Page 92 - Zero Net Energy Case Study Buildings-Volume 2

CASE STUDY NO. 10
WEST BERKELEY BRANCH LIBRARY
(Above) Shadow studies show that minimum roof height must be 24 feet to guarantee no shadowing from adjacent three- story building. (Diagram cour- tesy of Greenworks Studio).
(Below) “Shoebox” model in- cluding neighboring buildings— one existing and one potential future development.
Planning Concept and General Design Considerations
The concept design phase evaluated several alternative schemes for the small site, which was located in a commercial area along a very busy corridor connecting the Interstate highway with downtown Berkeley and the University of California campus. Design constraints on the schemes for this semi-urban site include the following:
• The city’s zoning ordinance requires a minimum two-story facade for this area;
• The same ordinance states that direct sun at 12 noon on December 21 into adjacent prop- erty windows may not be blocked by the new building; because of the residential units to the north, this sets a constraining height for the building and its roof features, including any
solar PV panel arrays;
• Athree-storyhotelislocatedfivefeetfromtheeastpropertyline,castingashadowonthe
site in the early morning hours;
• Traffic noise level along this corridor was measured at 70 dBA within the footprint of the
future building, preventing the possibility of openable windows for natural ventilation in the
public library space.
• Two large California redwood trees in the northwest corner of the lot were to be protected,
creating required open space on the small (12,000 sq. ft.) lot;
• The building program required a 9,500 sq. ft. building on the remaining buildable area of
the site.
Several two-story schemes and a one-story scheme were evaluated programmatically and for best potential for a ZNE design. Solar and daylighting access was the key determinant of the selected scheme from among several alternatives considered. Studies showed quickly that the limited roof area and early morning shading from the adjacent hotel would set a likely maximum amount of on-site renewable energy available to the building over the course of year, and that this amount would be highest for a one-story scheme. The studies included capturing daylight for the spaces below the roof as well as solar energy for electric power generation.
Parallel studies of floor plan alternatives for library operations led to the same conclusion: a one- story scheme was most efficient, with a single service point rather than requiring a second one in the case of the two-story schemes.
“Shoebox” energy modeling of the alternative schemes indicated that a design EUI for the build- ing of approximately 17-20 (kBtu/sq.ft. per year) would match the maximum on-site energy pro- duction possible with the one-story scheme. The two-story schemes, with the lower possible on- site energy production, would require a design EUI so low in order to achieve ZNE performance that it would not be feasible given the fixed construction budget amount.
(Right) University Avenue street elevation, showing urban con- text of the library building.
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Zero Net Energy Case Study Buildings: Volume 2