Ask This Old House
I was watching Ask This Old House. They were helping a homeowner with a 2 story home in a warm climate- furnace was in garage. It did have a furnace/ac. The home has 13 rooms and the zoning system installed cost $5,000 -6,000.
To the product being installed. It created a zone system using the existing duct work. It consisted of balloons being installed in the ducts a couple of feet in from the register. A small diameter air line was fished from each register back to the furnace. All the air tubes were connected to pump that inflated and deflated each balloon individually. There was a master thermostat and small wireless thermostats in each room. If the upstairs was to hot the ac would come on. When a room reached its desired temp the balloon would inflate blocking air to that room.
Even deflated the balloons would have to restrict the air flow by at least 25%. It seem like this alone would hurt the efficiency of the unit. Then when multiple balloons were inflated the air flow would be severely reduced.
It seems like so many of these shows are more of a commercial for bad renovations or in this case an improper fixes to the real problem.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part