Ann Arbor’s City Hall goes live with green roof

When it rains, the green roof on Ann Arbor's Larcom City Hall will be grateful for the soaking. The 18,000-square-foot expanse of roof will be planted during the first week in September, says Nancy Stone, a spokesperson for the city of Ann Arbor. The roof will have 10,318 square feet devoted to sedum plantings, with alium (wild onion) plants interspersed for a mix of height and color. The plants come in four-inch-deep trays, over 5,000 of which will be used. The remainder of the space will be topped with walking pavers. The installation is costing roughly $450,000, or $25 per square foot, according to George Cook, chief executive of roof installer CEI. "Using the promenade open space over the exposed original flat roof of the first floor of the Larcom City Hall was a natural location for a green roof. This type of vegetative roof absorbs rain water to prevent flooding and helps insulate the building, keeping it warmer in winter and cooler in the summer," Stone says in an email. Excess water from heavy rain will flow into roof drains and then ground-level rain gardens and cisterns around the building.   Green roofs last two to three times longer than standard roofs, according to an estimate by Live Roof, the city's vendor. It offers protection in the form of shielding it from UV radiation, temperature swings, wind, and perforations. The rooftop, which will have seating areas, will be accessible to visitors once the stair rails are installed at the end of September, Stone says. Sources: Nancy Stone, spokesperson for the city of Ann Arbor; CEI chief executive George Cook Writer: Tanya Muzumdar Image courtesy of city of Ann Arbor