Though Councilwoman Deborah Scott called the cost "outrageous," the City Council on Tuesday night approved installing a "green roof" at City Hall for $314,169.
Ms. Scott cast the only no vote. She said the cost for a standard roof was $80,000.
R.T. Construction, a Chattanooga firm, had the low bid of $280,000. But city officials said it was found that a roofing material being used by the firm did not meet the specifications.
The city then fell back on the second - and only other - bidder.
That was from Two Rivers Roofing of Madison, Tn.
David Crockett, who heads the city's Office of Sustainability, said the green roof will pay for itself. He said the current roof is leaking and badly needs replacing.
Mr. Crockett said sedum will be placed on the green roof and it will soak in rainwater and also work to save energy inside the building.
He said he hopes the city's example "will lead to 100 green roofs downtown." He said the motto is "No Green Roof Left Behind."
Mr. Crockett said he believes owners of downtown buildings will realize the savings they can achieve with green roofs, including cutting down on their stormwater fees to the city.
The project was funded through a federal grant.
Larry Grohn told the council that the federal funds "are not free money" and the council should take another vote on the issue and turn it down after getting more answers about the project.