Aid in the Shade: Coming Development Wave to Include Sophisticated Shading Devices
- Feb 10, 2012
Over more than a decade, commercial property executives in Germany and other European nations have come to rely on an energy-conserving mechanism that has yet to catch on in the United States: exterior sun-shading devices.
But as domestic developers gear up for the next round of activity and strive to minimize solar heat gain amid rising mechanical cooling costs, it appears many of America’s future commercial facades will be adorned with a variety of static or motorized shading systems.
In fact, while it may not be obvious to the casual observer, millions of dollars worth of intricately engineered devices are already deflecting direct sunlight (and consequent heat) from the facades of sustainability-leader Hines’ latest U.S. mega-developments.
Often made from extruded aluminum and tinted glass, these shelves, fins, tubes and the like are affixed in varying combinations to the new Hines-developed high-rises 300 N. LaSalle in Chicago, BG Group Place in Houston and the Devon Energy headquarters in Oklahoma City—and will likewise highlight the big project set for launch at Tysons Corner Center in Northern Virginia.
And these are no small-scale experiments with energy-efficiency strategies: The four projects alone will comprise some 5.5 million square feet of Class A space, representing hundreds of millions of dollars in invested capital. While to the untrained eye these proper- ties’ shading devices may appear to be add- on architectural articulations—and technically, they are—critical functional benefits will ultimately cover their construction costs, stressed Jerry Lea, Hines’ vice president of conceptual construction.
But do not expect the quick three- or even five-year payback periods profit-minded developers seek with most efficiency-enhancing upgrades. Modern high-rise shading devices require considerable engineering and design effort and expense to optimize and integrate their primary benefits, and also to minimize any unwanted collateral effects, Lea explained. As a result, with corporate and institutional buildings, payback might take 10 to 15 years.
On the positive side, many users feel that is fast enough to justify the up-front costs, and so-called life-cycle financial assessments favored by some institutional and public-sector occupants might consider benefits realized over three or four decades.
There are also collateral cost benefits. Their fundamental function is to deflect direct sunlight away from glazing and other façade surfaces, thereby substantially reducing solar heat gain as well as pesky interior glare. Some reports suggest the most effective such devices can reduce heat gain 80 percent or more as they deflect sunshine from as much as 40 or 50 percent of a given façade’s surface during the highest-exposure hours.
The lower the heat gain, the less expenditure required for mechanical cooling—not to mention the improved productivity of glare-free workspaces. “So if you can reduce that solar heat gain, you won’t have to spend as much on your HVAC mechanical plant,” explained Rob Kistler, founding principal of specialty consultant The Façade Group.
Indeed, Hines’ detailed energy-use analyses confirm that shading systems boost project bottom lines, as less costly cooling systems are required to keep occupants comfortable, Lea concurred.
Of course, designers and engineers are challenged to minimize detrimental impacts on revenue-boosting views, and on desired day- lighting effects, as well. “It’s certainly a challenge to provide all that ‘vision glass’ that tenants want, along with natural daylighting and a comfortable room temperature, and still be exceptionally energy efficient,” Lea is quick to acknowledge.
Those high-demand westerly and southerly view spaces can cost a lot to cool on bright summer afternoons, added Mark Perepelitza, associate partner with sustainability-minded Zimmer Gunsul Frasca Architects, who has studied European shading strategies. Not to mention the blinding glare that motivates occupants to engage internal shades that block those coveted vistas. But the latest insightfully designed shading devices can be extremely effective in reducing cooling costs and glare, while still maintaining those great views and daylighting benefits.
An analytical strategy that helps profit- minded players like Hines and its partners justify shading-system costs entails assessing their impacts as aesthetic as well as functional features. The “double-duty” enhancements of both architectural distinctiveness and energy performance help justify the lengthier financial payback, Lea noted.
To wit, shading systems incorporated into some of Hines’ latest projects can be quite striking visually. For instance, with the 50-story Devon tower’s symmetrical triangular shape, the design team—including Pickard Chilton as lead architect—created a regular series of vertical glass fins and horizontal tubes running along windows throughout the periphery, rather than just on the facades subject to heavy solar heat gain.
The effect promotes artistic consistency in addition to the primary motivation of energy efficiency, Lea explained. Indeed, such shading systems can communicate cultural statements about projects’ designers, developers and occupants, he continued. “They show you’re thinking about sustainability and energy efficiency.”
While designing shading devices into original construction plans can pencil out over a reasonable payback period, attaching them to existing structures in conjunction with energy retrofit programs is a trickier matter. To a great extent, financial viability depends on whether the façade is strong enough to handle the additional weight—and support window washers, as well, Lea related.
Due to the costly bracing or other reinforcement required to accommodate the greater weight load, shading-device installations are not likely to pencil out in retrofits of larger commercial properties absent a comprehensive re-skinning, Perepelitza agreed. But at least one substantial example of such a project is underway in ZGF’s headquarters city of Portland.
The extensive retrofitting of downtown’s 516,360-square-foot Edith Green-Wendell Wyatt Federal Building—tapping $133 million in federal economic stimulus funds—does indeed entail radically revised facades, as well as one of the more visually striking shading devices ever devised. And it is slated to become one of the GSA’s most energy-efficient office buildings, with ambitious targets of 40 percent beyond-code energy-efficiency, a 97 EnergyStar score and a LEED Platinum rating.
The GSA engaged SERA Architects and Cutler Anderson Architects to help design the 18-story tower’s retrofit—including creative solutions for shading a west-facing façade subjected to considerable “late, low afternoon sun,” noted SERA senior project manager Jennifer Taylor.
Team members value-engineered a number solutions, including a mechanical shading device, ultimately opting for a varied series of fixed extruded-aluminum “reeds” hung from six columns of steel armatures.
The device now nearing completion achieves the client’s goal of shading half the façade at critical times while also preserving excellent views, Taylor continued. And the “repeatable randomized pattern” staggering reed widths, lengths and placements helps avoid any connotations of a barred barrier, she added. “I think we’ve worked it out pretty effectively.”
With the south and east facades, more traditional horizontal shelf-type devices above and below windows will provide the bulk of the needed shading, assisted by a few vertical reeds.
Taylor also emphasized that the shading system is designed to operate in tandem with the building’s highly efficient new radiant hydronic heating and cooling system—which taps outside air for ventilation and hence tolerates very little solar heat gain on warm and sunny days. “Once we choose a radiant system for a building like this, the shading becomes integral” to achieving energy-efficiency goals, she explained. “We really couldn’t have one without the other.”
The GSA’s required life-cycle cost analysis considers financial, environmental and other impacts over 40 years. The building achieves its goals within that generous time period with flying colors: Calculations project “dramatic” energy savings all around for the Green/Wyatt retrofit, Taylor noted.
For more details on the merits of dynamic versus static systems, see “Dynamic or Static?“