A breath of fresh air
As a major share of any building's operating budget, heating and cooling costs must be considered from the very inception of the design phase. To keep facilities competitive, overall design and heating, ventilation and air-conditioning (HVAC) systems should drive much early decision-making. That means balancing HVAC technology against budget criteria and properly investigating building orientation, roof color, landscaping and other issues that can minimize solar gain in the summer and maximize it in the winter.
With energy costs and awareness rising, such basic notions as shade-and more sophisticated phenomena, such as "evapo-transpiration" from landscaping features-are now guiding principles for building design and operations.
To reduce heating and cooling costs, project planners can first minimize HVAC load by means of massing, orientation, fenestration and landscaping. "Building orientation is something you really need to focus on today," says Ben Houston, president and COO with TD Industries, Dallas, a large mechanical contractor, "so you have minimum solar exposure in summer, but get some simple heat gain in the winter."
Of course, this relatively simple concept is often difficult to pull off in the real world, notes James S. Baker, facility manager and mechanical engineer at Armstrong World Industries Inc., Lancaster, Pa., which just completed 350,000 square feet of new construction and renovations started in 1995, including its corporate headquarters. Baker's group gets involved at the earliest stages of the planning process. "HVAC is a prime consideration at that time," he says.
Early on, designers and facility managers carefully reviewed the configuration and orientation of the new headquarters. "Ideally, we could have focused strictly on the most advantageous orientation based on energy-cost savings alone," says Baker. "However, at least some of that decision was based on the location of other buildings on the campus and their orientation." The project, he adds, also needed to have a high profile and world-class design. "So we spent a lot of time on both the general footprint as well as orientation," he recalls.
To determine how the sun would affect the facility and its occupants, the building team built a full-scale model of one of the offices, which was mounted on wheels. "We were able to move it around and see what the angle of the sun and the orientation of the offices would do to its relationship with sunlight," Baker recalls.
The existing HVAC system-a 2,500-ton chiller plant with direct digital controls-was installed in 1995 in preparation for the new projects and with energy consumption in mind. The system had enough redundancy to comfortably cover 990,000 square feet of existing space as well as the new structure, but more energy-control measures were planned for renovated areas.
HVAC R & D
"As we installed new energy-efficient windows in the existing buildings, we retrofitted with other energy-control devices, such as occupancy sensors that regulate not only lighting, but also heating and cooling," Baker explains. "Our energy savings went up, and we were able to actually save additional chiller load."
In fact, a wide range of energy-saving heating and cooling technologies were reviewed for the project, but many were found to be impractical. Indeed, many industry experts agree that many products and systems that look good on paper may not be economically feasible for larger commercial buildings. Renewable resources such as geothermal, wind and solar power, for example, may be useful on a limited basis. Improvements to existing technology, on the other hand, more commonly make inroads into the final building specifications."
Over the past few years, we've seen major improvements: more energy-efficient chillers, better heat-recovery-type chillers and higher-efficiency motors, just to name a few," says Robert Pawlicki, director of facilities engineering for Baxter Healthcare Corp., Deerfield, Ill. "Another big savings has come from improvements in variable-frequency drives. Prices have come down, and they've become much more reliable. We use them more extensively now."
TD Industries' Houston agrees. "Variable-speed pumping and drives are becoming somewhat a matter of course.we can meet the load requirement more easily that way than with any kind of step control," he explains.
The real potential for cutting HVAC costs, however, is managing overall load with an energy-management system. "Recently, energy-management systems have become very sophisticated," Houston contends. "They can permit load-demand limiting, load shedding at different hours and turning the systems off and on when they're not in use. We can program them to respond to special requirements for night occupancies, [even] on an intermittent basis."
Energy-management systems have helped other HVAC approaches, such as thermal storage, Houson adds. His firm regularly installs water- and ice-based thermal-storage systems, and he expects demand to continue as energy becomes more expensive and less reliable.
"As energy pricing fluctuates on a daily and even hourly basis, we can control [thermal storage] systems to cool during periods of peak loads to save on the higher prices of electricity during those times," Houston says.
Of course, technologies can't make up for basics that are overlooked.
"A recent study shows that oversizing building equipment is one of the biggest energy-wasters," says David T. Williams, mechanical department leader with LHB Engineers and Architects, Duluth, Minn. "You have to make sure equipment is able to operate at its optimal point, so it can work as efficiently as possible."
The first step is to conduct an energy analysis, says Williams. "As designers, we're criticized for not specifying enough capacity, while we're rarely criticized for having too much capacity," he notes. "Yet, the latter can be just as bad."
Still, says Baxter Healthcare's Pawlicki, the bottom line in HVAC energy savings is research and legwork during design development.
"When you talk about saving on HVAC costs, there seem to be a number of products that work well, and we tend to gravitate back toward those products," Pawlicki notes. "But you never want to get stuck on older methods when newer ones would work better. So there's always a search for better products, and fine-tuning the ones you have used successfully in the past."