In Minnesota, fighting climate change means changing how to heat buildings Heat pumps help large commercial, residential sites cut costs, emissions. May 1, 2021 — 4:46pm Text size Copy shortlink: Brian DeGidio admits he hasn't thought much about the environmental benefits of the air-source heat pumps he's working on atop a large apartment complex under construction in St. Paul. It's a drizzly Friday and DeGidio is hooking refrigerant lines to condensing units that look like window air conditioners lined up across the roof. Greenhouse gas emissions aren't top of mind. But the HVAC system he's working on swaps fossil fuels for cleaner electricity, and DeGidio is part of a quiet revolution underway in Minnesota as the state chases ways to cut global-warming gases. Buildings — and the fossil fuels to heat and cool them — are a big overlooked source of the heat-trapping gases.