Energy Efficiency and Indoor Air Quality: A Changing Equilibrium
By Tim Visutipol
Earlier this year when commercial buildings were fully occupied, tenant comfort would take precedent over energy conservation. Setpoints were set at comfortable levels and recommendations to change them frequently overruled. As a result, best practices guided building operators to limit the amount of outside air needed to be conditioned to reduce the energy load, potentially detrimental to indoor air quality. There has been a change since March as the world locked down due to COVID-19. Now with near-vacant buildings, priorities have shifted for many building teams with new focus and balance between energy conservation while maintaining high indoor air quality for the essential workers at the buildings.
There has been new scrutiny of all equipment and their run hours, only operating what is necessary for the few occupants. Property managers and building engineers have experimented with turning off equipment early with the reduced internal heat load, expecting that the space temperature will stay comfortable through to the time the last tenant leaves. Temperature deadbands were increased and temperature setpoints raised, resulting in large reductions in energy consumption.
This reduction was initially measured against a four-week average, but as the weather started to warm, performance against a weather model built with prior year data is used instead to account for seasonality. Hatch Data found building energy use has declined on average about 25% since March, but there are InSite client buildings that far exceed this, reducing consumption by as much as 50% from the weather normalized model.
Building operators are guided to further reduction strategies during regular meetings. Temperature resets and schedules are discussed and verified with the building team, often resulting in further savings after the meeting. In another largely vacant office building, to ventilate each floor the building engineer scheduled all air handlers to operate for two hours each day. All floors were, however, scheduled at the same time resulting in high peak demand. By adjusting the schedule of these units to unoccupied hours, the building’s peak demand was significantly reduced.
Reduced operating hours at client building
With a live data feed and ongoing remote monitoring, clients continue to be alerted to any anomalies as building operators aggressively change building operations. In one building, all but one air handler had its outside air damper position changed to 100% to maximize outside air intake. The building engineer made an oversight and left one at 10%. This was corrected upon notification, allowing the unit to not only economize during the mild spring weather but also improve indoor air quality.
This leads to another important consideration for building operators during this time, which is ensuring high indoor air quality for the essential staff required at the building. ASHRAE guidelines for commercial offices are recommended especially on the various issues of ventilation, pressurization, filtration, and humidity. Data is reviewed to ensure levels are maintained, monitoring CO2 levels, damper position and outside airflow, indoor temperature, and humidity. A dashboard has been developed to easily display this data to clients. The updated ASHRAE guidance can be found here.
InSite’s Building Health Dashboard
Despite reduced consumption and limited equipment operation during these uncertain times, it is vital to maintain conversations to ensure issues are being corrected and schedules and setpoints are appropriate. Initial discussions regarding reopening the building have commenced, as that is in the imminent future for many around the country. As tenants start returning to the buildings, the principles guiding building operation in the past may no longer be applicable, and a new balance must be found between operational efficiency, energy conservation, indoor air quality, and health risk mitigation.