. I've done a few commercial blower door tests where the fire doors aren't sealed, smoke coming through them and know plant rooms and things that are supposed to be sealed. They're supposed to be sealed for fire right? Plant rooms? Yeah, not at all.

Sean Maxwell (21:57)

Yeah.

Let's see again.

Jess Kismet (22:00)

The plant rooms are supposed to be sealed for fire, right? Yeah, yeah, well, I've seen many that aren't at all.

Sean Maxwell (22:03)

Absolutely, yeah.

Yep. I think so a lot of those things could be tested qualitatively and quantitatively. You could get a number on them. Yeah.

Jess Kismet (22:22)

Okay, question. Still on the regulatory stuff, NatHERS star ratings and air tightness is something else that is an up and coming development in Australia. So NatHERS is the National House Energy Rating Scheme in Australia. And that is how we get our star ratings for energy compliance. When you build a house, you get a star rating. Right now the minimum

compliance number is seven stars, it used to be six, it's just gone up to seven. And there is there's been talk for quite some time that I believe you have been pushing Sean about including air tightness as an upgrade or as a specification in a star rating. Because there, as we know, this the assumed level of air tightness in a a NatHERS model is not at all necessarily what gets built on site and no one's checking to make sure they match up.

So the energy efficiency of what goes into your model usually doesn't match what gets built. So this air tightness number is quite important. So could you give us bit of an update as to what's going on there?

Sean Maxwell (23:27)

Sure. So Department of Climate Change, Energy, Environment and Water, they're the ones that run NatHERS which is the National Home Energy Rating Scheme. They commissioned a study over the past two years that I was heavily involved in, where ATTMA members around the country, or in several states, did testing under the ATTMA scheme and submitted the data to ATTMA Lodgement so that we could analyse what is the

typical level of airtightness being delivered for new homes. So these homes had to be built within the past few years and had to, by definition, we wanted to find ones that were normal. So there were some that were sort of aiming for a passive house and wanted to be included because they wanted a free blower door test. why not - The offer was for a free blower door test. But really we declined projects like that and wanted to find

"typical" which most homes are typical. And I don't blame people for saying when they answered the questionnaire, "Was air tightness a high priority for your construction?" Most people said no. And I don't blame them. Most people are just looking for the first place that they can afford. Like what is the first house that you can afford? If you ask me, would air tightness be high on my priority list? If I could afford to buy a home? No, it wouldn't.

I can always do something like that and make that better later, but first people just want a home, please. So we're trying to really look at what's typical. And what we found is the results were a little bit better than probably the average assumption in the NatHERS model would be. So if the average in the NatHERS model would say the house should have a permeability, is air leakage per unit of surface area of that house, a permeability of eight.

cubic meters per hour per square meter. The typical result from this study we found for single story houses was around six and a half or something cubic meters per hour per square meter. And for double story houses, it was about seven or eight cubic meters per hour per square meter. So, but both of those are tighter than the average assumption in the NatHERS model. So what this means is that was the average actually.

And so it means that people often, often there are some, some people that are being promised a house that was pretty airtight. So if you consider eight to be airtight, they're being promised something like that in the energy model. But then what they're actually getting was more like 10 door 12, 14, so much leakier. that's disappointing that they're not getting what they paid for.

But then there were many that were getting much tighter than what they were expecting. And so, and if you're looking for energy code compliance, there's different ways you can get the energy savings that need to represent the energy efficiency of this house. So you could do more insulation, you could do better windows, you could do better heating and cooling systems. There's lots of different

energy efficiency measures, but air tightness is not really one of them. It's not a lever that you can directly pull in your energy model. So what this study for CSIRO showed was there's actually an opportunity here. So a lot of builders for, mean, a lot of them, by definition, we wanted people that really weren't trying extra hard for airtightness. So without even really trying, a lot of them were getting better than they're getting credit for in the energy model. So there's an opportunity for.

a lot of construction to get credit where credit is due for doing better than assumed. And so we see it as a big opportunity to help drive the industry because we saw not only were they doing better, but we also saw so many huge problems, code violations, actually like no dampers on the bath fans when they should have a damper and a lot of really dumb practices and just poor workmanship.

that easy fixes all of them. That you could, if you're looking for energy savings to get your NatHERS star rating, there's some easy energy savings on the table here. So we see it as a big opportunity for helping drive positive change.

Jess Kismet (28:07)

Yeah, massive, massive opportunity. So now when the energy modeller or the consultant is modelling up your house in the NatHERS star rating tool, instead of increasing the insulation from say R2.5 to R2.7 in the walls, for example, they can go to a different field and they can say, let's aim for 5 air change, permeability of 5 cubic metres per hour.

per square metre air tightness score. So they can enter that instead, which is less than the assumed level of air tightness in a typical model. So that is used as an upgrade. Is that how it works?

Sean Maxwell (28:42)

Mm-hmm.

That's how it will work. Yes. So that's what we want to be able to do. This is how it works in the UK, where ATTMA has been going for a long time. And ATTMA lodgement has been in use for more than 10 years. So you put into the energy model, what's your target? And now the target is creeping down and down and down because the industry is getting better and better and better. So it's getting very close to a permeability of four is the average assumption in the energy model. And so if you stay on your energy certificate,

Jess Kismet (29:12)

Right.

Sean Maxwell (29:16)

your energy model that we're going to get four door less, then you have to do your blower door test and you have to get four or less. Otherwise you don't get your certificate of occupancy. You're not doing what you said. So that's why that number is creeping down. that is coming to Australia, coming to NatHERS hopefully as soon as possible, but maybe later this year. But even a step shorter than

Jess Kismet (29:24)

Yep. Yep.

Sean Maxwell (29:44)

a step short of that to just state, like you said, when you put in your energy, a NatHERS model, we have this many downlights and this many windows and this many brick vents and things like this that you put into the model about what leaks will exist in this house that isn't yet built. You put this into the model. It generates an airtightness figure that it uses in its calculation, but no one ever sees that. goes into a black box and no one ever sees what that number really

evens out to. So what they're going to start doing hopefully soon is just state on the certificate, what was the assumption, please just tell me what you were aiming for, what this star rating is based on, what assumption did you use for airtightness? And then let me check it because what we'd like to show a lot of builders is, Hey, look, you in the model, it says your permeability should be eight or less, but you got four and look, there's energy savings that you're not taking credit for here.

you could do this. And not only that, but I see some big leaks that you could fix for close to no cost. You could get some major energy savings by just doing a little bit better with the air tightness. So it's a huge opportunity.

Jess Kismet (30:56)

Yep, yep. And how would somebody achieve an air tightness? if they, if someone came to you and said, Sean, I'm building this house with such and such builder who knows nothing about air tightness. How can I make sure that I achieve my air tightness goals?

Sean Maxwell (31:13)

lot of this stuff is super basic. so one thing I often point to is, the Building America Solutions Centre it's a website of the U S government with tons of free resources about, how to do basic air sealing. All the stuff they have there is super simple. It's using available materials on site. Like a lot of, a lot of the leaks that we find are missing plasterboard or something. So you talked about the, washer.

That's a big one. find ovens in Australia leak. It's not the oven that's the problem. It's the fact that behind the oven, they didn't just use plasterboard all the way on the wall. So you can basically, if you move the oven back, you could access the wall very easily if you were a rat or a cockroach. So that means a lot of the stuff, we're just talking about some cheap stuff that's there by the truckload already. Plasterboard, caulk.

Stuff like that behind cabinets, just boxing out cavity sliding doors, just some basic seals at where duct registers meet the interior finish. It's all really cheap and simple stuff that you can, that all add up to pretty big gains in air tightness.

Jess Kismet (32:35)

And what about the red pen test? Could you explain what that is?

Sean Maxwell (32:38)

Sure, sure. The red pen test is where a designer or an advisor like yourself door a NatHERS assessor could look at the plans and say, look, I see this border between the garage and the house and there's a bathroom bordering the garage here, but I know that the bathroom is going to have a bunch of penetrations, plumbing penetrations in it and it's bordering the garage. I bet you're going to get communication leakage from the garage into the bathroom wall because of this.

It's easy to see those things. It's easy to see this on a house that hasn't even been built yet. So with the red pen test, can trace around that house to say, where's the air control layer going to be in here and see where some likely problem is going to show up. And you can see that years before a building is built.

Jess Kismet (33:24)

Yeah, yeah, so you just draw that on the floor plan, right? Like, yeah, you just get the architecture. It doesn't even need to be a detailed plan. It can just be the concept plan, like literally basic drawing and the pen doesn't have to be red. It can be any color. It's just a nickname. And you just draw a line. And that tool is used to communicate with the construction site, the construction team, right?

Sean Maxwell (33:36)

That's right. Yeah.

Yep, absolutely.

Jess Kismet (33:50)

Yeah, because if we can draw all the red pens we like and we can specify all the air tightness we like in the Nat HERS model, but if the carpenters and electricians and plumbers and plasterers on site don't know that there's an air tightness test target or they don't know that there's a blower door test being done, then they won't worry about their attention to detail.

Sean Maxwell (34:10)

Yeah, so there are studies, there's a study done by ASHRAE, for ASHRAE, that showed what, was trying to find what's the difference between buildings with a quote "air barrier" and without a "air barrier" And they found a really big difference in performance between those with a declared air barrier. And so what's the magic in that? Is it just declaring that you have an air barrier? Well, not really. It's like, it's number one, it's looking on the plans to say, here's where the

air barrier will be in this building and defining that, it's specifying that. And then it's also, so it's something you can point to on the plans, but it's also something you can point to in real life to say, this is where the control layer shall be. And so you can say, look, I'm a drawing here. have a nice big red line here. It says there should be air control here. Look at all these things that are penetrating. There's missing plasterboard here. The plasterboard doesn't go all the way to the roof underside. So like,

You can point to it on the plan and point to it in real life. That's where the air barrier should be.

Jess Kismet (35:11)

Hmm. And there are so many things that you don't even think of until you think about airtightness as a thing that you need to address. Like you said, cavity door slide, like cavity doors. Never occurred to me that they would leak air, but they are literally a hole that is open to the wall, which is open to the roof. And if you've got a couple, two door three cavity sliders in your house, that's massive. It can be.

Sean Maxwell (35:33)

Yeah, yeah. And there's other things,

there's other things like, interesting during the, for the study we did for CSIRO, testing houses with building cavities, like wall cavities as ductwork, like a return. It's kind of funny, we're trying to find the correlation between, when we remove the register, we'd take a look inside and say, and count the number of dead crickets in the wall. And we're trying to find out, is there a correlation between,

the blower door number and the number of dead crickets in the wall. And there does seem to be a correlation between number of dead crickets. So I'm not saying that's a good code compliance strategy, but.

Jess Kismet (36:17)

less

than less than two dead crickets that tick

Sean Maxwell (36:19)

Yeah, we want zero dead crickets is the goal. Zero dead crickets would be

the goal because you only want air to go in and out of your duct system, not crickets.

Jess Kismet (36:28)

No, no, and you don't want your air to go in and out of the wall cavities. Okay, good. Thank you. Thank you for clarifying the dead cricket measure. CSIRO study, we've sort of danced around that. So could you give us just a bit of a summary of, because this study was done twice, it's been done twice now. So the first time you were involved was, were you involved in the first one?

Sean Maxwell (36:41)

Hmm. Yep.

Jess Kismet (36:58)

No, you came just after. Just after you were...

Sean Maxwell (36:58)

It was published in 2015 and when I got here I

was shocked. I was just shaking my head for many years afterwards to say, wow, the average air tightness that they found there was 15.4 air changes per hour for houses around the country, which is shockingly bad. And the average we got this time was more like seven or eight. So about half that.

Jess Kismet (37:13)

Yeah.

Yeah.

Sean Maxwell (37:26)

What the heck is the difference? These two studies were done nine years apart. Why is the leakage down by half? Well, two big things that I think really stand out. then a third, the third one is that I think there's just more awareness for that houses need to be sealed and we're not afraid of sealing up houses. So there's more general awareness of that, that this is not a bad thing to seal up.

houses and walls at least. But there are some changes in practice. So when I first got here, it was very common to find houses being built with no exterior water-resistant barrier, no exterior wraps, just bricks. That was it. you know, like they built, used to build them a hundred years ago, building them that way in 2015. I got lots of pictures of that. I was kind of shocked. No sheathing, no wrap, no nothing. But it became more common and now it's

Jess Kismet (38:11)

Mm.

Sean Maxwell (38:25)

basically universal that every house now has a sarking or a membrane wrap of some, some sort to repel water, which is just good building building practice to keep the water out first, keeps the control your water first, and then go after air leakage second. But just using the wraps on the outside does a big, that's a big first step. Could do a better job with it. And we'll see some major gains from doing better. but.

That I think is a big difference between now and back then. Pretty universal wraps they used to building wraps And another one is just some of the products now are just better. Like the bath fans leak less than they used to. And things like downlights, we counted the number of downlights in the houses because we wanted to see, or actually wanted to prove that the number of downlights used to matter to the leakage of the house because

Jess Kismet (38:58)

Thanks saying.

Sean Maxwell (39:23)

all these halogen lights everywhere, they just leaked a ton. so you got like a lot of the houses has 50, 75 down lights in them. It's crazy number, but each one of those used to leak a lot. so if a house has 50 down lights in it and each one of them leaks, that's going to add up to quite a lot. Whereas now we directly measure the leakage through each down light and it's very little. The new LED lights that we have that are all IC rated, can put insulation right on top of them.

No reason to have lots of space and ventilation around those. They're pretty tight and they don't leak. those are some big changes. Changes in products, changes in practices. We're just building more airtight.

Jess Kismet (40:04)

Yeah, yeah. And also the first test, the first study only had a fairly small sample size, didn't it? It was a much smaller sample size.

Sean Maxwell (40:12)

Yes.

Yeah. 20 houses per state. including, it was Victoria, New South Wales, ACT, Queensland, Tasmania, and WA. Whereas this one had, the one in this one we just published last year was just Victoria, ACT of South Australia, Queensland, and New South Wales.

So yeah, little bit, each one, fewer states this time, but many more per state. So was more like 50 homes per state this time.

Jess Kismet (40:49)

Yeah, yeah, it was like

three times the number of houses were tested. So it was a much better, much better sample size. Yeah, yeah. Yeah, so I will link, I will link that study in the show notes for anyone who wants to go and have a look at that.

Sean Maxwell (40:55)

More statistically significant. Yep.

Yeah.

Take a look at the scary pictures at the end of the report, because there's a lot of big leaks there and things that we really should focus on. There's some, some that are really, really a big one. Duct work is a big one. not the duct work itself that's leaking. It's the connection of that duct work to the interior finishes and the use of building cavities as duct work. just got to stop that. That's a big one.

Jess Kismet (41:26)

Yep. Cool. So what are you working on at the moment? Anything interesting?

Sean Maxwell (41:32)

Well, we're trying to help bodies like the Green Building Council to take a step out ahead and lead the way for the building code to say, yes, we can do this more widely. So incentivise testing of whole commercial buildings, like large commercial buildings, through extra credit. It would be great. So things like that.

We're trying to push net-hers to just be upfront about what the assumptions are in the energy model and then also incentivise better practice by giving credit for better airtightness. Those are things this next year. We're also doing a push in New Zealand to raise awareness and to show the Kiwi authorities that airtightness is within reach as a viable savings strategy for getting carbon savings for their country, for sure.

So those are the pushes. mean, if you asked me five years ago, what were the pushes that would have been the same thing, but it's, yes.

Jess Kismet (42:37)

Yeah, yeah, it's a slow moving boat, but

I think that it's not stationary. are things being, things are moving forward, it is, but you do have to really care because if you don't, yeah, yeah.

Sean Maxwell (42:52)

Yes, you do. You got to be patient. got to be patient. Something about

building codes and standards, you got to be patient. Nothing happens fast. You just got to be persistent.

Jess Kismet (42:59)

Yeah, yeah, yeah,

yeah, yeah. One day, one day things will, you'll look back and go, look how far we've come. Yeah, absolutely. All right, well, my last question is what is the one thing you want people to know?

Sean Maxwell (43:08)

Yep, yep, it's a marathon, not a sprint.

Hmm. Well, if it were, I think, for the listeners to your podcast, I think, probably not so much an argument you need to make to homeowners that air tightness is a good thing. because I think you, you could make that, argument that, about livability and comfort and air quality. Those are valid, valid things you can get for an airtight house that's well ventilated, but,

I think the main message would be to builders that really, guys, this is not that hard. We can help you do it. When you see the blower door and you feel the air leaks yourself, where they're coming from, you're going to be infected with this bug that makes you think, why? Why is that happening? Why is this thing leaking? And where do I find, how do I, it's just going to bug you that you can't figure out why that's leaking. so,

You will get infected by this bug and try to do better and try to do better. That's the cool thing about comparing numbers is you're always going to try to do better, mate. Try to do better than the next guy. So let's start a competition for who can build better and better.

Jess Kismet (44:31)

I like that and I can vouch for that. I've seen many, builders come to my blower tests and they're like, wow, what's going on there? they're not afraid of it at all. They're really interested. yeah, yeah, I like that. Cool. Thank you so much, Sean, for joining me. That discussion was fantastic and I'm sure everyone got quite a lot out of it. So thank you very much for joining me. I appreciate it.

Sean Maxwell (44:44)

Yeah, cool. Cool.

Yeah, thank you very much, Jess. All right. Okay, bye-bye.

Jess Kismet (44:59)

Bye.