Building a Home for a Better Seal | Part 3

John: Today I’m with Berkhard from CARBONlite. We’re going to talk about good practice for weather resistant barriers and common practice for weather resistant barriers. Berkhard, we’ve got a common sort of installation and sarking here. What are the issues with this?
Berkhard: Well here we’ve got a scenario which could be built to common six star rating – if you like. So you’ve got a non diffusion, non-permeable sarking in this scenario the main aim is to keep the weather out and make make it wind resistant and weather resistant. But as you can see here, most of the joints are not sealed. Then you’ve got the joints around the window, the gaps around the windows, are not sealed. If they’re sealed, sometimes you see them sealed really poorly with duct tape, lasts about a couple of weeks and all come off. And like just lasts long enough for the cladding to go on. It’s it’s not a solution that will last for decades.
John: So that that’s with the junctions around windows, but also with how they’re overlapping potentially as well, or if penetrations go through, you know, nothing is really continuous.
Berkhart: No, there is no.. you can see some of the gaps around the windows here are all open. So it’s, it’s just not even …. we’re not even talking about high performance,it’s just simple rain actually getting into the structure. So you won’t just have your reduce, massively reduced thermal performance of the house, you will also actually have water getting in, and resulting in structural damage, and rot and mould. John: All right then, let’s move over now to good practice. Okay Berkhard, so this is now good practice with a membrane. Show us have this differs from what we just saw. Berkhard: Yeah, so if you imagine this wall is perfectly sealed, weather-tight and wind resistant with the membrane continuing through. Now if we start cutting a hole into it, we would have to recreate that connection to our window. In the conventional construction you saw that on the other side, it’s just cut flush with it the subframe opening. So there’s no tape, there’s no seal connection, there’s no water tight connection. So water has got unrestricted access to the building. Now in this scenario here, we’re creating, on the bottom we’re creating, a seal flushing before installing the window. Then the window frame is prepared with the double-sided tape, okay, so that tape is on the window first, simple installation and then we’re folding it and taping it onto the membrane. Now we’ve got a completely sealed weather-tight and diffusion-open connection to the window, and we can rely on this membrane to keep the weather out before cladding goes on.
John: So for this weather resistive barrier, let’s hit it with the hose, and see how both sides perform. So Berkhard, we’re simulating 30 km/h winds on this enclosure right now, which is blower door testing. Let’s hit it with some water and see if, how much of it goes inside.
Berkhard: Yep. We’ve got two settings, so I’m just going to put a light rain, so I mist, and then we’re moving on to a bit more pressure. Real life scenario, you know, we don’t want to…
John: You can clearly feel airflow around this window, especially on the sides too, right? Berkhard: Yeah, and it’s 30 km/h winds, you know, it’s not anything outrageous we’re talking about.
John: And if this water gets in, all the insulation under the window is going to get saturated.
Berkhard: Well it’s not just the insulation that it’s, the most concerning part are the structural components in there. So if the structural components start being wet inside inside their wall, then you’ve got a non diffusion of the membrane and all of a sudden you closing that moisture into the wall structure and and that really results in in structural damage, you know? That’s a real concern. So this is now the shower function, so a bit heavier rain right?
John: Yep. Berkhard: That’s that’s heavy rain, right? We’re trying to showcase the point here. John: Okay, let’s check out the other side with good practice. Berkhard: Yeah, let’s do it. John: Okay, Berkhard, now without hosing me down, let’s see what this one does.
Berkhard: Alright, well just got this on mist alright, so we’re just trying to do it, we’re going to do a couple of runs. One in like light mist, and then a bit of heavier rain.
John: Yep! Berkhard: Okay. So we’re just trying to get a realistic scenario off to the decent rain, and we can also set this at a higher…
John: I mean you can see that it’s the water’s just not going anywhere, right?
Berkhard: No, it’s just it’s just running off. I mean, it is just doing what it’s supposed to do. This thing is this is completely sealed. There’s no problems at all. And this is not just water, this is also wind obviously, as well. John: Alright so now let’s go and have a look inside. Using amazing building materials is only part of the story. The most important part of constructing a building, is making the important connections for air tightness and weather-proofing. If you think this footage doesn’t show common practice well enough you should take a drive around any major construction site in Australia. You’ll find many examples of exactly the same level of workmanship. When we talk about building for a better seal, we’re not talking about sealing up houses so that people can’t breathe. We’re talking about keeping our homes dry from rain, and from rotting from the inside and the outside. We want to protect the occupants by providing good ventilation, and proper sealing. Build Tight and Ventilate Right. The future of residential building in Australia will be strongly influenced by consumer demand for energy efficiency, comfort, climate resilience and quality. But the Building Codes Board and Australian Governments are committed to the COAG trajectory for low energy buildings and this will affect building regulations including the NCC. Builders will be expected to place increased emphasis on meeting and proving energy efficiency compliance. You’ll be asked, more and more, to understand and deliver both code compliance and long-term building health and performance. You will need to Build Tight and Ventilate Right.


  1. What about using ZIP2 for wall construction ?
    Zip 2 systems come with various level of insulation attached and tapes and sealers to use for joints, windows and doors.

  2. All new buildings need to be energy efficient and be built to last with great weather proofing.
    It only takes a little more effort to do a quality job.

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