A system for providing a comfortable environment within the passenger compartment of a vehicle. Controlled ventilation is utilized, along with a heater, an air conditioner, or an integrated heater and air-conditioner system. Linked to the setup is a windshield defrosting and defogging system capable of clearing the windshield as specified in a timed test, as required for all passenger cars manufactured for sale in the United States. Some vehicles have a ventilation-air filter which cleans the outside air that enters the passenger compartment through the fresh-air inlet. The increasing glass area of many passenger vehicles places an additional load on the air conditioner. Many vehicles incorporate solar-control glass to reduce solar transmission to the interior.