Fiberglass Ducting and Air Conditioning; need to remove?

Hi! I have six window air conditioner units in my house and central heat for heating. The insulated ducting for the heat, installed in 1975, is fiberglass with a foil exterior lining. Do I need to use another type of ducting due to mold potential?
Also where do I find an energy calculator for window units vs. central air? I want to have only one window unit- and in a room not used that often. Thanks KAT Macon, GA where it's hot as heck
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