Roof of the County Office Building
Chicago based photographer Brad Temkin is documenting green roof landscapes around the United States. In May 2011, Temkin traveled to Allegheny County to document several green roofs in the region. Our very own County Office Building Green Roof is featured in two recent online publications:
The National Science Foundation highlights the research work our partners, Penn State University, are doing to measure the impact of green roofs.
The Allegheny County Green Roof is designed as an education model to demonstrate the benefits of green roofs and green roof technology. Construction started in April 2010 and was completed in June 2010.
The benefits of a Green Roof are numerous.
- Stormwater Management – retain the water. Assists in decreasing combined sewer overflows, helping to reduce the need for the construction of major storm sewers (gray infrastructure) translating into cost savings for residents
- Reduce the “urban heat island” effect, reducing the level of heat in dense concrete areas. The Allegheny County Green Roof has shown a 40-50 degree difference in temperature in the past 2 months
- Extend the life of the roof, reducing maintenance costs
- Reducing of heating and cooling costs. We expect a 10-20% reduction in overall costs.
- Looks nice to others from above
- Improved air quality
- Space for local food production. Allegheny County will partner with the Art Institute on growing hard to find herbs for their culinary program.
The Allegheny County Green Roof has four (4) types of green roof technologies.
- Intensive – 8 to 12 inches of soil and growing shrubs and plants needing the soil depth.
- Semi-intensive - 6 inches of soil and able to grow plants and shrubs.
Both intensive and semi-intensive require the roof top to be able to handle the additional weight.
- Roll out Mat – set on 4 inches of soil, this pre-grown sedum mat provides instant cover.
- Tray system – easy to install, pre-grown sedum and lightweight.
The mat and tray system are lighter and allow installation on rooftops that have a weight restriction.
Demonstrating the benefits of a roof were important, so our project has significant monitoring in place. Allegheny County has eight dataloggers collecting data from a network of around 90 sensors located around the green roof and conventional “control” roof.
The weather station monitors current weather conditions on the rooftop. The sensors monitor a range of green roof and convention roof conditions such as temperature of the roof, soil moisture and water flow and water retention during wet weather events.
Data from sensors are collected every 15 minutes. As an example of a subset of the data that summarizes the essence of our experiment, you can access the County Office Building weather station. Note: there are selectable “Past Day”, “Past Week”, and “Past Month” tabs that you must click on to get the graphical display of data for the period. Note: “roof drainage” values must be divided by 3 to make directly comparable to rainfall amounts.
You can also access information some of the raw data concerning the rainfall and waterflow that percolates through the soil. (Note: roof drainage must be divided by 3 to make directly comparable to rainfall amounts). Also available online (Adobe Flash Player is required) are details of monthly hydrologic performance a summary of rainfall, roof runoff, and avoided roof runoff (click the large tab at the top of the graph to select between "Runoff" or "Avoided Runoff" volumes).
For information on the Allegheny County Green Roof, please email
Green roof completed
Green roof matured
Green roof Spring 2012