What is this measure?

The retro-commissioning package includes operation and maintenance measures. Estimates for these measures come from the Department of Energy's Advanced Energy Retrofit Guide. These include:

Reduce envelope leakage

Air leakage through the building envelope most often occurs where building envelope elements are connected together. Leakage is typically a result of either improper design or construction, lack of maintenance, or normal degradation over the life of a building. Envelope leakage is most pronounced when the HVAC system is off, i.e., when the building is not mechanically pressurized. Significant night-time air leakage causes the HVAC systems to operate harder upon morning start-up, to bring the building back to setpoint temperature.

Energy savings can be achieved by identifying significant air leaks in the building envelope and sealing them. Specific methods of sealing will vary depending on the component(s) being sealed. In general, large gaps should be sealed with a structural material before applying caulk.

For office buildings, common areas of air leakage include curtain wall structures, soffits, roof-to-wall joints, expansion joints, parapet flashing, and roof penetrations. Infrared cameras can help identify air leaks in buildings.

Air leakage can affect occupant comfort, HVAC system performance, window and door performance, and building energy usage.

Revise air filtration system

Many large built-up air handling systems include both pre-filters and final filters for cleaning the air before it is supplied to the zones. The pre-filters are installed to extend the life of the final filters, yet typically they do not achieve this since it’s easy for dust to pass through and around the pre-filters. In addition, the pre-filters impose significant additional pressure drop, resulting in higher fan energy use and maintenance costs. Extended surface area filters are now available that can replace both the pre-filter and final filter. These extended surface filters have a long life (high dust holding capacity) and low pressure drop characteristics. Both maintenance (labor) and energy savings can be achieved by using these types of filters.

Calibrate air-sensors

HVAC systems rely on input from sensors to determine how to operate. However, these sensors can drift out of calibration over time. Sensors found in typical HVAC systems can include, but aren’t limited to, temperature, pressure, and flow sensors. If these sensors are not calibrated - i.e., if the value being reported by the sensor does not match the actual condition – this could negatively impact equipment performance and occupant comfort, and could result in energy waste due to simultaneous heating and cooling. Calibrated sensors are necessary for automatic control sequences to operate properly, and for accurate diagnoses of system performance.

This measure requires developing and implementing a sensor calibration plan. In general, sensor calibration consists of comparing reported sensor readings (e.g., at the building automation system) with readings from a calibrated device, and taking corrective action where there’s a significant difference between the two readings. Corrective action might include simple offsets or multipoint calibrations to align the readings. If the sensor is significantly out of calibration, replacement may be necessary. For example, if the supply air temperature setpoint is reset based on outside air temperature, it’s important to ensure that the outside air temperature sensor is calibrated and located in a representative location.

Re-enable the supply air temperature setpoint reset

For multi-zone air systems, whether CAV or VAV, automatically changing the supply air temperature setpoint to better match the needs of the zones can result in lower reheat energy use due to reduced amount of zone reheat (simultaneous heating and cooling). The supply air temperature setpoint is typically reset based on either outside air temperature or an indication of zone demand - e.g., average difference between zone temperature and zone temperature setpoint.

Care should be taken when implementing this measure to verify that internal zones receive enough cooling at higher supply air temperatures. While significant reheat energy can be saved by implementing this measure, there is usually a slight increase in fan energy usage due to internal zones requesting more airflow at the higher supply air temperatures to maintain space conditions. This fan energy penalty should be weighed against the reheat energy savings.

Reduce HVAC runtime, close outdoor air dampers during unoccupied periods

The maximum energy savings related to an HVAC system can be achieved by shutting the system off when not in use to minimize run time. This measure reduces the scheduled operating hours of the HVAC system, including fans, pumps, chillers and boilers, to more closely match the occupancy of the building.

In addition, many HVAC fan systems operate with the outside air damper open whenever the fans are operating, even during morning warm-up and cool-down periods, prior to the occupied period. Since ventilation is only required during occupied hours, the outside air dampers can be closed during non-economizer operation in unoccupied hours. This feature eliminates the energy associated with cooling and heating outside air when ventilation is not required.

Reduce economizer damper leakage

An airside economizer cycle utilizes outside air for cooling a facility when the outside conditions are cooler than inside conditions. Economizer cycles reduce the amount of mechanical cooling energy necessary for cooling a facility. During integrated airside economizer cycle operation, when the outside temperature is cooler than the indoor temperature yet warmer than the supply air temperature necessary for cooling the space, the outside air dampers are fully open and the return air dampers are fully closed.

If the return dampers are leaky, meaning if they don’t have blade and jamb seals and/or they are not adjusted to close fully when commanded to do so, the effectiveness of the economizer cycle is reduced and more mechanical cooling is required than would be necessary if the dampers leaked less.

Some HVAC systems include a morning warm-up/cool-down cycle. During this cycle, the space is cooled or heated to address the heat gained or lost during the night (unoccupied period). Typically this cycle occurs prior to the start of the occupied period, and the minimum outside air dampers remain closed during this period. If these dampers are leaky, more outside air would be drawn in than is necessary, adding an unnecessary load on the HVAC system.

Minimizing the air leakage through closed outside and return air dampers can reduce HVAC system energy use during integrated economizer operation and morning warm-up/cool-down cycles.

Calibrate water sensors

HVAC systems rely on input from sensors to determine how to operate. However, these sensors often drift out of calibration over time. Typical waterside sensors can include temperature, pressure, and flow sensors, to name a few. If these sensors are not calibrated – i.e., if the value being reported by the sensor does not match the actual condition – this could negatively impact equipment performance and occupant comfort, and could result in energy waste due to simultaneous heating and cooling.

This measure consists of developing and implementing a sensor calibration plan. In general, sensor calibration consists of comparing reported sensor readings (e.g., at the building automation system) with readings from a calibrated device, and taking corrective action where there’s a significant difference between the two readings. For example, if chillers are staged based on measured chilled water flow, then it’s especially important to regularly calibrate the chilled water flow sensor to maintain performance, equipment reliability, and energy efficient operations.

Shut down the cooling plant when there is no cooling load

Facilities often run their cooling plants continuously during occupied periods of the cooling season. This includes the chiller, cooling tower, and related pumps. However, there may be periods during the cooling season when the plant does not need to run, especially when airside economizer cooling is used at the air handlers. If there is a space that requires continuous cooling, even after hours, it may be more efficient to install a small cooling system to serve this space, and turn off the larger plant.

Automatic controls can be added to turn off the entire cooling plant when cooling is not needed in the facility during occupied hours. Two common automatic methods include:

• Outside air temperature or enthalpy-based lockout. These controls would turn off the cooling plant when the temperature or enthalpy drops below a certain value.
• Enable plant based on the cooling demand. These controls would turn off the cooling plant when there is no cooling demand (e.g., all air handler cooling coil valves are closed). Adequate time lags and proper trigger points need to be programmed with this strategy to prevent the plant from cycling on and off excessively.

 

Before this measure is implemented, the retro-commissioning team should ensure that the cooling plant is not operating after hours. Turning the cooling plant off during unoccupied hours is typically easier to implement than cooling plant shutdown during occupied hours, due to greater building operator buy-in.

For facilities with multiple chillers, the chiller staging strategy can have a large impact on the energy consumption of the plant. It’s often beneficial to shut off chillers at low load, to reduce pumping energy consumption and increase chiller efficiency. Each facility is different, and will have its own optimal chiller staging strategy. BAS software overlays are available that will continually optimize the performance of a chilled water plant.

In addition to energy savings, this measure should result in increased equipment life due to less run hours for the cooling plant.

This measure may not apply to smaller buildings, which typically do not have a cooling plant.

What is this measure?

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.

 

What is this measure?

The deep retrofit package includes the following measures, and estimates for these measures come from the Department of Energy's Advanced Energy Retrofit Guide:

Retrofit interior fixtures to reduce lighting power density by 11%

Overhead interior lighting accounts for a significant portion of overall energy use in a typical office building. Utilizing more energy efficient lighting technologies to reduce the amount of energy devoted to the lighting end use can result in significant whole building energy savings.

This measure may not apply to smaller buildings or partial building tenants.

Available lighting efficiencies have steadily increased over the last few decades. Minimum efficiencies prescribed in building energy codes and federal regulations are frequently increased to keep pace with these improved efficiencies.

When evaluating lighting technologies, other factors should be considered in relation to cost besides energy savings and first cost. These include:

• Human productivity. The new lights should provide at least the same level of quality as the existing lights.
• Lamp replacement frequency and costs, including labor costs.

A lighting retrofit requires lighting design to achieve appropriate illumination with minimal energy usage. The design should evaluate the existing lighting system in terms of lighting orientation, layout, type, and control. It should evaluate each activity area and fixture individually, accommodate future changes in activities and space layout, and stress visual quality.

An efficient lighting system consists of efficient lamps, fixtures, control, and light path. All four of these should be considered as part of lighting design for a retrofit.

Lighting power density reduction goals can be met by replacement of existing lamps and ballasts with the latest current technology.

Install occupancy sensors to control interior 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.

 

Add advanced on/off control of office equipment

Office equipment; including computers, monitors, printers, and copiers; make up 9% of a typical office building’s overall energy usage. Office equipment typically consumes over half of the overall plug load for a typical office building. Besides the electric power draw of these loads, they also have an impact on the building’s HVAC system, creating an internal heat gain on the system.

Technologies are available to turn off plug loads when they’re not in use. These include:

• Adding computer power management software to optimize the energy performance of computers
• Rewiring electric circuits and implementing controls to shut off office appliances such as printers and copy machines based on sensed occupancy from motion sensors.
• Using “smart” power strips that use personal occupancy sensors to turn off task lighting when spaces are unoccupied
• Adding VendingMiser, CoolMiser, and SnackMiser controls on vending machines
• Adding time switches to turn off water coolers and coffee makers

Reducing the power draw of plug loads can also reduce the overall HVAC system energy usage.

 

Special Considerations

• Since significant energy savings can be realized from reducing computer and monitor usage, a company’s information technology (IT) department should be engaged in evaluating technologies. Server rooms, while typically small in floor area, can consume a significant amount of energy, so server equipment should be evaluated for energy savings opportunities as well.

 

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.

This measure may not apply to smaller buildings or partial building tenants.

Special Considerations

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

 

Add roof insulation

Roofs can be a significant source of heat loss in cold climates and heat gain in warm climates. For roofing systems that have insulation entirely above the deck surface, which is a common roof arrangement in commercial office buildings, it’s relatively simple to add insulation to reduce heat transfer into or out of the building. Adding insulation to the roof will likely require the removal of the existing membrane. Most owners may consider this measure when the existing roof is in need of replacement. Also, replacing the membrane with reflective coatings, such as a cool roof, at the time of the insulation installation may also help to decrease overall cooling loads in hot climates.

Widen zone temperature deadband and add conference room standby control (DDC 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). Putting the HVAC system in standby mode for zones that are unoccupied will also result in energy savings. Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. In general, for centralized HVAC systems, 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

• For hybrid systems (digital control at the plant, pneumatic at the zones), extending DDC control to the distribution level and providing enough capacity in the DDC system to allow for communication between the central equipment and the distribution system paves the way for implementing advanced control sequences that will help minimize energy consumption of the HVAC system, especially during non-peak heating and cooling periods. Extending digital control to the distribution level also allows operators to monitor performance of these systems and troubleshoot issues faster.

 

Lower variable air volume (VAV) box minimum flow setpoints and reset duct static pressure (digital 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). In addition, reducing or resetting the duct static pressure setpoint will also result in energy savings. Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. In general, for centralized HVAC systems, 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

• Lowering the VAV box minimum flow setpoints mostly involves TAB (testing, adjusting and balancing) work. If a system already has DDC control at the distribution level, the minimum flow setpoints can be lowered at the main operator workstation.
• Prior to lowering the duct static pressure setpoint or implementing an automatic reset strategy, it’s a good idea to verify the integrity of the duct system. Check to see if there is excessive leakage in the system. If a certain area has recurrent comfort complaints, check to see if there are obstructions in the ductwork (e.g., duct liner that has peeled away from the duct, closed fire dampers). Also check to see if there are an excessive number of duct elbows in the ductwork serving that area.
• VAV box damper position is a good input variable to use for resetting the duct static pressure setpoint: raise the setpoint if a certain number of dampers are 100% open, lower the setpoint if most of the dampers are less than 100% open.

 

Add demand control ventilation

Adequate ventilation air, or outside air, is required to maintain acceptable indoor air quality. In general, the greater number of people in a space, the greater the amount of ventilation air required. This ventilation air increases the energy used by an HVAC system due to the energy required to heat, cool, humidify, and dehumidify the ventilation air, depending on the outdoor conditions and the needs of the space.

Most office building HVAC systems, especially older systems, are designed to deliver a constant amount of ventilation air during occupied periods, regardless of how many people are in the space. Energy savings can be realized by controlling the amount of ventilation air provided based on the ventilation needs of the space. For office buildings, this is typically accomplished by sensing the CO2 concentration in the space, and adjusting the amount of ventilation air accordingly between preset maximum and minimum values. When using this method, it’s important to consult and consider ventilation rate standards such as ASHRAE 62.1 – Ventilation for Acceptable Indoor Air Quality. This standard covers demand-controlled ventilation strategies.

Demand-controlled ventilation is most cost-effective in buildings that have highly variable occupancies or high minimum outside airflow rates. In buildings that schedule their HVAC system to operate according to the building’s main occupancy schedule, there’s typically not enough variation in occupancy during equipment operation to make demand-controlled ventilation cost-effective. However, this measure is worth evaluating for any facility, as there may be enough HVAC system operating hours during partial occupancy to make this measure cost-effective.

Special Considerations

• Calculating the necessary ventilation rate is usually easier than controlling the HVAC system to maintain that ventilation rate. It’s not as great a challenge with constant air volume systems (compared to VAV systems), but it’s still something to consider. With constant volume systems, even though the minimum outside airflow rate should not vary significantly, it’s important to recognize that the percent that the outside air damper is open probably does not correlate directly with the outside airflow percentage, due to damper performance characteristics.
• With VAV systems that use a fixed minimum outside air damper position, the outside airflow rate will change depending on the amount of system supply and return airflow. Directly measuring the outside airflow rate is the preferred method of maintaining minimum airflow rates with VAV systems, even though this requires regular calibration of the outside airflow sensors.
• For systems serving multiple zones, it’s preferred to sense the CO2 concentration in multiple spaces, not just in the return air duct, for a more accurate representation of space ventilation needs. As with other HVAC sensors, CO2 sensors are prone to drift out of calibration, and thus require periodic maintenance.
• For VAV systems that operate often in economizer mode, it may be cost-effective to reset the VAV box minimum airflow settings downward during economizer operation based on sensed CO2 concentration in the space, for fan energy savings. VAV boxes have minimum airflow settings for maintaining adequate ventilation to the space, and these settings are typically based on minimum outside air operation. Since the supply air during economizer operation has a higher percentage of outside air than during non-economizer operation, the minimum airflow can be reduced while still providing adequate ventilation to the space. This strategy can realistically only be accomplished if the zones are DDC-controlled.
• Energy recovery ventilators, which transfer energy between the outgoing exhaust/relief and incoming outside air streams, can help reduce energy usage. These systems are more cost-effective in extreme climates, with hot, humid summer and/or cold winters.

 

Replace supply fan motor and variable frequency drive

This measure involves replacing a facility’s supply fan motors and VFDs with premium efficiency motors and VFDs with current technology. Standard motor efficiencies have steadily increased over the last few decades due to improvements in motor design and manufacturing, and VFD efficiencies have increased greatly over the past 10 years. Minimum motor efficiencies prescribed in building energy codes and federal regulations are frequently increased to keep pace with these improved efficiencies.

Special Considerations

• Most facilities do not consider upgrading motors or VFDs with higher efficiency models until the existing motors or VFDs need to be replaced due to failure or system replacement/reconfiguration. However, it may be worth replacing large, old VFD/motor combinations that operate frequently with more efficient models even before failure.

 

Shut down heating plant when there is no heating load

Facilities often run their heating plants throughout the year, even on warm days. This is often done to satisfy year-round reheat loads that are inherent in multi-zone VAV systems commonly used in large office building. Summertime reheat loads can occur in zones that require ventilation yet have relatively low cooling requirements. Reheat is provided to prevent overcooling these zones, which are typically interior zones. In humid climates, reheat may also be required at the air handler level to reheat the air after dehumidification.

If the reheat load can be reduced, then there is less need for heating plant operation and energy can be saved. If the reheat load can be eliminated altogether, greater savings can be achieved by shutting off the entire heating plant (boilers and pumps) to reduce standby and distribution losses, and to reduce auxiliary equipment operation.

Special Considerations

• A common strategy for implementing this measure is to shut down the heating plant when the outside air temperature is above a certain value, e.g., 75°F. To be able to do this, though, reheat loads above this temperature must be eliminated or, at least, greatly reduced. Many HVAC systems in large commercial buildings operate with a certain amount of simultaneous heating and cooling, due to the nature of the systems. Minimizing this paves the way for shutting off the heating equipment.
• In addition to energy savings, this measure should result in increased equipment life due to less run hours for the heating plant.

 

This measure may not apply to smaller buildings or partial building tenants.

Increase efficiency of condenser water pumping system

This measure applies to cooling plants that use water-cooled chillers, which is a common type of cooling plant for large office buildings. Condenser water pumps circulate water between the chiller and the cooling tower.

Most cooling plants use constant speed condenser water pumps piped in parallel, with one pump dedicated for each chiller. For systems that have multiple chillers, the condenser water system pumps are typically balanced when all of the chillers and condenser water pumps are operating. During part load conditions, however, when fewer chiller/pump combinations are running, these systems can be out of balance due to pressure characteristics of the common piping system.

Reducing the speed of the condenser water pumps at part load conditions (when chillers are shut off) to the design condenser water flow will yield energy savings.

Special Considerations

• For most HVAC applications, VFDs are controlled to maintain a setpoint of some measured variable, e.g., temperature or pressure. With the strategy outlined above, the ‘part load’ speed is a set speed. Continuing with the example above, when both chillers are operating, each condenser water pump would operate at 100% speed.
• When only one chiller operates, the speed of the one operating condenser water pump might be 80% speed. The ‘part load’ speed should be determined by measuring the condenser water flow, and manually adjusting the speed until the flow equals design flow.
• The discharge valves related to constant speed condenser water pumps are often throttled slightly, as a way to balance the system to design flow with all chillers operating. If VFDs are installed, these valves should be opened up for additional energy savings. Modulating condenser water pump speeds below design flow is typically not recommended for system performance, energy efficiency, and maintenance reasons

 

This measure may not apply to smaller buildings or partial building tenants.

Increase efficiency of condenser water system

Many large commercial office buildings use water-cooled chillers to transfer heat from the building to the outdoors. In these systems, heat is ultimately rejected at the cooling tower through the condenser water system. Two common measures that can be applied to condenser water systems to increase the energy efficiency of the system include adding VFDs to the cooling tower fans, and adding a condenser water supply temperature setpoint reset strategy. Many older cooling towers use constant speed (on/off) or two-speed (high/low/off) fans that cycle to maintain the condenser water supply temperature setpoint. Adding VFDs to the cooling tower fans and varying the speed of the fans to maintain the condenser water supply temperature setpoint yields energy savings with no associated pump penalty or sacrifice in performance. In most situations, chiller efficiency increases with decreasing condenser water temperature, typically by 1-1.5% per degree reduced (Doty, 2009). Therefore, lowering the condenser water supply temperature setpoint will reduce the energy consumption of the chiller. There is a tradeoff, though – to achieve that lower temperature, the cooling tower fans will need to run harder. This should be accounted for in determining the energy benefit related to resetting the condenser water supply temperature setpoint.

Special considerations

• To achieve maximum energy savings when adding VFDs to cooling tower fans, it’s more efficient to run multiple fans at the same low speed than to run one fan at a higher speed. Pumping energy and control should also be considered when determining the optimum number of fans to operate.
• Before implementing this measure, it’s necessary to verify that the existing chiller(s) will accept cooler condenser water temperatures. Some chillers, especially older models, will not operate correctly at cooler condenser water temperatures.

 

This measure may not apply to smaller buildings or partial building tenants.

Change cooling plant pumping system to variable primary

This measure applies to cooling plants that use chillers, which is a common type of cooling plant for large office buildings. Chilled water pumping systems generally fall into one of two categories: primary-only, and primary-secondary.

In primary-only systems, one set of pumps circulates chilled water between the chiller(s) and the air handler(s),. These systems can either be constant flow or variable flow. In primary-secondary systems, the primary pumps circulate chilled water through the chiller(s), and the secondary pumps draw from that loop to circulate chilled water to the air handler(s).

In general, primary-only variable flow systems use less energy than primary-only constant flow and primary-secondary systems, due to reduced pumping energy usage. However, they are usually more complex to design and operate. They are generally better suited for larger facilities with multiple chillers and sophisticated operating staff.

Special Considerations

• For proper operation of a primary-only variable flow chilled water system, it’s especially important that:
  • The control sequences are designed and implemented to maximize energy efficiency without impacting performance
  • The control loops are tuned properly
  • The chilled water flow meter is calibrated regularly
• Complex control systems such as a primary-only variable flow chilled water system especially require proper setup and adequate maintenance to maintain performance and avoid chiller staging issues. Minimum required flow through the operating chillers must be maintained at all times, which is typically accomplished through use of a flow meter and bypass valve.
• If controls complexity is a barrier to implementing this measure, another measure worth considering is converting the primary-only constant flow system to a primary-secondary system. Changing to this type of system involves replacing and adding pumps (VFD-equipped for the secondary pumps), modifying the chilled water piping in the mechanical room, and modifying the controls. While this system would not save as much energy as a primary-only variable flow system, it’s less complex to operate, and would consume less energy than a primary-only constant flow system.
• BAS software overlays are available that will continually and automatically optimize the performance of a primary-only variable flow chilled water plant.

 

This measure may not apply to smaller buildings or partial building tenants.

Add a variable frequency drive (VFD) to one chiller

This measure applies to centrifugal chillers, which is a common type of cooling plant for large office buildings. At low load, the efficiency of these chillers is less than the full load efficiency. Also, these chillers have limited turndown capability. Part-load efficiency and turndown can be improved by converting the compressors from constant speed to variable speed through the addition of a VFD.

For cooling plants with multiple chillers, one chiller can be retrofit with a VFD and used as the lead, since it will operate most efficiently at part load. The other chillers in the plant can come online when the load increases beyond the load of the one chiller. Then the VFD-equipped chiller modulates to maintain the setpoint while the other chillers operate fully loaded.

This measure may not apply to smaller buildings or partial building tenants.

Special Considerations

• Not all centrifugal chiller compressors can be retrofitted with a VFD, due to refrigerant performance and torsional resonance. The chiller manufacturer should be consulted before adding VFDs to the compressors.
• The VFD retrofit should be designed for the particular chiller model, and installed by a qualified person. To maximize energy efficiency, the existing chiller staging strategy should be modified to allow part load operation of the VFD-equipped chiller and full load operation of the constant speed chillers.
• The energy savings related to this measure depends on the building cooling load profile and the number and size of chillers in the plant. The more variable the cooling load profile and the fewer number of chillers, the greater the energy savings potential. It may be more efficient to install a small chiller to handle low loads than to install a VFD on one of the existing compressors.

 

Replace boilers and change heating plant pumping system to variable flow primary

Most large office buildings, especially older facilities, use non-condensing boilers in a primary-only constant flow piping arrangement as their heating plant. Replacing the boilers with condensing boilers and converting the piping system to a variable flow primary system would reduce energy usage of the heating plant through increased boiler efficiency; reduced pumping energy due to VFDs installed on the pumps, and reduced heat loss through the secondary piping due to lower loop temperatures.

Unlike non-condensing boilers, condensing boilers are designed to allow the flue gases to condense in the boiler and flue. These boilers are more efficient than non-condensing boilers, and operate even more efficiently at lower return water temperatures. Lower water temperatures will also reduce piping conduction heat losses.

Implementation of this measure requires replacing the boilers and pumps, changing any 3-way heating coil control valves to 2-way valves, adding differential pressure sensors, and modifying the control of the heating water plant to keep the loop temperatures as low as possible while still satisfying the heating load.

This measure may not apply to smaller buildings or partial building tenants.

Special Considerations

• This measure is most suitable for facilities that operate at part load heating for a significant amount of time. Part load heating allows for reduced pump speeds and reduced heating water supply temperature, increasing the efficiency of the system.
• Lowering the heating water supply temperature, and thus the return water temperature, will increase the boiler efficiency. However, the performance of the existing heating coils must be evaluated at lowered heating water supply temperatures. In some instances, the coils may not perform adequately at lowered temperatures, especially with heating coils that have a low number of rows. In these instances, either the heating coils must be replaced, or the heating water supply temperature must be kept high enough to maintain adequate coil performance.
• Minimum flow rates must be maintained through the boiler(s). This is typically not a major issue, but is one that should be considered during design and operation of the system.
• Differential pressure-based pump speed control and heating water supply temperature setpoint reset are both strategies that increase the efficiency of the system, but care must be taken in implementing these strategies together as they often overlap. For example, for a given heating load, lowering the temperature setpoint will result in increased pump speeds since the heating valves will open in response to the lowered temperature setpoint.
• The pumps typically operate to maintain a constant differential pressure setpoint in the system. Resetting this setpoint based on an indication of load (e.g., heating water valve position) would result in more efficient operation.

 

What is this measure?

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.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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). Putting the HVAC system in standby mode for zones that are unoccupied will also result in energy savings. Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. In general, for centralized HVAC systems, 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

• For hybrid systems (digital control at the plant, pneumatic at the zones), extending DDC control to the distribution level and providing enough capacity in the DDC system to allow for communication between the central equipment and the distribution system paves the way for implementing advanced control sequences that will help minimize energy consumption of the HVAC system, especially during non-peak heating and cooling periods. Extending digital control to the distribution level also allows operators to monitor performance of these systems and troubleshoot issues faster.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

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). In addition, reducing or resetting the duct static pressure setpoint will also result in energy savings. Specific zone control energy conservation modifications will vary by HVAC system type and the specific needs and capabilities of each facility. In general, for centralized HVAC systems, 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

• Lowering the VAV box minimum flow setpoints mostly involves TAB (testing, adjusting and balancing) work. If a system already has DDC control at the distribution level, the minimum flow setpoints can be lowered at the main operator workstation.
• Prior to lowering the duct static pressure setpoint or implementing an automatic reset strategy, it’s a good idea to verify the integrity of the duct system. Check to see if there is excessive leakage in the system. If a certain area has recurrent comfort complaints, check to see if there are obstructions in the ductwork (e.g., duct liner that has peeled away from the duct, closed fire dampers). Also check to see if there are an excessive number of duct elbows in the ductwork serving that area.
• VAV box damper position is a good input variable to use for resetting the duct static pressure setpoint: raise the setpoint if a certain number of dampers are 100% open, lower the setpoint if most of the dampers are less than 100% open.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

This measure involves replacing a facility’s supply fan motors and VFDs with premium efficiency motors and VFDs with current technology. Standard motor efficiencies have steadily increased over the last few decades due to improvements in motor design and manufacturing, and VFD efficiencies have increased greatly over the past 10 years. Minimum motor efficiencies prescribed in building energy codes and federal regulations are frequently increased to keep pace with these improved efficiencies.

Special Considerations

• Most facilities do not consider upgrading motors or VFDs with higher efficiency models until the existing motors or VFDs need to be replaced due to failure or system replacement/reconfiguration. However, it may be worth replacing large, old VFD/motor combinations that operate frequently with more efficient models even before failure.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

Multi-tenant commercial office buildings often include small server rooms scattered throughout the building that house the tenants’ computer servers. These spaces are typically unoccupied, and are often cooled by a small dedicated DX cooling fan coil unit. For many large office buildings, these spaces are located near the core of the floor plate, making it difficult to locate a small dedicated condensing unit outside to reject the heat from the fan coils. For these spaces, heat is typically rejected to a building fluid cooler/condenser water loop dedicated for the server rooms. With this system, heat is ultimately rejected to the outdoors through the building’s cooling tower, or a dedicated fluid cooler. Fluid coolers are often used in cold climates, where the cooling tower is drained during the wintertime. They usually utilize a glycol/water mixture as the fluid, to prevent freezing during cold outside air conditions. Energy savings can be realized by replacing the server room fan coils with units that have higher-efficiency compressors and waterside economizer capability. These units would have two cooling coils: one using condenser/fluid cooler water to cool the air (first stage cooling), the other using refrigerant to cool the air (second stage cooling).

Special Considerations

• The reduced mechanical cooling energy usage due to the waterside economizer must be weighed against the increased energy usage of the fluid cooler/cooling tower to cool the water to a lower temperature and the added air pressure drop due to the second cooling coil. It may be more efficient to have a higher water loop temperature setpoint at warmer outside air conditions (for DX cooling at the server room units), and a colder water loop setpoint at cooler outside air conditions (to allow waterside economizer cooling at the server room units).
• Tenant server room HVAC equipment is often owned and operated by the tenants. Implementation of this measure would likely be driven more from the tenants than the building owner.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

Airside economizers are used to increase the amount of outside air drawn into a building when outside conditions are cool and the system requires cooling. They reduce the amount of energy required for mechanical cooling.

For most commercial buildings, outdoor climate and indoor climate needs are the main factors in determining whether or not to use an airside economizer cycle, and which type of control to use. Ongoing maintenance costs can also be a factor in choosing which type of control to use.

In the hot and humid climate zone, economizer cycles are typically not used since outside conditions are not cool enough for enough hours to make their use cost-effective. For other climates, many economizer control options exist, including single point dry bulb temperature (OA), differential dry bulb temperature (OA & RA), single point enthalpy (OA), and differential enthalpy (OA & RA). This measure consists of upgrading the economizer controls for more energy efficient operation and reduced maintenance costs.

While enthalpy-based economizer control may be more energy efficient than temperature-based control in some climates, especially humid climates, enthalpy sensors are often inaccurate due to the typical high level of error related to relative humidity sensors, even in new sensors. It is often more cost-effective to use temperature-based economizer control when sensor error and maintenance costs are factored in.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

Facilities often run their heating plants throughout the year, even on warm days. This is often done to satisfy year-round reheat loads that are inherent in multi-zone VAV systems commonly used in large office building. Summertime reheat loads can occur in zones that require ventilation yet have relatively low cooling requirements. Reheat is provided to prevent overcooling these zones, which are typically interior zones. In humid climates, reheat may also be required at the air handler level to reheat the air after dehumidification.

If the reheat load can be reduced, then there is less need for heating plant operation and energy can be saved. If the reheat load can be eliminated altogether, greater savings can be achieved by shutting off the entire heating plant (boilers and pumps) to reduce standby and distribution losses, and to reduce auxiliary equipment operation.

Special Considerations

• A common strategy for implementing this measure is to shut down the heating plant when the outside air temperature is above a certain value, e.g., 75°F. To be able to do this, though, reheat loads above this temperature must be eliminated or, at least, greatly reduced. Many HVAC systems in large commercial buildings operate with a certain amount of simultaneous heating and cooling, due to the nature of the systems. Minimizing this paves the way for shutting off the heating equipment.
• In addition to energy savings, this measure should result in increased equipment life due to less run hours for the heating plant.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

This measure applies to centrifugal chillers, which is a common type of cooling plant for large office buildings. At low load, the efficiency of these chillers is less than the full load efficiency. Also, these chillers have limited turndown capability. Part-load efficiency and turndown can be improved by converting the compressors from constant speed to variable speed through the addition of a VFD.

For cooling plants with multiple chillers, one chiller can be retrofit with a VFD and used as the lead, since it will operate most efficiently at part load. The other chillers in the plant can come online when the load increases beyond the load of the one chiller. Then the VFD-equipped chiller modulates to maintain the setpoint while the other chillers operate fully loaded.

Special Considerations

• Not all centrifugal chiller compressors can be retrofitted with a VFD, due to refrigerant performance and torsional resonance. The chiller manufacturer should be consulted before adding VFDs to the compressors.
• The VFD retrofit should be designed for the particular chiller model, and installed by a qualified person. To maximize energy efficiency, the existing chiller staging strategy should be modified to allow part load operation of the VFD-equipped chiller and full load operation of the constant speed chillers.
• The energy savings related to this measure depends on the building cooling load profile and the number and size of chillers in the plant. The more variable the cooling load profile and the fewer number of chillers, the greater the energy savings potential. It may be more efficient to install a small chiller to handle low loads than to install a VFD on one of the existing compressors.

Estimates for this measure come from the Department of Energy's Advanced Energy Retrofit Guide.

What is this measure?

Lighting is often an area targeted for improvement in existing office buildings. Lighting upgrades can come in many forms, including light-emitting diodes (LEDs), high-efficiency fluorescents, or downsizing from T-12 fluorescent bulbs to T-8 or T-5 bulbs. Lighting accounts for 30-40% of commercial building energy consumption, and these technologies can reduce lighting energy usage from 35% (T-8 high efficiency fluorescent) to 75% (LED).

Special Considerations

• When replacing fluorescent tubes with higher-efficiency, longer-life LEDs, consider replacing the entire fixture to avoid incompatibilities between the bulb and the ballast which could degrade performance, shorten bulb life, or create a safety hazard.  Alternatively, use an LED tube with an integrated driver.
• Consider bundling this upgrade with occupancy and/or daylight sensors for additional savings.

Estimates for this measure come from the Department of Energy’s Energy Efficiency in Separate Tenant Spaces Feasibility Study.

What is this measure?

Energy Star independently certifies appliances and their operation costs. Products include refrigerators and dishwashers for kitchens, vending machines and coffee makers for break rooms, and a large portion of computer and office equipment. Though a premium of $50-200 can apply for an Energy Star certified product, the energy usage is usually 10-40% lower than non-certified products, providing a typical payback within 1 to 3 years.

Special Considerations

• Energy Star also administers the Portfolio Manager program, a free resource that tracks energy and water usage of your building, which can lead to an Energy Star certification for your entire building!

Estimates for this measure come from the Department of Energy’s Energy Efficiency in Separate Tenant Spaces Feasibility Study.

What is this measure?

Energy management and information systems are software tools that interface with a building to manage and control energy use. In addition to benchmarking and utility tracking (like Energy Star’s Portfolio Manager), building automation systems (BAS) are a common form of EMIS. A BAS is a computer based tool that allows the facility manager to control everything from HVAC to lighting to security systems. The Department of Energy has extensive information on EMISs through the Better Buildings Program.

Special Considerations

• There are many different types of systems that qualify as energy management systems. Learn more about the specifics and how they can save you money with this report from the Lawrence Berkeley National Laboratory:
• Energy Information Systems (EIS): Technology Costs, Benefit, and Best Practice Uses

Estimates for this measure come from the Department of Energy’s Energy Efficiency in Separate Tenant Spaces Feasibility Study.

What is this measure?

As buildings age, their envelopes can lose efficiency and require upkeep to avoid excessive heating and cooling costs. Recaulking windows is a cheap and cost-effective way to seal up the building and prevent heating/cooling loss, saving anywhere from 3-12% in HVAC costs. Solutions can in also include adding automatic shades or blinds and introducing a vestibule at the entrances of the building to prevent energy losses dependent on the outside temperature. Thermal imaging (see picture) can be used to identify areas of your building particularly prone to energy loss and due for upgrade.

Special Considerations

• The cost of improving your building’s exterior will vary based on the technology chosen. Consult the Department of Energy’s Energy Efficiency in Separate Tenant Spaces Feasibility Study for details on ways to improve your building envelope’s performance.

What is this measure?

New systems that integrate sensors and analytics are simplifying the submetering process and driving costs down. A full-panel submeter provides a compact data acquisition system that can monitor up to 42 separate circuits simultaneously. The system is typically mounted adjacent to the electrical panel and connected via metal conduit.

GSA's Green Proving Ground (GPG) program found that a new full-panel system was an effective solution for improving tenant billing practices and optimizing building operations via fault detection and diagnostics (FDD) and energy conservation measures (ECMs). A GPG testbed assessment found a one-year payback based on more accurate overtime tenant billing. Metered energy use was double the estimate.

Special Considerations

• High-accuracy current transformers (CTs) with a phase angle shift of <0.5° are necessary to support tenant billing.
• Size CTs to estimated power levels, as opposed to rated breaker values. An ammeter can estimate amperage draw.
• Tracing loads to individual circuits can be challenging due to inaccurate panel schedules, obscure naming conventions, or lack of circuit tracing. Tracing loads may be an expensive process in locations with many low-load receptacles. Define monitoring goals prior to deployment.
• A registered electrician is required to install the system. A spare breaker for the voltage tap will facilitate system installation.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

More than 25% of total energy consumed in US office buildings is used to power plug-in devices, many of which continue to draw power even when turned off. Advanced power strips (APS) that employ pre-programmed timers to de-energize such devices significantly reduce power usage:  26% at workstations and 50% in printer rooms and kitchens.

Special Considerations

Load-sensing and combination controls provided limited energy savings and relatively high simple payback. One reason for this is that when applied to kitchens or printer rooms, load-sensing control aggregates power-state data from APSs in surrounding workstations. Because all workstation APSs are monitored in search of a “master” device whose threshold would de-energize auxiliary devices, “slaves” are de-energized only when all workstations are de-energized, which seldom occurs if occupants are present.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

The wireless pneumatic thermostat (WPT) is a new technology that can be retrofitted to an existing pneumatic control system. WPTs give conventional pneumatic controls the energy-conserving functionality of more contemporary control systems, such as direct digital controls (DDC), but at a fraction of the cost. Payback was as low as two years, using only the most basic occupied/unoccupied control strategy. If other strategies were implemented, the potential for energy savings and financial viability would be greater.

WPT represents an economically viable technology that can reduce HVAC energy consumption, resulting in lower energy costs across a wide variety of office types and climate zones. It should be considered for any facility that currently uses conventional pneumatic controls with their HVAC system.

Special Considerations

It is advisable to perform pre-installation tests to determine how well wireless signals can be transmitted within a building where a WPT retrofit is being considered.

Planning for a WPT occupied/unoccupied control strategy should take into account the possibility of reduced energy savings in areas where high thermal mass stabilizes temperature over longer periods of time. During the WPT assessment, some interior areas within the concrete-and-steel Wilson Center did not demonstrate temperature changes normally associated with an occupied/unoccupied schedule, though other indicators suggested that such a schedule was in effect. After exploration of the issue, it was determined that the high thermal mass of the interior spaces was slowing temperature changes that were occurring more rapidly in the building’s exterior spaces.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

Condensing boilers capture the heat that is lost through steam in conventional boilers and are therefore more efficient. Under the right conditions, they will outperform conventional boilers by a substantial margin. GSA tested condensing boilers at the Denver Federal Center and the Peachtree Summit Federal Building in Atlanta, Georgia and found energy savings greater than 14%.

Special Considerations

• Conduct a thermal load calculation to select a boiler that meets maximum thermal load without excess capacity. Relying on previous plant sizing is not necessarily reliable.
• Select boilers with a low turndown ratio and low minimum flow requirement.
• Operate multiple smaller boilers in parallel at low loads.
• For “condensing mode” to be achieved, The Return Water Temperature (RWT) must be below 130°F. Ensure a return water temperature below 130°F by implementing some or all of the following strategies: reduce supply water temperature in response to outside air temperature, zone temperatures, or control valve position; reduce the hot water flow rate, particularly when the building is unoccupied; optimize valves with the use of pressure independent control valves, two-way valves, and variable speed drives on booster pumps; install heating coils that provide temperature drops between 40°F and 60°F; use a primary piping system with one water loop that circulates water through both the boilers and the heating coils.
• Use condensing boilers for 75% of a building’s heating load with a conventional boiler as backup during the coldest weather. This strategy has the potential to increase condensing mode operation and lower initial condensing boiler costs.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

Cogged V-belts and synchronous-drive fan belts are a low-investment way to reduce the inefficiencies in ventilation fans caused by belt slippage and bending resistance. GSA, Rocky Mountain Region, put both belts to the test on two different fans in Denver, Colorado, and found significant energy savings with a simple payback of less than four years.

Special Considerations

• Synchronous drive belts and cogged V-belts provide a relatively simple, low-cost way of achieving energy savings, but they must be installed correctly and applied in appropriate situations.
• For VFD fans, the synchronous drive belts performed well and showed savings at all ranges of fan operation.
• For CV fans, cogged V-belts are the best solution. Synchronous drive belts pose risks when combined with the CV fan’s high-torque starts and increased operational speed.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

Small circulator pumps (< 2.5 horsepower) propel fluid through closed-loop heating and cooling systems to regulate air or water temperature. Researchers evaluated new high-performance variable-speed circulator pumps with automated control that adjust pump speed to meet changing demand. They tested the technology in two common applications at the Denver Federal Center, a domestic hot water (DHW) recirculation system and an air handler unit (AHU). They found that the pumps reduced energy use 26% to 96%, with payback of less than 6 years. The new variable speed pumps should be considered as end-of-life replacements for all constant speed circulator pumps.

Special Considerations

Because differential pressure and accurate flow readings are not readily available for smaller constant-volume circulator pumps, use one of the following methods to right-size the pumps:

• Determine pipe sizes and lengths and then calculate actual head loss from the pipes to estimate the flow (GPM) and head required for the pump.
• Observe supply and return temperature differentials to make an educated guess about the existing pump’s suitability for that system. For example, if the Delta-T is extremely small (2°F to 5°F), the pump is most likely too big.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

What Is This Measure?

Variable Refrigerant Flow (VRF) is an HVAC technology that can simultaneously heat and cool different spaces in a facility and allow for greater temperature control while conserving energy. (VRF) systems use refrigerant as their cooling or heating medium. A compressor unit, typically located on a roof, is connected through refrigerant lines to multiple indoor fan coil units, each individually controllable.

This technology has the potential to achieve 34 percent energy savings compared to older systems.

Special Considerations

VRF has proven to be effective particularly in retrofits of older buildings where room for additional ductwork is limited. For new construction, target larger-scale high-performance buildings.

See GSA’s Green Proving Ground for more details on the  field demonstration findings.

What is this measure?

What Is This Measure?

Standard approaches to calcite mitigation rely on chemicals, which must be replenished frequently, or ultra-fine-membrane filtering, which uses large amounts of water and energy. Researchers assessing catalyst-based non-chemical water treatment (NCWT) at the Frank E. Moss Federal Courthouse in Salt Lake City, Utah, found that the technology dramatically reduced calcite buildup and had immediate payback when compared to a chemical (salt-based) system. The harder the water, the more likely non-chemical scale prevention will be cost-effective.

Special Considerations

• Initially, calcite buildup and overheating continued because the device was sized based on design flow rather than measured water flow. A flow test using ultrasonic meters should be used to determine appropriate device sizing.
• The technology was certified by the National Sanitation Foundation in 2013. Currently, there are approximately ten thousand U.S. installations.
• Remote locations, where access to power, chemicals, and labor makes conventional water softening impractical and expensive, may benefit particularly from this technology.

See GSA’s Green Proving Ground for more details on the field demonstration findings.

What is this measure?

New systems that integrate sensors and analytics are simplifying the submetering process and driving costs down. Single-circuit submeters provide the ability to monitor individual circuits within an electrical panel in a building, providing detailed power and energy consumption data at a much more granular level than was previously achievable in a cost-effective manner.

GSA's Green Proving Ground program found that single-circuit submeters are easy to install; integrate with existing GSA enterprise systems, such as GSA Link; and can provide insightful high-resolution data allowing building managers to identify energy conservation measures (ECMs) leading to measurable savings. Single-circuit submeters with voltage taps provide the accuracy needed for tenant billing (<2% average measurement error). Wireless current transformers (CTs) that clip onto circuit-panel electric wires and measure the current flowing through the wire are even easier to install but they lack the accuracy needed for tenant billing, (7% average measurement error with -10% to + 25% total error). Wireless CTs do accurately capture on/off states of equipment and can support fault detection and diagnostics (FDD) and identification of energy conservation measures (ECMs).

Special Considerations

• High-accuracy current transformers (CTs) with a phase angle shift of <0.5° are necessary to support tenant billing.
• Size CTs to estimated power levels, as opposed to rated breaker values. An ammeter can estimate amperage draw.
• It is critical to independently verify the installation and configuration of CTs to ensure the intended operation.
• If using a single CT on three-phase equipment, the load should be well balanced.
• Tracing loads to individual circuits can be challenging due to inaccurate panel schedules, obscure naming conventions, or lack of circuit tracing. Tracing loads may be an expensive process in locations with many low-load receptacles. Define monitoring goals prior to deployment.
• A registered electrician is required to install the system. A spare breaker for the voltage tap will facilitate system installation.

See GSA’s Green Proving Ground for more details on the field demonstration findings: wireless current transformers and single-circuit meters.