Mitigating global greenhouse gas emissions will require futuristic and high-profile clean energy production breakthroughs like nuclear fusion and enhanced geothermal systems, but it will also depend on many smaller and significantly less sexy developments in tandem. In fact, some of the lowest-hanging fruit have some of the biggest payoffs when it comes to reducing emissions. Seemingly small tweaks like making residential heating and cooling more efficient can have massive impacts on global carbon footprints. “Energy efficiency is one of…