The Vashon Island School Board, facing slightly higher construction costs than anticipated, is slated to vote tomorrow on whether two resource-saving green systems will be included in the new high school building.

The board had previously approved both an air-to-water heat pump and a rainwater harvesting system for the $47.7 million high school project.

But according to Superintendent Michael Soltman, bids for the project recently came in about 2.5 percent higher than expected, forcing the board and district to reconsider some of its decisions. The board, he said, can choose to use contingency funds to cover the added costs or opt to go with less expensive options, nixing, for example, the two green systems it had previously approved.

“That’s what they’re wrestling with — the real value of what we’re going to get by having these two systems in,” Soltman said.

At last week’s board meeting, commissioners discussed the costs and benefits of the systems. They wouldn’t save the district much money, some noted; electricity savings from an air-water heat pump, for instance, are nominal. But installing the pump rather than a large boiler would allow the district to rely less on natural gas and eventually switch to solar energy, some commissioners said.

The board will meet at 7 p.m. Thursday at McMurray Middle School