Greenhouse vents and ventilation.
Here are many examples of greenhouse vents and how they work.
I hope one of these can solve your ventilation problem.
If you live in a mild west coast area, little frost, cool summers, then a passive vent made out of shade cloth might be enough.
![Greenhouse side vent made of 2x2 cedar and polycarbonate with a gigavent. - grid24_12 Greenhouse side vent made of 2x2 cedar and polycarbonate with a gigavent. - grid24_12](/images/grid24_12/7000/garden/howto/pictures/vent/horizontal-side-vent.jpg)
Then we found these solar vents. (The little ones on the left.) which led to the one on the right.