Chapter 8 Tactics

1. Maintenance and commissioning

The efficiency of existing HVAC systems can be maximized through a combination of regular in-house maintenance and periodic commissioning. In-house maintenance typically involves cleaning and replacing worn-out parts. Commissioning is a process by which equipment is tested to make sure it is performing according to design intent. Testing, adjusting and balancing (TAB) are examples of commissioning tasks. Most commissioning services are completed by professional technicians specializing in particular building systems.

Chap8%20Tactics.JPG

Regular maintenance of heat exchange equipment should involve:

• Removal of deposit buildup from heating coils/chiller tubes
• Replacement of HVAC air and water filters
• Boiler tune-ups
• Checking steam traps for leaks

Commissioning is performed by a specialized commissioning technician. A commissioning technician should:

• Verify that HVAC system components are functioning correctly
• Identify and correct any problems with the system controls
• Ensure that the HVAC system is providing proper indoor air quality
• Calibrate temperature sensors and controls to align with original design specifications

Financial case study: HVAC maintenance performed by Cushman and Wakefield at Adobe Towers in San Jose resulted in tune-ups including modified boiler control programming, which cost $600 in labor and saved $41,779 in annual energy costs. An additional correction to chilled-water pump controls cost $1,200 and netted $43,000 in annual energy savings.


Additional information

For more information on maintenance and commissioning see:
• US EPA, "Energy Star® Building Upgrade Manual—Recommissioning." December 2004. Accessible at http://www.energystar.gov/ia/business/BUM.pdf
• Ellicott and Rothstein, National Conference on Building Commissioning. “Procuring Commissioning Services—Who, When, and How.” 2005. A vailable online at http://www.peci.org/ncbc/proceedings/2005/11_Ellicott_NCBC2005.pdf


2. Efficiency tune-ups

Complete envelope upgrades. An energy efficiency engineer can evaluate whether upgrades to the building envelope can reduce heating/cooling load. Envelope upgrades include:

• Locating and sealing air leaks in windows, doors, roofs and walls. Eliminating infiltration due to air leaks in a large office building typically saves up to 5% of heating/cooling energy.1
• Installing window films/shading. Window coverings block solar radiation from entering the building and reduce internal heat loss through windows by improving insulation. The typical cost for specialized window films is $1.35–$3.00/sq ft. Window films have a typical lifetime of five to seven years.2

Financial case study: Equity Office Properties installed 140,000 square feet of window film on floor to ceiling windows throughout One Market Plaza in San Francisco (a 1.4-million-square-foot complex). The project qualified for efficiency incentives from PG&E and reduced heating and cooling costs significantly. After the PG&E rebate, the project had a payback time of less than two years.3

• Tune/install thermostat controls. An HVAC engineer should compare the host company office’s heating/cooling patterns with its occupancy schedule to determine whether controls should be adjusted to reflect occupancy. Additional savings can be accomplished through the installation of combined automated control systems for HVAC and lighting (see Chapter 10, Energy Management Systems). HVAC and lighting can then be continuously monitored and adjusted based on occupancy and environment.4 An HVAC engineer should evaluate the feasibility of preheating or precooling the building at night using off-peak electricity.

Financial case study: Cushman and Wakefield performed a modification of temperature and runtime settings of boilers for Adobe Systems, costing Adobe $400. The adjustments reduced the boilers’ natural gas use by 20% for an annual savings of $42,960, representing an immediate payback on investment.5


Additional information

For more information on building envelope upgrades see:
• US EPA, "Energy Star® Building Upgrade Manual—Supplemental Load Reduction." December 2004. Page 73–95. Accessible at http://www.energystar.gov/ia/business/BUM.pdf


3. Equipment replacement/purchasing

Full replacement of up-to-date HVAC systems is unlikely to be cost effective if undertaken solely to increase energy efficiency. However, many modern office buildings are operating with outdated and inefficient HVAC systems. Especially if a building has experienced performance problems with an older system, an upgrade to a higher efficiency system should be considered.

The principle objectives of HVAC upgrades are:
• Improved year-round occupant comfort and convenience
• Higher energy efficiency with lower operation costs.6
• Install outside air economizers.
Air-side economizers use a damper to control intake of outside air. When outside air is cooler than return air, the damper adjusts to maximize air intake; when outside air is warmer, the damper reduces outside air intake to the minimum required in building codes.7 Air-side economizers can also be used to precool buildings at night.
• Correctly size and retrofit HVAC fan systems.
Fan systems (which distribute heated or chilled air throughout a building) are often more economical to replace than heating/chilling components. Fans are often oversized—a recent EPA study found that 60% of U.S. office buildings had fan systems that were at least 10%
oversized, with an average oversizing of 60%. In general, correctly sizing a fan system results in a 50% decrease in energy drawn by the fan system.8

Constant volume fan systems, which circulate a set volume of air and regulate temperature through heating or cooling air, are common in office buildings, but are relatively inefficient. Variable air volume systems (VAV), which regulate temperature primarily by varying the volume of circulated air, are typically more efficient. Conversion of a constant volume system to a VAV system can reduce horsepower requirements
for fans by 40–60%.9

VAV systems can be retrofit to control fan speed using a variable-speed drive (VSD). VSD devices vary fan speed according to need, resulting in energy savings from reduced fan speeds. A recent EPA study found that installing a VSD to an existing VAV system achieved a mean savings of 52% in fan system energy requirements.10 (For more information on VSDs see Energy Star® Building Upgrade Manual, p.107–108).

Once energy requirements of fans have been reduced, an engineer can determine whether downsizing a fan motor to a more efficient size is appropriate.11

Financial case study: A 36-story high-rise in San Francisco at 100 Pine Street is currently undertaking a retrofit conversion of its constant volume air system to a variable air volume system. The retrofit project will cost approximately $848,000, but 100 Pine Street will receive $179,000 in utility incentives and expects to save $473,000 in annual energy costs, for an adjusted payback period of 1.3 years. (See Appendix F).

Financial case study: A variable frequency drive was added to the fan system at Adobe Towers in San Jose, enabling the system to adjust air volume and fan power to meet cooling load. The retrofit cost $126,960 and received a $63,500 rebate. Estimated annual energy savings are $78,000, representing a ten-month payback period.12

• Measure existing heating/cooling loads and correctly size HVAC heating and chilling components.
An HVAC engineer should remeasure heating and cooling loads to capture savings achieved through previous efficiency improvements and assess whether heating/chilling components can be downsized. Generally, HVAC engineers will take an “integrated system approach” to evaluating opportunities in heating and cooling systems. If heating systems and cooling systems are assessed separately, the process will be more time consuming and whole system efficiency upgrade opportunities may be missed.

• When feasible, replace outdated or highly inefficient HVAC systems.
“Reheat systems,” which cool and circulate a set amount of air and then reheat the cooled air as necessary to achieve desired temperatures, and “multizone systems,” which mix cooled and heated air to produce desired air temperatures, are extremely inefficient. An HVAC engineer can consult on the feasibility of converting these types of systems to more efficient ones.

Financial case study: While renovating First Financial Plaza, a 223,000-square-foot (six-story) office building in Encino, California, Glenborough Realty Trust replaced an outdated chiller during an HVAC system retrofit. The 375-ton R-12 centrifugal chiller was near the end of its life, so a new chiller was required. Glenborough selected an energy-efficient Carrier 19XRV as a replacement, which has reduced annual energy costs by $15,500. After the receipt of a $15,750 utility rebate, the net cost of the chiller replacement was $273,884.13,14


Additional information

For more information on heating and cooling systems, consult:
• US EPA, "Energy Star® Building Upgrade Manual—Heating and Cooling System Upgrades." December 2004. Page 116-142. Accessible at http://www.energystar.gov/ia/business/BUM.pdf


Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License