Green Per Square Foot

Energy audits vs. retro-commissioning — which is right for your building? July 29th, 2014

An energy audit identifies opportunities for efficiency improvements in an existing building and one of these opportunities is frequently the need for a building “tune-up,” or retro-commissioning (RCx).

How they work

An energy audit is like a snapshot of a building, whereas retro-commissioning is more like a video of the building. An energy audit focuses on measures that if implemented, will save energy. Many of these measures involve purchasing and installing new capital equipment, such as new chillers, pumps or boilers. RCx focuses on how the existing equipment is controlled.  RCx measures are mostly repairing, recalibrating and reprogramming controls and control devices such as temperature sensors and damper actuators.

Retro-commissioning may follow the energy audit, but sometimes the facility manager realizes the need for both right away and procures the retro-commissioning to include energy audit or energy analysis.
 
RCx is a team sport involving the commissioning agent (CxA), your maintenance personnel and controls contractor.  The CxA, probably the one who completed your energy audit, will lead the team to implement the cost saving Operations & Maintenance measures that will move your building back to its original operating condition and design intent.

Financial considerations

RCx measures are typically inexpensive to implement and typically offer simple paybacks of two years or less. An RCx study is typically more expensive than an energy audit, however, when you combine the cost of the RCx study with the cost to implement the measures identified in the report, you will find that RCx is typically less expensive than energy audits, as energy audit measures often have longer paybacks.

Is it time for a retro-commissioning?

Ask yourself the following questions:

  1. Have energy bills (measured in units of energy , not dollars) risen inexplicably?

  2. Have there been major remodels of spaces within your building that consisted of moving walls around without corresponding changes to HVAC or controls?

  3. Were there previous maintenance personnel who were less trained than yours who may have overridden controls they didn’t understand?

  4. Does your maintenance staff respond to comfort complaints with Band-Aids instead of with bone fide troubleshooting?

  5. Has technology marched on and left your building behind?

  6. Has it been five years since your last tune-up?

If you can answer yes to one or more of these, perform a Level I energy audit and see where it takes you.

ASHRAE Energy Audit Levels


Below are the recommended practices of the American Society of Heating Refrigeration and Energy (ASHRAE).

Walk-through Energy Audit / ASHRAE Level I Energy Audit

The walk-through audit provides recommendations on “low-hanging fruit” — the easily implementable and low to no-cost solutions.

Retro-commissioning / ASHRAE Level II Energy Audit

Retro-commissioning relies on testing and short-term diagnostic monitoring to uncover and systematically evaluate energy and cost-saving opportunities associated with system tune-ups and other low-cost and no-cost measures.  In this process, most minor and major energy consuming systems in your facility are investigated to identify operational inefficiencies.  Studies show retro-commissioning typically provides savings of 10-20% of a building’s annual energy costs.

Investment Grade Audits with Energy Modeling / ASHRAE Level III Energy Audit

To evaluate opportunities involving capital measures, AEC combines detailed energy auditing and monitoring with building modeling, using state-of-the-art computer simulation tools. By developing a detailed and calibrated model that corresponds to measured building performance, we can simulate various alternatives to determine the most cost-effective investments in HVAC equipment, controls upgrades, and other system changes.

Resources

FacilitiesNet

Abraxas Energy Consulting

 


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