Statistics
Building Info
Location:
Program:
Project Cost:
Project Size:
Project Height:
Washington DC
Mixed Use | Retail/Residential
$155 Million
591,900 SF
10 Stories | 134 FT
Project Team
Owner:
Architect:
Structural ENGR:
MEP ENGR:
Civil ENGR:
Landscape Arch:
Geotechinical ENGR:
MRP Reality
Hord Coplan Macht
SK+A Structural Engineers
Jordan & Skala Engineers
Bowman Consulting Group
Oculus
Geotechnical Solutions
Architecture
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Architecture:
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The Wren DC is a mixed use 592,000 SF, 110’ high, 10 story building situated in NW Washington DC. The program of the Wren includes 3 levels of underground parking, a Whole Foods Grocery store to go on the first floor and mezzanine level which take up most of the site foot print. The remaining nine stories will be composed of residential units totaling 428. Amenities for the residents are distributed between the second floor, third floor, and roof. The roof has outdoor amenities such as a dog park, pool, garden, and a 107’ long bridge connecting two sides of the building.
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Codes:
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2013 DCMR 12
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2012 International Building Code
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2012 International Energy Conservation Code
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2012 International Fuel Gas Code
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2012 International Mechanical Code
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2012 International Plumbing Code
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2012 International Fire Code
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2010 ASHRAE 90.1
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2012 International Green Construction Code
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2011 National Electrical Code, NFPA 70
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2010 Americans with Disabilities Act (ADA)
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ANSI A117.1 2009 American National Standard, Accessible and Usable Building and Facilities Fair Housing of Amendments Act of 1988 (FHA)
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Zoning
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The Wren is in a Commercial Residential Zone and the project is designated in the Mixed-Use Medium-Density Residential/Medium-Density Commercial land use category. This zoning area allows for the mixed use retail and residential uses for this project. The zoning also requires that 30% of apartment units are reserved as affordable units reserved for families that has income less than 50% AMI creating an economically diverse community.
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Historical Requirements:
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Not Applicable: The project site was previously an on grade parking lot and warehouse both of which were razed for the new construction.
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Building Enclosure
Façade:
The façade of the building is a curtain wall system alternating between an insulated unit glazing system and a brick cavity wall with 6” metal stud. The glazing system is required to have an average U-value of 0.38BTU/sq.ft.xh, a condensation resistance factor no less than 45, and a solar heat gain coefficient no greater than 0.35. The typical system indicted on the drawings on the residential units is an Oldcastle Series 6000 Thermal MultiPlane, with Low-E glass the U-factor is 0.38 and the condensation resistance factor is 63. The cavity wall is not load barring and has an R-value of 23. See Figure B for cavity wall composition.
Figure B: Typical Exterior Wall Detail
Figure A: Typical Building Elevation
Roofing:
The roof of the Wren is utilized for amenities giving the tenants spaces such as a dog park, community garden, green courtyard, and pool. Despite the variation in usage the roof system is affectively the same across all the areas with variation on whether pavers, soil, or synthetic turf is placed on top. Below, Figure C, is a detail of the base roofing system on the pool deck level. Water travels through the upper surface and goes around the rigid board insulation to a drainage board where it is then directed to roof drains. In the courtyard on level 2 since it is a green roof, the roofing system there is a bit different, see figure D. There is additional layer of drainage board added above the insulation directly below the soil allowing the water to be taken in by more of the vegetation before going to the roof drains.
Sustainability Features
The Wren meets LEED Silver requirements with a score of 59 to reduce the environmental impact of the building as well as improve how the building interacts with community and public transportation. In addition on the roof the building has 2209 SF of solar panels to produce approximately 1% of the project’s residential power demands. The Wren also has a community garden on the roof, which will help reduce heat island effect and control storm water runoff.
Figure C: Pool Level Base Roofing System
Figure D: Green Roof System
Electrical/Lighting
The Wren’s electrical system’s switch main electrical room and switch gear is location in the first parking level. There are 3 supplies for the residential units each have conductor capacity of 3000 amps. All residential units have their own panel board and are supplied from one of two electrical rooms on each level. In the electrical room there are electric meters for each unit. There us on site power generation, on the roof there is a solar array to supplement residential power demands as well as an emergency natural gas generator. The electrical supply for the retail, parking levels, and public areas is also 3000 amps. Lighting in the Wren is supplied entirely with LED luminaires
Mechanical
The building’s HVAC system consist of closed loop water source heat pumps. In the penthouse there are two water pumps and boilers, one for residential supply the other for the retail space. In the case of the residential units, each unit has a water source heat which the pump on the roof circulates water between the units where heat is exchanged to condition each space. Out side air for each unit is supplied by a duct run in the hall way which is connected to an air handler in the mechanical penthouse.
Structural
The structure of the Wren is composed of cast in place reinforced concrete. The parking and retail levels utilize 10” or 12” thick two-way flat plate slabs with drop panels. On the residential levels to minimize floor to floor heights an 8” two-way post tension flat plate is used. Columns are on a rough grid with an average bay spacing being 20’ x 30’. Lateral loads acting on the building are primarily resisted by concrete moment frames and are supplemented by 5 concrete shear walls.
Fire Protection
The fire protection system of the Wren consists of both passive and active systems. There are one hour fire rated wall assemblies around the residential units and two hour rated wall assemblies around vertical circulation spaces and electrical rooms. There is a fire alarm system monitoring circulation and amenity spaces. Stairwells are pressurized to keep them smoke free in event of a fire. The basement mechanical room contains a fire pump connected to building stand pipes located in the stairwells.
Transportation
Elevators are the primary means of vertical circulation in the Wren of which there are 12 total. The retail tenant has a bank of 5 that run between the parking levels and main retail level with some of these and one additional lift servicing the mezzanine level. The remained of the elevators are there for the residential tenants, with 5 hoist operating from level 1 to the roof and one other elevator to connect the elevator lobby with the parking garage. In addition to the elevators there are three stair well that traverse the whole height of the building.