Who Can Install Solar Air Heating?

Where in the USA can you install solar air heater systems? The system can be installed in most of USA except the dark red area shown to the right (most of Southwest USA). Customers in the blue area may get lower performance.
Why does the solar air collector panel work better in the winter if it's mounted on a wall instead of a roof? The angle of the sun during the winter allows for better results if you install your solar panel on the wall, but it will work fine if installed on the roof.
Where on my house should I install the solar air heating system collector panel? We have all the information needed to help you set the panel in the best place on your house in order to get the best air heating performance.