For the past nine months the Chilmark planning board has been working diligently on the question of how and whether to regulate very large houses in town. In-depth research, listening and open dialogue have marked the work of the subcommittee assigned to the task. Much information has been collected, and drafts and re-drafts of sample bylaws have been put on the table for discussion. Against the backdrop of this work and research, the planning board is considering requiring houses that are larger than a certain size to go through an extra layer of review and obtain a special permit. The actual size that would trigger the review is still under discussion.

As the board reaches the final stages of crafting a bylaw for voters to eventually consider, this week Chilmark town counsel Ronald H. Rappaport weighed in on the matter, advising the members that the town cannot legally set an absolute cap on the size of houses, but that setting a threshold size that triggers a special review could pass legal scrutiny if carefully done. Rather than create an entirely new zoning bylaw, Mr. Rappaport suggested that the town make good use of its existing districts of critical planning by writing new rules that regulate house size under the umbrella of these overlay planning districts. Created through the enabling legislation for the Martha’s Vineyard Commission, DCPCs have special rules that are incorporated into town zoning bylaws, written in concert with the regional planning commission and subject to exhaustive public review. All DCPCs involve areas that deserve special protection not afforded under ordinary zoning laws. Some are Islandwide districts, such as the one that protects the scenic qualities of Island rural roads, and another that protects coastal areas from ruinous development. Others are specifically created within town boundaries, such as the Squibnocket district in Chilmark, and the wild and scenic north shore district that spans the towns of West Tisbury and Chilmark.

Picking on houses strictly based on their size is a tricky business to be sure. Opponents often cast the issue as an effort to legislate taste, but in fact there are sound environmental reasons for communities to take special care before allowing large new buildings.

Leveraging existing planning tools seems like a sensible approach to dealing with this issue, and DCPCs — which by their definition target areas deemed especially sensitive — carry the extra legal strength of the Martha’s Vineyard Commission, as Mr. Rappaport explained to the planning board at their meeting on Tuesday night.

Other Island towns have watched as Chilmark has worked hard to get this right, and the planning board is to be commended for its thoughtful, deliberate approach to the so-called McMansion discussion which has been heated and fraught with emotion. The direction in which the board is headed is prudent and fair.