01-04-2018, 08:45 AM
Metal conducts heat very efficiently. So the, foil by itself is poor insulation but an excellent barrier to hold in moisture which makes it useful to keep a baked potato moist but let some of the 350 degree heat escape and not scorch your tongue. In truth any metal will conduct heat from the higher point to the lower point. it is a poor insulator. But if it is put around a good insulated like fiberglass or ceramic material it will present an excellent barrier against air and moisture and make the insulation more effective.