Housing was constructed with local materials. Now most of our food is grown with chemical fertilizers, treated with herbicides and pesticides, processed with additives and preservatives, wrapped in plastic or foam material, and sent thousands of miles away to be consumed. Water is chemically treated and distributed through pipes which impart traces of metals or plastics. Our clothing is made with artificial fibers treated with synthetic dyes, finishes, moth-proofing, and fire retardants. Indoor air pollution can be a major problem to your health.
Air change is measured in how much indoor air has been replaced by fresh outside air in one hour.
Opening an exterior door usually takes care of this exchange. Another method being investigated in colder climates is a breathable envelope. The exterior wall allows colder outside fresh air to move through the wall under a very slight negative interior pressure by way of an exhaust fan. This system keeps the exterior wall temperature cooler and drier. For Louisiana climates it seems that it would work that way only with a positive interior pressure pushing the cooler air to the exterior.