What are the differences between a downflow and upflow furnace in terms of their efficiency and performance?

Downflow furnaces are typically more efficient than upflow furnaces because they utilize gravity to push warm air downward, which can result in better heat distribution. Upflow furnaces, on the other hand, may require more energy to push air upward, potentially impacting their efficiency. In terms of performance, downflow furnaces are often preferred for basement installations, while upflow furnaces are commonly used in attics or crawl spaces.