Energy efficiency considerations for operating buildings amid a pandemic

As states, local governments, and companies across the U.S. plan for reopening based on a range of unique situations, facilities are beginning to plan for their employees or tenants to return to offices. Amidst the need to change how building mechanical systems operate to provide safe environment for occupants, opportunities exist to help mitigate potential energy and cost impacts. This post is intended to provide actionable information relative to your facilities operations to help minimize the impact on energy use and costs for equipment you have now and potential retrofit options that can be evaluated and implemented in the future. This post does not attempt to provide suggestions on how to prepare buildings and office spaces to reopen for occupancy safely.

Energy & Cost Savings Opportunities

A number of resources are available to building owners and operators describing best practices for building operations, such as ASHRAE’s COVID-19 Preparedness Resources for Reopening, the requirements of ASHRAE Standard 180-2018 Standard Practice for the Inspection and Maintenance of Commercial HVAC Systems, and IES/NALMCO Recommended Practice for Lighting Maintenance. This post draws from the themes of these documents, describing a few key energy and cost savings opportunities for consideration:

— Operations & Maintenance: Building Tune-Up

— Energy Efficiency Building Flush

— Aligning Equipment Schedules with Occupancy Patterns

— Energy Audits & EBCx

Operations & Maintenance: Building Tune-Up

During these times building owners and operators should remain focused on verifying their building systems are functioning properly and maintenance routines are kept on schedule. Not only does comprehensive, preventative operations and maintenance (“O&M”) procedures promote the health, safety, and welfare of the building occupants and staff, these procedures also promote energy and cost savings. Performing the following as part of your O&M procedures can help avoid increased energy use and costs:

• Confirm systems are functioning properly (i.e., systems are operating per their intended control sequences). For example, air handling units operating at a fixed supply air temperature instead of conforming to the programmed supply air temperature reset scheme can result in higher energy use and costs over time.
• Confirm the operation of actuating devices (e.g., dampers, valves, etc.). For example, airside economizer dampers are used to reduce building cooling energy use when ambient conditions are appropriate (e.g., when outdoor air temperatures are below return air temperatures). Broken linkages or seized actuators can prevent airside economizer dampers from achieving their purpose and may increase energy use and costs.
• Regularly replace filters and clean coils. The pressure drop across filter media and coils increases as they collect air particulates, such as dust and debris. These pressure increases can increase fan power and associated energy use and costs.
  • For filter media, refer to the manufacturer recommendations to determine when filter media needs to be replaced.
  • Coils should be inspected for debris and damaged/bent fins at least once a quarter and cleaned and brushed as necessary.
• Regularly clean or replace strainers. The pressure on pumps increases as strainers collect debris, which can increase the pumping power required to achieve the same level of service and associated energy use and costs.
  • For filter media, refer to the manufacturer recommendations to determine when filter media needs to be replaced.
  • Coils should be inspected for debris and damaged/bent fins at least once a quarter and cleaned and brushed as necessary.
  • Strainers should be inspected for debris at least once a quarter and cleaned or replaced as necessary.
• Regularly check lighting fixtures and their controls and repair/replace faulty components as necessary.
• Regularly check automatic receptacle controls and repair/replace faulty components as necessary.

Energy Efficiency Building Flush

Flushing the building with outdoor air pre- and post-occupancy should be performed to assist in removing contaminants from the building. According to the ASHRAE Building Readiness recommendations for Ventilation Control, the building flush should be performed for a period of time that is sufficient to reduce the concentration of airborne infectious particles by 95%. Instead of calculating the necessary air changes per hour (“ACH”) of outdoor air and flush duration, ASHRAE suggests that scheduling the building flush to be performed for a period of two hours both pre- and post- normal occupancy times (for a total of 4 hours) should be sufficient for most HVAC systems meeting minimum ventilation standards. This suggests that the building air handling units would need to operate in an occupied mode for four hours or more per day when the building is unoccupied to reduce the concentration of airborne infectious particles by 95%. When performing the building flush, the following can be implemented to help minimize the energy use and cost impacts (Note: any demand controlled ventilation schemes should be disabled):

• For buildings that have a Building Automation System (“BAS”)
  • In the BAS, adjust the Time-of-Day (“ToD”) schedules for each air handling unit to operate in their Occupied Mode for an additional two hours prior to normally occupied hours and two hours after normally occupied hours, or the time duration needed to reduce the concentration of airborne infectious particles by 95%.
  • In the BAS, adjust the ToD schedule for each air terminal unit to command the space temperature set points to setup/setback to their unoccupied temperature set points that are most suitable for your building (e.g., 60°F for heating and 85°F for cooling).
  • For each air handling unit with humidity controls, program the BAS to control the building humidity to not exceed 60%RH as sensed in the return air or critical space(s), whichever is most appropriate for your building and system configurations.
• For buildings that have programmable thermostats
  • Consult the thermostat manufacturer’s instructions to perform the following:
    • Adjust the fan control to run Continuously rather than Cycle.
    • Check that the thermostat is configured for automatic changeover between heating and cooling modes.
    • Adjust the space cooling and heating temperature set points to setup/setback to 85°F for cooling and 60°F for heating when the building is normally unoccupied.
• For buildings that do not have a BAS or programmable thermostats
  • Consider replacing the existing non-programmable thermostats with WiFi-enabled 7-day programmable thermostats with automatic changeover controls. This type of programmable thermostat will allow the building operator to remotely review the how the building systems and spaces temperatures from their mobile device.
  • Implement steps 2.1.1 to 2.1.3 above.

Aligning Equipment Schedules with Occupancy Patterns

It’s typical these days for buildings to be operating with reduced occupancy and/or business hours. This presents an opportunity for building owners and operators to remain connected with their tenants to make sure HVAC and lighting equipment are scheduled to operate in their Occupied Mode at the right times of day.

For HVAC systems, buildings that use either a BAS or programmable thermostats to control thermal comfort can take advantage of potential savings to adjusting ToD schedules for HVAC systems to better match building occupancy schedules, while also performing the Building Flush discussed above.

For lighting systems, occupancy-based lighting controls (e.g., occupancy or vacancy sensors) are typically already configured to control the connected lighting fixtures based on presence or absence of people around the sensor. Buildings that use a lighting control system can adjust the ToD schedules to better match building occupancy schedules.

Energy Audits & EBCx

Energy audits and existing building commissioning services (“EBCx”), such as Retrocommissioning and monitoring-based commissioning, are not new to the industry. Energy audits and EBCx have been shown to provide financial and operational benefits to building owners and operators. These services typically require an experienced professional to perform an assessment of the building to identify and analyze energy conservation measures (“ECMs”) for consideration by the building owner and operator for implementation. One key difference between the two types of service is EBCx tends to focus more on controls and operations improvements, while energy audits can also evaluate more capital-intensive measures (e.g., equipment retrofits and replacements).

Determining whether to perform an energy audit or EBCx depends on a variety of factors, such as the age, condition, and type of the building equipment and whether the building has a BAS. For example, performing an energy audit may be more appropriate for a building with aged equipment and controls past their effective useful life, or for a building that does not have a BAS. Conversely, performing EBCx may be more appropriate for a building where the equipment and controls are within their effective useful life and has a BAS. Furthermore, monitoring-based commissioning can be used to virtualize the EBCx process of identifying ECMs for buildings with a BAS and IT network architecture sufficient to support this approach.

Local utility incentive programs may be available to assist in performing energy audits and/or EBCx. Many local utility companies offer incentives or rebates to building owners to perform energy audits or EBCx on their buildings, and additional incentives or rebates for implementing identified ECMs. Also, many of these utility programs qualify service providers for participation in their programs, which helps ensure the services are provided by qualified service providers that are experienced performing the required services and understand the expectations of the utility program. Funding for these programs is often allocated on a first-come-first-served basis, and the utility representative for the building should be able to assist in making the connection to the appropriate program managers.