Sustainable Builders Yak
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Sustainable Builders Yak
Ep #60 Building Science & The Air We Breathe: A Deep Dive with Sean Maxwell
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In this episode, Sean Maxwell from ATMA (Air Tightness Testing and Measurement Association) breaks down the essential intersection of building science, air tightness, and occupant health.
He dismantles the industry myth that "houses need to breathe," explaining why modern buildings must be airtight to stay durable while the people inside receive controlled, filtered air. Sean shares insights on the global growth of testing data, the shift in air tightness metrics, and why a well-ventilated, airtight home is the ultimate secret to a restorative night’s sleep.
Episode Highlights:
- The myth of the "breathing" house
- ATMA’s global data on air tightness
- Surface area vs. volume metrics
- The critical role of HRV/mechanical ventilation
- Controlling moisture and "drying" potential
- The luxury of quiet, fresh-air bedrooms
Guest: Sean Maxwell – ATMA / Scheme Manager
Company: ATMA (Air Tightness Testing and Measurement Association)
Company URL: https://www.atma.com.au/
Sustainable Builders Alliance (SBA): https://www.thesba.com.au
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This episode is proudly brought to you by Craftwood Hardwood, Wunderbuild, and Powerhaus.
Welcome to the Sustainable Builder Jack, the podcast that gives you the confidence to build high performing sustainable homes.
SPEAKER_00We're here to cut through the noise with honest conversations from the front lines of the industry. Talking with builders, designers, consultants, and the change makers driving a more sustainable future.
SPEAKER_02Whether you're on the tools, behind the drawings, or just curious about what makes a home truly sustainable, you're in the right place.
SPEAKER_00Get comfy, get curious, and let's have a yak about the future of building better.
SPEAKER_02The info shared in this podcast is the icing on the cake. Sweet but not substantial. For the real deal, tap into the wisdom of experts who can provide advice on your specific situation. Stay sharp and say sustainable. We'd like to acknowledge the traditional owners of the land on which we meet today and pay our respects to elders past, present, and emerging. G'day folks. On today's Yak, we caught up with Sean Maxwell from Atma, or the Air Tightness Testing and Measurement Association. This is an international association tasked to recording, documenting, educating, and certifying and anything else that goes along with it for air tightness testing, or as most of us know it, blower door testing. Now I've known Sean for many years, and he's been around the scene for as long as I have, if possibly longer. Hailing from Boston in the USA, he is currently the scheme manager for Atma in Australia and New Zealand. When we started off with a chat about Sean's past and how he got to Australia, and as always it's a great yarn, we then went and did a deep dive into the process of airtightness testing and how it actually carried out. Sean went into detail about the setting up of the blow door, how the measurements are recorded and what data actually means with respect to airtightness of a home or a building. Now, Sean Dunn explained the reasons behind the airtightness testing, and that was a great chat. He explained the importance and the benefits of it. He also explained how it affects a building's ability to perform better, the impact on health to the occupants, the durability for the structure, and the efficiency for the energy consumption. He also explained in depth the process of airtightness needing to be coupled with better building envelopes to experience true results. Now that was a very, very good chat. There's not many people would delve into that depth of detail, but that's Sean. We then went into depth explanation of how airtightness affects outcomes on a building's internal air quality and the basic requirements for mechanical ventilation, be it HRV or ERV. Now Sean's well versed on this. He is a very, very educated man, so it was really good to hear from an industry professional on this topic, as this is often misunderstood and misguided. It was a pleasure having Sean on, and while he sounds quite timid and unassuming, he is anything but he is a true industry champion. I hope you enjoy this one, guys. It's a really good listen. Thanks. Uh you too. Probably more so, yeah. All right, Sean, look, we'll get stuck straight in, mate. Let's start off as we always do. Uh tell us a little bit about yourself. Uh, who is Sean? Where did you come from? How did you get here? And then explain your role within the within Atma uh when you get a chance.
SPEAKER_01Thanks, Matt. Sure, sure, sure. So um you can hear from my accent that I'm originally from America, from Northeast, uh Massachusetts and New York. Uh started out doing blower-door testing. It was a first job out of college uh back in 2004, and then um uh did that for a few years in in Massachusetts with Energy Star Homes programmed, um, and then moved on to New York and worked on multi-residential buildings for about seven years, and then uh moved up to Sydney to chase a girl.
SPEAKER_02As it often does, as you do. Yeah. So uh can I stop you for a second? When you came out of college, what were you studied in college and how did you end up becoming an airtight necessarily? Because I I'm unaware of a college course.
SPEAKER_01Oh, there isn't. No, no, no. So um I I just uh during summers in uh in college I worked on uh house construction sites. Um so just asked I advertised that uh I was a young, willing guy and and wanted to learn about construction. So here's cheap labor. So I just learned about um there's actually a guy doing uh pretty high efficiency uh home. And so I learned a lot about um he had mechanical, uh he had heat recovery ventilation throughout and double stud walls and and uh uh uh vapor barriers and uh control layers everywhere. So it was pretty pretty good learning experience for me. And then uh after college, I thought that I want to do that stuff, that's cool. So uh I got a job doing um I didn't know really what it was, but it was something in uh green building, and then uh I got in the first week was just a crazy uh deep dive into building science. Uh I became a um HERS rater. Uh that's Hers is part of uh ResNet in the US.
SPEAKER_02In the US, yeah.
SPEAKER_01And um just took a deep dive into building science and never looked back. Uh yes, yep. Home energy rating scheme. And um there are uh tens of thousands of of HERS raters across the US and many, many more blower door testers. So um I never looked back. I I thought this is awesome. I learned I seriously learned more in my first six months after college than I had in all of college because I just soaked it all up as much as I could. It was just awesome.
SPEAKER_00Yeah, wow. In 2004, you were doing blower door tests. I I wonder whether a unit, a testing kit, was even in Australia at that point in time.
SPEAKER_01Oh, there were, yeah, there were. Um, yeah. Uh yes, there've been some it's been around for a while. Uh, there's some people who've been doing this for a long time. Uh from Master Builders, uh, he's uh with Master Builders, he had he came from Canada to Australia and uh has a blower door, and um so people have been looking at it for a while, uh, but very few. Very few people.
SPEAKER_02So where did Atma come into all this?
SPEAKER_01Well, when I moved to Australia, like I said, I moved here, uh I married married the girl that I chased. Uh, and then um we uh I didn't know anybody here. Uh there was one guy I had met uh that was traveling in New York, um, working on uh large building ventilation systems. And um I so I I had that contact, and when I got here, um just was looking for people that were doing the same sort of stuff that I was, and I found a couple other blower door testers, John Constantinous from Efficiency Matrix and a couple others. And um I was basically walking around with my hat in my hand saying uh to universities and uh people, uh, can any money money for a database, sir? Money for a database, sir. Because I wanted to do that. Was the last thing I was uh doing in New York was organizing a database of our blurred or test results, which we then used, we put in front of the um uh New York State uh building codes uh to uh guide their adoption of testing in in that state.
unknownYep.
SPEAKER_01So the database I thought was really powerful. And so I was Googling Air Titanist database, and then this thing, Atma Atma came up and Atma Lodgement is a database. And uh and I said, hmm, I wonder, can we can we so I uh messaged them, uh, can we join and use your database? And they said, sure. So uh pretty quickly, um well, I I joined, I was the first one down here that joined, and then uh every other tester that I met, I said, you should join too. And so so we did pretty pretty soon. We were a group of at least 20 testers that had all joined Atma and um and it started growing uh slowly but surely um over the years. Yeah.
SPEAKER_00And Sean, for those that don't know, what does Atma stand for and what is Atma?
SPEAKER_01So uh it's been it goes back a long time in the UK, um, I think since 2002, something like that. Um it was a trade association for a long time. Um and then in uh about 2015, I think um testing became much more widely required in the UK. And so um they came up with they thought, wow, this is gonna be big and we better organize ourselves, otherwise, we're gonna suffer the consequences of being disorganized. So they created this database uh called Atma Lodgement and a tool where these days all the the blower door tests that you do are um uh computerized, and so you can upload the results to this database and it's a computer, it will scan it for make sure all the data checks out, and then um it gives you a certificate that says yes, this is a legitimate test. So it's a good uh pretty simple quality control step. And that's how uh Atma really grew is by gathering now, they've got uh what 1.5 million test results in in their database, and it's growing by 150,000 a year. So um it's really and and it's a great compliance tool that we thought, well, yeah, all right, let's use that. Let's let's do that in in Australia too.
SPEAKER_00And it's all collecting data of air tightness testing throughout the world.
SPEAKER_01Yeah, uh so there are some members in the US, uh UAE, um uh gosh, there have been inquiries from uh Singapore and Malaysia and um yeah, uh lots lots of different um Yeah, lots of European countries as well. Yeah, yep. Yeah, so it's pretty uh it's just a good idea. And so we're trying to coordinate with others around the world. Basically, it's not that they have to use Atma Lodgement, but this is a just a plain good idea that you should copy, and that and we can learn from others as well.
SPEAKER_02So just uh can you clarify um how to become a broader tester really quickly? Sure, sure. Because that's important.
SPEAKER_01You you need to know how to use the the equipment, which uh there's different manufacturers of equipment, and so you need to learn how to use your particular equipment. Uh there are differences between the kits, but basically it's it's still a pretty fundamentally universal concept. You use a fan, uh you call it called a blower door, um, because it's a blower you put in a door. It's a fan to put pressure on the building, and then you measure the flow required to make that pressure, and you do some calculations and say, well, all right, at some standard pressure, this is the amount of flow you need. And um so you learn how to do that process, and then you also learn about, well, once you have a number, how do you compare that number? Like how big is this house? Uh, is it good or bad? Well, you gotta have some basis of comparison. So uh to become a tester, you have to learn how to use the equipment, and then you need to learn the process of say calculating the volume or the surface area of the building that you're testing to um know how to compare. So that's what uh becoming an Atma tester is about. You need to take a course uh in how to do all that other stuff, some of its math. Um, and and then there's policy, like how do you do this properly uh by a set standard? Um, so that's what the course covers, and then also you have to obviously know how to use your blower door. So you get assessed on all those things. You take exams about envelope calculations, exam about um the theory and the policy and the practice of of doing this, and then you uh do a practical demonstration that you actually know how to use your your blower door. Yep.
SPEAKER_02And then there's there's two different processes for your reporting as well. So there's the Passive House standard and then there's uh the Australian standard stuff.
SPEAKER_01Um it's the same process.
SPEAKER_02I mean the same process, but your your result is slightly different.
SPEAKER_01Um well, there's just like I said, there's different ways of comparing results. So um, like you could say, well, I I get a thousand cubic meters an hour from my blower door at 50 pascals, some pressure.
SPEAKER_03Yeah.
SPEAKER_01Um is that good or bad? Well, uh, I don't know. Is it um are you trying to build a passive house? Well, that's probably not good enough. Um or is it uh a large refrigerator warehouse? Well, that's amazing. So there's different ways of comparing. You gotta be able to compare big building, small building, long building, the short building, tall building, uh, fat building, skinny building. There's lots of different ways to compare. So um uh passive house historically, and some US codes have used um air changes per hour, which uh is a volume-based comparison.
SPEAKER_02Yeah, it's volumetric, yeah.
SPEAKER_01Yeah, and it's pretty easy to imagine what we're talking about. If I say one air change per hour, you think well, if I look at all the air in this room here and they lose all that air in one hour, that's one air change per hour. It's easy to wrap your head around, right? Yep. But um the thing is that the smaller the building is, uh, or the larger the building is, the more that stops making so much sense. So um uh for apartments, it becomes uh the number of air changes per hour becomes pretty hard because there's actually quite a lot of surface area for an apartment. Uh and the surfaces do the leaking, it's not the volume that actually does the leaking. So over time in uh the UK and and actually passive house in um the US, the commercial codes in the US, and uh basically it's gradually shifting to surface area metric because, like I said, volume doesn't leak at all. It doesn't matter like how many people you have in the room taking up the volume when you do the test. It's uh the air will just go right around the people and out through the blower door, comes in through the envelope, surface area, around the people and out through the blower door. So the surfaces do the leaking, not the volume. So we think it's just more universally fair for big buildings, tall buildings, short buildings, long buildings, skin, uh fat buildings. The surface area is really the thing that we're trying to do quality control on. So um we think that uh surface area is the one that we advise the building codes board here to use uh for the NCC. And we think that's what we should be using for passive house as well. It'll take a long time to change the mind of the passive house people, but uh we think that's more fair.
SPEAKER_00Sean, can air tightness is still generally new thing in Australia. I I think some people can get you know, when we're in an echo chamber, we can think it's very uh well established, but yeah, a lot of builders I'd say even myself, you know, I've I've been in this sort of sustainable space um and on the periphery of passive house, but not you know, uh sort of too involved or or committed. Um but yeah, why do we need airtight homes?
SPEAKER_01Uh when you say airtight homes, I I've I think what we need to focus on communicating is we're talking about airtight building assemblies or airtight uh walls, floors, and ceilings. That's what we need, airtight. We don't uh need to uh make uh people have this idea that when you build airtight, you're gonna suffocate. But really, all we're talking about controlling is how much air is going through the walls and the floors and the ceilings. You can't tell me that it's actually a good idea to have lots of air flowing through the through the walls. Um, people can get that. Like, why would you want a draft through your wall? Um so we need to separate uh talking about airtightness and ventilation. Absolutely, we need good ventilation. Um, in fact, we should start there, have good ventilation, good air quality, um, and then we can start building our assemblies more airtight to protect them.
SPEAKER_00So it's more about being well, be having control of the air that flows within and and out of a home. Sure, sure.
SPEAKER_01And and if you want to say for um for ventilation, uh come up with uh a slogan, uh, you can't control what you can't contain. So that's totally true. For ventilation, um, ventilation systems work better in an airtight enclosure. So uh just so many things. If you think about uh driving in a car, uh there's lots of benefits to having the car very well sealed. It's quieter, it's more comfortable. Um and uh so uh no one would say, Oh, you know, I actually want more air coming through the doors in the in the car. No, it's actually good to have it well sealed, and then you can actually use your AC and have it mean something, have it do something.
SPEAKER_00I I hate to ask this next one, but it feels it still feels like it's still a block in the industry. People it they they say our home needs to breathe. What's I I I know we've gone back and forth on, I think, over the years, Brian, but um, I know it's still a thing within many in the industry. The industry industry still well, it's very slow in the uptake, of course, you know, which appalls to the NCC and you know, blow blower doors are only what a suggest or blower door test is only a suggestion at this point, so it's still quite foreign. But what do you say to people, I suppose, that believe a home needs to breathe?
SPEAKER_01I would say to them, people need to breathe. And uh another slogan is people need to breathe, houses need to dry. So um, and that's the whole reason is that yeah, we we when people used to say houses need to breathe, really they meant like, well, we've got bad construction that's gonna mean that we're gonna get leaks in the walls, and the house needs to um to let that dry out, just a lot of airflow will help. And that's true. Uh, if you build a bad house that leaks, uh then more airflow is good to relieve that. That's how a lot of older buildings stayed up for so long, is because they just had so much leakage and so much energy waste to dry out the building after a leak that uh the air leakage didn't matter. You just spend a lot of energy doing that. So um when you start building with more insulation, you start reducing the drying potential. And so uh because there's less energy flow, energy is needed to make a building dry out. So when you start adding more insulation, you start reducing drying potential. And when you start reducing drying potential, you need to let that building dry. So you need to build more intelligently. Uh higher quality control for waterproofing, number one, uh air leakage reduction to um prevent uh moisture-laden air from getting into your walls and leaving the moisture there. And then once you start doing those things, you can start affording to build tighter and get control over the airflow through the building, uh building surfaces, and then provide ventilation that actually does something.
SPEAKER_02So I have an opinion on this one, Simon, if I can. Go on, cracking. Right. That phrase pisses me off, it irks me. People breathe, buildings need to be vapor permeable. They are two different things, two very different things. And that phrase comes from years and years and years ago when buildings did leak all over the joint. And in order for them to stop rotting, you needed airflow through the structure to dry them out.
SPEAKER_03Right?
SPEAKER_02So when they say buildings need to breathe, that is an incorrect term. It's not a right term and it shouldn't be used in the industry, in my opinion. This is just Brian's opinion. He can stick it up his bum as far as everyone's concerned. But the correct phrase, in my opinion, should be people need to breathe, buildings need to be vapor permeable to remain healthy. If you do that, then you've hit you you've nailed it. That's that's just Brian's side opinion, sorry.
SPEAKER_00Yeah, no. I'll try not to bring it up again.
SPEAKER_02I've shot it down a couple of times in the past when people say, especially when you get it to the to the brick industry, yeah, it comes up quite a bit.
SPEAKER_01There's there's a cool book uh by Alison Bales uh called uh A House Needs to Breathe. Or does it? Yeah. And it's a really good book about um just really essentials of building science. It's really good.
SPEAKER_02Um that might even be a gata for it.
SPEAKER_00Okay.
SPEAKER_02Yeah.
SPEAKER_00Yeah, wow. Yeah, I I I'm I don't know whether this is your area, Sean, but I'm beginning to recognise that with airtight uh homes comes uh the added risk of of health of unhealthy air within the home due due to PM 2.5 not being able to escape through our leaky walls. Of course, you know, we can also get PM 2.5 that comes within, but um when when homes had no insulation and and no you know weather-resistant barriers, you know, it was just and we'd have a you know a fire inside. You know, the fire would be leaking smoke inside. But the health risks weren't as high as if you had a a home today that was built really well, had a really good um weather resistant barrier and insulation, and you had a fire inside, that could be real disastrous without the appropriate ventilation systems.
SPEAKER_01Yep. Yeah, so you could get away with really stupid stuff like having open flames. In your house with using incense and lots of candles and other things that actually add pretty toxic things to the air, you could get a get away with stupid stuff. But now I would say absolutely we need good ventilation. We also need to think about source control. So a lot of the things that we say are very nasty. People need continuous ventilation to dilute. One uh there's a there's a bit of a battle. The solution to pollution is dilution. Uh which people people will fight about that. Um, so um the first solution to pollution is source control. So make sure you're not doing dumb stuff in your house like burning things. Uh Joe Joe Sebrick uh from Building Science Corp says Um if it smells bad, it's bad. If it smells good, it's bad. Basically, if it if it smells, you shouldn't be smelling. Uh you there's there's actually very few things that you want uh going into your lungs, pretty sensitive organs. Uh and you don't want to be doing the filtering with your lungs. So source control is number one. So building products that we're bringing in, we don't want to bring unhealthy things that are being the source of these VOCs and uh other pollutants that we're concerned about. We don't want the uh PM 2.5, so cooking fumes. Uh we want good extraction of those cooking fumes. Uh we want good uh control of moisture with good ventilation in in bathrooms and where there's high occupancy, we want uh dilution of constant uh gathering of moisture from breathing. So uh we we need to uh first concentrate on uh source control and then the sources we can't control, like people breathing, we need to get that moisture out. Uh, and then then we that that those are places we should start. Yeah.
SPEAKER_02So there's a misconception. I'm gonna step it back a little bit, um, if I can, Sean. So when we talk about airtightness and then good in air quality, how are we balancing that? Like there's it comes up quite often when clients start a process of trying to build you know a higher performance home, and then they start talking about, oh, let's make the home airtight, and then you bring in the conversation about HRV, and they're like, Oh, yeah, right, so now I can get rid of the air conditioning, and I don't need air conditioning because I have a HRV and all this. Can you to have us a little chat with us about like the importance of airtightness versus good indoor air quality and how that's achieved? Because that's that's an important conversation.
SPEAKER_01Yeah, well, good air, uh good indoor air quality is where you should start. Yeah, so everyone should be getting uh good air distribution, uh, good healthy air to breathe. Now, um, once you start on that premise, then you can talk about reducing the airflow through your building assemblies, your walls, floors, and ceilings, as much as possible. You can go as tight as you want. How do people live for months and months on end in the International Space Station, which is almost perfectly airtight? They do it because they have pretty good air control. Uh it's pretty pretty airtight. Uh and sounds like you can open a window. You can't can't open a window. So um, yeah, so airtightness in itself is uh not uh a bad thing for air quality, but you do need good ventilation. We need to start with good ventilation, and then you can afford to build as airtight as you want.
SPEAKER_02Okay. And then the HRV system itself is part of a process um that needs to be integrated at the very start of the design. So if you decide you're going to do an airtight house, you must have HRV or ERV, depending on what climate you're in.
SPEAKER_01Uh yeah. I mean, well, it it starts to make more sense. If you have a really airtight house, then an HRV, you start to realize the energy benefits of having an HRV. So if you have a very leaky house, um putting an HRV isn't gonna save you much energy at all uh compared to a standard ventilation system because, well, uh it's true. Um an HRV uh usually has uh a supply fan and an exhaust fan, and they run in opposite directions. And so there's two fans there, two. So um a simple ventilation system like a constant extract uh extraction fan, it's only one fan. So you put two of them on the table and you turn them both on, you say which one's using more energy? Well, the HRV uses more energy, it's got two fans and more filters, more pressure drop. It's uh so um in a very leaky house, which one's using more energy? The HRV, actually. Yep. Because there's so much air going coming going through the building envelope that uh that HR the heat recovery part of it doesn't actually matter because there's just so much other energy exchange going on.
SPEAKER_02That's the efficiency of it. You're getting into the efficiency of the actual system then.
SPEAKER_01Yeah, so well, I I guess what I'm saying is um in a leaky house, an HRV isn't recovering uh the energy that is recovering is basically way outsized by the leakage through the building envelope.
SPEAKER_02It's just an extract fan, essentially. It's bringing in fresh air and bringing out air. It's not really doing anything for the temperature control.
SPEAKER_01Yeah. So once you start to build tighter, though, you start to realize those energy benefits. And again, here's what I'm gonna say. Uh go back to this thing about starting with the ventilation, end-door air quality. In HRV, uh, it's bringing fresh air to it or can be designed to bring fresh air to where the people actually are.
SPEAKER_03Yeah.
SPEAKER_01So in in the houses you build, Brian, you're you're ducting fresh air to people's bedrooms, right? Yeah.
SPEAKER_03And living rooms, yeah.
SPEAKER_01Yep. I mean, if you told me that uh I could be breathe fresh air while I sleep, yes, yes, I want that. I want fresh air while I sleep. Talk about a I want a good night's sleep, please. Can I please have some fresh air? Everyone always talks about, oh, it's too stuffy. I want fresh air. Yes, let's start there. Good filtered fresh air. Then uh that's that's what makes an HRV better than an extract only. An extract-only system, which is how a lot of builders comply with the requirement to have some ventilation. It's it's just a it's sort of a shortcut, a hack. Like, yeah, we gotta, yeah, well, it does, it's better than nothing, which is where we're at in Australia right now. Uh there's no requirement for continuous ventilation. No. So um that's not good. The thing that it does is it's it slowly dilutes some of those interior pollutants we're talking about, VOCs, particulates, uh, moisture. Um, it slowly dilutes those constantly. Um, but uh it doesn't give the fresh air to uh like you're supposed to pull out air from one part, yeah, and then the air is supposed to come in through all the other places, like bedrooms. But we're in transition, to be fair.
SPEAKER_02Yeah, yeah, yeah, yeah. Absolutely. Yeah, that's that's not happening.
SPEAKER_01Like exhaust only is better than nothing, but it's nowhere near as uh ideal as uh heat recovery ventilator that's ducted to where the people actually are.
SPEAKER_00That that's a it's a great thought for someone like me that takes health seriously to have be breathing in fresh air as you sleep while you you know replenish your energy. It sounds like the dream. Yeah.
SPEAKER_01Think about the the benefits of building two passive house. If uh some of the most compelling uh videos and and things I've seen are people um saying, uh just uh moving into my passive house here, I just want to show you what it's like here. And they go over to a window and they they open up the window and they can say hear that construction next door? Okay, yeah, hear that? Well, and then I close the close the window and then it's absolutely silent. And if you just if the one thing you try to sell people is, I'm gonna give you fresh air all night long and it's gonna be quiet all night long, you're gonna get a better night's sleep. Isn't that a good selling point? Because everyone on earth needs a good night's sleep to function at their fullest and be healthy. So it's it's about longevity. If you said I can give help you get a better night's sleep every night that you sleep in your own bed, that's a great selling point. So that's ventilation and air tightness right there, equal a better night's sleep. Go for it.
SPEAKER_02You have a number for us, Sean. A number for so this comes up all the time. So obviously, we know we got COPs on heat recovery ventilation systems, right? That is directly related to airtightness. Yeah. Um, is there a number? I know there's a number in the code, but for you for you, um, is there a number where people should say, if we're looking at airtightness, we need to be considering HRV at this number?
SPEAKER_01Um, well, there's some some math you can do. Um so the thing about a blower door is it's uh you're pulling air out, uh, you you measure the pressure, say 50 Pascals, and then you pull you measure how much air is needed to make that 50 pascals. So you're taking pressure and you're uh measuring the flow. The other way you can do this is you could say with flow, say an extract-only system, if I know it's pulling 50 liters per second, how much pressure is it going to put on the building? You use the math in the opposite direction. Yeah, yeah. And um once you start doing that and you play around with some scenarios, say like a house, a three-bedroom house uh with this extract rate, if you rely on something like an unbalanced system, a continuous extract, below about two air changes per hour, something like that, or a permeability of two, the the pressure you start getting on the building gets higher and higher. And below one, it gets exponentially higher than it's a good thing. It's a bell carve. Yeah. Yeah, it's it's a pretty pretty wild uh exponential curve. So once you get to pretty airtight, um this the fans just don't work like you think they're gonna, or like you expect them to. So that's when uh so it's it really depends on the size, the flow rates, all this stuff. There's lots of factors. Um but below about two air changes per hour, those uh unbalanced systems stop working like you want them to.
unknownYeah.
SPEAKER_01So that's when um, just from a physics point of view, like airflow, a balanced system is really the only thing you should be using below a permitted two. Yeah. And below that point, you really start realizing the energy benefits of an HRV below below below that level. Once you start going to higher leakage light rates, uh the energy benefits don't um materialize as much as you would hope.
SPEAKER_02Yeah. So I'm happy to be corrected here, but I'm pretty sure the code says five. So we we need a form of mechanical ventilation, and what you're referring to is the two different types of HRV and mechanical ventilation. The code says five. We advise all clients to put in HRV all the time, but if somebody's insistent, our number is three. And the reason we do three is because most of the HRV systems, or specifically the certified ones, those systems will say that they will not guarantee performance above three air changes. Their COP just drops off, it's useless. They'll have maximum at 0.6 because they're certified to pass standards. So they'll have they'll hit their CRP or their maximum performance at 0.6. But at three air changes or less, that's when they see their performance start to do that bell curve. So our advice is anything below five is always HRV. Um, if a client is insistent, we will say, All right, we'll go from five to three on mechanical ventilation. Anything below three, it's got to be HRV, no questions, or we're not doing it. Sure. That's that's a good good way to do it. That's just our stance. It doesn't mean we're right or wrong, but that's just our stance, and that's what it's based on.
SPEAKER_01And and the basic the basic math is yeah, below three, two, um the you'll start to get the energy benefits, and uh it's really the only system that will appropriately work below those levels. Above that, uh you're getting into the more of the selling points about um ducting fresh conditioned air right to where people actually breathe. That's a great selling point as well. So um uh yeah, and then above five, then well, you just better start fixing your building. Yeah, yeah, yeah. Yeah.
SPEAKER_02It's not that it's pointless, but there's no efficiencies there.
SPEAKER_00But the NCC currently expects all homes to be under 10. Is that correct?
SPEAKER_01Uh I mean, well, so it says uh one of the verification methods to prove that you fixed your your building, um, that you sealed it adequately is to do a blow or door test. That's one of the ways to prove that. Um, unfortunately, almost no one uses that option. Uh so and the the number they picked was a permeability of 10, which there's other ways. Reasons they picked that mostly because that's awful. And building code is a definition of awful. It's like the definition of the worst that you can build, right? Legally, any worse than that, and you're you're violating the law. Okay, that's what the code is, it's a minimum. So 10 should be the absolute worst, is is what their suggestion is. And then um it says if you build uh to an air tetra less than five cubic meters per hour per square meter permeability, then you need to have continuous ventilation. There's different ways you can do that.
SPEAKER_02So my again, I could be way off. My understanding at the moment is that integration into code is in transfer period right now, right? So they got to start with a number, right? So they did I don't know how many tests. They did how many tests on new buildings, XXX, and they said, right, the majority of these are sitting on 10 or just below 10. So they just put 10 in. The reason you put in number is you have to have a number to enter into the software. So your burrs or your NATOs or whatever they're using, there has to be a pathway for you to start entering better numbers. So you have got to start somewhere. So they've just put 10 in and saying, right, well, we assume it's not it's not saying you have to, it's just saying that's an assumption at the moment. So their assumption is that standard new homes built today are at 10. They're not asking you that you have to, right? So the pathway then in the code is it's 10. We're assuming it's 10. But if you start to test and you're 10 to 5, you're okay. But if you're below 5, you have to have continuous ventilation. I that's my understanding of it. And I again, Sean, I'm happy to be corrected here, man.
SPEAKER_00And if you're above 10, oh, you just average out with the rest. That's what they presume.
SPEAKER_02Yeah, but you don't have to do anything.
SPEAKER_00You don't have to do anything, yeah, exactly.
SPEAKER_02You don't have to do anything. That's just an assumption for them to put, and it's basically here's your first start.
unknownYeah.
SPEAKER_01Yeah. So I mean, I could talk about NatHirs for a while. Um, so we're we have um I'll try not to talk too much about it. But uh just I'll tell you how it is right now and then where we need to move to. So the way it is right now in the NatHurz software, NatHurz for people who don't know, is a national home energy rating scheme. And um that's how they will say something like 85% of all homes, that's houses and apartments, use NatHurz to demonstrate compliance with the energy requirements of the building code. So in the Natur software, you define what are all the things in your house that are gonna leak when you build it. So you you say, well, we're gonna have windows, we're gonna have doors, we're gonna have, believe it or not, it says we're gonna have fireplaces and wall vents. Extraction fans, dry forests, down lights. Yeah, so um, well, you you tell it in the software, these are the things that will leak when we build the house. And you actually tell it, how tight are these gonna be? Like, are they well sealed or uh normally sealed something? But it's it's completely subjective. Yeah. Um, what you and and also how is it ever possible to check that? Like if you were you're gonna go down and say, oh wait, this window is supposed to be uh uh tightly sealed, but it's not tightly sealed, it's only moderately sealed. There's no way to actually check this. So for a builder right now, there's no incentive to do any better than what's these defaults that get put into the software. Because there's no penalty if they do worse. Like it's impossible to check if they've done done done well. Uh you can put a broader on it, that'll tell you pretty quick. Uh what I'm saying is with with with that, the the Natters way of defining the leakage path, these discrete leakage paths uh method, there's no way to check if a builder has actually adequately sealed it. Um there's also no way to incentivize the builder to do any better. Like they, if they seal it better, they if they build a house-to-passive house, according to Natters, who cares? Because there's no way to reflect that level of airtightness. So you can't show any benefit for it. So the Natter's system, when it comes to airtightness, is broken. So what Natters is gonna do is they have this right now in non-regulatory mode where you can say, all right, I'm proposing that I'm going to build my building to an airtightness of uh permeability of three or less. Yep. And so you put that in there, and you'll see on your your star rating a little bump from that because airtightness is one of the cheapest ways to save energy uh compared to um, say, better windows or thicker insulation or whatever. Um, so it's super cost effective. Right now, it's only available in non-regulatory mode. They've said for many years now that they're gonna allow it in regulatory mode so that you can put your uh target into the software, you say you're gonna get an air tightness of three or less, then okay, fine. It's gonna say right on the certificate, this number has to be checked. Yeah. And you have to check it with a blow or door. So it's coming. Yeah. Uh, and then when when this happens, builders that um can do better are gonna get credit for doing better in their natural star rating. And it's gonna be just like it is in real life, one of many ways of saving energy. So it'll just be like any other way of saving energy. So that day is coming. The pathway is there at the moment. Yeah, it's there. You just can't use it yet, you're not allowed to use it. Yeah, there's there's reasons why things that have to be thought through before they say, Yeah, all right, yeah, fine. Yeah, yeah. Uh allow you to use that lever. The things that you have to think through are like, what happens if you I mean, if you're a builder that doesn't know, they're like, oh, look at this. If I put my air tightness at zero, I get a whole star boost. Yeah, yeah. Sweet, let's build, let's do zero.
SPEAKER_03Yeah, yeah.
SPEAKER_01Well, you know, Brian, I don't know how close to zero you've gotten, but you you can't get to zero, right? No. Talas. Fuck. Come on, almost. Almost. 0.24 is my best ever. Nice. Yeah. Well, so but you can't can't get to zero. So if um there need to be limits on what's reasonable, like, and also advice like for the builder who's done doing this for the first time, you want to say, maybe you want to start small. Yeah. Unless you've done this before, uh, maybe don't pick uh two as your target, pick five. Because above that, you know, usually it's big holes that you can probably fix. So there's there's both guidelines and and guidance needed before this gets enabled. But once we can do it, then just every builder will be able to start uh getting rewarded for doing better. So positive feedback loop.
SPEAKER_03Yeah, yeah.
SPEAKER_00Air tightness seems to be one of the only correct me if I'm wrong, but one of the only things that can actually you can have a target and then you can miss it or not. Like then it can be measurable. You know what I mean?
SPEAKER_01Like so above or below, true or false. So the good building. That's whereas like every other way of assessing compliance is like uh someone's opinion about in fact, opinion between two different assessors will be totally different. Oh yeah, yeah, two different certifiers will be very different, and your past relationship with them will you know dictate effect. Absolutely. Whereas with with a blow or door test that gets fact-checked by the Atma Lodgement system, you upload it and it's true or false. It says pass or fail right on the certificate, and there's a QR code that the certifier can then scan and say, hmm, is this forged or not? Like, is this for real? Yeah. It's all done by the software and all verified by the software. So there's the amount of uh messing around you can do is a lot less.
SPEAKER_00Numbers don't lie.
SPEAKER_02Tests are tests. And even if you have somebody so we've we've trialed this once where we've put in different rings, you'll know what I mean, Sean. Um, and that will give you a false reading. Uh but you run the risk of losing everything. If another blower door tester comes in and tests after you, you're in a lot of trouble. You lose your accreditation essentially.
SPEAKER_01Yeah, and there's yeah, there are also ways to uh with the data, if if you look at it uh closely enough, you can tell when uh dodgy things are being done.
SPEAKER_02Yeah, yeah, yeah. Yeah. If you get the full report, you can tell.
SPEAKER_00Sorry, Sean. So you work in the US. Is that is polar test mandatory on as you know, to test at the end of buildings? End of Amazon. United States.
SPEAKER_01Uh the United States, the that's kind of a funny word, the United States. Um there are 50 states, and some of the states have uh so there's at least 50 different versions of the building code. And some states don't even have an a statewide building code. So there's um there are something like more than 3,500 counties uh in the US. And so uh you could say there's 3,500 building codes. Most states use some version of the a model code called the International Energy Conservation Code. And in the uh later versions, uh since since 2012, they've had in there blower door testing as part of the International Energy Conservation Code. Some states have adopted that version of the IECC and then just said, yeah, well, we're just striking that part out. It's still optional. But there are many states. So my home state of New York, it's mandatory. Massachusetts, Vermont, Rhode Island, California, actually, not statewide California, Washington, Oregon, many states, uh, Florida, uh, just so many states, um, even localities in Texas and uh around the country, there's patchwork where blow or door testing is mandatory. You don't get your certificate of occupancy unless you show your blow or result.
SPEAKER_03Yep.
SPEAKER_00Do you expect that will be the case someday far off? Maybe maybe more not so far off in Australia?
SPEAKER_01Um uh I think there's different ways of I mean, yes, uh, but probably I honestly don't know if it will be uh truly nationwide, like in the remo most remote parts of the country, if they will require you to truck a blow or door out there, that actually doesn't seem to make much sense for me economically. Yeah, uh tropics it makes a whole lot of sense. Okay. It makes a lot of sense in the tropics. You do not want humidity getting into your walls, it will cause problems. No, very bad. But um uh in most most of the population centres of Australia, I expect that it will become um eventually become mandatory. Who who knows how many code cycles that will take? Um, and I think rather than people like us uh pushing for mandatory air tightness targets, the stick approach, we're gonna go for the carrot approach, which is the Natters thing. Like get get let's start with rewarding those that do better.
SPEAKER_03Yeah, yeah.
SPEAKER_02Do you ever see um I have this vision so that eventually this will come in and we'll know everything that we build moving forward will have an energy rating, an actual energy rating rather than a piece of paper that tells you what you want. Um but I think at some point we'll have an actual energy rating that is efficient, so similar to most countries in Europe or a lot of countries in Europe. Um and then at some point we will do carbon capture so we know what we're actually building and what we're we're counting our carbon. Um but I also think that at the point of sale, we should have some kind of a process where there's uh a correct energy efficiency put on the house that's when it's sold. So eventually, like it will take a long time, but eventually you would have a huge you know database of the actual performance of your homes. You know what I mean? So even if it was a really old home, you still have to go in and do an energy assessment at the end of the so that would mean a blower door test, what insulation's in the walls, what glazing, what windows, you know what I mean? So that when that house is sold, it's the responsibility of the seller to do a correct energy efficiency report on that house when it's been sold, and then boom, yeah, it's logged. You know what I mean? Yeah, and then over time, because houses will sell eventually, it's it's a property market, isn't it? Everything sells, um, eventually you would have this huge database of exactly how your country is performing.
SPEAKER_01Well, so uh one of the reasons that the airtightness um lever in the in Natters um was put on hold for uh a little bit was that Nature's pivoted to taking their rating system from only new construction to existing buildings as well. And one of the pushes is to make in some states uh is to make uh a Nature's assessment of um house performance mandatory at the point of sale or lease. Yeah, which is which is great, and other other countries have that. Um so uh that will give a renter some information about just how uh I think uh not just how energy efficient is it, but how comfortable is it? But even in buying it.
SPEAKER_02Yeah. Like they that they're informed about how the the performance and the quality of the home.
SPEAKER_01Yeah, so I mean, I will uh say that it could be improved. Um the nether's thing for existing homes could be improved because again, right now it's still it's only a visual assessment that's required. Or there's there's two options in it. It says you can do a blower door test. Uh, we recommend a test by an amma tester, or you can do a visual assessment in which the assessor goes around and counts the number of lights and counts the number of windows and says whether the gaps are big or small. So all that stuff goes into the black box of the uh software and spits out an airtightness assumption, or you can do it with the blower door. So there's two options. Most likely, most people are not gonna do the blower door. Um, so um yeah, uh I think there's a missed opportunity there. Um yeah, because um I think even a quick and dirty blower door test would be better than this silly visual assessment. I think it should just be made mandatory.
SPEAKER_02And like blow or something house, yeah, like it's not a huge amount of money.
SPEAKER_01Like no, I I I agree. And and it gives a lot of information about how the building performs.
SPEAKER_02Yeah.
SPEAKER_01So um uh I can tell you this. So we're renting this house here uh outside Melbourne, and there are things that you could not see with a visual inspection. So when we rented the house, um they said there's just a note on the controller for the evaporative cooler that says uh not working. So they it was just on the listing that said it has uh the evaporative cooler is not working. Uh and so we accepted that because there's AC installed, there's a split system installed anyway. So they thought not a big deal, we'll just use the split anyway. And uh, of course, me being me, when I got here, uh when we moved in, I grabbed one of the first things to do was grab my ladder and go up into the roof and take a look around, of course, because you want to see what the insulation's like. These are the things you can't see when you're when you're uh uh inspecting for a rental. It's really fast, it's like 10 minutes that you get to see. So a renter doesn't really know all the ugly secrets. And I I'm sure that the real estate people don't know either all the or don't care what the ugly secrets about the house. So I went up there and one of the ducts for the evaporative cooler was ripped and disconnected. So basically, it's just leaking your house air to and from the roof space all the time. So it's it would be really hot in the summer and really cold in the winter. I measured the uh air tightness of this place, there's a permeability of 31 cubic meters per hour per square meter. 31.
SPEAKER_00Wow, yeah, wow.
SPEAKER_01So once uh we put uh temporary um uh plastic over the uh over the uh outlets for the um evaporative cooler, and I put insulation in there to get rid of that thermal bridge, did some sealing of the wall vents and things like that. So I brought it down from 31 to 18 by doing those things that uh a renter can do. These are all temporary things. So um that uh of course I would love to have known that the place was a permanent bit of 31 before renting. So uh an assessor here is just walking around and looking, would not be able to see this stuff from below. So this visual assessment thing that's in nutters for existing homes is far inferior to the blower door test. So if anything, if it's not mandatory, I think uh the state governments could give an incentive if you at the time of assessment you want to do a blower door test to give you the the credit for for doing that.
SPEAKER_04Yeah.
SPEAKER_02All right, I uh I think we'll wrap it up now, if we can at all, Sean. And let's uh I think we'll jump into our quick fire questions. You ready for these? You've done your research. We'll see what happens. All right, who's the most famous person in your phone book? Oh uh I don't know.
SPEAKER_01Joe Steebrick, we'll just say that. All right. Uh favorite sporting team? Chicago Bulls. I grew up uh rooting for Michael Jordan, of course.
SPEAKER_02Passive house or passive solar design? Passive house. Uh timber brick or alternative construction. Timber brick? Timber or brick? Oh, or alternative construction.
SPEAKER_01Uh I guess alternative construction. I'm not sure what you mean. You mean uh hemp, rammed earth, panels, rammed earth, whatever. I think we should uh try new try lots of things. Okay, so alternative. Tim Tam or Anzac.
SPEAKER_02Oh, uh it's gotta be Anzac. Yes. Fuck Anzacs are winning this year for sure. Absolutely. John, thanks so much for joining us today, man. Really appreciate it. I know you're a very busy man, so really appreciate you taking the time out to come and have a chat with us today, man. Awesome. No, I wish we could uh talk longer. Thanks very much. Thanks. See you Simon.
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