Designing, enhancing office buildings: Energy efficiency
Office buildings might seem like relatively simple structures, but engineers with experience in the field know differently. Energy efficiency and sustainability improve occupancy rates and the overall performance of the building.
Christopher Arnold, PE, Vice President, Wick Fisher White, Philadelphia
Saied Nazeri, PE, CPD, LEED BD+C, Senior Vice President, WSP | Parsons Brinckerhoff, San Francisco
Reardon D. Sullivan, PE, LEED AP, Principal, WFT Engineering Inc., Rockville, Md.
Jill Walsh, PE, LEED AP, Principal in Charge of Mechanical Engineering, OLA Consulting Engineers, Hawthorne, N.Y.
Michael Walsh, Project Manager, PEDCO E&A Services Inc., Cincinnati
CSE: Energy efficiency and sustainability are often a request from building owners. What net zero energy and/or high-performance systems have you recently specified on an office building (either existing building or new construction)?
Nazeri: We have employed a buoyancy-driven cooling system strategy (often referred to as passive downdraft) on several recent projects in different climates. As an energy-saving alternative to fan-driven air distribution, this innovative design approach uses columns of cold air to generate a downwards piston effect that drives conditioned air through the building. The system delivers 100% outdoor air with no recirculation, which enhances indoor air quality. We have used mixed-mode systems that use both natural ventilation and air conditioning to maintain comfort conditions year-round. When outdoor air is sufficiently cool, a green indicator light within the office space notifies the occupants that it is advantageous to open the windows. At times of high temperature and/or humidity, the indicator light turns red and notifies the occupants that the windows should be closed. We have used ground-source heat pumps to deliver high-efficiency heating and cooling on a number of projects. A variety of ground-coupling techniques has been applied including foundation-integrated heat exchange (both vertical and horizontal) and heat exchange with municipal sewer systems (sewer mining)..
CSE: Many aspects of sustainability (power, HVAC, maintenance, etc.) require building personnel to follow certain practices to be effective. What, if anything, can an engineer do to help increase chances of success in this area?
Arnold: It is important to open a dialogue with the building's facility staff early in the design process. Educating end users and starting the change-management process with those that operate the building infrastructure is vital. Many issues can arise that could result in major problems if not addressed early on. For example, most buildings have multiple contracts for maintaining building systems. We have encountered projects where the maintenance of waterless urinals was a gray area. After turnover of a project, facilities management and janitorial services both claimed it was in the others' purview. The end user must know, upfront, the advantages and disadvantages of any system installed. As a consultant, it is our job to ensure this occurs at all times.
Michael Walsh: It is more important than ever to not just provide clear sequence of operations during design, but also to get the operations staff involved upfront in the design process. Not only does it help them to understand the end result better, but it also helps them feel more invested in the end result because they were part of the team making decisions during design. It is also important to properly commission the systems to verify operation. The commissioning process is another great time to involve the operations staff members so they can be trained on the systems in a live environment. Engineers and designers also need to do a better job explaining the necessity of regular maintenance of the equipment and controls so the systems can perform at a high level for the long term.
Nazeri: Where manual control is a fundamental aspect of the HVAC system (natural ventilation, for example) it is advantageous to make the user interface as intuitive and easy to use as possible. What may be second nature to a trained engineer may not be so obvious to a typical building user. As such, it is important that building users are fully trained in the use of their building and how to realize its full energy-saving potential.
Sullivan: The key is the "keep it simple, stupid" principle. The more complicated the systems area, the more likely they will not be properly maintained. The systems need to be serviceable. This is a joint effort of the architect and engineer to provide easily removable access panels that will allow proper servicing of equipment. Unfortunately, the required access panels may not fit into the architectural/interior design scheme and are often compromised.
CSE: Please share an office building success story in which you were able to enhance sustainability of an existing building. Annual statistics on energy savings and other supporting evidence would be helpful.
Nazeri: The NOAA Daniel K. Inouye Regional Center project in Hawaii is an excellent example of adaptive reuse in which two World War II aircraft hangers were repurposed as laboratory and office space. As part of the historic preservation mandate of the project brief, the entire building envelope was retained. The project benefits from a host of sustainable features including a fanless buoyancy-driven air conditioning system, 90% daylight access throughout the floor plates, a seawater-cooling system, and a solar thermal installation that meets 80% of the domestic hot water (DHW) demand of the building. The building consumes 65% less energy than a typical office building.
Arnold: Recently we renovated a 20-yr-old, 125,000-sq-ft office building. Although the client did not wish to pursue a formal LEED certification, their corporate culture required them to implement sustainable elements in all renovation projects. MEP elements that supported this initiative included the installation of LED light fixtures with individual occupancy sensors, the control of VAV boxes supporting noncontinuously occupied spaces from lighting-control occupancy sensors, replacement of existing air-handling unit components with high-efficiency, energy-saving elements, and the installation of waterless and low-flow fixtures. The project is currently approximately 60% through construction, and final energy savings are not yet available.
CSE: Please describe your experience in smart or intelligent office buildings.
Michael Walsh: Overall, we have had great experiences and results with smart office buildings. However, we have learned the increased importance of educating the client. This not only means the operations staff as discussed previously, but also the end users who will occupy the spaces. We have all heard anecdotal stories of people constantly calling operations to tell them a light fixture is burned out when, in reality, the fixtures are on daylight sensors. When we designed the passive chilled-beam system, an active display was created in a common area with educational posters and user-activated lighting that helped explain how the system worked and why they may not feel or hear the typical airflows they are used to with ducted systems. We believe this went a long way in helping everyone understand their new high-performance environment.
Nazeri: Many buildings that are designed to achieve high-performance design goals, fail to achieve them in actual practice. The root of this problem stems from the fact that our analysis models assume that a building and its systems will be installed and operated to perfection. Reality tells us that this is seldom the case. Buildings are not mass-produced in the same manner that manufacturing processes can be gradually fine-tuned and honed to deliver close to zero defects. Rather, buildings are individually designed and tailored to the specific context of the site and client needs. As such, each building is, in effect, a complex prototype-and as with all prototypes, some level of post-production fine-tuning should be expected. Historically, the construction process has been very poor in this regard. Building systems are typically commissioned in a 2- to 3-wk period at the end of construction. This process is useful in identifying if a system can successfully deliver design temperature, humidity, pressure, etc., but often fails to determine whether it does so using the requisite amount of energy that was predicted during design. In recent years, we have seen the use of smart building systems to help tackle this. Through a cloud-based interface, building-performance trending and diagnostic software enable engineers to remotely trend the performance of their buildings and to diagnose design or installation flaws that may have been missed during commissioning. Furthermore, diagnostic algorithms can be programmed that are able to automatically detect nonconformant operation and to notify interested parties. Through this process of post-occupancy refinement, we are beginning to see a far stronger correlation between predicted and actual in-use building-energy performance.