When we first went to forced air back so many years ago, we burned coal and used gravity furnaces. They didn't have a blower on them as they depended on gravity and natural convection to bring the heat up. This would require big registers and large ductwork.
The registers were also built into the interior walls to deliver the heat. Over the years, they found out that they had cold exterior walls, and they were moving all the furniture to the inside walls because that's where the heat was.
Now the registers are on the outside walls for more efficient heating, and the ductwork is much smaller.
Air conditioning changed this system completely because it needed adequately sized ductwork to reach the upstairs. Since heat rises, it was hard to use the same ductwork to cool the upstairs. As a result, they began installing almost two completely different duct systems, downstairs for heat and upstairs for air which has been very effective.
If you are interested in learning more about the ductwork in your home or if it needs to be updated, contact us today!