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Solar-powered courthouse?

Finance Committee members who agreed last month that a geothermal heating and cooling system is too expensive for the St. Croix County Government Center are considering solar panels as an auxiliary power source.

Last week the committee approved a contract to have Roof Spec Inc., St. Paul, begin engineering work for a replacement roof for the Government Center.

Roof Spec senior consultant Terry Thone will work with Karges-Faulconbridge Inc., engineers to investigate the possibility of placing a solar array on the roof.

Also last week, the committee voted to accept KFI's proposal to do the engineering work to replace the Government Center's failing heating/cooling system with a high efficiency chiller and condensing boiler system.

The fees for KFI's design, construction management and commissioning services for the entire heating/cooling project total $148,000. Trane Company, the manufacturer of the existing equipment, estimates the replacement system will cost $1.6 million.

Estimated time for finishing the heating project is six months, said Facilities Manager Art Tobin. He said he plans to get the boilers ordered early and expects that most of the air conditioning work can be done during the winter.

KFI engineer Robert Aschenbrenner said a 50-kilowatt solar array would take about 11,000 square feet of roof space, would cost about $460,000 to install and could save the county about $30,000 a year in utility costs.

Also, said Aschenbrenner, there are "a fair number" of rebates for solar projects and they don't take much maintenance.

A month ago the committee was looking at a mechanically fastened membrane roof as a replacement for the rock ballast roof now on most of the Government Center building.

But Tobin said difficulties with using mechanical fasteners on the concrete roof over the jail section of the building, the extent of wet insulation under the roofing and other factors have led to a change in plans.

"The wet area is a bigger, more mass area, than what we had thought earlier," said Tobin.

The mechanically fastened roof is not the way to go, agreed Thone.

"When that membrane shrinks, it pulls away," he said, drawing out a rough sketch of the polyvinyl chloride (PVC) roofing systems.

The shrinking pulls the roofing away from the perimeters, whether it is held down by rock ballast or mechanical fasteners, said Thone. He suggested using an adhesive to attach insulation to the roof and then roofing to the insulation.

Thone estimated it would cost a little over $1 million to remove the rock ballast and existing roof membrane, remove insulation, install new insulation with adhesive, add a new 60-mill fully adhered reinforced PVC roof membrane and install sheet metal flashing.

He suggested a timeline that would result in seeking bids in January and doing the work between April and June.

The adhesive works best when temperatures are "40 degrees and rising," said Thone.

The committee voted to enter into a contract for the first phase of engineering work for the roof project. The cost will be about $37,000.