The changes are subtle. Mount Si High School students might not even notice the new floors, skylights and heating system when they return to class next week.

But the new materials and technology, installed this summer during remodels at Mount Si, Chief Kanim Middle School and Opstad Elementary, are designed to save the Snoqualmie Valley School District some significant money.

Roughly $22 million of last February’s $27 million construction bond paid for repairs and improvements at the three schools. Additional funds came from a $785,674 grant from Puget Sound Energy for implementation of energy efficiency upgrades, and $442,463 from state matching funds for capital projects that went toward the new Wildcat Court.

The courtyard was proposed following flood repairs at the high school.

“It wouldn’t have happened if the bond wasn’t passed, because all of the capital projects funds would’ve gone toward upgrades,” said Carolyn Malcolm, Snoqualmie Valley School District spokeswoman.

All three schools got upgrades to heating and cooling systems. Mount Si now has a centralized geothermal heating and cooling plant, which uses groundwater from a nearby aquifer as an energy source. Opstad and Chief Kanim received refurbishment of existing air handlers and fan coils.

Mount Si will see a savings estimated at $125,000 per year, while Opstad and Chief Kanim will save about $55,000 per year combined for gas and electricity.

The schools’ general lighting fixtures have been replaced with ultra-high efficiency units. Lights will last 50 percent longer and provide 15 percent more light than the fixtures being replaced.

Occupancy sensors have been installed in all hallways and areas in the schools to turn the lights off after 15 percent of inactivity and daylight controls to reduce lighting down 50 percent when daylight is present.

Puget Sound Energy has estimated the district’s savings to about 57 percent in anticipated energy use, or about $18,000 per year.

“Everything about this in some way lowers your cost, in either energy or maintenance,” said Clint Marsh, district construction program manager. “When you change things, other things that have been there forever pop out.”

Other bond improvements include:

Opstad Elementary

• Roofing replacement and additional louvers to stop blowing snow

• Interior painting

• New security system

• New rubberized playground matting

Chief Kanim Middle School

• Roofing replacement

• New carpet in classrooms and rubberized flooring in science labs

• Interior painting

• New fire alarm system

• New rubberized running track and hurdles

Mount Si High School

• Wildcat Court: Additional 6,000 square feet of enclosed student-related commons space for food service and social activities; Two outdoor spaces for student and teacher uses

• Use of translucent wall and skylight panels allowing beneficial natural light

• Increase school capacity with 12 modular classroom complex

• Major improvements to fire alarm systems

• New carpet in all classrooms and rubberized flooring in science labs

• Interior painting

• New tennis courts utilizing post tension concrete slab construction

• Lighting upgrades for evening tennis court use

• Enhanced wetlands

• Upgraded softball field