by Bo Petersson, PE, LEED AP
Design and construction of high-performance buildings involves control systems that are increasingly more advanced. To get the facility to truly perform to its potential, these systems have to work together in an optimal way, interacting to ensure startup and commissioning do not slow down the project’s acceptance-and-completion phase.
This article describes the importance of high-quality contract documents, highlighting important aspects of the specifications to give the commissioning and closeout team a useful tool to help ensure performance as the owner takes over the building. The content is based on this author’s experience with multiple projects, particularly the Dartmouth College Class of 1978 Life Science Center (LSC).
Completed in late 2011, the LSC is a 16,400-m2 (176,000-sf) building consisting mostly of laboratories, auditoriums, and offices. It was designed by architect Bohlin, Cywinski, Jackson (Pittsburgh, Pennsylvania) along with mechanical/electrical/plumbing (MEP) firm, VanZelm Haywood and Shadford Engineering (Hartford, Connecticut).
During the design phase, the entire team focused on meeting an energy goal of no more than 310 kWh/m2-yr (100,000 Btuh/sf-yr)—a tall order for a science building. This number included all energy used in the building: lighting, elevators, plug loads, and a 344-m2 (3700-sf) greenhouse located on the roof. The building was awarded Platinum under the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) program, in no small part due to its energy performance. Since occupied, the actual building energy use has tracked close to the model. What role did the specifications play in this feat?
Brief building description
For the LSC to achieve these results, new collaborative thought processes and the best affordable technologies were required. Its main aspects of the design include:
- a high-performance building enclosure with sprayed polyurethane foam (SPF);
- triple glazing and a conscious design effort to reduce the amount of glass to an appropriate level;
- natural ventilation wherever possible;
- high-performance enthalpy heat-recovery wheels with low face velocities for improved efficiency;1
- laboratory equipment waste-heat recovery for outside air preheat;
- demand-control ventilation for laboratories, offices, and classrooms;
- chilled beams in laboratories, with radiant cooling and heating in most other spaces;
- two chilled water systems—a low-temperature system in the air-handling units (AHUs) and a medium-temperature system for chilled beams, radiant panels, and floors with radiant cooling;2 and
- high level of lighting control with occupancy sensors and daylight-harvesting controls.
There are numerous systems, with a proprietary building controls assembly as the hub. This building management system (BMS) technology interacts with the laboratory controls and the demand control ventilation system. The highly accurate sensors of the latter both monitor carbon dioxide (CO2) levels in classrooms and auditoriums and detect laboratory spills. It also measures relative humidity (RH) in the AHUs and spaces with non-condensing cooling systems. The BMS also interacts in a limited way with the greenhouse and lighting control systems. Additionally, the lighting system is fully computerized and addressable.
Importance of specifications
New construction projects are exciting—there is large equipment onsite, tight schedules, and interesting characters working on intriguing challenges and solutions. Well-thought-out and complete construction documentation is crucial for success. After all, there are often projects where the finer details make the difference between a few minor change orders or an endless stream of change orders and bulletins with resulting cost overruns.
The importance of getting the specifications correct cannot be overstated—not just from a commissioning agent’s perspective, but from the owner’s perspective as well. Additionally, a well-defined project scope makes the entire project easier for everyone involved. A project with fewer change orders reflects well on the whole team.
Time invested up front in the design phase will pay dividends throughout the project’s life, both in energy and in avoided change orders.
Division 01
Division 01?General Requirements is where much of the contractual, procedural, and definition language can be found. Sometimes, it feels as if few people want to venture into this part of the section to work on clarifications and definitions.
Submittal procedures
This process currently happens electronically on most projects. To improve the review process, one should request submittals be sent in a searchable format. The reviewer can look for key words and important features more efficiently.
Substantial completion
Most specification sections define substantial completion as ‘when most finishes have been completed and furniture is ready to move in.’ However, what may seem more difficult to define, and is therefore often ignored, is ‘completion of systems.’
When it comes down to the fundamentals, this is rather straightforward. It is advisable to recommend the testing and balancing work be complete, and the commissioning authority have been able to complete the functional-performance testing (at least the first series of tests) on all vital systems.
Operating and maintenance manuals
Operating and maintenance manuals (O&Ms) are often provided months after the owner has taken possession of the building. However, these documents should be ready before any equipment has been started up. The best way to ensure success for the early delivery is to connect it to the startup of systems and payments.
Use of permanent equipment
Permanent equipment will almost always be necessary to run during the end of construction. It is important all aspects of use are defined or problems may arise. Specifiers need to define who is responsible for upkeep, how it is documented, and what shape the equipment needs to be in when turned over to the owner.
MEP coordinator
On complicated projects, the ability, experience, and clout of the MEP coordinator are the keys to successful completion. While some of this is hard to quantify in writing, there are ways to do it. One should consider requirements for the individual’s background, experience on similar projects, years of experience in the trades, and where this individual exists in the organization chart.
Commissioning
This section is important for the construction-and-acceptance phases. The commissioning section needs to define who is responsible for what, and how the commissioning process will take shape. It is important to define labor hours for the trades to complete Integrated System Testing (IST) after substantial completion.
It is often the case commissioning time is planned for construction, but not after substantial completion. By defining the hours required by each trade after substantial completion, this potential change-order discussion can be eliminated.
Divisions 07 through 09
In high-performance buildings, enclosure performance is increasingly an important part of the HVAC system design. It is vital for how the systems will be sized, operate, affect occupant comfort, and make energy model predictions come true.
Minimum thermal and solar performance for doors, windows, and skylights must be defined; allowable air leakage is equally important. There are American National Standards Institute (ANSI) standards that can be used to define the building enclosure performance. Building enclosure testing is a little more difficult, but there are many skilled and experienced companies that can be used for air-leakage testing.
The team needs to define whether the air-leakage testing should be performed on a mockup, on part of the actual building, or, in the most extreme cases, on the entire building. Each approach has positives and negatives, and there is no single method that fits every project, budget, and schedule.
It is often forgotten that buildings such as laboratories and hospitals require internal pressure relationships that cannot be fulfilled unless the separating walls are properly installed. Once all penetrations have been made and sealed, it is important internal spaces are tested for airtightness. This is considerably easier than testing the building exterior enclosure. It is critical this work is scheduled late enough such that walls are nearly finished, but early enough to allow time to address systemic problems.
Divisions 11 through 14
The main energy impact issue is in Division 14?Conveying Equipment. Vertical transportation, especially elevators, can be a big part of a building’s electrical usage. Currently, there are many ways to accomplish energy-efficient vertical transportation. Depending on what systems are being selected, one should look for simple, yet effective ways to reduce the electrical consumption. More mundane hydraulic systems may benefit from simple items such as variable frequency drives (VFDs) and premium-efficiency motors.
Divisions 22 and 23
For plumbing (Division 22) and HVAC (Division 23), there is a dizzying array of considerations when writing the specification. Many of these will have a big impact on the final product, operating efficiency, and cost.
For instance, it is critical to ensure the energy efficiency metric cited is relevant and applicable to the particular project. The selection of condensing boilers for use in systems designed with 82-C (180-F) supply temperatures provides one example. The boiler will not operate in the condensing mode, making its rated efficiency irrelevant. While it is tempting to specify a boiler that is as efficient as possible for lower temps, it may not be as efficient as other options when considering the actual operating temperatures. Often, the design team can be challenged to construct a system that uses lower water temperatures allowing for the efficiencies of condensing boilers.
Another consideration involves specifying the efficiencies of the largest energy-users where the ‘biggest bang for the buck’ can be realized. Chillers, for example, are obvious components where the specifiers should consider factory testing to ensure the best possible performance.
Today’s buildings often contain multiple systems of electronics that need to interface with each other. While many find this side of specifications writing confusing and complicated, it is extremely important to get this right. Therefore, it is crucial someone in the design team with experience in control system architecture and how equipment can interface with each other, document how it should be done in the contract documents. Considerations such as self-contained controllers versus active controlling by the BMS need to be determined.
There are often two sides to this. It can be advantageous to take control of a device so one can clearly see in the BMS what it is doing and make adjustments. However, it can also be best to leave this to the device manufacturer, as it will know its system the best. This is a case-by-case judgment call.
Division 25
It is important control specifications are written correctly to ensure the end result everyone wants. The control sequences have to be reviewed carefully to make sure they meet CSI’s 4 Cs; that is, that they are clear, concise, correct, and complete. Further, they must be as straightforward as possible—complex sequences are often misunderstood and are more likely to be overridden with high-energy use over time as a result.
The specifications must also include monitoring and alarming of the smaller items that are often overlooked such as critical lab equipment and feed and condensate pump set alarm points. The reviewer shall also carefully consider what devices will benefit from features such as end switches and proper feedback loops.
One must define sensors that are of high quality and that will not drift over time, wasting energy due to sensors out of calibration. When a CO2 sensor is off by 20 percent, it can make a huge difference in how much outside air a system brings in.
Specifications should also include language for ample test time with the commissioning authority, and verification of sensor and actuator accuracy.
Divisions 26 through 28
The electrical specifications have many aspects that can affect the building’s energy performance over time. Light fixtures are an obvious example. The reviewer should consider what will likely be the best available technology at the time of construction. Light-emitting diode (LED) technology is rapidly evolving—what may be rather expensive today could be less expensive at the time of construction.
In this same vein, lighting controls have come a long way. There are new computerized systems with amazing capabilities. However, the application needs to be carefully discussed with the end users. Complex lighting control systems may be too hard to operate; for a particular project, it may be more suitable to use smaller and simpler lighting control systems.
The reviewer should also be informed of, and look for, the most efficient transformers.
Conclusion
There are many projects with lofty energy goals that may never be able to perform as intended because the specifications were not clear or developed enough to produce the end results that everyone involved wanted to see. While design reviews are important and often performed rather well, it is imperative the reviewer also spend a considerable focus on the project specifications.
Notes
1 For more on enthalpy wheels, see the article, “Reducing Building HVAC Costs with Site-recovered Energy,” by Stephen J. Pargeter, in the March 2012 issue of The Construction Specifier. Visit www.constructionspecifier.com and select “Archives.” (back to top)
2 The low temperature is supplied by the campus system. Medium temperature is generated from a local high-performance chilled water system. (back to top)
Bo Petersson, PE, LEED AP, is the director of engineering services at Cornerstone Commissioning. He oversees the development and maintenance of all technical processes and documentation, and manages the commissioning staff. Petersson has a master’s degree in mechanical engineering and has been working in the HVAC industry for 25 years. He has been a speaker at conventions and conferences including Labs21, Lab Design, and chapter-level (APPA) and American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) meetings. Petersson can be reached via e-mail at bpetersson@cornerstonecx.com.
