Aluminum does not keep things cold, but does act as a barrier to oxygen and vapor, which can transfer heat to the frozen food when it is exposed to air. It also prevents germs, odors and flavors from escaping or entering the packaged food. Aluminum is known for being a good conductor, but it is also a good insulator, as it reflects the radiation of heat back to its source.
Because of its ability to reflect heat, aluminum is broadly used in food and pharmaceutical packaging. Used in aseptic packaging system, aluminum foil is usually combined with plastic and paper to create a package container that allows a significantly less amount of oxygen to permeate. Aseptic packages help to keep the foodstuff fresh for months, even without refrigeration. It ensures that the product is protected and fresh from the source until it reaches the consumer.
Many buildings and residential homes use aluminum for thermal insulation, cable liners and heat exchanges. In order to retard heat flow, there must be an internal air space between the aluminum and the area that needs insulation. A foam board insulation backed with aluminum foil is commonly used to insulate residential homes. This prevents heat loss inside the home during winter and reflects back and keeps out the heat during warmer months.