People looking toward the Ohio River from many of the tall buildings in downtown Louisville, Ky., can catch a glimpse of the six-story American Life & Accident Insurance Co. building—and the largest privately owned vegetative roof system in Kentucky, which recently was installed on the building by Louisville-based American Roofing & Metal Co. Inc.
Even before the vegetative roof system was installed, the 40-year-old American Life & Accident Insurance building was somewhat of a Louisville landmark. It was designed by well-known German architect Ludwig Mies van der Rohe, who died during its construction; the building is known as his last piece of art.
When it came time to replace the building's ailing roof system, which was more than 20 years old, the building owner contacted Louisville-based Turner Construction, which contacted American Roofing & Metal.
"We originally were asked to provide budget numbers to reroof with a two-ply polymer-modified bitumen roof system," says Troy Huffman, American Roofing & Metal's project manager. "The building owner is environmentally conscious and asked for a cool roof coating. After the budget numbers were approved, we were asked to look into vegetative roof systems.
"After weeks of research, we selected a Green Roof Solutions vegetative roof system for the project," Huffman continues. "The cool roof coating was removed from the original contract, and the vegetative roof system was added."
Before American Roofing & Metal could install the building's vegetative roof system, the existing 16,384-square-foot roof system needed to be torn off. An eight-person American Roofing & Metal crew began tear-off in May 2009.
The existing roof system consisted of a structural concrete deck, 3-inch-thick polyisocyanurate insulation, coal-tar pitch and aggregate roof system, and elastomeric roof coating.
"The coating was cut into long strips using a motorized roof cutter and torn off by hand," Huffman says. "The tar and gravel roof and insulation were cut using a roof cutter and torn off by hand. All material was placed in a trash bin through use of a trash chute."
The only location where the trash bin could be placed was on an entrance ramp leading to a popular riverfront park.
"Because of the high volume of foot traffic, we installed a safety fence around the trash bin and positioned a worker on the ground at all times during tear-off," Huffman says.
A new roof
After tear-off was complete, crew members installed Johns Manville tapered polyisocyanurate insulation over the concrete deck with Johns Manville Insulation Adhesive.
"We loose laid a stainless-steel electronic field vector mapping grid over the insulation and adhered a 1/2-inch-thick Johns Manville DuraBoard® over the grid with Johns Manville Insulation Adhesive," Huffman says. "A Johns Manville three-ply polymer-modified bitumen roof system then was torch-applied to the entire roof area."
American Roofing & Metal fabricated and installed temporary safety rails around the building perimeter before tearing off the existing roof system and installing the polymer-modified bitumen roof system. The safety rails were removed, and a four-person American Roofing & Metal crew completed the building's sheet-metal, flashing and trim work, during which workers were tied-off 100 percent of the time.
Before installing the vegetative roof system, the building owner hired a company to install permanent handrails around the building perimeter; the handrails served as safety rails during vegetative roof system installation.
Installing the vegetative roof system required a 10-person crew, which American Roofing & Metal calls its "Green Team." The crew is led by Anthony Strickland.
The Green Roof Solutions multilayer vegetative roof system is composed of an aeration layer (plastic vented material with filter fabric); root barrier (virgin-blended linear polyethelyne); moisture mat composed of 35 percent post-industrial materials and 65 percent post-consumer recycled materials; 1-inch-thick drainage media consisting of kiln-dried expanded aggregate; filter fabric; 3-inch-thick engineered growth media from shaved, baked slate and worm compost; and sedum mats.
"This was our first vegetative roof system installation, and we faced a lot of challenges related to system design, as well as the process of learning about the detailed system," Huffman says. "We worked with Tom Cooper, Green Roof Solutions' managing director and principal, who made multiple trips from the company's Glenview, Ill., headquarters to Louisville during the design process. Cooper also was present during the installation process; he trained our crew in all aspects of installing a vegetative roof system."
In addition to vegetative roof system challenges, American Roofing & Metal faced some other dilemmas.
"The staging and loading area was located in a busy park," Huffman says. "Various festivals took place every weekend during the project, and we had to plan our loading of roofing materials around booths and loading and unloading of trucks for the festivals. Also, because of the location, we were not able to use a crane weighing more than 30,000 pounds."
Additionally, the building has significant negative air pressure, and American Roofing & Metal was concerned that torch flames would be sucked into the building at any openings or cracks in the concrete deck.
"We used Johns Manville cold adhesive to adhere the polymer-modified base sheet at all perimeter walls and penetrations," Huffman says. "We adhered the base sheet a minimum of 3 feet from the penetration or perimeter and past the first horizontal joint in the cover board to prevent 'suck back.' After the two plies of base sheet were adhered, the cap sheet was torched down. The base sheet provided a safety barrier against the pressure difference in these critical areas."
Realizing a vision
Despite a few obstacles, American Roofing & Metal completed work in August 2009 on time and under budget. Huffman considers the company's first vegetative roof system installation to be a success and great experience.
"All aspects of the job were rewarding," Huffman says. "We built a great relationship with a prominent business owner in Louisville, as well as continued our great relationship with Turner Construction. And we have had a lot of interest in the vegetative roof system from local newspapers and television stations; the building owner hopes the building will become a beacon of green in Louisville.
"Mies van der Rohe had a vision of this building being a natural extension of the park and riverfront area behind the building," Huffman continues. "With the vegetative roof system installation, we believe his vision has become a reality."
Ashley St. John is Professional Roofing's associate editor.
Project name: American Life & Accident Insurance Co.
Project location: Louisville, Ky.
Project duration: May-August 2009
Roof system type: Vegetative and polymer-modified bitumen
Roofing contractor: American Roofing & Metal Co. Inc., Louisville, Ky.
Roofing materials manufacturers: Green Roof Solutions Inc., Glenview, Ill., and Johns Manville, Denver