Episode 06: How to test the performance of your home

We have met Anthony Stagg a few months ago when we picked up our very own Retrotec blower door test kit. Anthony is the director of 2 businesses: Fire Protection Technologies and Energy Conservation Technologies, a company that sells blower doors and provides training to perform residential blower door tests.

We are so happy he took the time out of his busy schedule to sit down and have a chat with us about what a blower door test really is and how it can be useful for not only newly built homes, but also existing houses. He even shared some of his own experiences with his current renovation and how he utilised a blower door test to help identify the major weak points in his home.

Now, for anyone looking to have a blower door test and some thermal images done to their home, please feel free to reach out to us at Outlier studio as we do offer this service. But first, let’s get into this episode with Anthony Stagg from Energy Conservation Technologies.

Episode Transcript

Sandra Redlich  00:01

All right, thank you again, Anthony. This is going to be the episode with the two Anthonys. So pardon me if anyone listening is confused. We’ll try to make it as easy to understand as possible who we’re chatting to. But I’m hoping the majority of the time, it will be Anthony Stagg, who I’ve just introduced before. Thanks for taking the time today Anthony.


Anthony Stagg  01:52



Sandra Redlich  01:53

Yeah. And we’ve actually had the pleasure of meeting in person a couple of months ago when we picked up our own blower door test kit, and did a little teaching and workshop at your premises. And that’s kind of how that whole conversation between us started. So we already spoke about it a little bit. But maybe can you just tell our listeners what your background is and how you got started in providing knowledge and kits for blower door tests?


Anthony Stagg  02:22

Oh, by chance. So I actually was studying Architectural Technology when I came out of high school. And at that time there was, I think, a recession. So I finished the diploma in Architectural Technology, or an advanced diploma. And I had good drafting skills. So I applied as a trainee draftee for a fire protection company, and started to learn how to design fire systems, and drew up the plans for them. And it just evolved from there. From there, I completed a diploma in fire technology. And then continued on my journey in the fire protection industry, and then eventually finished some postgraduate studies in fire risk engineering. Yeah, so my career is very fire orientated. But now I’m also a director of a company called Energy Conservation Technology, which basically takes the blower door and uses it for energy efficiency, which is probably more what we’re going to talk about today.


Sandra Redlich  03:29

Yeah, that’s actually a good segway over to kind of how we got to know each other. It is through that new breaching out into the energy efficiency sector of things. So can you explain what is the approach within residential, or also commercial buildings I guess, what do blower door tests do? And I mean, I guess they identified air leaks. But why is that important?


Anthony Stagg  03:57

Well, if we start with the equipment, there’s really no difference between, you know, a fire blower door system and an energy blower door system. They do quantify leakage, they use different types of software, but they do quantify leakage. So the blower door system is comprised of a fan, a digital manometer, and we put that fan in a doorway. And basically we are depressurizing and pressurizing the enclosure and we take measurements with regards to induced pressures. And what sort of leakage rate we are having at those varying pressures. So typically, between energy and fire, the codes are slightly, or protocols are slightly different. But we’re taking differential pressure readings anywhere between sort of 10 and 75 pascals and at those particular induced pressure readings, we record these flow readings, and from that we can actually quantify in a singular point, what is the collective leakage of an enclosure? In Fire, we use that total leakage area. And we CFD model the, I guess the, the impact on the gases because they have a different density than air. And they behave differently across an opening with gravity pulling down these agents through these openings. So we can model that. And when it comes to energy efficiency, it’s interesting because we model that with regards to energy efficiency, just how leaky an enclosure is, because it can impact how much energy you’re using with regards to heating and cooling, and your comfort levels, as well as other things like, you know, pollutants and so forth. So, we don’t often visually see much leakage in an enclosure when we walk through. But if you do a blower door test, and you quantify that leakage in a single hole, you would be dramatically surprised how big that actual hole is, it would be like leaving a door open potentially or leaving a window open permanently. So when we see in a singular form, we realize that is unacceptable. But when you break that whole leakage area, single leakage area, into finer leakage points that you can’t see visually, we don’t notice it, and it can play havoc on our comfort levels and our energy bills.


Anthony Jenkin  06:26

Yeah, I have to admit that that was probably, still is, the most exciting part, is that initial depressurization of a home and just walking through it and just being astonished by where air is infiltrating and just how much… And I can’t speak more highly of the Retrotec software either, you know, just being able to quantify that and sort of give a real world example of how big that area would be. That’s, you know, if it was the equivalent of say, an open window or door.


Anthony Stagg  06:51

Correct. And that’s the har dest disconnect for the layperson, where they don’t quite understand, walking through and quantifying visually, whether they have a leaky home and the blower door system, to me doesn’t lie. It actually tells the truth. Like you said, when you subject a home to a depressurization, or a pressurization, and use a handheld smoke puffer on suspect leakage areas, there are so many that you can add up through every aspect of every area of your home, whether it’s through doors, windows, through power points, through wall cavities that haven’t been capped off, you name it, and through fans, exhaust fans, add all those up and you’re shocked. The total level of leakage area that your home has. And once you explain that to a homeowner and say, Look, I’m going to leave your window open permanently throughout the year, they would say you can’t do that. That’s unacceptable. I would be so cold or so hot during the summer and my energy bills are going to be enormous. But they actually have that data. It’s just broken up into smaller points in various parts of the house.


Anthony Jenkin  08:08

I suppose. Yeah. That probably leads into your own experiences with a leaky home, so maybe we can chat about your own home, Anthony, and share your thoughts.


Anthony Stagg  08:18

Let’s embarrassingly talk about my own home. It’s timely that this question has been asked because I live in the eastern suburbs of Melbourne. And I bought a home nearly a decade ago, original house was 1959. And there was an extension for the previous owners to increase the size of the house. And I haven’t really done anything to that home. I know it’s leaky. I have gone through with a thermal camera. Just to look how “well” the insulation was done throughout the house, which was horrific. But last year, I embarked on a renovation. Now I’m not going to the extent of passive house. But I did subject my house to a blower door test before we started the renovation and I’m going to complete, post renovation, I’m going to subject the house to a blower door test. My results on the existing house was about 30 air changes per hour at 50 pascals of induced pressure.


Sandra Redlich  09:37

Yeah, that might be a good little time to explain the numbers. I just had a reaction to that because I kind of have in the back of my head. What is a good number? What is a bad number? But maybe,could you give our listeners a little bit of an overview of what is good and what is not so good?


Anthony Stagg  09:56

Okay, okay. Let me quantify what an air change per hour is. So the volume of your house. So if the volume of your house, and I’ll try and keep the numbers simplistic, let’s just say that your house is 500 cubic meters of volume, you measured up all your area of your house and multiply that by the height to work out what the volume of the house is. One air change. So if my house was 500 cubic meters of volume, then one air change would be 500 cubic meters per hour. And my house was 30 times that. Now that’s at an elevated pressure at 50 pascals used with the blower door. So the process can be repeated with accuracy, the house is probably naturally not going to be subjected to 50 pascals of induced pressure unless you’re in some sort of Cyclone conditions. So the house does cycle with regards to external influences that put pressure, negative and positive, on the house. And they could range anywhere between sort of zero to possibly, you know, 5, 6, 7, possibly even 10 pascals, depending on the conditions, but we test at an elevated 50 pascals, so we can redo with accuracy. If we have to retest, there has to be some point where we can emphasize leakage and quantify it again. So yeah, one air change is one volumetric change of that house per hour. And mine was measuring 30 times that, which is atrocious. So you could imagine when you’re trying to heat or cool a home, if it’s that leaky, and the volume of that home is changing per hour, it would be just, it’s like leaving, you know, putting your heating and cooling on and just leaving a door or two open, is just money flowing out the door.


Anthony Stagg  11:50

Now what is good on the other spectrum, what is excellent, the Germans have developed a, what would you call it, a philosophy of construction techniques and materials of construction called Passive House, which you’re all familiar with very much, and Passive House takes seriously as part of the process of certifying that house, they take seriously air leakage or air permeability, whatever terminology you want to use, the exchange of volume of that house, and they set a benchmark for that, which is the other extreme end of the spectrum. So there, so my house was 30 changes per hour. Passive House, if you were certifying your house to passive house, it’s 0.6 of an air change. So it’s not even one air change. Because Passive House is really a quite a strict, you know, technique for design, materials, construction techniques to ensure that your house is very energy efficient. So they’re the two spectrums, I’ve got a very old house or half of my house was 1959. The extension done 15 years ago was, you know, had no input to it with regards to energy efficiency, and I’m measuring 30 air changes at 50 pascals. If I was building a house to passive house, and I wanted it certified at 50 pascals it would be 0.6 of an air change. That’s a massive difference.


Anthony Stagg  13:29

Now, in modern days, you know what is good, you would only go down to a 0.6 or close to 0.6 for passive house, if you had some sort of heat recovery system, because you do need some exchange of air. Because you have occupants, you have cooking, all these sorts of activities in the house. So you do need to change the volume of the house, but it needs to be controlled. And that’s what a heat recovery system does. You know what is good these days, I’ve done a couple of blower door systems for some new houses that should be sort of six star rated and so forth. And some of them are quite respectable at anywhere between sort of 8 and 10 air changes per hour. So yeah, what is good, I would say today, if you didn’t have any thought associated with air infiltration or air leakage, you know, 10 is probably a good point. And if you managed to get, if you’re getting really down low, you really need to start thinking about a recovery system.


Anthony Jenkin  14:36

Yeah, I think currently there’s a performance solution. So it’s voluntary in the National Construction Code. And, you know, that’s at 10 air changes. So one of the ways to test a building’s envelope for air tightness or permeability is the blower door and they’ve set that benchmark at 10 air changes. And I have recently heard they’ve just introduced or will introduce come September 1 with the National Construction Code that it’s still voluntary to test, but if you do use that method and it comes up at 5 ACH or less, you then have to introduce mechanical ventilation into the home. So that part will be mandatory. So don’t hold me to that. But that’s, yeah, I think that one came through the Builders Declare Podcast, so I’d check with them.


Anthony Stagg  15:26

Yeah, there you go. So if you’re at 10, naturally, that’s probably a good point, as a default point to start with, that should offer us some level of comfort and improved energy efficiency. And that’s exactly where I’m trying to get to with my house. So I’ve been educating my builder, who’s not a passive house builder. And it is a renovation, it’s not a new build from start, where I could probably plan a bit better for energy efficiency. So you know, I’m going through making them aware with regards to insulation and installation, making them aware of the gaps, because all the windows are going to be replaced with double glazed. And the existing building is not straight. Unfortunately, there’s gaps around windows. So in fact, this week, they have dropped off a bunch of low expansion foam. And we’ve had some briefings on site and I’m trying to educate my builder and the traders on site, just what to look out for, if you can see through the gap of a window to atmosphere, it’s only going to be sealed by an architrave. So, you know, they’ve gone through the last two days, basically putting foam in every gap that they can see at the moment, which will improve I’m sure the blower door tests when I get to do it. And then next when the plumbers come in and start punching holes through areas, I’ll have the same briefing with them to make sure that they’re trying to seal up whatever they’re penetrating through. So we are eliminating that open link between outside atmosphere, I guess we’re trying to define an air barrier within the house.


Sandra Redlich  17:08

Yeah, fantastic. That’s actually a great example to kind of hear your own personal experience with this, because I think a big question that people would have would be, is a blower door only something if you’re considering Passive House, which I think you’ve kind of already answered, that it’s not, and when is the right time to get a blower door test done? Because as I understood it from you talking before, there are several different occasions where you get the blower door test out in your home. Is that right?


Anthony Stagg  17:39

Yes, yes. So for anyone that’s doing a renovation or build or whether it’s passive house or not passive house, you would want to subject the house to a blower door system before the plaster goes on. Because once the plaster goes on, and sometimes you are using the plaster as the air barrier, but then it’s probably too late if you do have leakage points behind the plaster. So you don’t want to be ripping down your internal skin to try and find these large, potentially large or minor leakage points. So during the construction process, once the trades have gone through, whether that be electrical or plumbing, or even HVAC, you know, those trades going through, once they’ve gone through, it would be nice to subject the house to a blower door test because you can, one you can quantify where you’re at, with how many air changes on air permeability rates, cubic meters per hour per square meter of surface area. You can quantify it but not only that, you can use the blower door system to create a positive pressure of about 15 to 20 pascals. Walk around the house with either a thermal camera or just a handheld smoke puffer just to subject some of those suspect leakage points. And if you’ve got an induced pressure at 15 or 20 pascals it’s going to push that smoke out dramatically, you’ll be able to visually see the smoke being sucked out to outside because you’ve got a positive here. You’re inducing the house to a positive pressure, you’re blowing it up like a balloon. And it’s a great way to just walk around and just take note of where these leakage points are. Address those and then you put your plaster on and subject your home to a final blower door test. But anyone that… it doesn’t have to be renovation too,  it could be, you can still, you know, organise a blower door test for just a house that, you know, homeowners just want to improve their level of energy efficiency. So there are some basic things that they can do, whether it’s sealing up windows and doors a bit better or extraction ventilation, sealing up the cavities on top of walls, if they get into the roof cavity and space, there’s certain basic things that can be done just to improve a house that’s already been built. And that will improve your comfort levels with a minimal of cost really.


Anthony Jenkin  20:21

Yeah, it’s great you touched on that, because I agree, there really are basic things with a very minimal cost outlay. And it’s just not apparent to most homeowners or those who are, you know, about to start building. And those things can be, in existing homes, can quickly and easily be identified using a blower door test or in new homes. Just be mindful of it, be aware of it. So yeah, I’m glad you did. The importance, it is simple. It is easy to do. It’s not overly complicated,


Anthony Stagg  20:47

Correct. And it is, it raises eyebrows for any homeowner at whatever stage, even if it’s non renovation or non build stage, you know, just to quantify the amount of leakage the house might have and where it is coming from. It is a real eye opener for them. And certainly the quantification once you tell them that, hey, you’ve got a, you know, you potentially have half a meter by half a meter or meter by a meter total leakage area. It’s like, wow, yeah, it’s like living with a window open.


Anthony Jenkin  21:17

It’s literally the first thing that we point out on the report.


Anthony Stagg  21:22

Yep, yep. And then you show them that dimension. What are we talking about? You’ve got an area of length by width, that is open permanently with your house. And as I said, if it’s a single point, they would deem it unacceptable. If you said, Is this acceptable to you have a meter by a meter leakage in your house? I’d say no, that’s unacceptable. Well, you have that. What are we going to do about it now?


Sandra Redlich  21:45

Yeah, that’s a very good point. So what can people do? I mean, we’ve talked about the potential to get a blower door test done at your renovation, your existing house, even just to have as a starting point. But if I’m interested in a blower door test, are there any resources that you can recommend? Where can homeowners find further assistance with that topic?


Anthony Stagg  22:09

Sure, look, you know, the internet is a powerful search tool that we can find, if you typed in blower door, you’d get lots of things that come up, including our websites. So you know, for us, we can put homeowners on to businesses that have the appropriate equipment and certifications to be able to perform a blower door test with a level of competency. There is also the Air Infiltration and Ventilation Association of Australia, which we are a member of, that is an industry group that we developed many years ago, in order to provide a single point of contact for the industry, to engage with either government or to engage with customers. On that particular website, you would find blower door companies and technicians that are certified to perform a blower door test. So there’s a few touch points that you can find to find an appropriate company that can perform that particular test.


Sandra Redlich  23:15

Yeah, and maybe on that note, Anthony… Anthony J. I have to say, there we go. First time with the two Anthonys. Anthony J, can you maybe explain, as Outlier offers testing as well, what would be included in that service from your point of view?


Anthony Jenkin  23:33

So there’s probably two parts to that testing service. The first one is if you have an existing home, we can come and install the blower door. And depressurize or pressurize, we do both. But we usually find that the depressurization test, we’re able to feel the air coming in, literally with your hand. Sometimes it’s such a severe leak that it’s blowing you in the face like someone has a blow dryer on. I know that sounds like a lot. But it’s yeah, you’ll hear whistles, you’ll hear noises as the air leakage is occurring. So yeah, we’ll depressurize the home. First we’ll walk around, we’ll identify these leakage points. And we’ll use a thermal camera to then snap a picture of that and identify that defect. Whilst we’ve got the thermal camera out, we also check for any thermal bridging or any obvious thermal bridging, and also defective or insulation, if there’s any there at all. It’s pretty, pretty evident as soon as you have the thermal camera and what’s going on there with insulation. And then from that we basically prepare a report and issue that,  just identifying what the air permeability or leakage was. And, you know, provide those thermal camera images as part of that report as well identifying all the defects and offer some recommendation on how you can rectify that and improve the efficiency or energy efficiency of the home overall.


Sandra Redlich  24:49

Anthony S, we’ve talked about the building code before and that hopefully potentially by the end of the year, we’ll see a little bit more changes toward introducing blower door tests, or at least mentioning that possibility, from your point of view, just your opinion, should it be mandatory to perform blower door tests for new build homes?


Anthony Jenkin  25:13

And I might just add, and maybe what your opinion of what those parameters should be, or those performance values should be.


Anthony Stagg  25:19

I do believe it has a place in our building codes now and moving forward 100%. I mean, in a modern home, energy efficiency is becoming very topical with regards to energy bills, consumption of fossil fuels, and the impact on the environment and so forth. You know, it’s amazing how we can construct a home and we can have inspection points for foundations and inspection points for frames, framework and so forth. And we, so we have sort of three inspection points, I believe it is. And then you can get a certificate of occupancy. And there is no really, no mandatory requirement to test the home for its energy efficiency. So it seems to be that the building code is just stuck with, you know, certifying the structural element of our home, and not necessarily ensuring that it’s going to be comfortable and energy efficient for you know, the next 30 years. And what that could mean for that particular homeowner, whether that’s comfort, whether that’s a saving with regards to energy bills, and so forth. So it really does need to be a mandatory requirement of the building code, you know, for those positive reasons. At the moment, we, you know, our star rating system is a desktop audit, it really is, it’s a desktop audit, and we look at the plans and the energy reports and so forth, and we stamp them and say, Yeah, this is a six star home, in that assessment, and the software that we use for assessment of energy efficiency has assumptions for air infiltration. But there are assumptions, you can’t make up those assumptions. I don’t believe… You know, every house is different. And we need to be able to measure the impact. If the house isn’t at that assumption level, with our rating software, you know, we need to be able to have more flexibility with regards to having air infiltration, or mobility as an input to the total evaluation and certification of that house.


Anthony Stagg  26:27

Yeah, that’s what we want to push for. Absolutely, is to see that that’s validated. And I just don’t think we can highlight the importance of the forgotten air leakage. And  it’s discussed about, it’s talked about, but it’s really… I don’t think there’s a high enough importance put on that to be honest. And we have a tool to test it, unlike other things.


Anthony Stagg  28:03

Sure, that’s correct. And the thermal camera, if we get back to my own experience with a thermal camera, I mean, to have the ability to see through walls, you know, to have X ray vision with a thermal camera. When I went through my house years ago, I found leakage through a window. So I had water, I found water behind. I could see water damage behind the plaster. I found pockets of walls that didn’t have insulation. And I had the insulation in the roof that was the loose wool. Let’s just say not the blankets, because the roof junction was just so leaky that when we would normally have a certain wind direction from, mostly coming from sort of, I guess, the West, sometimes it pushed all the insulation from one side of the house. If you went up through the manhole and crawled along, you would see this massive mound of wall insulation that had just been pushed away from one quarter of the house. One corner of that house. And in fact, I think it was above our master bedroom, where it pretty much had no insulation in the ceiling space at all because of wind coming into that space. Incredible. So I’ll probably have to engage you guys to come through my house and we’ll probably do a blower door test together. And maybe you can bring his thermal camera and we can check for insulation and make the builder accountable.


Anthony Jenkin  29:36

I would love the opportunity to do that. Anthony. Yeah, definitely. I’ll take you up on that.


Anthony Stagg  29:40

Maybe that’s part two of this podcast.


Sandra Redlich  29:44

Yes, that time with video to actually show what we’re doing. Talking about that, I just want to quickly mention for anyone who is just trying to Google what a blower test looks like. We do have an infographic up and some pictures on our Instagram that kind of try to explain the whole setup. And then obviously also on the Retrotec or the Energy Conservation website, that we will link after this in the show notes, you can find a lot of information about that as well, if you wanted to just have an visual image of how it all works. Anthony, just to wrap it up, there’s one question we always like to ask our guests at the end of our episodes. I know we’ve touched on this a little bit before, but maybe picking back up and quantifying that answer as well. If you have a free wish for something that could be changed in the building code. What would that be?


Anthony Stagg  30:40

Well, I think it’s probably… I would touch on probably what Anthony J said, with regards to, you know, having that compliance, just another box to tick to make sure that your energy report, you’re validating your energy report basically, that, you know. And even if we, at the moment, we’ve got, you know, roughly about 10 air changes per hour, that’s going to be implemented into the building code, as a point in the sand for air infiltration, or air leakage, whatever you want to call it. But you know, if that’s the case, then we should subject that house to that particular point in the sand to make sure it does comply with that, and that the energy report is validated with regards to air infiltration, with regards to insulation, to make sure it’s done appropriately. So yeah, that would be my wish, that there is some form of validation of the energy rating that we construct homes to.


Anthony Jenkin  31:51

Yeah, fantastic. Yeah, again, even the current default of 10 air changes. It’s not difficult to achieve.


Anthony Stagg  31:58

It’s not, it’s not. I am a bit nervous about my own home. I’m hoping I’ve reduced it dramatically down from 30 air changes. I’m hoping to get down to at least that particular point.


Sandra Redlich  32:10

Yeah. Well, all the best with that. All fingers crossed. And yeah, we’ll definitely take you up on that offer. We’re happy to come by and bring our thermal camera. And yeah, maybe even, as you said, do a little part two of this and keep people updated on the progress of the project. That would be great.


Anthony Stagg  32:28

Yeah, I should take a few more photos too, so we can show a bit of sealing around windows and so forth. Around surface penetration and what we’ve done to sort of address those. So yeah, that would actually, that would be a nice little case study that we could demonstrate to our audience.


Anthony Jenkin  32:46

I think we’ve all signed off on it, we’re gonna make this happen.


Anthony Stagg  32:50

I’m committed 100%. I’m sure I’m gonna get massive improvements. So yeah, I’m confident I should be able to reduce my air changes, you know, 10 to 20. At least.


Anthony Jenkin  33:04

I’m confident.


Anthony Stagg  33:04

Let’s do it. Let’s do it.


Sandra Redlich  33:05

Awesome. Well, on that note, we’ll see you soon then.


Anthony Stagg  33:11

Thank you very much. I really appreciate the invitation. And yeah, let’s start organising part two of this podcast.


Sandra Redlich  33:19

Will do. Thanks so much for your time.


Anthony Jenkin  33:21

Thank you, Anthony. Really appreciate it. Thank you.