Do energy audits save energy?
Building owners and operators are increasingly concerned with lowering building energy costs and reaping the benefits of the various renewable energy and energy efficiency incentives available today. A traditional first step to improving energy efficiency is to perform an energy audit on building systems.
October 5, 2010 By Stephen Carpenter P.Eng
An energy audit is a report that indicates potential building improvements, such as replacing all T12 lighting fixtures with efficient T5s. However, such audits are often ineffective at accomplishing owner/operator goals and do not address the broader picture of improved building performance to include occupant comfort, water use or improving operations. In our experience, energy audits are too vague, have no implementation plan, and end up being read once and then shelved to collect dust.
A more effective approach to building energy efficiency is what we call Building Optimization. Building Optimization provides a holistic view of current building performance, potential no-cost and capital cost changes and a plan for how these changes should be effectively implemented together.
A Building Optimization study should look at all of the following building performance issues:
Potential energy and water savings
Yes, an energy audit should be conducted, but it should be done in conjunction with re-commissioning. Why produce a report that says to change operational settings when a commissioning engineer could make the changes during the audit process. A commissioning engineer should review current operating strategies in detail, implementing the no- and low-cost opportunities, and define capital cost solutions, including envelope improvements, that are harmonized with the owner’s goals.
Indoor environmental quality analysis
This includes occupant comfort and health issues, such as access to daylighting, lighting levels, air quality and temperature controls. This analysis frequently results in a significant impact on energy, as well as potential interior design retrofits, such as paint strategies, ceiling types, floor finishes and cubicle design.
Building envelope investigation
A key indicator of building performance, the building envelope is examined with an infrared camera that will highlight “leaks”, such as faulty windows and thermal bridging.
Current legislation means that refrigerants installed in most existing equipment can no longer be used within five years. If this equipment needs to be replaced, it is an opportune time to upgrade to more efficient equipment. Similarly, existing equipment replacement schedules should be examined and updated to reflect opportunities to improve energy performance.
No matter how well designed a building, if the building is operated in an inefficient manner, utility bills will suffer. For example, a well meaning operator who resets a VAV system’s supply air temperature set point to conserve heat energy may in fact cause increases in fan electrical energy. Training, proper supporting documentation, and a meaningful metering and controls strategy go a long way to addressing this frequently overlooked but proven solution.
If the operational policies do not support sustainability, it is not a green building. For example, improving indoor air quality through attention to the housekeeping chemicals and methods used will be more effective than just pumping in more air.
Many organizations are making carbon reduction pledges and will want to know how retrofits will affect their emission goals.
Building optimization often includes an energy model. The benefit of an energy model over a basic energy audit is the energy modeling allows owners to examine in detail all “what if” scenarios for the desired changes as well as taking into account the inter-relationship of potential changes to a system. For example, decreasing the lighting power density of a space sounds like a good idea, but the energy model would indicate how much this change would affect heating energy requirements and the potential to raise supply air temperatures to offset the lower heat gains.
Advantages of Building Optimization
A Building Optimization assessment should be conducted—or at least overseen—by one firm to ensure the plan takes into account potential synergies between recommended changes. For example, an energy evaluation could conclude that the roof should be replaced to improve the R-value and a renewable energy assessment may recommend 24 roof top solar panels. These changes should likely be conducted simultaneously; otherwise, the installation of the solar panels could compromise the roofing membrane.
Another example is that the refrigerant audit may indicate that an air conditioning unit should be replaced. This should trigger the energy assessment to immediately consider many options that may not have been otherwise apparent.
Because Building Optimization includes recommissioning, many no- and low-cost changes can be made immediately. Capital cost recommendations are integrated into capital/investment plans.
See the whole picture
Energy audits and other retrofit assessments typically look at decreasing energy use; however, this just tells part of the story. Indoor air quality, occupant comfort, practical operating strategies, water use and building-integrated renewable energy opportunities are also important considerations in creating a high performance building.
O&M Certification: Energy and water performance as well as operational practices form the core of the LEED EB:O&M credits. A complete Building Optimization service results in a plan that addresses over half of all credits available under the LEED EB:O&M rating system. EB:O&M certified buildings have a competitive advantage over conventional buildings in terms of enhancing owners’ and tenants’ green market status and decreasing operating costs.
Building owners/operators shouldn’t miss out on the energy incentives and cost savings available today. While energy audits are a common method for improving energy efficiency, a whole-building look with a view to no- and low-cost solutions that can be implemented immediately along with a long-term integrated plan can ultimately save the building owner money, as well as serve to green the facility.
Case study: Waterloo office/meeting building
The owner and operator of a 1950s building realized this facility needed an upgrade and planned to replace all mechanical equipment. Enermodal’s Building Optimization team looked beyond just the replacement of equipment to the building systems as a whole with an eye to reducing energy use.
The Building Optimization assessment examined the mechanical, lighting and envelope systems produced a schematic for the owner showing how the building systems currently operate together, and discovered the following items:
• The building was heated with two oversized boilers that operate 24/7
• Infrared imaging of the building revealed roofing problems, as well as uninsulated piping
• Building envelope deterioration due to humidity, operable windows left open during rain storms and dripping window air conditioning units
Enermodal made several recommendations:
• Replace the windows with energy-efficient versions with operable portions that do not let in rain.
• Downsize the boilers and chiller (which is possible when energy-efficient windows are used).
• Operable windows should have sensors built in to automatically shut off air conditioning (or set back heat) in the area when open. After hours, the sensors should let security personnel know if a window is left open overnight so it can be closed.
• Replace existing equipment with a dedicated outdoor air ventilation system, a heat recovery system, and a 2-pipe heating cooling switchover system that utilizes existing piping for increased equipment and HVAC efficiency.
These recommendations were presented in a report with a phased-in plan that took into account construction synergies. For example, new fire code requirements should be implemented simultaneously with lighting and ductwork renovations. The report also presented various retrofit options prioritized along with their incremental cost and incremental energy cost savings.
Stephen Carpenter is president of Enermodal Engineering and the chair of CaGBC’s Technical Advisory Group.
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