Integrated Design: Learning from Building to Building (SCROB and Cambria)
When the Pennsylvania Department of Environmental Protection (DEP) got involved with the design and construction of a building it was slated to lease as its Southcentral Regional Office Building (SCROB), DEP determined to make it a “Green Technology Model Project.”
With support from The Heinz Endowments, Alan Barak of the Penn Energy Project assembled a green team to assist with the design of the 78,000 ft2 (7,250 m2) building. The results, documented in an outstanding half-hour video (see EBN for review), were good enough for a Bronze rating under the U.S. Green Building Council’s LEED™ Pilot Program. Design highlights included:
•location on a brownfield site •ozone-safe cooling with a gas-fired absorption chiller •raised-floor air distribution •dessicant wheel energy and moisture recovery •split task/ambient lighting for a connected load of 0.85 W/ft2 (9.1 W/m2) •environmentally sensitive material choices •construction cost of only $78/ft2 ($840/m2), low for any office building in this market.
Actual performance of the SCROB, after it was occupied in May 1998, has not quite lived up to expectations. The engineer was concerned about sizing the chiller too tightly to the projected load and, since absorption chillers are only available in limited sizes, ended up specifying one twice as large as necessary. This caused inefficiencies in operations (absorption chillers are particularly sensitive to performance losses from frequent on-off cycling) and freezing of the salts. Only cavity-fill insulation was used in the steel-framed exterior walls, resulting in thermal bridging and lower performance. And the lightshelves were not modeled properly, which led to glare problems from direct sunlight reaching workstations and required retrofitting a less-than-optimal fix.
While many of these shortcomings are being addressed proactively by building management, they are indicative of a suboptimal process, in which the green team provided direction to the design-build firm but was not involved closely enough during implementation of those ideas. Fortunately, DEP persisted in recommending a sustainable design approach for its next building, and architect John Boecker and energy consultant Marcus Sheffer got another opportunity. For the design of the 36,000 ft2 (3,350 m2) Cambria Office Building in Ebensburgh, Pennsylvania, the entire team worked more closely together. Even with everyone in the same room, however, old habits persisted and there was a tendency for discussions to become fragmented. This fragmentation was happening, according to Boecker, during one session on locating mechanical systems, which consist of ground-source heat pumps and underfloor air distribution. One group was struggling with locating duct runs to and from the proposed penthouse air-handling systems, while others were working on other issues with the system.
At some point, both Boecker and Sheffer realized that the process had broken down, and they asked the mechanical engineer where the optimal location for the air handlers would be.
After recovering from his surprise at being asked such a question by the architect, mechanical engineer John Manning proposed that they be on the first floor, with one in each wing. The team then studied this idea long enough to overcome the conventional wisdom that first-floor space is too valuable for air handlers, and discovered that they could enlarge the floor plate slightly to accommodate them with a net savings of $40,000 in construction costs. This solution not only greatly increased air distribution efficiency but also improved the daylighting design, which had been hampered by the penthouse.
Similarly, when the designers first proposed an upgrade to triple-glazed, double low-e windows from Visionwall, the developer balked at the $15,000 increase in cost.
He was won over, however, when it was demonstrated that this upgrade allowed elimination of the perimeter heating zone for a savings of $15,000, downsizing of the heat pumps for another $10,000 savings, and a $5,000 gain in leasable space due to the smaller equipment and ducts.
With improved lighting design and daylighting, the connected lighting load at Cambria is 0.65 W/ft2 (7.0 W/m2). Insulated concrete forms from Reward Wall eliminate thermal bridging in the exterior walls. Water conservation measures include the use of waterless urinals and simple push-rod automatic faucet controls. Boecker discovered that with these controls they could use a single automatic mixing valve for a gang of lavatories, which allows just a single supply line to each, saving on installation and maintenance expense. Cambria’s construction came in at $88/ft2 ($946/m2), with an additional $10/ft2 ($108/m2) for sitework.
Comparing the two buildings, Boecker says: “Almost everything we did at Cambria is at a higher level.” The project has not yet been certified by LEED, but the designers are hoping for a Gold rating. Perhaps most remarkably, preliminary utility data is showing performance significantly
better than predicted. Since it was occupied in September 2000, Cambria seems to be using energy at the amazingly low rate of 62,300 kWh per year, or less than $0.18/ft2 ($1.94/m2), not including any contribution from the photovoltaic system. This performance is about 90% better than a typical base case. The building has not yet been through a cooling season, and monitoring is still being debugged, so these numbers are far from final. The Cambria project includes a 14.3 kW PV system, consisting of panels on the roof and on stand-alone tracking devices. At current usage rates, this system is projected to offset about 44% of the electricity cost. The electricity supplier, Green Mountain Energy Co. (GME), buys all of the output from this system (at a premium rate, because solar power is a small but critical part of its green electricity mix), so technically none is used by the facility. The DEP, in turn, buys its electricity from GME, which includes PV-generated power from this and other facilities in its mix. Even though, contractually, the PV system’s output is delivered to GME and other power is purchased, DEP does not pay distribution fees on this power (in Pennsylvania’s deregulated market, users pay for distribution separately from supply). Taken together, the revenue from electricity sales and the avoided distribution charges add up to about $8,630 per year for the State, according to Sheffer. If current estimates hold up, this solar contribution will exceed the facility’s entire energy bill!
For more information:
Dept. of Environmental Protection
P.O. Box 8473
Harrisburg, PA 17105
717/787-4190, 717/772-3278 (fax)
L. Robert Kimball and Associates
4400 Deer Path Road, Suite 105
Harrisburg, PA 17110
717/221-0770, 717/221-8860 (fax)