Extra Cost: <$100
What: Use healthy insulation without toxic chemicals.
Why: Those chemicals get through your walls and into the air in your house.1
How: Use a non-toxic insulation. I used, and highly recommend, EcoBatt, but there are others. The good news is that it costs roughly the same price as “normal” insulation.
Most insulation comes either backed by paper, or paperless. Contractors like the paper-backed insulation because it's easier to install and work with. However, paper is fantastic food for mold and locking in paper behind your walls is generally not a great idea. So ideally, use paperless insulation in your home.