Insulation installation and air tightness

Presented by:

Mark Pohlner – Efficiency Matrix

[The visuals during this video are of the presenter walking through a home during the construction phase and demonstrating the concepts that are being discussed.]

Mark: In this video, we're about to show you the best practice tips for fitting insulation in a standard brick veneer home, to make sure we achieve the best possible thermal performance. In 2019, the National Construction Code added a new requirement to the verification of a building envelope sealing specification. The new requirement aims for a building envelope to be sealed to meet a permeability rate of no greater than 10 cubic metres per hour per square metre at 50-pascal reference pressure, which is roughly equivalent to a 32 kilometre an hour wind. This can be met two ways. Through compliance, through testing, or through meeting the requirement of the National Construction Code in terms of building construction with a focus on sealing and insulating the building envelope. Sustainability Victoria has initiated and developed a new program for as-built verification. This sets out best practice for verification of air tightness and insulation integrity of a new building.

Mark: A blower door test is performed using a fan to simulate the wind blowing against the building's exterior to identify air leakage in the building envelope. Leaks in the building envelope of a home can cause it to feel draughty. When the test is performed, the tester can pinpoint where leaks are by using thermal imaging or using theatrical smoke near the typical problem areas. In a recent program called Zero Net Carbon Homes program, Sustainability Victoria wanted to eliminate uncomfortable draughts in the home by setting a measurable target of an air permeability rate below six cubic metres per hour at 50 pascals. Sustainability Victoria also wanted to ensure insulation integrity of the home reached 95% coverage of the walls and 95% coverage of the ceiling areas.

Mark: Thermal imaging was used to locate missing or poorly installed insulation that can result in the loss of heat and cooling energy, affecting the comfort of the home, and when followed up with visual inspection of the areas, where issues were identified and easily accessible. Failing to effectively install insulation and properly draught proof during lockup, fix and practical completion stages, can lead to failing the as-built verification. Rectification of these issues can be costly because they may involve post-construction remedies such as removing finishes, joinery and even plasterboard, to implement the air barrier and re-instate poorly installed insulation.

Mark: Just so we get a full understanding of how insulation is going to perform to its full potential and get the best value out of it, a couple of key considerations. One is the insulation should be the full depth of the stud. So we really want the installation sitting out here nice and flush with the front of the stud. We're going to be putting out plasterboard and our plasterboard is going to be the second key to the thermal performance of our building. It's going to be the air barrier. So we want our thermal insulation abutting the air barrier.

Mark: What concerns us is that if we get gaps and cracks in the insulation. So if we allow air to transfer from outside and then the insulation is set back to give us an airspace, this is the sort of scenario that will show up in our thermal imaging as a lower performing area of the insulation system. So it's a matter of making sure our insulation is fully recovered, out to the face of the stud, so when the plasterboard goes on, plasterboard our air barrier, abuts our insulation, and we knock out any of that thermal leak.

Mark: Within a wall installation, there could be numerous areas where the insulation will be performing poorly. So we're going to have a look at a number of those. We're also obviously going to be looking at all elements of insulation up in the ceiling. Again, we want nice tight fitting batts. We want them sitting level with the bottom of the roof trusses, ceiling joist or roof beam, so that when we apply the plasterboard, that's our air barrier and our insulation is abutting our air barrier fully with no gaps and cracks and opportunity for cold air or warm air to transfer through. So, that's what we're going to be looking at. We're going to go through those scenarios one at a time, look at some thermal imaging, just so it's fully explained to you at the end of a job when a thermal audit and the auditing process is carried out, you'll see what can possibly be poor performing areas so that we can avoid those in the construction itself.

Mark: Let's have a look at one of the scenarios that I'd like to bring to your attention, internal walls. You will generally, in nearly every case, find that this small cavity here on the outside of the building, will be completely uninsulated. So what's going to have to happen here is, as the external building wrap's going on. So in our case in Victoria, cold climate will be a vapour permeable wrap, as that's going on, we need somebody to go along and install these small pieces of insulation. They’ve got to go in all the external corners and all the locations where an internal wall frame meets an external wall frame. Otherwise, these areas here will show up as a thermal defect. Moving on to some other areas that we find commonly. Look, occasionally there'll be no insulation where the lintels occur, but commonly, we find a bit of insulation put in there, but there's nothing up here where the lintel is.

Mark: While we have quite a high performing insulation, a bit of 50 mm timber has a very low thermal performance. So that will show up on our thermal imaging. What we will prefer to see is a batt that's installed completely. It needs to be checked out. It needs to be installed neatly. And that's going to give us a much better result. Again, just to refer to no gaps and cracks, this is obvious here that there's insulation sort of poorly installed here. So, that's certainly going to show up on our thermal imaging when we audit the house. A situation here where we're using the offcuts of the insulation to fill up one of the stud spacings or void, this is really not acceptable. Again, we've got compression, we've got gaps, we've got cracks. The insulation's not protruding forward to be flush with the plasterboard and our air barrier.

Mark: So by the time you put in three or so pieces of insulation, that's about where we limit ourselves. At the point of when you're putting six and eight and ten pieces in, that is going to show up as an issue in our thermal imaging. So now, if we look at bulkheads, so it forms part of our thermal envelope. What we want to do is make sure that the insulation is hard up against our air barrier. So our internal plasterboard is our air barrier. So we recommend that the bulkhead itself be fully insulated. So we insulate the face, the base, the sides of the bulkhead, and we infill insulation inside the bulkhead so that it's all pushed hard against the plasterboard. So we maintain that air barrier insulation connection.

Mark: Just another important comment within a house, is that there may be a return air void that is unused, or it may be a decorative element of the house that's boxed out or the end of a wardrobe zone, cupboard zone. So what happens in this case, is we'll have a problem with our air tightness because outside of this void, we have ceiling plasterboard providing our airtight barrier. But within here, there will often be nothing in this place of the void. So we need to apply something at the early stages prior to the ceiling insulation, that caps off the tops of these decorative voids or unused return air ducts, ends of cabinets and so forth, to maintain that level of air tightness within the house.

Mark: Now we're just going to talk from another aspect of building health and it's in regards to your internal wet areas, bathrooms and laundries. It's a requirement that not only do we insulate the external walls, because we need the thermal performance for the building, we're going to insulate the internal walls of bathrooms and laundries to reduce what we call the temperature differential, which actually reduces condensation potential. So if we can reduce condensation to its minimum risk, we will reduce mould building up on the inside face of bathroom walls and reduce that health risk to the building. So again, from a health perspective, insulating all the internal walls of wet areas, to reduce condensation and the potential of mould.

Mark: While the insulation on the inside of the wall looks beautifully installed, when we come around to the back of the wall and we start to look at the locations of electrical wiring, you'll see your typical installation of wiring, where it's run through the centre of the stud, compresses the insulation. So we're reducing the thermal performance of the insulation in any area where the insulation's compressed. What is a better option? And our recommendation is to actually run the electrical wiring to the back of the stud by clipping it to the rear of the stud, that allows the insulation to fully recover, allowing the full thermal performance of the insulation. So there's no erosion of the performance of the insulation when we clip the wiring to the back of the stud.

Mark: We're constantly talking about the thermal performance of the building. One of those areas where the thermal performance will be interrupted, is if the switchboard and all the associated wiring, is within the external stud frame. So the requirement is to build a second stud frame to house the switchboard and all that wiring, so that it doesn't interrupt. As you can see behind, the insulation is uninterrupted by all the wiring and work required around a switchboard. Another interruption to the thermal envelope is going to be all your plumbing, hot and cold water pipes, in the external walls. So rather than just installing the insulation, compressing it around the pipe, of course, losing some thermal performance, what we would prefer to do here or what's required here, is to make a cut in the insulation where the pipe work is, opening it up and just encapsulating the pipe work in the insulation. So we get the full performance of the insulation. So it's fully recovered.

Mark: So as we referred to with our wall insulation, about the insulation being tightly fitting and sitting flush with the inside face of the stud. When the plasterboard goes on, the insulation's hard against our plasterboard, which is our air barrier. We need to achieve the same result at ceiling level. So here, commonly you'll see insulation batts a little up and down, so we just need to drop them into place, so they're sitting nice and flush with the underside of the roof trusses or ceiling joist. And in that case, when the plasterboard goes on, which is our air barrier, it will be hard to the insulation. There will be no air spaces, no gaps or cracks, and the insulation will perform to its full potential and the plasterboard will be our air barrier, which is hard against the insulation.

Mark: The plumber is also going to be running pipe work, hot and cold pipe work, through the roof space as well. Generally, he's going to be sitting it on top of the bottom quarter of the truss. So when we come to insulate, the insulation can't go underneath. It will be lifted up over the top. So no longer do we have the insulation abutting the plasterboard, we have this airspace. So the answer here is to remove the pipe work from above the top, sitting on top of the bottom quarter of the truss and relocate the pipework to the underside of the top quarter of the truss or one of the webs of the truss. So the insulation can be installed, hard to the plasterboard, abutting the plasterboard. So we get the full recovery, no air spaces, and the performance of the insulation of the ceiling is continuous and consistent across the whole house.

Mark: So this is a very important one because often what we find in most houses is that there'll be an equipment platform, which is housing your hot water service, ducted heating equipment. And often we find that this zone, being of reasonably large area of the ceiling, will be completely uninsulated. Or we find there is only a 90mm bottom chord or truss with some Structaflor or sheet flooring over the top, so we only find ourselves with 90 mm of insulation, when the actual ceiling batts are going to be at least 200 mm to 300 mm thick. So what's required under your equipment platforms, is to build them up, the required height, to accommodate the ceiling insulation specified. It's always going to be 200 mm to 300 mm thick. So these platforms need to be built up a lot higher than we typically see, to accommodate 200 mm to 300 mm of insulation.

Mark: Another critical element to the thermal envelope, is that you'll often find there'll be a conditioned room above a non-conditioned garage. So it may even be a master bedroom typically. So being non-conditioned below and conditioned above, we need to fully insulate the floor zone between the first floor and the garage. In this case, our airtight layer is going to be our panel flooring to the room above. So that's our airtight barrier. In all cases, we need the insulation to be hard to the airtight barrier.

Mark: So in this case where you will have 300 mm to 400 mm of what we'll call floor zone, we need to fill that zone 300 mm and 400 mm deep with insulation, so that it's pushed hard against the underside of the panel flooring, to the conditioned room above. This will require not a single batt, but most likely two batts. It might be two ceiling batts or a combination of a ceiling batt and a wall batt, to fill up that 300 mm to 400 mm zone. Making sure the installation is hard to the underside of the floor above so that we have that air barrier hard to our insulation zone. And again, it's fully insulated.

Mark: We're moving on to cathedral ceilings, where there is a vertical wall component. And this wall component is part of the ceiling system. This will also occur within things like skylights shafts or any recesses up into your ceiling and roof cavity. So the important fact here is, yes, obviously they need to be insulated. Generally it'll be a 90 mm stud wall. We need to make sure the insulation that's introduced into this vertical stud wall, is a high-performance batt. So that high-performance batt is going to be a 90 mm thick, R2.5 or a R2.7 glass wall.

Mark: Now because it's a vertical wall, there'll be no wall lining to the rear. So they'll need to be strapped in place to make sure that over time, they certainly do not fall into the ceiling cavity and you lose the thermal performance of the batt in the system. Again, nice and tight, flush with the face of the stud work, strapped from behind. We are now going to talk about a very important component of our roof, ceiling insulation. This is critical because what you'll find is your building documentation, your energy rating, will call up a ceiling batt. It may be a R4, R5, R6. Those batts are 200, 250 and nearly 300 mm thick. So let me show you that if in this case, this is a R4, 200 mm batt. If I pull that out and imagine that being installed in a ceiling, you can see that it has to be compressed in the place around the eaves. In which case, what it's doing is stifling any air flow into the roof cavity.

Mark: So the requirement is, that the specified batt can only be installed to a point where it maintains a minimum 25 mm clearance to the underside of the roof, for what we call roof ventilation. So what's the answer? The answer is, we're not going to leave this uninsulated, this perimeter of the building. So there's a requirement to introduce a perimeter batt. Very simply. I'm going to suggest we take a wall batt, a 90 mm thick wall batt. Now it gets installed first around the perimeter of the building, being only 90 mm thick, rather than possibly the 200 mm thick of the body of the ceiling insulation. It sits in place and it can be a half batt. So all the common batts are cut into a half, so that it sits around the perimeter, maintaining that airflow between the insulation and the underside of the roof.

Mark: So a perimeter batt, let's call it a half size batt, half length, followed by your R4, R5, possibly our R6 batt, maintaining that air space of 25 mm throughout. Then we get nice clean air flow from the eaves. Hopefully there are eaves vents and ventilation potential in the eaves itself. You may have a roof vent at the top. So now we get that relief air coming from the eaves and the roof cavity itself is freely ventilated. This is critical because there is a significant health issue. You stifle air flow to a roof space, you will build up moisture, create condensation, and that may very well grow mould in your roof. So that's a significant health issue. The reason for the perimeter batt, is to maintain the airflow to eliminate mould and any health issue associated with excessive moisture buildup in the roof cavity.

Mark: In this first video, we've looked at the installation performance around a typical home to make sure we get the best thermal performance out of the installation of the insulation. In the next video, video two, we're going to look at achieving an more airtight building, another critical element to achieving a far more efficient and comfortable building.

Presented by:

Mark Pohlner – Efficiency Matrix

Joseph Cheung – Efficiency Matrix

[The visuals during this video are of the presenters walking through a home during the construction phase and demonstrating the concepts that are being discussed.]

Mark: In this video, we will go through ceiling requirements at the plaster stage of construction in a standard brick veneer home. In 2019, the National Construction Code added a new requirement to the verification of a building envelope ceiling specification. The new requirement aims for building envelope to be sealed to meet an air permeability of not greater than 10 cubic metres per hour, per square metre, at a 50 pascal reference pressure, which is roughly equivalent to a 32 kilometre an hour wind. This can be met in two ways through compliance testing, or through meeting the requirements of the NCC in terms of building construction. With a focus on ceiling and insulating the building envelope. Sustainability Victoria has initiated the development of a new program for as-built verification. This sets our best practice for verification of air tightness and insulation integrity of a new building. A blower door test is performed using a fan to simulate the wind blowing against the buildings' exterior to identify leakage in the envelope. Leaks in the building envelope of a home can cause it to feel draughty.

Mark: When the test is performed, the tester can pinpoint where the leaks are by using thermal imaging or using theatrical smoke near typical problem areas. In a recent program called Zero Net Carbon Homes Program, Sustainability Victoria wanted to eliminate uncomfortable draughts in the home by setting measurable target of an air permeability rate below six cubic metres per hour, per square metre at 50 pascals. Air tightness is an important consideration when building a home. A home that is not airtight will feel draughty and will cost lots more to heat and cool. In this video, we will go through the ceiling requirements at plaster stage for a standard home. Failing to effectively install insulation and properly draught-proof during lockup fixed practical completion stages can lead to failing the as-built verification. Rectification of these issues can be costly because they can involve post-construction remedies. Such as, removing finishes, joinery, even plasterboard to implement an air barrier and reinstate poorly installed insulation.

Mark: I'm here with Joseph. Who's an expert in the air tightness aspect of buildings and especially homes. So as in video one, we spoke all about installation. We've mentioned that we use the plasterboard. The internal plaster board of the building as our air tightness layer to achieve a draught proof building at six cubic metres per hour, per square metre at 50 pascal.

Joseph: All that we are talking about is just how to create a continuous air barrier so that draught can be minimised.

Mark: So okay Joseph, let's look at it in a bit more details. Specifically, the major details are the junction at the floor, internal, external corners. The corners, be it a cornice or square set, commonly and even bulk heads. Give us a bit of an overview of the strategy.

Joseph: The good news for the plasterers is there's nothing too difficult for you to do. For all the corners, internal, externals, or the square set to the ceiling, it's just conventional practice. Just make sure you do it nicely. And when it's look good, it's air tight. For the junction to the floor, you want to seal it before you install the skirting board and the way to do it is usually because we having some unevenness on the floors lap. So we typically would recommend an 8mm gap. When you're lifting the plasterboard, you use some 8mm packers to hold it in place. Then after you fix the plaster board, all you need to do is to use a 10mm backing rod to stuff that in. Then you can use caulking to mask and seal the joints, and you will use the same techniques to deal with the ceiling junction, if you are installing cornices.

Mark: Again, it's a lot of sort of masticing, but of course, backing rods are obviously useful.

Joseph: And the good news is because we are going to install skirting board or cornices on top of it. So it doesn't need to be a very nice job.

Mark: Little question about bulkheads, because there's a really important point to be made.

Joseph: Well for bulk heads, practically, what you need to do is, you need to fully encase the bulkheads with plasterboard regardless, or there will be hanging cabinetry underneath it. Because it is very common when there is cabinetry or joineries installed, the plasterer don't sealed it with plasterboard, but because it's going to have the cabinet there anyway. But when we talk about air tightness, if you don't seal it with plasterboard, the gap between the joinery or the cabinetry and the frame would become a major source of draught that all your heating or cooling will lose.

Mark: Joseph, we've moved across to a little mockup of a return air conditioning system. It's not exactly typical, because you are going to explain what needs to happen to achieve a level of air tightness. Knowing that we know that these return airs leak like a sieve.

Joseph: This is very much one of the worst parts in your house. When we are talking about draught proofing. Believe it or not, the top of it is very typical as shown here, nothing on top of it to cap it off. The installer is just drop a flexy duct into it and voila, that's their return air planning. Also the size, they usually encapsulated with the interior plasterboard. Of course, we can air seal that by masticing it or the junction from the inside to the plasterboard. But believe it or not, it will cut your work by more than half, by lining the interior.

Joseph: Because when you look into it, you will see, if you line the interior, all you have to seal is just one junction along the two back corners. And then for this side, close to the front, you just seal that plaster board to the stud frame. And then all you need to do after that is before you install your final piece of plasterboard, put a bit of caulking there and then you install your final piece of plaster board. Then you got an air tight seal on all four side and for the top always have a cut out capping. So you put a bit of caulking before you screw down this final piece. And then the mechanical installer can have their duct work attached to it.

Mark: So this spigot goes on top. So actually this is not common practice that now your flexible duct hooks onto a spigot, the spigot sealed to the cap, the cap sealed to the framing. We've got internal lining all mastic and caulked, top, bottom. Very much like our internal plaster board.

Joseph: Exactly.

Mark: Treat this like internal plaster board. Mastic it at the corners, the floor, the internal corners, all that sort of stuff. And all of a sudden we've got a sealed unit.

Joseph: Yep.

Mark: Now it's not common to see it done this way.

Joseph: No, it's way easier to do it this way than you try to do the conventional way and try to find all the nitty gritty junction inside. Because I can guarantee you, you will miss at least 20% of those gaps.

Mark: It seems reasonably straightforward. Doesn't it?

Joseph: Yep.

Mark: I'm going to say I don't know a reason why this can't be done every time.

Joseph: Well, the only reason is most trades don't know they need to do it.

Mark: Yeah, that's right, exactly.

Joseph: Or the benefit of doing it.

Mark: So unfortunately when the air tightness audit and the test is carried out and we are not hitting the target, unfortunately we are just going to walk straight over to the return air.

Joseph: Yep.

Mark: And we are going to see what's happened inside.

Joseph: Yep.

Mark: And that's going to be the potential area of failure.

Joseph: If it is not seal, half of the conditioner is not returned to the system at all. It just go out to the roof.

Mark: Okay Joseph, we've got a lovely double-glazed PVC, locally made window in front of us. Just give us the overview of ceiling up doors and windows.

Joseph: Well doors and window, the treatment is virtually the same. All we need to focus on is this gap between the reveal and the stud frame. Traditionally, most people when they're doing with draught proofing, they are just dealing with the architrave around and seal caulking on both sides. While that may give you good result for the first six months to a year, because they are so thin, those seal can easily be broken with time and slight movement around. That's why if we want to do it properly, have long lasting results. We have to deal with the gap here.

Mark: So Joseph, are we playing with backing rod and caulking?

Joseph: Well, it really depends on how the window installer is doing, but most likely we are dealing with a gap more than 15mm. And it's not ideal to use caulking when you have a gap larger than 15mm. So what do we do? We use a product called Expanda Foam, but you can't use any Expanda Foam because the window is not as strong in a sense, or it's very restrictive, the gap. If you use ordinary Expanda Foam, you are running in the risk of that have too much a force when it expanding and bulk this reveal. So we always recommend, we put some backing rod towards the outside of the stud frame. And then we use a low expansion flexible foam to fill this gap. Then you can both have the performance of air seal as well as it provide insulation as well.

Mark: Right.

Joseph: Two birds with one stone. Why not?

Mark: So we've got the window installer putting a backing rod in from the outside and we've got expanding foam, low.

Joseph: Low expansion.

Mark: Low expansion foam, filling up the inside.

Joseph: Yep.

Mark: I've seen it expand out. So there's always the necessity, once it has sort of set or dried.

Joseph: And you trim it.

Mark: Trim it off.

Joseph: Yep.

Mark: Simple.

Joseph: And then it just conventional plaster board on, and then architrave on. And then the painter can do their finishing caulking as they like. Okay, now come to my favourite internal cavity sliding doors. Why is it my favourite? Because this internal cavity sliding door can leak huge volume of air because when the piece of door going in and out, you got big gap on both side. And typically when the plaster board being installed, it's not really flush to this frame and it create a big gap. Air can go around to the side, to the other part of the wall or go directly to the roof. To deal with that, we need to create an encapsulation. To do it, is not too hard.

Joseph: First, you need to identify which part of the stud frame forms the pocket housing this sliding door. Step number two, use caulking mastic to seal the junction of this pocket of stud frame, both top and bottom. And then, this is the interesting part. We use low profile memory foam strip. Typically, you use that for door and window sills to create a gasket all around this pocket. So, when you install your plaster board it create a compression seal all around. Or you, the plasterer needs to do is ensure you got plaster screw to have pressure all around this pocket.

Mark: In this video, we went through all the ceiling requirements at the plasterboard stage. For more details on the individual areas, referred to the as-built verification checklist available on the Sustainability Victoria's website to learn more about air tightness at the practical completion and insulation stage. Watch the remainder of the videos in this series.

Presented by:

Mark Pohlner – Efficiency Matrix

Joseph Cheung – Efficiency Matrix

[The visuals during this video are of the presenters walking through a home during the construction phase and demonstrating the concepts that are being discussed.]

Mark: In this video, we'll be addressing ventilation and airtightness, and insulation issues for plumbing, electrical, and joinery trade services at the practical completion stage of construction. In 2019, the National Construction Code added a new requirement to the verification of building envelope sealing specification. the new requirement aims for a building envelope to be sealed to meet an air permeability not more than 10 cubic metres per hour per square metre, at 50 Pascal reference pressure, which is roughly the equivalent to 32 kilometre an hour winds.

Mark: This can be met in two ways; through compliance testing, or through meeting the requirements the NCC in terms of building construction, with a focus on sealing and insulating the building envelope. Sustainability Victoria has initiated the development of a new program for as-built verification. This sets out best practice for verification of airtightness and insulation integrity of a new building. A blower door test is performed using a fan to simulate the wind blowing across the buildings exterior to identify air leakage in the building envelope. Leaks in the building envelope of a home can cause it to feel draughty. When the test is performed, the tester can pinpoint where the leaks are by using thermal imaging or using theatrical smoke near typical problem areas.

Mark: In a recent program called Net Zero Carbon Homes Program, Sustainability Victoria wanted to eliminate uncomfortable draughts in the home by setting a measurable target of an air permeability rate below 6 cubic metres per hour, per square metre, at 50 pascals. Finally, failing to properly ventilate the building can increase the risk of mould growth. It is recommended that the building have mechanical heat recovery ventilation if the permeability rate is below 3 cubic metres per hour, per square metre at 50 pascals.

Mark: Joseph, we're getting very close to the final completion of our home, achieving that thermal performance and airtightness, energy efficiency of a house. So, we've got our elaborate thermal box in front of us to elaborate on some of those final little requirements.

Joseph: Well, let's look at all the surfaces' penetration, including the plumbing, electrical, and also the exhaust. All these components are penetrating what we talk about from the last video, the plasterboard as the air barrier. So we need to deal with them, checking how are we going to reduce any air leaks or the gaps between those holes and the plasterboard.

Joseph: A lot of people worry about their switches, or GPO. But in reality, since we are not trying to build a super-duper air-tight house, so those small amount of leakage is acceptable. But when we talk about something like the plumbing, where you can see there is, in general, more than 5 to 10mm around them, then we need to do something to treat them. Typically the conventional way to deal with that hole is just to put a covering plate to make it look good, but it doesn't seal it to be any level of airtightness. What we recommend you to do is to use caulking mastic, to seal between the pipe and the plasterboard, then you can go through the traditional way to put whatever, make it look good.

Mark: Yeah. What, we're not relying on, being plumbing it's often tile, call it a shower recess, we're not going to rely on the tiles, for example.

Joseph: No.

Mark: It's got to be done at the plasterboard level; the mastic, the caulking, direct.

Joseph: Yes, exactly.

Mark: That's how it's got to be done.

Joseph: And if you have to do a waterproof membrane behind your tiling, that should be the point where you also do your air seal. And then we talk about the ceiling-mounted elements, which commonly we see are downlight or surface-mounted light.

Mark: So our typical download LED is going to be reasonably air-tight. There's no airflow through LEDs because they don't generate the heat.

Joseph: If you want to be particular, you should be looking for the IC-4 rated downlights. They are safe to be covered by insulation as well. The unit itself is air-tight.

Mark: It is always best practice that all downlights installed in a home are IC-4 rated. And the marking looks like this. They must be installed as per the manufacturer's instructions, which for IC-4 rated recess light fittings is usually to be abutted with insulation and covered, but must also be installed in accordance with AS 3000:2018. If the control gear is separate to the recess light fitting, it must not be covered or sitting on top of insulation. It must be fixed away from the insulation.

Mark: It is recommended that the following label is displayed at the manhole to reduce the risk of future occupants installing non-IC rated, do not cover recess light fittings, and unknowingly cover them with insulation. Also, there's nothing wrong, I always say nothing wrong with a surface-mounted or batting-

Joseph: Nothing wrong with that.

Mark: ... because they're always going to be really reasonably air-tight.

Joseph: Yep. You may got a tiny bit of air leaks through the screw holes, but when you look at the whole situation compared to your doors and window gaps it's nothing.

Mark: There's far larger gaps than that to worry about. And again, we're not aiming for a completely air-tight house. Some of these tiny little leaks around GPOs, light fittings are acceptable and are going to be-

Joseph: In 95% of the time. But-

Mark: Let's have a look at the cabinet because this is-

Joseph: The cabinet is where it can go really wrong because typically when we have a GPO inside a cabinet, the GPO is just mounted on the back of the cabinet. But when we look at the sideway, typically they are not really sealed to the plasterboard. What did happen is the holes is open to the rest, the entire air gap, and it opened up path for air to coming in from the wall cavity. So whenever you deal with cabinet in built switches, always, always mount it on the plasterboard and make the opening with the cabinet so you can reach it.

Mark: Well, it's simple. All the airtightness is achieved at the plasterboard.

Joseph: Always go back to the plasterboard.

Mark: Simple as that. And we've said it, how many times? The air tightness layer is the plasterboard and everything's sealed at the plasterboard.

Joseph: The other areas are the doors. Most of the time we have doors seal on the side, the top of the door, but the bottom, not always the case. So we need to consider some kind of seals is either drop seal in the more high end doors. Or you can install one of those flap seal that will provide a reasonable seal when the door is shut. And also the other door that is very commonly omitted for door seal is the door between your home and the garage. That door most people think is indoor and not worry about it, but there's no conditioning in your garage unless it's a man cave. That's a different story.

Mark: Yeah, no. And if your garage doors are up and you're facing the wind, the amount of wind that blows in and the pressure inside your garage, you'll leak massive amount in your garage.

Joseph: Yes. And every time you start your car engine in your garage all the fumes we'll just go indoor. We already covered that the insulation and the airtightness now is the last part of the trinity, the ventilation. For this program we recommend all the exhaust system go directly outside, unlike the traditional home, all the yucky stuff, all the odour, contaminant just blow and stored in your attic space. You don't really want that to happen,

Mark: Now with bathrooms and laundries and wet areas, commonly, you can turn them off and on yourself, but you can introduce a humidity sensor.

Joseph: It's a way better idea to rely on a humidity sensor. First of all, I don't know about you, if I'm using just a switch as soon as I finish, I leave the room, I switch it off. But typically, especially after shower, the bathroom will stay at a pretty high level of humidity for way longer than 10 to even 15 minutes. So if the exhaust fan have a humidity sensor, it will modulate and greatly, greatly reduce the risk of condensation and mould growth within your bathroom.

Mark: Great idea, of course, all these exhaust to the outside need a draught stopper.

Joseph: That's without saying. And for new building, there's no reason why you wouldn't put a draught stopper. If it is not already built into your fan, if you want to have a healthy and safe indoor environment. And if you have gas cooktop always install a CO sensor because you never know if there will be any failure of your gas appliance and the CO sensor can potentially save your life.

Joseph: Okay. One last thing. Usually, the last piece of puzzle constructing a new home is the attic hatch. Typically you just got a thin piece of plasterboard slotting to shut that hatch door. But when you consider how much insulation all around the hatch is wise to do this, where you insulate your attic hatch access.

Mark: Yep. Look generally we know that the ceiling insulation throughout a house is going to be R4, R5 and most likely R6, which is our very high performance of insulation. In this case here, we've got three layers of 25mm. It's basically R3. Okay. So that's what we're adopting as our minimum requirement, is a rigid foam at an R3 performance. And that's going to do the trick beautifully, compared to usually nothing.

Joseph: Oh, when you have nothing or if you try to use even more board to make up the R6, it may be too hard to close.

Mark: Exactly. Airtightness, insulation, and ventilation are important considerations when building a home. Not ventilating properly on any home can lead to a poor indoor air environment, which encourages the growth of mould. Typical problems to look out for at the final stages are building services. It's important that all trades replace and re-instate insulation, they have moved in doing their work, ensure that wet areas are vented directly to the outside.

Mark: For more details on this video and others in the series refer to the As-built verification checklist available on Sustainability Victoria's website.