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    Green Top Ten - Office Buildings

    1315 Peachtree Street, Atlanta, GeorgiaIowa Utilities Board Building, Des Moines, Iowa
    Mercy Corps Headquarters, Portland, OregonChandler City Hall, Chandler, Arizona

    1315 Peachtree Street • Atlanta, Georgia


    A public library occupies the second floor at 1315 Peachtree Street, as it did before the renovation. By removing a street-level parking garage, the design team was also able to create a new tenant space for the Museum of Design Atlanta — right across the street from the High Museum of Art.

    Since about 95 percent of the electricity sold by the utility Georgia Power is coal-generated, the Perkins + Will project team opted to meet a large portion of the energy needs of the 1315 Peachtree Street building through cogeneration: natural-gas-fired microturbines provide power, hot water for heating, and cooling from a hot-water-driven adsorption chiller.

    Partly because natural gas was considered to have a lower carbon intensity than coal, this system helps to decrease the building's carbon dioxide emissions by about 68 percent, in the firm's calculations.

    The building's total energy use intensity (EUI) is 28.4 kilowatt-hours per square foot per year (306 kWh per square meter per year), and its net EUI is 8.21 kWh/ft2/year (88.3 kWh/m2/year).

    That total EUI is a good figure for a contemporary U.S. building — but three times higher than the other three office buildings in the AIA/COTE 2012 green top ten. For perspective, consider also that to meet the Passive House standard, buildings have a maximum primary energy use of about 11 kWh/ft2/year (120 kWh/m2/year) — a far lower level than described for 1315 Peachtree Street.

    ArchitectureWeek is also skeptical about the installation of new fossil fuel energy infrastructure in an exemplary green building. The dirty nature of the local electric supply in Georgia is a real problem — but investing in expanded use of natural gas is hardly a viable alternative.

    1315 Peachtree Street looks like an admirable work of quality placemaking through effective reuse of an existing building. Its reported level of energy efficiency will likely require another round of retrofitting, sooner than comfortable.


    ArchWeek Image

    Extensively daylit open office space comprises about half of each upper floor of 1315 Peachtree Street. In concert with occupancy sensors and photosensors, daylighting reduces the building's energy use for lighting by an estimated 67% over code.
    Photo: Michelle Litvin Extra Large Image

    ArchWeek Image

    On the upper floor of 1315 Peachtree, a double-height multipurpose space looks out at its surroundings through a glazed, southwest-facing two-story wall.
    Photo: Eduard Hueber Extra Large Image

    ArchWeek Image

    This upper-floor terrace is one of the most prominent additions made during the renovation of 1315 Peachtree Street. With operable shading, the space serves as a gathering place for meetings and events.
    Photo: Eduard Hueber Extra Large Image

    Iowa Utilities Board Building · Des Moines, Iowa

    In Des Moines, Iowa, two state agencies that regulate and investigate the rates and practices of utility companies now share a highly energy-efficient new building at the edge of the state capitol complex.

    Designed by BNIM, the two-story, 44,640-square foot (4,147-square-meter) Iowa Utilities Board and Office of Consumer Advocate Building is divided into two wings, connected near their eastern ends by a shared lobby. The Iowa Utilities Board occupies the larger north wing, oriented northwest-southeast. The Office of Consumer Advocate occupies the second floor of the south wing, which is oriented east-west, with common spaces on the ground floor.

    The primary goal of this LEED Platinum-targeting project was to achieve an energy use intensity of 8.21 kWh/ft2/year (88.3 kWh/m2/year), equivalent to energy savings of about 60 percent beyond the ASHRAE 90.1-2004 baseline.

    The building's siting and east-west orientation provide a favorable starting point. The building envelope is simple, yet hyper-efficient: white Thermomass precast concrete with continuous insulation and non-thermally conductive ties. Through careful detailing, the design team eliminated thermal bridging at roof interfaces, foundation walls, and wall openings.

    Additional energy-efficiency strategies include a ground-source heat-pump system, a total-energy-recovery unit, low-power-density lighting with automated dimming, and occupancy sensors for lighting and workstation plug loads.

    Each wing's narrow floor plate permits daylight to permeate the open office environments, allowing artificial lighting to be left off during daylight hours in 98 percent of the facility. This is facilitated by extensive north and south glazing.

    On the south side of each wing is a system of louvered horizontal sunscreens, designed with a parabolic profile and oriented carefully to reflect summer sun and winter sun off different parts of each blade. The shading system also includes vertical fabric panels.

    Even before considering the contribution of the 45-kilowatt photovoltaic array, the building's actual performance has been better than targeted, achieving an EUI of 6.45 kWh/ft2/year (69.4 kWh/m2/year). The PV system reduces the net EUI another two points.

    Although energy conservation is a primary achievement of this project, it also appears to perform well in terms of water management and site ecology. The southern half of the six-acre (2.4-hectare) site combines a native tallgrass prairie restoration with onsite stormwater management — a strategy prompted in part by Iowa's devastating floods in recent years.   >>>

    ArchWeek Image

    The IUB-OCA Building uses exposed thermal mass to aid in heat regulation. The building's automation system sends an email to occupants when conditions favor opening windows for cross-ventilation.
    Photo: Farshid Assassi Extra Large Image

    ArchWeek Image

    Iowa Utilities Board Building section-perspective diagram.
    Image: BNIM Extra Large Image

    ArchWeek Image

    Built on a six-acre (2.4-hectare) former landfill site at the edge of the Iowa state capitol complex, in Des Moines, Iowa, the office building for the Iowa Utilities Board (IUB) and Office of Consumer Advocate (OCA) was designed by BNIM.
    Photo: Farshid Assassi Extra Large Image

    ArchWeek Image

    Thanks to energy conservation strategies such as a high-efficiency building envelope, use of an energy recovery unit, and reliance on daylighting, the Iowa Utilities Board Building has a projected energy use intensity of 6.45 kWh/ft2/year (69.4 kWh/m2/year), a reduction of almost 68% from the ASHRAE 90.1-2004 code baseline — and that's before counting the offset from its photovoltaic array.
    Photo: Farshid Assassi Extra Large Image

    ArchWeek Image

    Iowa Utilities Board Building ground-floor plan drawing.
    Image: BNIM Extra Large Image

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