Passive louvered ventilation doors

I was planning to make the passive louvered ventilation door. It was, I thought an original idea. I was over at a friends house this morning and was explaining my idea to him. He said, does it look like this. Someone stole my idea. It was exactly what I was imagining. Only his was installed on his house and was working perfectly. He said that he bought the unit at the materials store. I will track it down and list it here as soon as I find it. One difference between his unit and the one that I imagined was that the fan motor in his unit was quite a bit more powerful than the one I had in mind. I am thinking of a fan motor that operates on 10 to 20 watts. I am guessing that his fan is more like 500 watts. His ventilates a whole house, where mine is just for my little 8×12 greenhouse. 96 square feet vs 2500 sq ft.