If you own a two-story home in the San Francisco Bay Area, a zoned AC system may help improve your whole home comfort. Setting up a central air conditioner with one thermostat to evenly cool a two-story Bay Area house can be difficult. You might find that some rooms are perfectly comfortable, while others are still way too warm. Or are too cold! Your AC unit will struggle to deliver an air flow that cools hotter rooms upstairs without over-chilling downstairs rooms.