Top 10 Energy Audit Problems

… and how Prism Engineering carefully addresses each one.

Prism Engineering conducts an average of 50 energy audits a year.  Our highly-trained energy, electrical and mechanical engineers and technologists devote a great deal of their time and effort to conducting energy audits at commercial, institutional and multi-unit residential buildings.  So when we heard that the February 2011 issue of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Journal featured an article entitled “The 10 Most Common Problems in Energy Audits,” our ears perked up.

Ian Shapiro, the article’s author, was interested in why some energy projects achieve substantial savings while others do not. He looked to energy audits for possible explanations and found 10 common issues that greatly affect a project’s ability to deliver on promised savings. The study conducted a high-level review of 300 US building audits and then looked in detail at 30 of them: 15 commercial and 15 residential. Below, using the framework set out by the ASHRAE article, we review these 10 industry issues and explain what Prism is doing, in each case, to ensure that our audits remain as reliable, informative, and valuable as possible.

#10 Inadequate Review

Obvious mistakes other than calculations

The 10th most common issue with energy audits are non-calculation errors due to inadequate report review. This would include mistakes such as duplicating sections of reports, or making the assumption that a condensing boiler is automatically over 95% efficient. To avoid these kinds of obvious non-calculation errors, Prism follows a comprehensive quality assurance and review process. All reports are written using the newest version of our energy audit template. This avoids duplication or misnomer errors. After an energy report has been drafted, the report is reviewed by Prism’s Senior Energy Engineer, Ken Holdren. He begins with a detailed review of all calculation spreadsheets and then gives the report a thorough read-through for grammar, terminology and clerical errors. Ken, who has been with the company for nine years and has 30 years experience in the field, mentors Prism’s energy audit team and is responsible for quality assurance of all energy management projects.

# 9 Energy Savings Estimation

Overestimation of energy savings

When making energy savings calculations, it is impossible to account for all factors that affect energy savings. However, Shapiro found that over half of the energy audits studied had savings that were twice as high as could be reasonably expected. At Prism, we are carefully conservative about our estimates. This approach reflects the complex nature of building systems and the effect that the people occupying these spaces and managing these systems can have on the results. High energy savings estimates can create unreasonable expectations and may lead to poor prioritization of measures.

Last year, BC Hydro conducted an independent review of Prism Engineering’s energy audits and found that, on average, 87% of calculated savings were “approved”. The balance may have been realistic but exceeded the thresholds set by the utility. By using hourly bin models to calculate savings for all weather conditions, and equipment data sheets and part load efficiencies to accurately model the energy consumption of major building systems, we are able to predict with a high degree of accuracy how much energy each measure can actually save our clients. Using these tools helps prevent assumption bias errors and errors due to poor modeling. Our tools are either developed in-house, or by reputable organizations such as the US Department of Energy or Natural Resource Canada. They are updated regularly based on feedback from our trained energy auditors and our continuing experience in the field.

#8 Billing Analysis

Inadequate billing analysis for measures and projects

Over half of the energy audits that Shapiro looked at did not include adequate billing analysis. While the ASHRAE Standard is to study at least one year of monthly data, Prism typically analyzes three years worth of energy data. This gives our clients a better understanding of the consumption patterns and energy costs of their buildings. We are able to run better regression analysis (a statistical technique used to determine the relationships between variables in order to predict future energy use) which allows us to properly understand how variables that affect energy use, such as weather or occupancy patterns over a particular period, affect energy consumption. This provides us and our clients with a baseline standard against which to measure energy consumption in subsequent years.

#7 Building Description

Building components poorly described or missing entirely

All energy audits should include a detailed description of all components of a building. Description and analysis of some components listed in Shapiro’s article are more applicable to commercial and industrial buildings, while some are more appropriate for residential energy audits, such as infiltration, windows and wall/roof components. Prism focuses on HVAC and lighting systems for commercial, institutional and multi-unit residential buildings, because these are the systems that typically offer the best opportunities for energy savings in these building types. Our energy reports provide a detailed description of all major energy consuming systems and equipment in a building, based on all available information collected and observations made by trained energy engineers during site visits.

#6 Installation Costs

Installation costs underestimated or omitted

It is crucial that installation costs are properly reflected in the energy savings calculations. If no installation figure is provided for the implementation cost, there is a good possibility that the measures will be prioritized incorrectly and a more expensive project could be selected over a more cost-effective one. Furthermore, energy audit reports often provide an initial budget for implementing selected measures. If the installation cost is missing or underestimated, the project would be at risk of going over budget. Our installation cost estimates are based on 20 years of industry experience and the knowledge base of our diverse team of energy engineers. We are careful to conservatively estimate installation time, ensure that we have current quotes from suppliers, estimate any available incentives, and include all applicable engineering costs.

Installation costs are critical to the decision making process, but can be difficult to properly estimate because of fluctuating prices over time and between suppliers. We achieve a high degree of accuracy on lighting retrofit costing by having a detailed costing database. Developed in house, this tool helps our lighting team identify retrofit opportunities, model scenarios for different lamp and ballast options, and calculate payback for various alternatives. A recently implemented lighting retrofit measure at a B.C. university identified 800,000 kWh of projected savings, a 30% reduction in lighting energy costs. Using the database to calculate implementation costs, the project came in under the projected budget by 10%. Through conversations with our staff, we have discovered that we can provide even better information to our clients by creating an installation cost database for all mechanical systems and equipment types. Plans are underway to develop this tool with help from our mechanical department.

#5 Energy Savings Measure Selection

Selecting the wrong measure due to missing or incorrect information

The most common reason that energy auditors do a poor job of identifying and recommending energy saving measures is due to missing or incorrect information. According to the article, one of the most common errors is to recommend a measure with a longer payback than the expected life of the project. Other errors happen when energy auditors make biased assumptions, do not use life cycle costing, or underestimate equipment or installation costs. Our tight quality control process helps us catch potential mistakes and ensures that we are making good recommendations to our clients. The process begins with a well developed report template, includes careful calculations based on accurate data, and ends with a thorough final review by our Senior Energy Engineer.

#4 Life-cycle Costing

Failure to provide client with the “whole picture” afforded by Life-cycle costing

Unlike simple payback, life-cycle costing provides a holistic perspective on potential measures and helps clients and energy auditors make better decisions about which projects to pursue. In our energy audits, in addition to providing simple payback metrics, we also calculate the Internal Rate of Return (IRR) and Net Present Value (NPV) for all measures, as well as for the report as a whole. All of these figures are captured in a high-level overview table in the report summary to allow for easier decision making on the part of the client. This information helps our clients make the most effective business case to senior management, for the implementation of the energy savings measures. We also include various options for utility rates, such as ‘no price escalation’ and ‘2% annual price escalation’. We can’t predict the future but we can provide reasonable models for possible scenarios.

#3 Equipment and Project Life

Overestimated or omitted

Because equipment or project life is so critical to accurate life-cycle cost analysis, Shapiro included this issue among his top three. Missing or incorrect information regarding project life can lead to poor measure prioritization. At Prism, we include project or equipment life in all of our NPV and IRR analysis, calculating it for every measure we recommend.

#2 Scope of Opportunities

Weak description of scope of measures

We provide our clients with all pertinent details about a particular measure in our energy reports, including the location, quantity of items needed, and the energy rating of the equipment. All of our reports include an explanation of the measure intent and a list of assumptions used in the calculations. We also provide design schematics for the more complex measures. Although Shapiro recommends including testing requirements, we don’t often include this information in our reports. Given that some of our clients implement measures on their own after receiving our reports, we have decided to explore, with feedback from our clients, whether to include testing requirements in future reports.

#1 Missed Opportunities

Neglecting key opportunities

The most widespread problem in energy audits as identified by Shapiro is missed opportunities. Shapiro argues that comprehensiveness is widely recognized as a critical feature of all high quality energy audits. He provides a list of opportunities which he feels should be covered in every energy audit: high-efficiency HVAC, domestic hot water and lighting; lighting power density; lighting controls; wall or roof insulation; motors/drives; HVAC controls; and fenestration opportunities. While we agree that all energy audits should provide clients with a reasonable selection of options for implementation, his study combined results from energy audits of both residential and commercial buildings. In the context of Vancouver’s mild climate, building envelope opportunities for commercial buildings such as fenestration measures or wall and roof insulation do not offer good returns and are sometimes difficult or disruptive to implement. These types of improvements are more appropriate for mid-to-small scale residential buildings. This list, therefore, might not be entirely relevant to clients with commercial, institutional or large-scale residential building portfolios who are trying to determine the comprehensiveness of an energy audit.

Prism has over 20 years of experience working with industry and commercial sector clients. The information in our energy audits is the result of careful study, precise calculations and meticulous review. Our reports are comprehensive in scope and allow our clients to make better decisions about proposed energy saving projects. Through site visits and client consultations, we spend the time necessary to really get to know our clients’ buildings’ systems. Our calculations and energy savings models are based on well-developed tools and our energy audit report template helps ensure we do not miss any opportunities. Despite the numerous systems we have in place to avoid these industry problems, we are always looking for ways to improve our audit process. Our team of highly skilled and well-trained energy staff at Prism Engineering strives for continuous improvement of our tools and services, in order to better help our clients save energy.

Top 10 Retro-commissioning Opportunities Found In Your Building
With LEED and other building certification programs pushing the ‘energy efficiency’ envelope, building owners are constantly looking for ways to upgrade their older building stock in order to optimize occupant comfort while lowering utility bills. The challenge is knowing which operational changes and retrofit projects will yield the best results.

Retro-commissioning helps pinpoint specific opportunities to improve a building’s overall performance. Retro-commissioning studies can help resolve problems that occur during design or construction, or help address issues that may have developed over the course of a building’s lifetime.

To help building operators understand the types of opportunities that may exist in their buildings, we have compiled a list of the “Top 10 Retro-commissioning Opportunities”, commonly identified in our Retro-commissioning studies.

10. Eliminate Passing (leaky) Valves

Our engineers have found that passing valves that control heating or cooling coils can result in unnecessary energy consumption. The following conditions can interfere with a valve’s ability to fully stop the flow through the coil when in a closed position: an improperly connected, aligned or adjusted actuator and valve; insufficient seat load; debris or other contaminants caught in the seating surface; and equipment wear and tear.

9. Add or Improve Chilled Water Temperature Reset

We regularly find chillers operating at fixed supply temperature set points, rather than according to the building’s actual cooling demands. Increasing the chilled water supply temperature will improve the chiller efficiency. This can be achieved by revising the DDC system to provide chilled water supply temperature reset based on cooling valve positions, high temperature variance, or outdoor temperature, depending on the application.

8. Volume Control for Pumps and Fans

It is a common practice to install variable speed drive on pumps and fans in variable volume systems. However, inefficiencies result in the system when speed drives are continuously running at high capacity. This can be caused by excessive pressure set points, critical zone reset algorithms that do not address rouge zones, air intakes clogged with debris, operator overrides, and many other causes. Modulating pumps or fans to deliver the required flow will save energy.

7. Optimize Ventilation Rates

Optimizing ventilation rates in air handling units provides further opportunities for energy savings. For instance, an air handling unit serving a gymnasium could be outfitted with occupancy and carbon dioxide sensors which would provide demand controlled ventilation and maintain minimal outdoor air when there is limited or no occupancy.

6. Eliminate Unnecessary Lighting Hours

Even when building lighting control systems are programmed by a schedule, lights will occasionally remain on when the space is unoccupied. To minimize lighting hours, require the first person using the space to manually turn on the lights and set up the system to sweep off the lights at fixed intervals after normal occupancy hours.

5. Optimize Zone Temperature Set Points

When a system is programmed to satisfy the highest cooling demand in a space, a single zone with low set point can set the system in full cooling mode, while reheat coils serving other zones are open to provide heat. To rectify the situation, avoid having one zone dictate the supply temperature, limit the range of occupant temperature reset, and follow up by investigating the root cause of the problem.

4. Optimize Supply Air Temperature

Another energy saving opportunity is found when the supply air temperature set point is fixed instead of being on a reset schedule. In some cases, the set points are chosen based on the operator’s desire to minimize complaints. In order for the system to run optimally, temperature must be adjusted based on the actual requirements of the spaces and occupants.

3. Eliminate Simultaneous Heating and Cooling

Eliminating simultaneous heating and cooling offers an important means of reducing energy consumption. One prime example is when a Variable Air Volume (VAV) system is delivering a low supply air temperature but all the VAV boxes downstream are in heating mode. Another occurs when the building has a mix of DDC and pneumatic controls. With the pneumatic thermostat controlling the hydronic baseboard heaters and a DDC space temperature sensor controlling the VAV box, the same space may be simultaneously heated via the baseboard and cooled from overhead.

2. Optimize Economizer Operation

Our engineers often find economizer dampers that are failed in minimum position (which results in inadequate free cooling), incapable of full closure, or lacking full range operation. This often occurs with aging actuators and damper bearings that are overdue for maintenance.

1. Reduce Equipment Runtime

The most prevalent opportunity for increasing energy efficiency in buildings is reducing equipment runtime. In our experience, equipment is often left on by accident or by decision of the building operator. Instead of simply restoring the auto or scheduled running times, we work with the building operator to address the root cause of the problem, which yields better long term results. Use energy monitoring information to identify opportunities to reduce equipment runtime. Often, DDC schedules are not aligned with statutory holidays. The DDC system should be programmed to reduce equipment runtime, as when in unoccupied mode.

Our engineers, and the operators that oversee their buildings, use a variety of tools to assess and monitor a building’s energy performance. These tools include energy profiles, DDC trend logs, DDC graphics (for quick troubleshooting and verification), exception reports that generate alarms, and CUSUM analysis to track energy savings.

This list of Retro-commissioning opportunities is focused on restoring a building system’s optimal operational conditions. They are all non-capital, operational measures that have relatively quick paybacks of between one to three years. Ultimately, compared to the cost of wasted energy, additional maintenance, and equipment downtime, Retro-commissioning studies represent an excellent investment and offer an extremely cost-effective way to enhance the energy performance of existing buildings.

With maximum efficiency ratings in the range of 96%, condensing boilers are becoming a popular choice for building owners looking for improved energy efficiency, reduced operating cost and lower GHG emissions. However, many owners are not aware of the technology behind condensing boilers and the conditions required for achieving their rated efficiency. Mismatching the boiler with the heating system requirements can result in operating conditions that do not achieve the potential of condensing boilers.

The high efficiency rating for condensing boilers is primarily achieved by capturing latent heat from water vapour in the flue gas. This is done by condensing, or changing the phase of water vapour from a gas to a liquid. As the water vapour in the flue gas condenses, it releases heat that is then captured in a heat exchanger and transferred to the boiler return water flowing through the other side of the heat exchanger. For this process to occur, the return water temperature has to be below the dew point of the water vapour. The dew point for natural gas combustion products is typically around

55°C (130°F) under Stoichiometric conditions. To obtain complete condensing and achieve the maximum rated efficiency of the boiler, return water temperature needs to be approximately 20°C (68°F), which is extremely low and unachievable for most applications. Between return water temperatures of 20 to 55°C, condensing will partially occur but the boiler does not reach the maximum rated efficiency.

For condensing boilers to achieve maximum efficiency, the overall heating system, including distribution and end uses, should operate as an integrated unit. When recommending condensing boilers for existing facilities, the end use systems already exist and it is not usually practical to modify them to obtain lower supply and return water temperatures. There can still be improved boiler energy use, but the performance  will be limited according to the return water temperature.

To evaluate whether an existing building heating system is suited for condensing boilers, categorize the end use systems served by the boiler plant according to high/mid/low temperature return water. Domestic Hot Water is a high temperature load as it requires a high output temperature. This usually results in the boiler return water temperature being higher than what is needed for condensing. Other examples are hot water coils in air handling units, unit heaters and perimeter radiation systems. Medium Temperature loads need boiler supply water in the range of 40°C to 65°C (100 – 150°F). Low mass radiant heating is an example. Low temperature  loads, such as radiant slab heating, require supply water temperature in the range of 27°C to 50°C (80 – 120°F).

Low temperature loads are the best match for condensing boiler systems as their return water temperature is low and provides the most opportunity for obtaining high boiler efficiency. A building  that has mostly high tempera- ture loads is not an ideal candidate for condensing boilers unless operating practices include strategies such as hot water reset schedules that result in low temperature return water whenever possible. In these cases the most benefit from condensing boilers will be gained in the shoulder seasons when lower supply water temperatures, and hence lower return water temperatures, can be realized.

Here are strategies that can be used in existing facilities to decrease the supply and return water temperature requirements, and therefore improve condensing efficiencies:

1. Decoupling DHW. Consider heating the DHW and other non-weather related high temperature loads with a separate boiler rather than from the main boiler plant. This will allow the supply water temperature of the boiler to be lowered according to actual load requirements during shoulder season and non-peak periods. This also allows the boiler plant to be shut down dur- ing summer months when no space heating is required.
2. Demand Control for Supply Water Temperature (SWT). Control the boiler supply water temperature according to the demand from the building systems. If all heating valves are partially closed it indicates that the supply water temperature could be lowered without impacting comfort in the space.
3. Variable Flow. If the boiler can accept variable flow, another method of demand control is to adjust the flow according to the load requirement. A variable speed drive would reduce the flow during non-peak periods, resulting in a lower return water temperature and more condensing.
4. Cascade load types. Supply the highest temperature load requirements first, with loads with the lowest water temperature requirement near the return end of the loop. As an example, preheating DHW makeup water with a heat exchanger located next to the boiler return can be an effective strategy to lower the temperature of return water prior to it entering the boiler.
5. Burner Operation. If too much excess air is brought into the burner, the dew point for the flue gas will reduce, making it even harder to reach condensing conditions. Setting burners for lower excess air while still maintaining safety levels will improve efficiency of the boiler.
6. Operator Training. Ensure the operators know the requirements for optimum condensing boiler operation so they can operate the system as ef- ficiently as possible.

Condensing boilers are an important product for the market, but they are not necessarily the best choice for all existing facilities. Incorporating considerations of the overall heating system can help make their installation successful, but it takes a bit more work and some training to make it happen.