Skip to Content

Energy Audits

Energy audits are popular again. They were first offered in the ’70s and ’80s, but owners and consumers lost interest as fuel prices stayed low relative to income. Now, and with good reason, there is renewed demand for this service, particularly among commercial building owners. This interest is fueled by the desire to save money, the need to maximize operating profits from real estate in tough economic times, and a societal shift to a more sustainable environment.

Unfortunately, the practice of energy auditing is not well understood outside the realm of the practitioners. There is a wide range of options and technologies to consider. In this issue of Engineering Advisor, we hope to shed light on some of them.

Residential Energy Audits

Residential energy audits have been offered for many years by utility companies, government agencies, and various energy professionals. With a renewed focus on energy efficiency, new standards have been developed and/or proposed, including a Home Energy Rating System (HERS) offered by RESNET and RESNET-trained and certified providers. More information about residential audits is available in many places on the Web, including local government and utilities.

Commercial Energy Audits

Whereas the practice of residential energy auditing is fairly well defined, methodologies for commercial buildings have not been so clearly characterized until recently. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has published Procedures for Commercial Building Energy Audits which sets forth a baseline and three incremental levels of investigation:

1. Preliminary Energy Use Analysis – There are two main components to this basic service. The first is a review of historic energy usage. The second is to develop an Energy Utilization Index (EUI) so that the building can be compared to buildings of similar type. This fairly simple analysis can be useful in determining whether a building is currently performing well and whether there are significant conservation opportunities. A benchmarking database is published by the Environmental Protection Agency’s (EPA) Energy Star program. Buildings above the 75th percentile are eligible to receive an Energy Star rating.

While useful, there are currently two obstacles to this approach. The first is the ability to gather accurate utility information, especially from multi-tenantable buildings. The second is that benchmarks for multi-family buildings are not yet readily available.

2. Level I Walk-Through Analysis – In addition to the above, the Level I Analysis requires a visit to the site. It also includes a simplified energy analysis for low-cost/no-cost items and a list of potential capital expenditures to improve the overall energy efficiency of the building. It is still largely a qualitative, as opposed to a quantitative, analysis.

The Level I Walk-Through Analysis is appropriate for inclusion in a Property Condition Assessment (PCA) performed on behalf of a potential investor in the building as part of the due diligence and discovery process. Buildings that have greater than average energy consumption characteristics may yield a discount or become undesirable for investors

3. Level II Energy Survey and Analysis – A Level II analysis, according to ASHRAE, “will identify and provide savings and cost analysis of all practical measures that meet the owner’s constraints and economic criteria.” This is what most people envision when they refer to an energy audit. Some form of quantitative analysis is performed, generally using a computer program to evaluate heating and cooling loads under various scenarios. The analysis will also take into account local climate condition

4. Level III Detailed Analysis of Capital-Intensive Modifications – A Level III analysis involves a more detailed field data gathering and engineering analysis of major modifications or improvements, sufficient to support an investment decision in such capital improvements. The analysis incorporates many more parameters.

Such analysis is more appropriate to significant investment options such as renewable energy (solar/wind), combined heat and power, energy management systems (EMS), etc. These options often involve more sophisticated controls, rate structures and incentives, and time-of-day usage.

ASHRAE provides manuals and forms for many of these services.

Audit Tools

Although the engineering may be complex, only a few basic tools are required. These might include measuring tapes, light meters, and thermometers and hygrometers (to measure humidity). A Level III analysis may also require data loggers, volt meters, and clamp-on ammeters.

Additional tools may also be used for a more in-depth evaluation. These include:

  • Blower Door – This device is installed in the main doorway and used to pressurize the building. In doing so, one is able to measure the rate of air infiltration. Due to their design, blower doors are mostly used for residential and light commercial construction.
  • Duct Blasters – A tool that can help minimize the effects of leakage of heated or cooled air that flows through ductwork before entering the conditioned space. .
  • Flow Hoods – A major concern in commercial buildings is the balancing of air distribution. One area may feel cold, another warm, if the flow of air is not balanced appropriately. A flow hood helps accomplish that, not just when the building is first commissioned but also by adjusting periodically, as the distribution can become unbalanced over time.
  • Infrared Cameras – Infrared cameras have been around for many years and are useful for a variety of diagnostic functions. By detecting temperature differentials, the energy auditor can identify gaps in insulation, areas of heat loss, and other deficiencies.

How Accurate Are Energy Audits?

The thermodynamics of energy analysis are well known and established. However, variations of as much as 40 percent from what was predicted have been observed. At least two major variables routinely cause estimates to vary from actual performance. The first, of course, is weather. However, the human factor is even less predictable. It is not uncommon for occupants’ use patterns to inadvertently sabotage intended savings. Education is therefore a major component of any energy conservation program. Commissioning and maintenance are also important factors.

How Much Should an Energy Audit Cost?

Fees vary considerably but as a general range for commercial buildings, one might expect to pay around $500 for a preliminary analysis, $800–$1,500 for a Level I analysis, $2,000–$3,000 for a Level II analysis, and $5,000+ for a Level III analysis. Size and complexity are important factors in determining fees. Energy Star certifications are in the range of $0.01–$0.015 per square foot.

Who Can Perform an Energy Audit?

Right now, there are few, if any, regulations regarding who can perform an energy audit. A number of certifications exist, such as the Certified Energy Manager (CEM) awarded by the Association of Energy Engineers. Other private organizations are offering certifications as well. It is important to select a consultant with experience in the field rather than one who is just jumping on the bandwagon of the newest hot market.

Volume 21, Number 1

January 2010

Copyright © 2010

The Engineering Advisor is intended to enhance your knowledge of technical issues relating to buildings.  For additional information on any subject, please feel free to call us.  Our commitment is to provide you with timely, accurate information.