Unless you have your air ducts cleaned and inspected regularly you can have mold in your air ducts for several years without knowing it. It frequently takes years for symptoms to emerge and equally as long to diagnose mold related health problems.
The access hatch to your attic is a major source of heat loss in your home. Using attic door insulation will significantly reduce your energy wastage and costs.
Insulating your garage can help keep it cooler in summer and warmer in the winter. It can also keep condensation out. If the walls of your garage are finished you don’t really have an option to install insulation on them, but you can insulate your garage door.