Local pool builders, contractors and Chilmark selectmen showed up to a public hearing of the planning board Monday afternoon to discuss a proposed amendment to town zoning bylaws.

The amendment would require heated swimming pools built in the town to use solar thermal heating systems as the primary source of energy to heat that pool. The planning board hopes to put the amendment on the warrant for an Oct. 29 special town meeting.

Those that attended the meeting applauded the planning board’s effort to conserve energy, but were critical of using pools to do so and of the wording of the amendment.

“What is all this about?” asked David Handlin, a Boston-based architect who has been working with the town on the Middle Line Road affordable housing project. “Why are we focusing on swimming pools?”

“We are here today to create something that’s a beginning of the process and we thought this was something we could easily bite off,” board member Tim Lasker replied.

Chairman Rich Osnoss said solar thermal heating systems are the simplest possible solution to the high energy demands of heated pools.

Warren Doty, chairman of the selectmen, echoed the benefits of solar thermal systems. “Solar thermal is the single fastest payback for energy application. It’s not a crazy idea. The reason it is being proposed is because it works the best,” he said.

Mr. Osnoss said he had consulted David Sprague, an Island plumber and co-owner of Nelson Mechanical Design, who said the amendment did not preclude using geo-thermal systems in place of solar thermal.

Both Mr. Handlin and Gary Maynard, a Chilmark contractor and pool-owner, criticized the limited wording of the amendment. Mr. Handlin expressed concern that in specifying only solar thermal systems, the amendment could restrict the use of other alternative or renewable energy sources to heat pools.

“It’s an extremely oversimplified proposition,” said Mr. Maynard. He suggested the board consider other effective ways to conserve energy in heated pools.

When building his pool, installed after his house was built, Mr. Maynard researched solar heating systems, but found he would have had to cut down up to 12 significant trees to install the panels. Instead, he used an automatic pool cover and put a dark finish on the bottom of the pool.

This summer, his family has not turned on their heating system and on Monday, the temperature of the pool was 82 degrees. He suggested adding zoning board regulations requiring pool owners to use a dark finish and install pool covers.

But Bob Andrews of Island Pools and Spas argued that pool covers can be quite costly and that a dark finish makes it hard to gauge water depth.

Mr. Maynard urged the planning board to look in other directions to conserve energy. “I am a big proponent of alternative energy, but a small amount of our energy goes to heat swimming pools in Chilmark in the summer,” he said.

Mr. Handlin also had other suggestions including requiring new buildings to exceed Massachusetts energy codes by a certain percentage and researching Leadership in Energy and Environmental Design certification.

Mr. Andrews helped paint a picture of pool building on the Island. Mr. Andrews has installed between 120 and 140 pools on Island and each one has a heating system. He estimated that less than 10 per cent of those pools have covers.

The proposed amendment does not apply to spas, but many of the pools he has built have spas attached, he said. He also explained that not all pools are installed for luxury and cautioned against the high cost of solar heating systems. “The idea behind what you’re proposing is terrific,” he said. “But, what I’m reading is too narrow. It’s a tough onus to put on homeowners.”

The planning board voted to continue the hearing to Monday, Sept. 24 at 4:30 p.m. at Chilmark town hall. Members of the board admitted that the issue may be bigger than they originally thought and a proposed by-law amendment could take time to finish. If the board intends to put the amendment on the warrant for special town meeting, it must submit final wording by Oct. 5.