I understand my gas forced air heating system to a reasonable degree thanks to this forum. It's in a L-shaped ranch house- and pretty centrally located in the basement. When it was installed 24 years ago, the HVAC guy suggested zoning, since one side of the house was bedrooms and bath- the other side living and kitchen and half bath. I passed on the zoning idea due to a severe lack of knowledge on my part. I was the one that wanted the furnace in the middle of the basement believing that a more central location would give me the best comfort level from room to room. Anyhow, my question: Since learning a bit about how important sizing (furnace/air/duct-work) is- how does a zoned system keep the correct amount of air-flow within/through the furnace when a "zone" is in use and another zone isn't? Wouldn't closing down the living room at night mess up the air going in and out of the furnace? How is this addressed? Sorry for the long post- just curious since zoning may be a consideration when the equipment is replaced. Hope this isn't too vague. Thanks.