Let’s Talk Building Science with Emily Livesey

[Emily Livesey] So my name is Emily Livesey. I'm a Senior Building Enclosure Engineer with Oculus Building Science and Facades. Just a little bit about Oculus. We're a group of probably about 18 building enclosure engineers, technical specialists with building science backgrounds, and a couple with architecture backgrounds. There are about 12 of us in Auckland, which is where the head office is. There are two in Wellington, two in Christchurch, myself here, and a colleague who is based in Monaco. When I started putting this presentation together, I was thinking about what I should talk about. What I realised is that not everyone has had the absolute pleasure of working with a building enclosure engineer or façade engineer before. It's not uncommon when we get involved in a project, or even when I'm talking to people generally, for them to ask, "What is that? What do you do? How do you get involved in a project?" So I thought tonight I would provide some of those insights and run through what Oculus does, what building enclosure engineering is, how and when we get involved in a project, and what it is we typically do on a project. I'll also take you through an example project and some of the design discussions and considerations that we have. I'll try to keep this concise, but I do tend to get a bit excited about it, so we'll see how we go. So, building enclosure engineering, building envelope engineering, building science, building performance, façade engineering. There are all these different terms. A lot of the time when we talk about façade engineering, people think of vertical surfaces, walls, windows, cladding, and cladding attachment. But the reality of what we do is the entire enclosure. It's everything from below-grade walls and windows all the way up to the roof. It isn't just the pieces on the outside. It's about how we manage heat, air, and moisture between the inside of the building and the outside. All of the things that separate the interior from the exterior are the things we spend our time looking at and talking about. The typical code clauses we deal with are the major ones around building performance. When we get involved in a project, the key clauses people are usually looking for advice or commentary on are E2, External Moisture, and alongside that B1 and B2. Oculus also specialises in H1 modelling, and because heat, air, and moisture are so interrelated, we'll always comment on E3, Internal Moisture, and condensation-related issues as well. One of the key things you can see when talking about heat, air, and moisture management is that you need a clearly defined boundary between the inside and outside. Ideally, and really almost always, that boundary needs to be continuous. If there are gaps in that boundary or gaps in those layers, it becomes extremely difficult to engineer, design, and control those flows. At the highest level, what we do is take a building design and match the loads that building will experience throughout its lifetime with products, systems, and detailing. The loads we look at are location-based and site-specific. We consider wind loads, rain, water penetration resistance, groundwater, sun and UV exposure, thermal expansion and contraction, inter-storey drift, structural deflection, and any movement the building may experience over time. Any way that building is going to move, and any loads it's going to be subjected to, we need to understand those conditions and then select products and systems that can accommodate them. The goal is to demonstrate compliance. We typically work in the alternative solution space because if a building is complying primarily through Acceptable Solutions, there may not necessarily be a need for someone to review it from a different angle. We tend to get involved when something falls outside the scope of an Acceptable Solution, whether that's because of detailing, wind loads, building height, or some other factor that pushes it beyond those limits. That's where we operate most often. The other piece that I think is probably just as important, if not more important than compliance itself, is understanding and meeting client expectations. The reason I would argue that client expectations are sometimes more important than the compliance pathway is because the New Zealand Building Code is fundamentally performance-based. If a building can achieve the objectives of a code clause, then technically it is compliant. However, the majority of buildings are designed through the Acceptable Solutions pathway, and those pathways often focus on individual code clauses in isolation. The challenge is that heat, air, and moisture are all interconnected. You can't really talk about insulation without discussing ventilation. You can't discuss ventilation without discussing internal moisture. You can't discuss internal moisture without considering external moisture. What we often see are buildings that have successfully ticked all the boxes for various Acceptable Solutions, yet the actual performance of the building doesn't meet the client's expectations. I had a conversation recently that related directly to this. It involved a brand-new house where the owner was experiencing significant condensation on the windows. The house was likely built to comply with E2 AS1, E3 AS1, G4, and H1. Every box had been ticked individually. Yet the owner was looking at the result and thinking, "This isn't how I expected my house to perform." That's a good example of how a building can satisfy multiple compliance requirements while still not delivering the level of performance people expected. The window detailing that satisfies E2 AS1 can, in some situations, create challenges for internal moisture management because it pushes windows and thermal breaks toward the exterior and can reduce thermal performance at those locations. Building performance is somewhat unique because the tolerance between success and failure can be subjective and quite broad. For me, a little condensation on the windows in my own house might not be the end of the world. I've lived there for years. But for someone who has just spent a million dollars on a new home, even water on the windows may be considered a building failure. Understanding what the client expects is absolutely critical. When everyone has a clear understanding of what the final outcome should be, you're often in a much better position because we've definitely seen cases where internal moisture issues have led to disputes and litigation, despite everyone being able to point to the fact that the relevant Acceptable Solutions had been followed. So how do we get involved in projects? Pretty much anyone and everyone can call us, and that's fine, but in reality there are a few common pathways. A lot of the time our involvement can be council-driven. Certain councils provide very clear guidance around when an enclosure engineer or façade engineer is required. Other councils have little to no guidance, or guidance that is fairly vague. It really depends. We often suggest that if a project is pushing beyond the limits of E2 AS1 through height, detailing, risk profile, or other factors, then a pre-application meeting with council can be useful because we do see situations where projects are about to be submitted and someone suddenly realises they need a façade engineer. We also get engaged directly by architects and designers. That's usually when they're dealing with unique details, new systems, products from overseas, or something that sits outside typical New Zealand practice. Sometimes they simply want peace of mind and another set of eyes over a project. We also work directly for clients. A good example would be the Ministry of Education, where we may undertake a high-level weathertightness review or provide a PS2. Increasingly we're getting engaged directly by contractors. That might be for pre-construction reviews where we review drawings and identify risks before construction begins. It can also be for construction monitoring or site reviews where they want a second set of eyes on a specific issue or on the building enclosure generally. One thing we've found through that process is that it's been quite eye-opening to see what sometimes gets consented and is about to be built. There are definitely occasions where you look at something and think perhaps that should have been picked up earlier. As for timing, the earlier we're involved, the better. We don't necessarily need to be involved during concept design, but from preliminary design onward is a great time to engage us. The point where we really don't want to get involved is after construction because that's usually when we're dealing with failures, investigations, remediation work, or mediation. So, I'll run through a sample project. This is a local project that I'll call Project X just to protect the privacy of the architects, client, and project team. It's a non-residential building. The project is currently under construction. Stage one includes below-grade spaces and below-grade car parking. Stage two, which is currently in detailed design, includes the above-grade areas. We're involved with the entire enclosure, which includes external insulation to the walls, warm roof systems with ballast, and waterproofing for an external trafficable courtyard. For the purposes of this discussion, I'm going to focus specifically on the waterproofing systems rather than the walls and windows, because those are really a whole discussion on their own. If anyone wants to discuss external insulation afterwards, I'd be happy to. For the below-grade stage of the project, E2 AS1 doesn't cover below-grade waterproofing, so by its nature, below-grade waterproofing is treated as an alternative solution. One of the first things we always try to be very clear about with clients and designers is the difference between damp-proofing and waterproofing. Damp-proofing does exactly what its name suggests. It can resist moisture vapour. However, if liquid water reaches it, there should be absolutely no expectation that it will keep that water out of the building. Tanking systems, on the other hand, are specifically designed to resist liquid water and higher levels of hydrostatic pressure. That then leads to another conversation. What water are we actually talking about? People often imagine groundwater pushing in from below, but there are really three directions water can come from. It can come from below, from the side, or from above. If it comes from below, we're usually talking about groundwater. If it comes from the side, it might be a perched water table, seepage, or adjacent water sources. If it comes from above, it's generally rainfall or irrigation. The next thing we discuss with clients is how the space will actually be used. A back-of-house storage space will have different performance expectations from a retail or habitable space. We take all of those things into account and then determine the most appropriate treatment. Generally speaking, if groundwater is present, we'll recommend tanking. If there is a lift pit, we will usually recommend tanking even if groundwater isn't present because it's the lowest point in the building and naturally where any water is likely to collect. We also need to consider groundwater contaminants because certain membranes can be affected by groundwater chemistry. I recently worked on a project where water testing showed unusually high electrical conductivity levels. We had a hydrogeologist involved because the results were so unusual. Additional testing eventually confirmed that it had simply been an anomalous sample, allowing us to proceed with an appropriate membrane selection. For this particular project, the design initially included full tanking to the walls and beneath the slab, external PIR insulation, and drainage protection. It was a fairly standard below-grade waterproofing arrangement. The question was eventually raised as to whether the system could be changed to a DPM. That's a common value engineering question we receive. Our role in that situation is to determine whether the proposed level of treatment is actually necessary and whether there are opportunities to save cost without compromising performance. We reviewed the geotechnical information and whether groundwater was present. The original investigations showed no groundwater and no hydrostatic pressure. Additional test pits were excavated below the proposed development level, and no groundwater was encountered. We then assessed the intended use of the space. In this case it was a car park, potentially housing some nice vehicles, but also including washdown activities. The idea that the space would remain permanently dry was probably unrealistic anyway. The project also included perimeter drainage and significant sealed surfaces at grade above the underground area. We provided our assessment to the client and contractor and advised that, based on the site conditions, the risk appeared low enough that the change could be considered. However, we also made it very clear that if liquid water did reach those locations, there could be no expectation that they would remain completely dry. The client understood the risks and accepted that outcome. The final detail was a very standard below-grade tanking detail. We reviewed membrane terminations at the footing and at the top of the wall. Around the same time, the XPS protection board system became available, which provided a useful opportunity to replace the originally specified PIR insulation and drainage layer. XPS is very well suited to below-grade environments because it doesn't readily absorb moisture and incorporates drainage channels. In this project it effectively allowed two functions to be combined into one product. One lesson from that detail was ensuring the drainage channels were installed vertically. On one of the early projects where I saw it installed, I specifically told the contractor to make sure it went in vertically. Not long afterwards I received a photo asking whether the installation was correct. It had been installed horizontally. Fortunately they caught the issue before it progressed any further. Waterstops at cold joints are another important detail. If a below-grade structure is going to leak, it will often occur at cracks or construction joints within the concrete. Making sure those details are appropriately addressed is critical. At the time of this presentation, that project is still under construction. The tanking membrane extends down the walls, wraps over the footing, and terminates at the base. Drainage systems, XPS protection board, perimeter drainage, and additional geotechnical drainage measures are all included as part of the final solution. The next element of the project is a trafficable courtyard located above the below-grade parking area. This courtyard not only needs to be waterproofed but also insulated because it forms part of the roof over the enclosed space below. When we first started looking at this area, everything was on the table. We examined waterproofing above the slab, above the insulation, and within the concrete itself using additives. We looked at different materials including liquid-applied membranes, hot rubberised bitumen, clay-based systems, concrete additives, and torch-on membranes. In the end, we had to step back and focus on what the space actually needed to achieve. It would be trafficable by vehicles, meaning we had to account for wheel loads and turning forces. The project had restrictions around height, slope, and weight. It required insulation. The membrane had to function at very low gradients. It had to integrate into surrounding drainage channels and connect seamlessly to adjacent waterproofing systems. To work through all of those requirements, we held multiple workshops involving the architect, client, contractor, structural engineer, H1 modeller, waterproofing applicator, and the wider project team. Ultimately there were probably several ways the design could have been approached, but the final solution was the one that best balanced all of those requirements. One of the biggest lessons from the process was the importance of involving contractors early. Because the contractor was engaged early, we were also able to bring the waterproofing applicator into the discussions. I can't overstate how valuable that was. Without that input, you end up with a small group of people sitting in an office looking at lines on a drawing. The reality is that designers don't always have all of the practical installation knowledge that contractors and specialist applicators bring. Having those people involved early made a huge difference to the success of the final design.