Stress-skin insulation has shown positive impacts on the quality, comfort and energy savings of structures, but also created the need for controlled ventilation. Many of today's indoor airborne pollutants can be effectively controlled, actually increasing the comfort and livability of a structure. Mechanical ventilation has been proven effective in mitigating fumes from combustion appliances, radon, formaldehyde and even pollutants such as excess humidity and tobacco smoke. In order to remove the contaminated air, an exhaust is essential. Typically, that exhausted air is replaced with fresh air from outside the structure.