AMHERST — Various changes to the plans for the Jones Library expansion and renovation project, aimed at reducing costs before general contracting bids are sought for a second time later this year, are being approved by the Planning Board.

With members expressing a strong preference for a more expensive synthetic slate for the roof on the 1928 section of the building, the Planning Board Wednesday voted 4-0, with three members absent, to reaffirm findings and conditions as previously approved for the $46.1 million project last December.

The revised findings and conditions come with minor tweaks, such as a requirement that the site’s stormwater management is satisfactory to the town engineer.

A memo from Planning Director Christine Brestrup provided an explanation about the changes in the architect’s drawings for the project, which will expand the building from 48,000 square feet to 63,000 square feet. These changes follow a series of so-called value engineering adjustments, aimed at bringing down costs, including the possibility of asphalt shingles, the removal of the roof monitor — a second roof structure running along the crown of the roof, which would provide natural light inside the building — and the possibility of not having new double-pane windows in the oldest section of the building.

Planners supported the asphalt roof, but only as a backup plan.

“We wish you the best and we hope you have the money to put on the synthetic slate,” Chairman Doug Marshall told Library Director Sharon Sharry and trustees President Austin Sarat, along with the architects from Finegold Alexander of Boston.

“I’d rather backslide to asphalt if money isn’t available than to see the project stop,” Marshall said.

Before the meeting, the Planning Board received concerns from the Design Review Board about aspects of the project, including that the roof materials be more slate-like for the oldest part of the building and that historic windows be replaced so long as they are consistent with the existing appearance.

Tony Hsiao, who handles design work for Finegold, said costs are driving the changes. “The library is very carefully considering those alternates to replace the synthetic slate originally proposed and to keep the windows that were originally there intact as part of a cost-saving measure,” Hsiao said.

Other specifics of changes were presented by Rachel Loeffler from Berkshire Design Group, explaining that the project no longer includes a children’s courtyard with Goshen stone benches and removing the building’s stormwater garden planting.

Josephine Penta, also with Finegold Alexander, said while a net-zero energy building is not being produced, all sustainability measures are continuing to be examined.

Even with several people providing public comment orally and in writing, both for and against the project, Marshall said at the outset of the meeting that the Planning Board wasn’t in a position to reject the plans. “We really can’t say no under state law,” Marshall said.

Sarat told the the Planning Board that while so-called value engineering is taking place, the library building committee has asked that there be no changes that “would affect the essential integrity of the project.”

“We believe we have done that,” Sarat said.

Even with the cost savings, the library will be a significantly more sustainable and energy-efficient building than the existing library “under any scenario,” Sarat said.

Despite claims that energy efficiency is being compromised by the changes,  Sharry said the building will be net-zero ready.

The only remaining town review is by the Historical Commission, which meets Aug. 22 to consider the project under the demolition delay bylaw, due to the extent of potential changes to the facade of the original building, and an existing historical preservation restriction.

Scott Merzbach can be reached at smerzbach@gazettenet.com.