Half-empty office buildings don’t translate into green energy savings, report finds

Mia Jensen

October 30, 2024

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While hybrid work has left many office buildings — including ones in Ottawa — partially empty for extended periods, researchers from Carleton University say having fewer people around doesn’t necessarily result in the kind of energy saving you might expect. A new report from researchers Farzam Sepanta and Liam O’Brien found that office buildings aren’t constructed to adapt their energy usage when partially empty. That means that, even when half the staff are working from home, the building is still using as much energy as normal. “At least some parts of the building are operating, regardless of the occupancy,” Farzam Sepanta, one of the researchers, told OBJ. Sepanta said office buildings are typically designed around occupancy schedules, which determine approximately how many people will be in the building throughout the day. But few buildings ever reach 100-per-cent occupancy, and those occupancy numbers are even lower with the rise of hybrid work. “The problem is the partial occupancy,” he said. “When people start teleworking and the offices are partially occupied, the energy use does not go down as much as we expect.” Some systems, such as HVAC, have particular difficulty when it comes to decreased office activity. According to Sepanta, buildings benefit from the presence of people for heat gain. When there are fewer people around, HVAC systems have to work overtime to compensate and maintain a baseline temperature for the employees who are there. With building operations and construction accounting for one-third of global fossil fuel emissions, Sepanta said smart technologies are needed to adjust the energy usage of office buildings based on occupancy. The research examined how four types of smart-tech – occupancy-based lighting, smart plugs, demand-controlled ventilation, and occupancy-based thermostats – impacted the adaptability of a building. Sepanta said even small changes saved energy. For example, thermostats: “When the buildings are occupied, we try to keep them at a certain temperature so everybody feels comfortable. But if the building is empty, this gives us an opportunity to maybe adjust the temperature. If our building is completely empty and we adjust by just one degree in a cold climate, our study showed that savings will be around 15 per cent.” Smart lights, which utilize motion sensors or other tech to illuminate areas only when they’re occupied, have gained traction over the years. Sepanta said the study found that installing them was worth the effort. “We have a lot of that happening right now, either smart or partially-smart lighting,” he said. “We want to keep some lights on for security and safety reasons, but we want to also make sure that the entire office, especially those open-concept offices – you don’t want to light up the entire office for one person.” The study found that at 100-per-cent occupancy, combining the technologies could result in energy savings of five to 10 per cent. For an office that’s half occupied, that could jump to 12 per cent or as high as 42 per cent during periods when it’s completely empty. “Just doing that, it gives us a lot of potential to see what we can do with our offices now that everybody is teleworking,” he said. “Technology can save a lot of energy.” While smart-tech is gaining momentum, especially for new builds trying to meet sustainability targets, it isn’t without its challenges. Privacy concerns, for example, are top of mind for employers, who want to ensure employee activity isn’t being inadvertently tracked while in the office. Upfront costs can also deter property managers from adopting new technologies in older buildings. “The number-one barrier is cost of installation,” said Sepanta. “Sometimes it can be as easy as installing (the technologies) and switching them on, but some of them require some deep work, deep retrofits. If you’re talking about the scope of existing buildings, it’s going to be a bit costly to implement.” As incentives continue cropping up to encourage everyone from homeowners to employers to pursue sustainability, Sepanta said raising awareness among stakeholders about energy use and ways to reduce it is needed to accelerate the adoption of smart-tech. “Stakeholder engagement is super important and achieving sustainability goals is a collective effort, and everybody needs to work towards it,” he said. “Property owners, employees, developers, and also the government. Everyone needs to be on board.”