The age of your house and its construction will impact the effectiveness of any HVAC steam humidifier.
If your house is more than 50 years old, it probably lacks proper house wrap and modern insulation technology. If that house has not been renovated in a while, there is a good chance that its doors and windows have drafts that can let air pass through them.
Houses less than 50 years old without proper and regular renovation are also considered to be loosely built. In such settings, the mist from the humidifier will be lost through uninsulated walls and drafty windows and doors.
Average build houses ~25 years of age often have a house wrap and upgraded windows and doors along with other renovations. They are better able to retain moisture indoors but are still subject to some losses.
Tighter-built houses less than 20 years old are usually equipped with much better insulation technologies and sealed windows. They are very good at retaining moisture from a humidifier indoors.
In short, a humidifier with the same coverage area and capacity will perform much worse in a loosely sealed house than in a tightly sealed house.
For example, a steam humidifier with a size rate of 4,000 sq. ft. might only cover 1,250 sq. ft. in loosely sealed home, 2,000 sq. ft. in average sealed home, and 4,000 sq. ft. in tightly sealed home.
Therefore, make sure that the room size rating of the humidifier is sufficient to match the needs of your building, age and construction.