Thin Flats, an urban infill project in the Northern Liberties section of Philadelphia, is a modern take on the Philadelphia row house. Developed by Onion Flats, a design-build-develop firm, the 20,000 square foot (1,858 square meters) project is the first duplex building to be certified LEED-Homes Platinum in the US.
Onion Flats is run by a team of brothers McDonald (designer Tim, master plumber Pat, realtor Mike) and architect Howard Steinberg. The firm specializes in sustainable projects and has a knack for revitalizing an entire neighborhood with well placed, well designed, and well planned buildings. Their many mixed-use infill projects integrate retail and residential and have kickstarted development in neglected former industrial areas of the city.
The eight apartments that make up Thin Flats are each 18 feet wide (standard width for houses in the area) and two stories tall. The designers improved on the long, skinny forms of traditional Philadelphia row homes by rearranging the interior spaces and playing with the exterior facade. Thin panels of glass, metal, and wood composite exaggerate the proportions of the slim row house form and obscure the boundaries of each unit.
The southern elevation is made of two exterior walls. The outermost wall is pushed out three feet to create an air space that makes an entrance area on the ground floor and balconies above. The space also draws warm air up and out, acting as a thermal chimney.
The Thin Flats are almost 70 percent more energy efficient than required by code. The project’s sustainable elements include:
- Solar thermal panels that provide domestic hot water needs
- Green roofs that also provide valuable exterior living space
- Rainwater harvesting cisterns below the parking area that water gardens
- Low flow faucets and fixtures which reduce water consumption by 50 percent
- Double pane, low-E, argon filled, thermally broken windows and doors
- Centralized and programmable lighting, heating, and cooling to monitor and minimize energy use
- Radiant in-floor heating
- Heat recovery ventilation
- Electric car charging port
Rents for the units run between 2,000 and 3,000 USD, with purchase prices up to 680,000 USD.
Because of the constraints of urban scale and existing, adjacent structures, small infill projects often require and display innovative design solutions. The projects demonstrate how one small building can transform an entire neighborhood.
Images: courtesy of Onion Flats