Newly built houses, with their sizable carbon footprints, don’t just contribute to climate change. For many Americans, they’re also too expensive—a bitter irony in cities rife with vacant buildings and record evictions.

Given the urgency of both issues, projects that retrofit livable housing into existing low-carbon shells (the initial embodied carbon was spent long ago) might be worth a closer look. We searched for them and came across a handful that promise a cure for housing insecurity and excessive greenhouse gas emissions.