Which materials are typically NOT used for hot water tank insulation?

Hot water tank insulation is vital for maintaining the efficiency of the tank and minimizing heat loss. The materials commonly used for insulation include foam, rubber, fiberglass, cellulose, mineral wool, and polystyrene, as these materials have good thermal resistance properties and can effectively reduce heat loss.

Metal and glass, on the other hand, are not insulating materials; they are conductors of heat. While metal can be used as a structural component in tanks and glass for linings or coatings, neither of these materials provides the necessary thermal resistance to serve as effective insulation. Thus, they do not contribute to the heat retention properties of hot water tanks. Instead, they can actually facilitate heat transfer away from the water, which is counterproductive in a hot water system. This understanding emphasizes why metal and glass are not typically chosen for hot water tank insulation.