There are a few ways to assess the insulation needs of your home. Obvious signs of poor insulation include:
Drafts
Unusually hot or cold spots on the floor
Poor indoor air quality
Poor sound isolation
Moisture infiltration
Unusually high energy bills
Difficulty keeping your home comfortable
If you’re experiencing any of these symptoms, you almost certainly need to re-insulate your home.
For more subtle cases, you can compare your existing insulation to the recommendations from the Department of Energy for your climate zone. Different materials have different R-values per inch of thickness, and the DOE has suggested total R-values for different parts of your home you can look at.