This is the size that many large homes used in the early 1900s when there was no air conditioning available. These were typically mounted above the top landing over the stairs in 2 story homes. This is the first time such a large fan has been installed high in the attic so the loud propeller sound is muffled.

The air flow is divided into 4 20 inch ducts for connection to individual rooms or hallways or a combination of those.