Hidden hero: the importance of BMS 

The BMS is really the brain of any building. You can have the most energy-efficient equipment available, but if the controls that manage those systems aren’t working properly, then you won’t see those gains.” 

This is how Chris Stamatis, M.AIRAH, explains the importance of building management systems (BMS). As the director of CopperTree Analytics Australia, the associate director of AIRAH’s Big Data and Analytics Special Technical Group, and an AIRAH national board member, he knows a thing or two about the topic.  

Stamatis has offered to take my colleague – AIRAH Advocacy and Policy Manager Mark Vender – and me behind the scenes of a commercial building in Melbourne so we can get a sense of how a BMS functions and what can happen when things go wrong. 

The site we’re visiting is a 34-floor office building at 50 Lonsdale Street, and our accomplished tour guide for the morning is Trevor Smith, Affil.AIRAH, Victorian service manager at Delta Building Automation. Smith and Delta manage the maintenance of this BMS and many others across the country.  

Before we embark on the tour, Stamatis gives us a glimpse of the BMS itself. The manifestation of this complex system is a software interface that can be monitored and controlled from a web browser. I’m sure it’s breathtakingly complicated in its entirety, but to someone who doesn’t really know what they’re looking at, it seems quite logical and user-friendly. 

More importantly, I’m excited to learn how this piece of software connects with the brick and mortar building around us. 

Handle with caution 

Our first stop within the building is to check out an air handling unit (AHU) on level 18. This is situated behind a closed door labelled “HVAC”, in an area that is bigger than I expected. 

If the BMS is the brain of the building, then the AHUs are its lungs. These systems draw in air from outside and exhaust it, as well as recirculating the air that is already in the building. This is a balancing act; while the internal air might already be at the desired temperature, it will eventually become too high in CO₂, volatile organic compounds (VOCs) and other pollutants from inhabitants, at which point it needs to be exhausted and replaced with outdoor air.  

Outdoor air will be cleaner – especially once it’s been filtered – but is likely to require heating or cooling to get it to the optimal temperature. To manage this, each AHU has two large vent systems: one for outdoor air and one for recirculated air. The BMS is responsible for maintaining the balance between the two. 

Many buildings operate with only a handful of AHUs, meaning that if something goes wrong with one of them, a large chunk of the building could experience uncomfortable conditions. 50 Lonsdale Street is much better kitted out than most: it has multiple AHUs on each floor, giving the overall building HVAC system much more flexibility in managing conditions in different occupancy zones. 

Smith opens one of the panels on the AHU so we can look inside. We see an array of pink, pillow-shaped filters, whose job is to filter out particulates. These filters are almost brand-new and in pristine condition, but if they’re not replaced regularly, they’ll soon become clogged and unfit for purpose.  

The installed filters are rated to the MERV-13 standard, meaning they’re highly efficient at reducing PM10 particulates. It’s no coincidence that we’re looking at almost new filters; they get replaced on a regular basis – before the end of their lifespan – to minimise fan energy consumption. 

There is also an array of air conditioning coils, allowing AHUs to tweak the temperature of intake and recirculated air. This is important for the next link in the chain: variable air volume (VAV) systems. 

Going with the flow 

VAVs are the points at which the air from the AHU gets released into the occupied space. It might be pushing our metaphor slightly to suggest that VAVs are like the building’s blood vessels, but they serve a similar purpose in terms of circulating oxygen throughout the space. 

The BMS controls when the VAVs open, how much air they release at any given time, and the temperature of the air that comes out. A well-programmed BMS can make the most of these VAVs, ensuring that the building heats and cools when it’s most energy efficient to do so. 

For example, if the outside air is cool enough, the system can go into economy mode and use the outdoor air to provide free cooling, rather than calling on the building’s chiller to do the work. 

Each floor of 50 Lonsdale Street has at least 30 VAVs. As Stamatis and Smith point out, the complex way in which thermal energy and air move throughout buildings means that, even on the same floor, certain areas might need to be heated while others are simultaneously cooled. Thankfully, the BMS is smart enough to manage this complex balancing act. 

Transparent problems 

Thermal load is a major consideration for any office building, where a huge percentage of the external walls are typically glazed. Regardless of the quality of glazing, the windows are a major source of thermal loss or gain, depending on factors such as sunlight and outdoor air temperature.   

“Within the same floor, you’ll have some zones close to the windows and others towards the centre of the building,” says Smith. “Those zones near the windows are much more variable; strong sunlight will cause them to warm up dramatically, whereas cold outdoor air will cool them down a lot. This means that you often need to simultaneously heat and cool different zones within the same floor.” 

Because of this, certain VAVs are fitted with a reheat coil, which allows the air coming out of that VAV to be heated at the point of release, depending on what’s required. Typically, those VAVs closest to windows or areas where temperatures fluctuate regularly will have a reheat coil, while those towards the centre of the floor – where thermal mass keeps temperatures much steadier – don’t need one. 

As we move towards the next stop on our tour, Stamatis points out some of the additional challenges that a layperson wouldn’t be aware of when thinking about a building HVAC system. 

“If you look at this floorplan, it’s mostly open plan, but then you’ve got these small meeting rooms in the middle of the floor that don’t have any external windows,” he says. “Trying to balance the needs of the open plan area with the special requirements of small, enclosed areas like this is one of the biggest challenges in designing an HVAC system and a BMS to manage it.” 

Sensory overload 

We’ve already identified the brain, lungs, and blood vessels of the building. Let’s expand our metaphor to include the many connected sensors placed throughout the occupied space, which function as the building’s nervous system. 50 Lonsdale Street has a whopping 950+ zone temperature sensors and 4,100+ sensors in total. All of these provide real-time data to the BMS to keep the HVAC system operating smoothly.  

This is where, according to Stamatis, good design and programming are vital. While at first it might seem logical for each sensor to have complete control over the area it monitors, there’s a very good reason why this isn’t the case. The BMS is programmed to use data from multiple sensors – typically four or five – to calculate airflow and temperature for each AHU, then adjust the flow through the VAVs accordingly. This means that if one sensor fails, the system can adapt and use the average readings from the other sensors to keep conditions comfortable. 

The alternative is much less palatable, both from a thermal comfort and energy-efficiency perspective. 

“If the BMS isn’t programmed well, one faulty sensor could be enough to derail the whole system,” Stamatis says. “You could have a sensor that faults and starts reading -50°C. If the BMS isn’t flexible enough to recognise that as a fault and adapt, you’ll suddenly get one zone where the VAV is pumping in extremely hot air to compensate. 

“Not only will you have a lot of unhappy workers in that zone, but you’ll be putting a huge amount of unnecessary energy through the boilers to heat the air up.”   

It’s now time to make the journey to the top of the building and inspect those boilers. 

View from the top 

Our ears pop as we take the service elevator up to the 34th floor of this skyscraper, where some of the most serious HVAC equipment sits. Parts of the plant room are enclosed, but most of the kit sits out in the open air. This includes the large intake vents and the cooling towers. Thankfully, it’s not too hot or windy today, so being out on the roof of the building is quite pleasant. 

I take a second to admire the view over Melbourne’s eastern suburbs from the freshly waterproofed roof. It’s a truly spectacular sight, but it also reminds me of how high up we are and just how megalithic a building we’re in. Keeping such a beast operating seamlessly must be a tremendous responsibility; I have a newfound admiration for the largely unseen work professionals like Smith and Stamatis do. 

We head indoors to admire the building’s three huge gas-fired boilers. The BMS tells these boilers when to switch on so they can heat the water that is eventually pumped down to the AHUs when needed to heat the air. In the 15 or so minutes we’re in the plant room, only one of the boilers briefly fires up, suggesting that this is a low-demand period. 

I register my surprise that, in a building such as this with a 5.5-star NABERS rating, fossil fuel boilers haven’t yet been replaced by an electrified system. Smith points out that, while transitioning from gas-fired boilers to heat pump systems is necessary to achieve decarbonisation goals, it’s not always as easy as it sounds.  

“Unfortunately, to replace this set-up with an equivalent heat pump system would take up about three to five times as much space,” Smith says. That kind of accommodation can be planned for a new build, but in an existing building that is already limited by tight space constraints such as this one, it’s an extremely difficult ask. 

Aside from the space requirements, simply getting the equipment up to the roof of the building is far more challenging than I had considered. As Smith notes, the elevators wouldn’t do the job; the only ways to get such heavy equipment up to the top of a 34-storey building would be to hoist it up with a crane or fly it up with a helicopter.  

As I remember that giddy feeling from the roof just a few minutes ago, neither of those two options sounds particularly appealing.  

Licence to chill 

From the top of the world, we plummet down to look at the building’s chiller system, nestled five floors below ground in the basement. The role of the chillers is to remove heat from water, then pump that water back through the building and the AHUs to produce a cooling effect. 

The BMS is crucial in managing the chillers; it calculates when to switch the systems on to maximise energy efficiency. Indeed, Smith says the chiller system at 50 Lonsdale Street is only operational about 120 days of the year, when cooling demands are highest. 

Stamatis notes that this contrasts with many buildings in the USA and the UK, where chillers often run 24/7 regardless of needs. I’m shocked to hear this. Stamatis estimates that running the chillers continuously uses two to three times as much energy as a system like the one at 50 Lonsdale Street.   

Vender asks whether it would be more efficient to put the chillers on the roof, so that the condensing water wouldn’t have to be pumped up more than 30 floors to the cooling tower. However, as Smith and Stamatis point out, the sheer weight of the chillers makes this difficult. 

Remembering the challenges of getting the boilers up onto the roof, I ask how these humungous pieces of equipment can be swapped out when the time comes. The solution here is much simpler: the kit can be disassembled and literally wheeled out through the carpark. Sometimes amid all this complexity, the simplest solution is the best. 

AIRAH’s Big Data Guideline 

Chris Stamatis, M.AIRAH, is the Associate Director of AIRAH’s Big Data and Analytics Special Technical Group (STG). In 2024, the STG release its highly anticipated Big Data Guideline – a best practice guide for anyone applying the principles of big data and analytics to the HVAC and building services sector.  

The guideline is available for free online: simply search “AIRAH Big Data Guideline”. 

No performance without maintenance  

Of course, with all these components, there’s plenty that can go wrong. Both Smith and Stamatis emphasise just how important it is to not only conduct regular maintenance, but also to look for continuous improvement. 

“We’re moving away from scheduled maintenance to data-driven maintenance,” Stamatis says. “That means we use data from the system to show which sensors or components of the system aren’t performing at their best and target them.” 

“If we were to spend 15 minutes checking each of the VAVs in this building once per year, it would take months,” Smith says. “The data allows us to isolate, say, our 10 worst-performing VAVs and check them, instead of going floor by floor throughout the building.” 

I ask whether AI and big data can help predict when to perform that maintenance.  

“The ultimate goal is predictive maintenance, where the system can use data to forecast when a component is about to fail,” Stamatis says. 

However, while that sounds great in theory, the reality is much more complex. 

“It’s not that difficult to forecast when something like a chiller needs to be replaced,” Stamatis says. “The data shows a steady decline over a long period of time, and at a certain point, we know it becomes more economical to replace it with a new one. 

“With electrical components, some components last for 20 years, while others break after a few months. We dream of being able to model and predict all of those factors, but we’re not quite there yet.”  

Lessons learnt 

As we finish up our tour, I come away with an overwhelming sense of just how many components go into keeping a building habitable, something most of us take for granted. I also realise that my understanding sits at the absolute tip of the iceberg; Stamatis and Smith could probably have taken 10 times as long to explain each piece of equipment in minute detail. As a layperson, I’m quite grateful that they didn’t. 

The other striking realisation is that, without the BMS, none of this would work. Connecting and controlling everything from the massive boilers and chillers to the most obscure sensors, these all-encompassing systems are quite clearly a work of genius. 

If there’s one message Stamatis and Smith want to get across, it’s that we need to invest the right time, money, and expertise into improving our buildings over time – and the BMS is a key part of this. After all, what good are the most advanced systems if we don’t look after them?