Not only are energy-efficiency implementation mistakes being made, but these mistakes are being adopted as common practice and slipping past overseeing groups, such as the USGBC. In 2009, the USGBC realized that 53% of buildings it certified through 2006 were not achieving Energy Star label status, based on measured energy consumption.
Furthermore, 15% of these LEED certified buildings were actually performing in the bottom 30% of the comparable national building stock on an energy-per-sq-ft basis (Navarro 2009). As an energy efficiency consulting company that conducts building commissioning, energy auditing, and efficiency measurement and verification work, we feel we have a perspective from the front lines of why buildings are not performing as intended, and how they are outfoxing standards and checks put in place by organizations, such as USGBC, ASHRAE, government, and utility programs.
HOW INEFFICIENCY GETS IMPLEMENTED
Poor energy efficiency implementation often begins with poor technical understanding or inattention by building owners and designers. Building owners cannot be expected to fully understand the different energy efficiency technologies available to them and how to properly select them. This is why design firms and consultants are hired. Without proper guidance, an efficiency-ambitious building owner may quickly spend money on the first vendor that talks to them.
For example, a school system we worked with purchased two hot water condensing boilers costing over $90,000, based on our estimations from “RSMeans 2011 Mechanical Cost Data.” These condensing boilers were applied in a building system that did not allow them to condense, and therefore the new boiler system was only slightly more efficient than the existing system. The performance contracting firm estimated annual savings of over $16,000/yr, but actual savings will be less than $5,000/yr. Thus, the simple payback of this project is around 18 years. This school had many other areas they could have invested that money that would have dramatically reduced their energy bills. However, the owner was not able to understand the potential savings on his own or double check the accuracy of the contractor’s questionable savings calculations. Over the years, we have seen many building owners coerced into making bad investments in energy efficiency.
Approaching building designs with an energy efficiency objective requires design teams to challenge their old practices and invest time and effort into developing new approaches and intellectual infrastructure. In most cases, it is necessary for designers to disregard their old design templates and practices that developed without efficiency in mind and to assess the energy efficiency performances of multiple system options and perform cost benefit analyses.
As enhanced commissioning agents in the design phase of buildings, we help to push for these changes and contribute to the cost-benefit analyses of different efficiency options, but we are often met with resistance. Many firms try to hold on to their old methods and practices. Some of these poor practices include excessive system oversizing and applications of old, familiar inefficient equipment.
An example of applying old, yet familiar, inefficient equipment can be seen in a school we audited that recently received a brand new constant air volume dual duct HVAC system. This system type is inherently inefficient, developed in the 1970s as an early way to create multizone HVAC systems with simultaneous heating and cooling. This technology, as a new install, is generally banned by code in areas of California (E Source Technology Atlas Series 1998). However, it is not banned in Ohio, and this design firm applied it to a school renovation. Despite this system, the school was able to receive Ohio State House Bill 264 financing, because little scrutiny is conducted by the state over the efficiency retrofits, and the total savings from all of the school’s retrofits are lumped together, so distinguishing the bad investments from the good is difficult.
HOW INEFFICIENCY OUTFOXES ENERGY EFFICIENCY PROGRAMS
After bad designs and implementations have made their way into a green building, these errors often sneak their way through reviews by organizations, such as USGBC or utility company rebate programs. These programs are capable of being duped for multiple reasons.
For example, the typical way for LEED buildings and rebate efficiency programs to assess relative energy savings in new construction is to utilize ASHRAE 90.1 standards to set a baseline scenario for building systems. ASHRAE 90.1 is a very useful tool built on years of development and knowledge. However, it is only a set of general baseline standards and cannot cover all the variables that greatly impact the efficiency of a building. Building designers and energy modelers cannot rely solely on ASHRAE 90.1 and must use their own expert judgment to address all system variables.
Furthermore, accurate energy modeling takes years of experience and advanced understanding of building energy systems and thermodynamics. There are so many important details that must be input into a model that it is virtually impossible for an organization, such as the USGBC, to fully inspect each model. It is not a stretch for any modeler to intentionally or unintentionally skew the energy savings of a model in ways that a model reviewer would have difficulty finding.
Even if the model is created with 100% accuracy, a building that exceeds ASHRAE 90.1 baseline is not necessarily an energy-efficient building. We reviewed the energy models of a LEED-certified school located in Ohio. In this project, the baseline energy model appeared to be correctly created according to ASHRAE 90.1-2007 guidelines and the proposed building exceeding the energy savings by 40%. Yet, if we were to treat the baseline energy model as a real building and enter its information and performance into Energy Star Portfolio Manager, the baseline building only performs in the low 40-percentile range. Thus, the baseline building is below average in energy efficiency, relative to other existing buildings.
Another reason poor energy efficiency projects can occur is because often measurement and verification (M&V) is not required and nobody is held accountable for actually delivering promised energy savings. In most efficiency scenarios, M&V is more complicated than simply evaluating energy bills. It typically requires a team of unbiased third-party engineers to conduct the measurements and distinguish the energy savings achieved. For LEED certification, buildings are currently not required to receive M&V of energy efficiency performance. However, this may be coming in the near future. LEED does currently provide credits for owners who opt to have their building’s efficiency measured and verified.
CASE STUDIES OF POOR EFFICIENCY IMPLEMENTATION
Installing condensing hot water boilers in non-condensing applications. Condensing hot water boilers are capable of achieving efficiencies above 90%, compared to conventional hot water boilers that typically only achieve around 80% efficiency. Therefore, if a building’s main source of heat is from a hot water boiler, the space heating energy consumption can be reduced by around 10% from utilizing a condensing boiler. However, for a condensing boiler to achieve above 90% efficiency, it must operate with a feed water temperature below 130°F, which allows for condensation to occur in the boiler flue gases and extra energy to be captured. Unfortunately, most hot water coils in HVAC equipment are designed to use entering water temperatures between 180° and 160° and leaving water temperatures between 160° and 140°. Therefore, the temperature of water returning to the hot water boiler is typically above 130°.
To fully take advantage of a hot water condensing boiler, an HVAC designer must think beyond traditional heating system designs that return water above 130°. For example, larger heat exchangers may need to be specified throughout the building so that colder water can be returned to the boiler. This can be difficult in a new construction project, since the designer needs to explore different equipment options or heat delivery techniques compared to a traditional building. This can be even more difficult in a boiler retrofit scenario where the building’s old HVAC equipment already exists and is designed to operate at high supply and return water temperatures.
Between 2009 and 2011, we studied three buildings with new hot water condensing boiler systems. One building was a new construction LEED office building and the other two were existing schools receiving major renovations through the Ohio House Bill 264 mechanism, which allows schools to finance energy-efficiency improvement projects without adding to their net indebtedness. Of these three projects, none utilized the new hot water condensing boilers with return water temperatures below 130°. On all three projects, we measured the boiler efficiencies to be around 80% to 85% efficient, rather than the 90% to 95% efficiency the building owners were led to believe they would achieve.
Poorly applied hot water condensing boilers can easily make it through the LEED review process, as the only area where this technology’s performance is tested is in the building energy simulation model. In these models, it is unlikely a reviewer would catch a mistake since the modeled boiler efficiency is buried deep into the model, and there is no practical way for a reviewer to know the boiler’s designed feed water temperature. The only person in the process who can ensure this is done correctly is the modeler themselves, and many modelers might not understand how condensing boilers work. They simply input the rated +90% efficiency from the product literature.
Poor sequence of operations for demand-controlled ventilation. DCV is very advantageous in areas with intermittent occupancy and large occupancy swings, since this provides the best potential for ventilation reductions. DCV is often installed in areas such as offices, meeting rooms, gymnasiums, presentation halls, and cafeterias. Through building energy modeling and energy auditing experiences, we often find DCV to be one of the most effective technologies for reducing heating and cooling costs. We commonly calculate DCV to have the potential to save total space heating energy consumption by 15% to 30% in Ohio projects. In retrofit projects, we typically estimate DCV to have a simple payback of less than four years. This simple payback is much faster in new construction projects.
Unfortunately, we rarely see this technology properly implemented without the strong assistance of an outside commissioning agent. Between 2009 and 2011, our team commissioned five LEED buildings in Ohio and Tennessee with DCV. Of these five, none initially designed and installed the DCV in a way in which energy savings could be achieved. In fact, one of the buildings installed the controls in a way that actually increases energy use. In all projects, the issues were due to insufficient construction document instructions to the contractors. To properly install DCV, a lower ventilation rate for zero occupancy and an upper ventilation rate for maximum occupancy must be specified by the design team along with instructions of how to modulate ventilation between these two limits based on the zone’s CO2 levels. These specifications did not exist for four of the five projects. On these four projects, the installer simply did not tie the CO2 sensors into the ventilation system, and ventilation rates were kept constant at the maximum occupancy design rate.
On the project where specifications did exist, the specified logic was incorrectly written so that ventilation could only vary between the maximum occupancy design rate and 100% outside air, based on CO2 levels. Therefore, ventilation rates would actually rise higher than necessary in these buildings if CO2 sensors were reading high levels.
In energy efficiency programs, poor implementation of DCV can easily go unnoticed. On the projects we have worked on, the design teams had no awareness of how the systems were actually being installed. Additionally, most energy modeling software, such as Trane Trace and eQuest, simply provide a DCV button that simulates a best case scenario of reducing ventilation rates. Therefore, energy modelers can unintentionally overestimate the energy savings from installing DCV.
Finally, we suspect the terminology “minimum outside air” is contributing to the confusion. Engineers and installers generically refer to the ASHRAE 62.1 required airflow rates as “minimum outside air”, and believe that outside airflow rates cannot be reduced below this “minimum,” even with DCV. However, if the system does have DCV, a more accurate and complete description of the guideline is “minimum outside air at maximum occupancy.” It could be described as “maximum outside air when not economizing.” In this way, the maximum ventilation rate has been interpreted as the minimum ventilation rate by most design firms.
Excessively designed ventilation rates. Minimum ventilation codes are applied to buildings to help ensure safe and comfortable building environments. Building codes ensure that designers do not under ventilate building areas, but typically there are no codes ensuring that designers do not grossly over ventilate areas. As a result, building designers tend to err on providing excess amounts of ventilation air.
Furthermore, to save time, many of the engineering design firms we encounter develop conservative rules of thumb for airflow rates per square foot for different building areas. These rules of thumb can be quickly applied without specifically referring to codes or investigating the space’s occupancy intent or ventilation delivery system. Through our commissioning and energy auditing of buildings, we often back-calculate the building’s designed ventilation rates and compare them to the rates that ASHRAE 62.1 standards recommend.
In most cases, we find ventilation rates to be significantly higher than those recommended by ASHRAE 62.1. Though sufficient ventilation is a necessity for buildings, over ventilation comes at an energy cost, since it requires more outside air to be heated and cooled to room temperature. By replacing ASHRAE or state mechanical code ventilation calculation guidelines with conservative rules of thumb, many design teams are creating less efficient buildings. In addition to increasing building energy consumption, over designing ventilation rates can lead to increased capital costs due to the larger equipment needed to meet the excessive air flow rates.
Heating and cooling ventilation air is a very significant portion of heating and cooling loads in buildings. In a large hospital we audited, for example, we estimated potential energy savings of over $300,000/yr from reducing ventilation rates in several large areas. It should be noted that the design engineering team was also consulted to help ensure that reducing the existing ventilation rates would still result in a rates that exceeded local code for the area types. These savings are partially so large because the existing system ventilation rates were based on older standards, and the existing systems were designed with energy recovery wheels that were no longer functional.
Improper utilization of VFDs on fans and pumps. VFDs are often most cost-effective when applied to motors that experience variable loading throughout the year, or on oversized motors that chronically operate under-loaded with heavy pump throttling or fan dampening. However, through commissioning and energy auditing, we often see VFDs installed on pump and fan motors in ways that do not achieve maximum energy savings.
One common problem we find is that facilities purchase and install VFDs on motors with constant loads and are always operated 100% loaded. We have commonly seen this taking place during energy auditing of facilities aggressively trying to reduce energy consumption. As a first initiative, the facility managers talk to vendors and are convinced to install VFDs on all of their large pump and fan motors, regardless of the existing load profiles. We have seen this on dozens of pumps and fans over the past three years in buildings such as hospitals, industries, schools, and exhibit spaces, among others. Most building owners and efficiency advocates are aware that VFDs exist and can save energy. However, many do not realize exactly how they save energy and when they should be applied.
Another common issue we find with VFD installations is when a VFD is being used on the pump or fan motor simultaneously with throttling or dampening. For maximum VFD energy savings, a fluid system should be operated 100% open and only the VFD should be utilized to slow the motor down, as a means to reduce fluid flow. This issue does not just occur in retrofit scenarios, but also in new LEED buildings where new motors with VFDs are balanced and calibrated with the use of throttling valves and dampers, rather than with the VFD. An example of this is a constant volume makeup air unit we observed with a VFD controlled supply fan. The fan was balanced by closing of the damper and the VFD was left to constantly run around 100% full speed. The energy-efficient way this should have been done was to leave the outside air damper 100% open and to balance airflow by slowing of the VFD.
One of our most egregious examples of misused VFDs was found in an industrial facility. A 1,500-hp pump motor was equipped with a VFD and run at part speed. However, a valve was throttled 50% closed in the system. For over two years, facilities staff had misunderstood plant engineer’s directions for operating the system. Unthrottling the valve saved about $50,000/yr in electricity at no cost.
These poor applications of VFDs can be difficult to catch, since much attention needs to be placed on how the systems are tested and balanced, along with the typical load profiles of the designed systems. This is information rarely given to a building energy modeler, who simply clicks a button on the modeling software to indicate a motor is VFD controlled.
Inappropriate applications of green technologies. Design firms commonly specify systems to buildings simply because they are marketed as green, without evaluating their appropriateness for the project or fully understanding how they operate.
For example, we worked on three LEED projects with one design firm that has specified new variable refrigerant flow (VRF) HVAC systems for three consecutive buildings. These VRF systems have the capability to dramatically reduce energy consumption in buildings with simultaneous heating and cooling loads because the system can extract heat from one zone receiving cooling and relocate it to another zone needing heating. Thus, the heating is free in this scenario. Unfortunately, without accounting for the free heating during simultaneous heating and cooling periods, these VRF systems do not save significant energy savings over normal high-efficiency air source heat pumps (ASHP), but they cost significantly more.
In all three of the projects where this design firm specified VRF systems, there were no significant simultaneous heating and cooling loads. On top of this, the design firm did not design and specify the systems correctly to take advantage of the free heat during simultaneous heating and cooling. Therefore, the building owners simply paid more money for a system that sounds greener but will not actually perform better than less expensive, standard ASHP systems. The main cause of this issue is that the design firm did not fully understand how VRF systems achieve energy savings. After several meeting with the design firm to discuss the selection of the VRF system, it became clear to our team that the designers only understood that the system was known to be a cutting-edge energy efficiency technology. They did not fully understand how it achieved its claimed energy savings and left the majority of the designing tasks to the vendor selling the equipment.
Another example of misapplied green technology is a school that installed a state-of-the-art ice storage system to supplement their air conditioning. This system allows the building to generate ice during the night hours when the building is unoccupied then use this generated ice as a cold sink to cool the building during the day. This technology is very appropriate for air conditioning-dominated regions of the country where electric demand costs represent a large portion of their energy bills. An ice storage system actually increases a building’s cooling energy consumption but offsets peak power demand.
The school district staff claimed the ice storage system saves almost as much energy costs as a ground source heat pump, citing the mechanical design engineer. However, this is not true since Ohio is a heating-dominated region of the country and the school is currently closed most of the summer due to the academic schedule.
SOLUTIONS TO THE PROBLEMS
Overcoming a culture of inefficiency will become easier once parties responsible for design and implementation of efficiency projects are held accountable through third-party measurement and verification. This process is beginning to take place in LEED projects, as continuous M&V is likely going to be offered as an option for additional credit in LEED 2012. It is also rumored that standards and requirements for measurement and verification of LEED certified buildings will continue to get tougher over the years and may eventually become mandatory.
Along with M&V must come a better understanding of baselining and benchmarking standards and when each is appropriate. Baseline standards include ASHRAE 90.1 standards, and they are a great tool for defining the technologies and design practices that should be minimally expected in a non-energy efficient building. Comparing building designs to a good baseline helps define a starting point from which to define what energy-efficient design entails. However, comparing a building system to a theoretical baseline system does not necessarily indicate how a building actually performs with regards to energy efficiency. The only way to do that is to benchmark the building.
Benchmarking is a means of evaluating how a building’s actual energy performance stacks up against itself before efficiency retrofits, or how it stacks up against other peer buildings. A popular benchmarking metric for commercial buildings is Energy Star Portfolio Manager. This program allows for facilities to check their performances relative to a large database of peer buildings from the Commercial Buildings Energy Consumption Survey (CBECS). If a facility is implementing retrofit efficiency changes, it may be necessary to benchmark its actual energy consumption against itself prior to the retrofits. We call this a past-performance benchmark, as opposed to Energy Star, which is a peer-performance benchmark. This can sometimes be problematic since outside variables such as weather and building occupancy patterns can affect energy consumption regardless of the efficiency retrofits. Thus, this type of benchmarking often needs to be performed with statistical analysis by an unbiased technical expert.
Both baselines and benchmarks are necessary to evaluate the success of energy efficiency initiatives. Gradually evolving baseline standards help push the design practices in a more progressive direction, while benchmarking standards make it possible to evaluate the effectiveness and impacts of the more progressive changes. The two interact with each other. As both become more embedded into energy efficiency programs, facilities will be able to better understand where they are and how to best make improvements. It will also be possible to better hold parties accountable for poor design practices.
Another large change that would significantly reduce poor energy efficiency implementation is for building owners to change their expectations and attitudes towards engineering designers. Typically, projects are expected to move fast, and design firms are not paid enough or given enough time to actually think critically about the systems they create. Building owners can add a lot of value to their buildings if they set the tone with design firms that heavy design work and comparative system analysis should take place before any design decision can be made.
At this early stage, it is also advantageous to bring in other experts, such as enhanced commissioning agents or a technical owner’s advocate. Though these upfront engineering requests may cost a building owner slightly more in design fees, it should pay back significantly throughout the project. Examples of where this practice pays back should be found not only in energy savings from a more efficient design, but through reduced equipment and construction costs. By forcing design teams to evaluate multiple system types, the owner can actually select systems that achieve the most energy savings per dollar invested, rather than getting stuck with a potentially more expensive system that saves little to no additional energy.
Also, the design teams should be forced to take their time and design better lighting, ventilation, ductwork and piping systems, rather than applying excessive rules of thumb. This should result in smaller systems and less equipment and construction costs in addition to lower energy consumption.
Lastly, technical reference manuals used by state incentives programs to quantify energy efficiency project savings must be continuously reviewed, critiqued, and updated to ensure calculation methodologies and baseline assumptions are appropriate as technologies change.
CONCLUSIONS
The keys to getting to where we need to be will require the efforts of designers, installers, building owners, and efficiency program directors. All parties will need to learn how to break out of their old decision-making habits, which were often developed without energy efficiency in mind. As parties are held more accountable for achieving stated savings, a competitive market will force design teams, building owners, and program directors to make better decisions on how to invest in energy efficiency. ES
