With a modest increase in construction costs, the proposed cold-storage warehouse on West Commercial Street could be a handsome gateway building for Portland’s waterfront – not simply a box 40 feet high (“Developer is sought to build cold-storage facility on Portland waterfront,” June 18).

The warehouse will span more than 2 acres of land, making it the largest landmark for anyone entering Portland from Interstate 295 onto Commercial Street, by air during descent into the Portland Jetport and over the Casco Bay Bridge.

As one element of the design, a green roof would be striking. It would generate significant good will and good press. It would reduce stormwater runoff on the site. And it would reduce the building’s substantial energy demands by as much as 10 percent.

A built-in-place green roof would cost upward of $8 a square foot, but that would be offset by utility and maintenance savings. Cooling equipment would last longer, as would the roof itself, protected from temperature extremes and ultraviolet radiation.

(A dozen years after the Ford Motor Co. planted out a 10-acre factory roof in Dearborn, Michigan, the living roof continues to thrive and has a life expectancy of another 25 to 50 years.)

In its search for a developer, the Maine Port Authority should insist on a building that reflects the creative, progressive spirit of our state. Forward-thinking design would be worth the investment as we put Portland back on the map as an international shipping hub.

Mark McCain