Whether it’s auto repair, homebuilding or designing a green roof, having the right tool for the job often makes the process go much more smoothly. This was especially true in the case of the Palisades of Towson — a newly certified LEED Silver apartment home in Towson, Md.

Environmentally friendly features were planned and built into each aspect of the 18-story community’s 361 apartments, 8,000 square feet of retail/office space and what is possibly the largest mechanized parking garage of its kind in the U.S. The project aimed for LEED certification from the outset. Part of that plan included a white reflective roof to help achieve the appropriate credits.

The plan initially called for underground stormwater management tanks. Not only would these tanks help to meet municipal stormwater quantity and quality requirements, they would also help satisfy some Water Efficiency credits. The problem with the white roof/underground storage tanks was it required removal of massive amounts of bedrock to accommodate the tanks. “Doing that was going to cost a fortune,” says Jim Stamer, president of Prospect Waterproofing Company.

Stamer talked the issue over with Jeff Thomas, president of Thomco Inc, the local manufacturer’s representative for American Hydrotech. Together, they looked at the possibility of putting a garden roof on the Palisades of Towson to accommodate the water requirements. A green roof would eliminate the need for the storage tanks and the need to remove copious amounts of bedrock, thereby saving the owner a sizable chunk of change. But would the municipal and LEED requirements be met with a green roof?

The Right Tool

American Hydrotech’s Hydrotech Hydrology Tool (also known as HHT with its shortened, car-like initials) was used to definitively determine how a garden roof would help meet overall stormwater requirements and goals. The HHT aggregated project component performance data, integrated project-specific municipal/ LEED guidelines and then overlaid a variety of “real life” retention and detention abilities such as site-specific storm events and other unique regional climatic conditions.

“Our tool takes into account the growing medias that are local to that area and climate, local climatic data for evaporation, the amount of rainfall, the performance of the products being considered for the project and all the different types of variables that the engineering industry is looking for,” says Nathan D. Griswold, associate ASLA, Garden Roof Coordinator for American Hydrotech. “We met with their engineers, architect and GC, and ran the HHT, with its recognized engineering calculations, to prove that they would meet all of the necessary requirements for both LEED and the municipality.”

“This is the first tool of its kind that uses more than 100 years of climactic data for any particular region and tests every variable within the assembly,” says Dennis Yanez, national marketing manager for American Hydrotech. “Rather than making a generalization about how much water it will hold, it offers hard, quantifiable data that can immediately be taken back to a municipality for approval.”

Some reinforcement of the structure was necessary to accommodate the amount of stormwater the system was going to handle, but after careful analysis and customization of various garden roof components to optimize the assembly and meet project LEED goals, the underground storage and filtration requirements were completely eliminated.

Not only does the new roof help the owner to showcase its sustainable features and attract eco-conscious residents with its LEED Silver rating, the building owners saved more than $75,000 on project completion by eliminating the underground storage tanks. No rooftop access is granted to the residents, but the garden roof also adds a marketing flair for the client even though it’s strictly functional. And it was all possible thanks to some quick thinking, teamwork and having the right tool for the job.

 The Palisades of Towson used HHT to add a green roof and save the owner money. Images courtesy of American Hydrotech.