Managing occupant comfort levels has always been a tricky science. The pandemic has made this even more challenging, with the addition of required safety masks. Many people feel constricted when wearing a face covering, which complicates airflow and comfortable room temperature perceptions. With this psychological aspect intermingled with the need to adjust settings to increase fresh air circulation, building operators face finding a magic formula that keeps customers happy and safe.
Different energy strategies
One strategy is to start-up air conditioning systems before building occupancy. Chiller and boiler plants need a few hours to cycle and subsequently cool and/or heat spaces, so Building Management Systems (BMS) should schedule them to turn on roughly two hours prior to operation with setpoints from 72-74 degrees, with a 2-degree tolerance depending on the space.
For retail spaces, reducing this setpoint between 70 and 72 degrees may be preferable, as occupants tend to be moving around the store. This strategy will give the building a baseline temperature that can be adjusted slightly to meet comfort levels based on the number of customers entering the building without overtaxing the system.
Or another strategy is to maintain always occupied setpoints, which is a strategy that PetSmart employed at the height of the pandemic (and during scorching summer temperatures) with great success. PetSmart opted to eliminate a 70° overnight setback and put systems on an occupied 73°, rather than lowering temperatures to 71°, which worked really well for them across their 1,600+ locations and did not significantly increase their energy spend. (You can learn more about this in our recorded webinar Balancing Cost and Comfort: The case for always occupied setpoints.)
Balancing Temperature and Air Quality
Once a building becomes occupied, maintaining comfort levels while adjusting for air quality to mitigate recycled air becomes a concern. BMS systems have to increase the air turnover rates in enclosed spaces, meaning your system will need to run longer. But this works in tandem with the need for additional outside air. CO2 monitors can measure the amount of CO2 being produced in a building from occupants, giving an indication of how people are breathing air in a space.
This information can be used at the BMS to request releasing more outside air. Adjusting CO2 levels down allows more fresh air into the space to improve air quality. The unit will then need to operate to condition this air, whether it is a chilled water system or direct expansion, to cool the unconditioned outside air to the desired temperature. During warmer months, this requires the unit to call for cooling to lower the temperatures, but as the temperatures begin to drop, outdoor air can be used as an economizer to aid with cooling. Using this semi-passive cooling method can assist with regulating energy consumption.
Individual Space and Automatic Controls
A step further in finding the balance between customer comfort and safety is installing and programming a sophisticated controls system. At a building operations level, setpoints for temperature, humidity, and CO2 can all be maintained at optimal levels, so they never fall out of range but are maintained at levels that are both safe and economical. These controls give building operators a way to maintain energy systems benchmarks while also appeasing occupants at timeframes or in specific spaces requiring temperatures to be adjusted to meet circumstances.
Individual spaces can also be supplied with controls to adjust the airflow within a specified tolerance. This is useful in retail spaces where office dwellers may have low occupancy and movement than the large retail space where many customers are moving around in face masks and interacting. In this case, a building operator can allow individuals in offices to adjust the office's temperature up several degrees while reducing floor temperatures to meet comfort and allow more fresh air to enter the building.
Finding the right balance between comfort and safety is a new layer that building managers must consider. Using a baseline temperature, you can switch to occupancy mode adjusting setpoints slightly to meet comfort levels. By changing the settings for CO2 readings to read at a lower PPM, the BMS can call systems to provide more fresh outdoor air. On warmer days, cooling can be called in to reach the desired temperature. But as temperatures get lower in the winter months, outdoor air can aid in cooling as well. Finally, providing individual controls in different areas of the building can give occupants control over individual spaces. This control allows floor personnel to move the temperature down for customers that feel stifled in their masks while enabling office workers to adjust temperatures up to their comfort levels.
For more building management tips, including automation tools and a look at healthy building reports for those wanting to maintain compliance records, please see our comprehensive whitepaper Shopper and Employee Comfort & Safety in a COVID-19 Environment.