The answer is it depends on the leakiness of the building. The maximum flow through a Model 3 fan at 50 Pa is about 5,800 CFM. A 10,000 square foot house that was built with airtightness in mind may not have 5,800 cfm of leak while a 1,200 square foot Georgian with huge holes to various parts of the building may not be able to reach 50 Pa with the Model 3 fan at full speed. With this information, that is why our fans are rated based on the amount of flow each can generate.