Exemptions are supposed to be exceptions to the rule, which is why it's unsettling to see height limits lifted as often as they are.

A story by Advertiser writer Mary Vorsino chronicles the mounting pressure on developers to seek higher building allowances. They can do so because of a state law that allows certain exemptions in exchange for increasing affordable units in the project.

But these exemptions must be carefully reviewed, and issued judiciously.

Unfortunately that doesn't appear to be the case. Of eight projects proposed under that 2006 law, four have exceeded the height limit in their areas. The project at the center of the current discussion is the planned Holomua high-rise tower at 1315 Kalakaua Ave. Its builders want to go 70 feet beyond the 150-foot height limit.

The problem isn't with this project individually. It's not the only tall building in the vicinity. The nearby Banyan Tree Plaza stands 350 feet tall.

The problem is that the piecemeal decision-making sacrifices any sense of community cohesiveness.

And nobody is tracking what the community is gaining in return for that sacrifice. In the case of Holomua, for example, 51 percent of its for-sale units are being kept affordable for a decade. But this kind of short-term gain may not pencil out in the long run, considering the permanent loss of views and the increased burden on roads, water, sewers and other systems.

The City Council has enabled higher height limits for Kapolei, and is anticipating more dense development in Honolulu with the advent of the rail project. It passed a resolution urging the Department of Planning and Permitting to recommend maximum heights where limits are flexible in the urban core.

Promoting compact development is reasonable. But the resolution doesn't provide enough direction. The council needs to update the city's zoning districts and set firmer height limits that make sense for the neighborhood's capacity. And, unless we want Honolulu to become a miniature Manhattan with an unbroken line of glass-and-concrete towers, there must be variations in the skyline.

City Councilman Charles Djou, who introduced that resolution, wants to avoid urban sprawl, and he's right.

But the city needs to steer carefully toward that goal, with a clear and thoughtful review of how those decisions will collectively change Honolulu's skyline forever.