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checkEvaluate setback of temperature and airflow settings at night.

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Description

Evaluate and, if appropriate, implement night and weekend setbacks for supply air temperature (SAT) and ventilation rates in areas that are occupied less than 24 hours a day, seven days a week.

  • Project Talking Points

    Programming cooling, heating, and ventilation to ramp up only when spaces are occupied will increase energy efficiency and extend the life of HVAC equipment.

  • Triple Bottom Line Benefits

    • Cost benefits: Setback during unoccupied hours can result in significant energy savings, reducing utility costs. See case studies for specific examples. 
    • Environmental benefits: Reducing energy consumption reduces carbon emissions associated with energy production Benefits Calculator page).
    • Social benefits: Depending on the improvements made, thermal comfort and controllability may be improved, which enhances patient and staff experience. Money saved by reducing energy consumption can be applied towards the mission of the hospital, increasing patient and employee satisfaction.
  • Commissioning Connections

    The ASHE Health Facility Commissioning Guidelines and accompanying Health Facility Commissioning Handbook are good information sources for undertaking this performance improvement measure. In both the guidelines and handbook, see the following section:

    Chapter 6.1 The Retrocommissioning Process

    (23) Develop weekly occupied/unoccupied or on/off schedules for air-handling units and other equipment.

    An additional commissioning resource is the California Commissioning Collaborative’s California Commissioning Guide: Existing Buildings

  • Purchasing Considerations

    If you have suggestions for purchasing considerations, or suggested sample contract language for any product or contracted service, please participate in the discussion below.

  • How-To

    1. Determine who’s on the team. This can include the facilities manager, building engineer, MEP engineer and building automation system (BAS) manager.
    2. Review the facility occupancy schedule to identify which areas are not occupied on nights and weekends.
    3. Conduct an occupancy survey in these areas to establish a preliminary occupancy schedule, including details regarding occupancy level, daily hours of operation, and seasonal fluctuations in occupancy. (Coordinate these steps with performance improvement measure Reevaluate HVAC equipment scheduling.)
    4. Review historical data from the BAS to identify whether or not HVAC systems are cycling down at night and over the weekend. At a minimum monitor trends for the following criteria: duct static pressure, supply fan status, outdoor-air temperature, outdoor-air damper position signal, discharge-air temperature.
    5. Perform a walk-through of these areas. If occupancy sensors have been installed, note which systems they control (i.e., lighting, ventilation, air temperature) and whether they are linked to the BAS.
      • Off hour operations such as building cleaning should not necessarily trigger the HVAC building to go to occupied mode.
    6. Consider supply air temperature reset (see performance improvement measure Set thermostats to balance efficiency and comfort ) to save energy while also maintaining thermal comfort. Supply air temperature can be reset higher during certain times of year which provides energy savings while also providing the same or better thermal comfort. 
    7. If existing occupancy sensors can be configured to include control of air supply temperature and ventilation rate, configure the BAS to trigger automatic setbacks when the zone is unoccupied.
    8. If occupancy sensors are not present or cannot be reconfigured, use programmable thermostats or configure occupancy schedules for non-24/7 spaces via the BAS. Configure the system to turn off the lights, set back the air temperature to a seasonal baseline (as outlined in performance improvement measure Set thermostats to balance efficiency and comfort), and reduce air supply ventilation to the minimum allowed by code during the hours the space is typically unoccupied. Allow for adequate pre-occupancy warm up and cool down periods especially in any critical spaces where temperature setpoints need to be achieved rapidly.
    9. Ensure the system can be overridden by building occupants if a space is activated during off-hours.
    10. Monitor space use, including the number of overrides, on an ongoing basis to verify that the setback occupancy schedule reflects actual building use.
    11. Incorporate an assessment of the controls in the facility’s commissioning program (see performance improvement measure Retrocommission HVAC controls) and preventive maintenance program (see performance improvement measure Practice preventive maintenance of major HVAC equipment).
  • Tools

    California Commissioning Collaborative, Existing Building Commissioning Toolkit

    If you have an ROI tool, calculator, or similar resources to share, please contact us or participate in the discussion below.

  • Case Studies

    Saint Francis Care

      • Key Points
        • Used data from the facility’s temperature control system to identify areas in need of a revised occupancy schedule for air temperature setpoints and ventilation levels.
        • Estimated savings from lowering ventilation rate and introducing a night setback and economizer in a 30,000 sq. ft. area: $9,100 per year.
        • Awarded ENERGY STAR® label

    Seven Oaks General Hospital

      • Key Points
        • Occupancy schedules for the Daycare, Geriatrics, and SkyView Terrace were developed as part of the hospital’s retrocommissioning program.
        • The hospital achieved an annual savings of $1,995, and the project had an immediate payback.

    Providence St. Peters Hospital (slides 27-28)

      • Key Points
        • Installed dual occupancy sensors (infrared and ultrasonic) in OR rooms, which are unoccupied 47 percent of the time.
        • Set high sensitivity and 3-minute delay before the motion detector is activated (to avoid false positives).
        • Project cost: $3,300
        • Less than 1-year ROI. 
  • Regulations, Codes and Standards, Policies

  • Cross References: LEED

    • LEED for Existing Buildings: Operations + Maintenance
      • Energy & Atmosphere Prerequisite 1: Energy Efficiency Best Management Practices—Planning, Documentation, & Opportunity Assessment
        • Document the current sequence of operations, develop a building operating plan, develop a systems narrative, create a preventive maintenance plan, and conduct an energy audit that meets the requirements of the ASHRAE Level I - Walk-through assessment.
      • Energy & Atmosphere Prerequisite 2: Minimum Energy Performance
        • Establish the minimum level of operating energy efficiency performance by achieving an energy performance rating of at least 69 using the EPA’s ENERGY STAR® Portfolio Manager tool; or, demonstrate energy efficiency at least 19% better than average following the LEED Reference Guide for Green Building Operations & Maintenance; or use the alternative method described in the LEED Reference Guide for Green Building Operations & Maintenance AND have energy meters that measure energy use.
      • Energy & Atmosphere Credit 1: Optimize Energy Efficiency Performance
        • Achieve increasing levels of operating energy performance relative to typical buildings of similar type utilizing any of the methods described in Energy & Atmosphere Prerequisite 2.
      • Energy & Atmosphere Credit 2.1: Existing Building Commissioning—Investigation & Analysis
        • Develop an understanding of the building’s operation through a commissioning process or an ASHRAE Level II Energy Audit.
      • Energy & Atmosphere Credit 2.1: Existing Building Commissioning—Implementation
        • Implement minor improvements, provide training for management staff, demonstrate financial costs and benefits, and update the building operating plan as necessary to reflect changes.
      • Energy & Atmosphere Credit 3.1: Performance Measurement—Building Automation System
        • Utilize a computer-based building automation system (BAS) that monitors and controls major building systems.
      • Energy & Atmosphere Credit 5: Measurement & Verification
        • Develop a Measurement and Verification plan by incorporating the Calibrated Simulation method; or the Energy Conservation Measure Isolation as specified in the International Performance Measurement & Verification Protocol Volume III.
      • Indoor Environmental Quality Credit 2.3: Thermal Comfort Monitoring
        • Have in place a system for continuous tracking and optimization of systems that regulate indoor comfort and conditions in occupied spaces.
    • LEED for Healthcare: New Construction and Major Renovations
      • Energy & Atmosphere Prerequisite 1: Fundamental Commissioning of Building Energy Systems
        • Designate a commissioning authority to commission the heating, ventilating, air condition systems and associated controls.
      • Energy & Atmosphere Prerequisite 2: Minimum Energy Efficiency Performance
        • Establish the minimum level of energy efficiency for the proposed building and systems by a whole building energy simulation; or a prescriptive compliance path utilizing the ASHRAE Advanced Energy Design Guide (AEDG) for Small Hospitals and Healthcare Facilities; or a prescriptive compliance path complying with ASHRAE Standard 90.1.
      • Energy & Atmosphere Credit 1: Optimize Energy Efficiency Performance
        • Achieve increasing levels of energy performance beyond the prerequisite standard to reduce energy usage.
      • Energy & Atmosphere Credit 3: Enhanced Commissioning
      • Energy & Atmosphere Credit 5: Measurement and Verification
        • Develop a Measurement and Verification plan by incorporating the Calibrated Simulation method; or the Energy Conservation Measure Isolation as specified in the International Performance Measurement & Verification Protocol Volume III.
      • Indoor Environmental Quality Credit 6.2: Controllability of Systems - Thermal Comfort
      • Indoor Environmental Quality Credit 7: Thermal Comfort – Design and Verification 
  • Cross References: GGHC

    Green Guide for Health Care Operations Section

    • Facilities Management Prerequisite 1: Energy Efficiency Best Management Practices—Planning, Documentation, & Opportunity Assessment
    • Facilities Management Prerequisite 2: Minimum Energy Efficiency Performance
    • Facilities Management Credit 1: Optimize Energy Efficiency Performance
    • Facilities Management Credit 3.1: Existing Building Commissioning—Investigation & Analysis
    • Facilities Management Credit 3.2: Existing Building Commissioning—Implementation
    • Facilities Management Credit 3.3: Existing Building Commissioning—Ongoing Commissioning
    • Facilities Management Credit 4.3: Building Operations & Maintenance: Building Systems Monitoring
    • Facilities Management Credit 6: IAQ Management: Maintaining Indoor Air Quality
  • PIM Synergies

  • Education Resources

    If you have any information or resources to contribute, please contact us or participate in the discussion below.

  • More Resources

  • PIM Descriptors

    Energy

    Level: Beginner

    Category List:

    • Commissioning
    • Contracted Services
    • Controls
    • HVAC

    PIM Attributes:

    • Optimize Operations
    • Repair or Optimize Existing Systems (fix what you have)
    • System Upgrades

    Improvement Type:

    • Commission/Retro-Commission
    • Retrofit/Renovations
    • New Buildings
    • Operations and Maintenance

    Department:

    • Engineering/Facilities Management
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