The West Tisbury historic district commission this week approved the major parts of a proposed $5.1 million renovation of town hall. The renovation project, slated for a vote at annual town meeting on April 8, is the latest in a series of renovation proposals to voters dating back to 1997.

Between April 1997 and 2005, voters approved several design and development requests ranging between $10,000 and $75,000 for two separate architectural firms. In 2003, annual town meeting voters narrowly rejected a $3.8 million borrowing plan to fund the renovation.

At that point, the town formed the space needs committee charged with creating a comprehensive renovation plan. The space needs committee prioritized capital projects, putting town hall renovation first followed by construction of a new police station and expansion of the library.

“What is also different about this [town hall] plan compared with prior plans is that it’s more modest,” said Beatrice Phear, chairman of the town hall renovation committee.

“The huge basement with meeting rooms is gone,” she said. “Parking has been reduced from 36 to 20 vehicles. There is less site impact, much more energy efficiency and more use of sustainable and recyclable materials.

“We have more realistic estimates because both space needs and the renovation committee conducted estimates,” she said. “The difference between space needs’ $4.9 plan and our $5.1 million plan is the use of super insulation.

”The space needs committee did a good job,” Ms. Phear said, adding that the prioritization allows the town to manage its debt and gives the library time to raise funds and seek state grants for its project.

The six-member historic district commission Monday night closely examined details of a proposed plan before approving the overall design plan, the building foundation, the use of manmade materials in siding and windows, and landscaping. All were critical pieces of the plan submitted by the town hall renovation committee and prepared by architects Keenan & Kenny Architects Ltd., Falmouth.

The scope of renovation work includes construction of a 792-square-foot, three-story addition with an elevator, four rest rooms and a second stairway, addition of twenty parking spaces, renovation of the exterior of the existing building, replacement of the granite foundation with concrete and the replacement of all windows.

The commission also approved a landscaping plan that includes removal of two small live trees and two dead elm trees and relocating three holly trees and some shrubs to new locations.

Still to be approved are installation of 14 to 16 solar panels slated for the roof of the expanded facility and final approval of railing profile design.

Ms. Phear noted that the energy saving solar panel system is not a formal part of the budgeted renovation and was not critical to the approvals her committee sought Monday evening to present the plan to voters before town meeting. She said that she expected funding grants would provide for the purchase and installation of the solar system.

Following the meeting, Ms. Phear said the historic district commission will hold a public meeting at the Howes House on Wednesday, March 26 at 7 p.m. to discuss the renovation plans.

She said the plan’s goal is to have “no significant impact on the taxpayer.”

The committee proposes a $4.8 million bond to begin in 2010.

“That would create a spike in debt service since bonding expense for the new public administration building will have five more years to run,” she said. “We have approval from the conservation preservation committee for $500,000 per year in community preservation act funds at $100,000 a year for five years to significantly offset the spike.”

Ms. Phear and Antonia Kenny and John Keenan, owners of Keenan & Kenny, presented an updated illustration, called an elevation, of the project. The architects answered questions for one and one half hours before having to leave for the return ferry to Falmouth.

Ms. Phear fielded questions for another hour with occasional project details provided by building inspector Ernest P. Mendenhall and by Chuck Hodgkinson, space needs committee chairman. Member Ben Moore left generally positive comments about the submitted plan before leaving to attend another meeting.

The goal of the discussion was to marry style with substance and to weigh tradition against economic pragmatism. Commission members, for example, sought reassurance that the use of manmade materials for reconstruction would retain the original authentic look of natural wood products in the finished project, and that new work would meld visually with parts of the renovated structure that are retained.

One example is replacing wood windows with thermal aluminum-clad replacements.

The commission probed details such as width of window mullions and learned that the 7/8s of an inch wood mullions would be replaced with 5/8s of an inch mullions in the replacement version. The renovation committee held the difference would be indistinguishable to the naked eye. Mullions are non-structural vertical strips between the casements or panes of a window.

The detail is important since some original window frames are to be retained.

Another significant point of the tradition versus economy discussion was the use of AZEK-shingled siding to replace cedar shingles on the exterior. AZEK is a cellular PVC product that feels and works like pine, though heavier and more flexible.

“We have a terrible history of maintenance in West Tisbury,” Ms. Phear asserted, “and AZEK will help us to avoid that problem.”

Mr. Hodgkinson offered research suggesting that triennial cost of repainting wood exterior would cost about $70,000. “Available research on AZEK suggests repainting will occur every ten years and will cost less than repainting wood,” he said.

His research suggested a 10-year expense model of more than $200,000 for wood repainting against less than $70,000 for the plastic building material.

Board chairman Sean Conley, members Anne Fischer, Nancy Dole and Allan (Lanny) McDowell also focused on replacement of the current granite foundation with cement, a move that will lower the foundation by eight inches.

Ms. Phear noted that landscaping will obscure most of the visual foundation and vowed that the granite would be retained and displayed prominently.

“Just promise me the granite won’t be made into benches,” a committee member said, drawing a chuckle from attendees.