Windows are the “weakest link” in the so-called thermal envelope of a building. In summer, too much heat is transferred inside through the glass. In winter, too much heat escapes outside — and the cost of window energy waste in the U.S. has climbed to more than $45 billion per year.

If this year felt different, that’s because it was different. More urgency. Less dogma. A bias toward action.

In fact, 2021 was the most consequential year in climate policy, climate technology and climate markets that the world has ever seen.

We all know what didn’t happen in Glasgow: The establishment of binding, near-term emissions reduction targets for the world’s largest economies, enforceable under international law.

But while most of the news coverage and after-action analysis is focused on what didn’t happen, we shouldn’t ignore what did.

According to the Lawrence Berkeley National Laboratory, “windows in the U.S. consume 30% of building heating and cooling energy”

The climate crisis takes center stage in Scotland this month, and Bloomberg writer, Marc Champion, astutely noted, “Among top producers of climate-harming emissions that world leaders plan to address at COP26 in Glasgow in November, buildings are the summit’s largely ignored Cinderella.”

Take a look out your window. Have you ever stopped to think about how much money that glass is costing you? Or, have you thought about its harm to the planet?