Description:

Estimates for these measures come from the Department of Energy's Advanced Energy Retrofit Guide. The standard retrofit package includes the following measures:

Install occupancy sensors for lighting

Since lighting is typically required only when people are present, fixed lighting operating schedules may use more energy than necessary in zones with intermittent occupancy. Installing occupancy sensors in applicable zones will automatically match the lighting operation with occupancy. This helps minimize lighting run time and saves energy when compared with fixed operating schedules

Special Considerations

• Occupancy sensors work best in locations where there will be a minimal amount of false triggering, and where the lighting fixtures can respond (turn on) quickly
• The most common occupancy sensor types are ultrasonic (motion detection) and passive infrared (heat detection). In general, ultrasonic sensors are more suited for larger areas, and passive infrared sensors are more suited for smaller areas, within a 15-foot range.
• Occupancy sensors are most cost-effective when they serve spaces that are intermittently occupied, such as open offices, closed offices, conference rooms, restrooms, stairwells, and break rooms.

 

Install daylight harvesting sensors

Daylight harvesting sensors require the installation of photocells to sense the space lighting level and control the overhead lighting in the perimeter zones to maintain a constant light level in the space. This measure also includes replacing the overhead lighting with dimmable ballasts, since dimmable ballasts are necessary to realize energy savings.

Special Considerations

• The lighting next to the exterior windows needs to be on a separate circuit from the other lighting, so that these lights can be controlled separate from the interior zone lights.
• The design of a daylight harvesting system should account for sensor location, sensor orientation, and number of sensors. During installation, the light sensitivity settings need to be adjusted so that the desired lighting level is maintained in the space. Also, the system should be periodically tested for proper functionality.

 

Retrofit exterior lighting fixtures to reduce lighting power density (LPD) and exterior lighting control

This measure involves replacing a facility’s parking area lighting fixtures with more efficient fixtures that will deliver the same illumination at reduced power draw, and reducing the lighting level during unoccupied periods. Parking areas are traditionally lit with high-intensity discharge (HID) lighting fixtures, typically metal halide or high pressure sodium lights. Replacing these fixtures with newer, more efficient technologies such as light-emitting diodes (LED) will yield energy savings.

For office buildings, exterior lighting typically consists of parking area, walkway, and building façade lighting. This lighting is typically turned on at sunset and turned off at sunrise, based on photosensor or astronomical timeclock control. Energy savings can be realized by lowering the exterior lighting level below full load power during times when nobody is present.

Special Considerations

• Overall lighting system efficiency, fixture life, light output depreciation, maintenance, environmental impact, and controllability should all be considered when replacing lighting fixtures.

 

Widen zone temperature deadband (pneumatic zone controls)

Deadband is the difference between the zone heating and cooling temperature setpoints. Widening the zone temperature deadband of the HVAC distribution system (e.g., piping, ductwork, terminal units) will result in measurable energy savings at the HVAC central equipment (e.g., boilers, chillers, air handlers). It’s common for HVAC systems to operate with little to no deadband, meaning that there is one temperature setpoint during winter and summer seasons.

Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. It’s important to integrate the controls of both the central equipment and the distribution system for maximum energy efficiency and occupant comfort.

Special Considerations

• Widening the deadband with pneumatic controls will likely involve replacing the thermostats with ‘zero energy band’-type thermostats that have an adjustable deadband and manually setting the deadband at each thermostat. If a system already has direct digital controls at the distribution level, widening the deadband can be as simple as a global change to the heating and cooling setpoints made from the main operator workstation.

 

Lower variable air volume (VAV) box minimum flow setpoints (pneumatic zone controls)

For HVAC systems with variable air volume (VAV) systems, reducing the zone supply airflow during periods of low cooling and heating load will result in measurable energy savings at the central equipment (e.g., boilers, chillers, air handlers). Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. It’s important to integrate the controls of both the central equipment and the distribution system for maximum energy efficiency and occupant comfort.

Special Considerations

• During periods of no heating and cooling, VAV boxes must still deliver air to the zones in order to provide ventilation air for the occupants. For commercial office buildings, this airflow rate, the “minimum airflow”, is almost always a fraction of the peak airflow rate required during peak cooling periods. Oftentimes these minimum airflow rates are set higher than needed – a common strategy is to set the minimum at 50% of the maximum, even though less than 50% of maximum airflow is required for ventilation. Energy savings can be realized by lowering the minimum airflow rate to a level that still provides adequate ventilation air for the occupants, but will result in reduced fan and reheat energy used by the system.
• The minimum airflow rates should be calculated for each zone, since each zone will have different requirements.
• Lowering the VAV box minimum flow setpoints mostly involves TAB (testing, adjusting and balancing) work. If a system already has direct digital control at the distribution level, the minimum flow setpoints can be lowered at the main operator workstation.

See DOE’s Better Buildings Decarbonization Resource Hub for more information on energy efficient lighting and HVAC technologies that can help to cost-effectively decarbonize buildings.