The kit comes with one vent for each door. You just have to sit in the cabin on a sunny day to realize that one in not enough. I choose to mount a second vent about knee level.
A note of caution concerning parking outdoors on a sunny day :
** The magnifying effect of the sun shining through the bubble can damage your interior at best or catch fire at worst.**
I had my ship setting outside on a sunny day recently with the sun just over the pilot's left shoulder. The sun melted a spot about 2" long by 1/2" wide on the co-pilots floor mat. I'd hate to think what may have happen if I hadn't noticed the smoke.
The factory reports that the ship should be positioned INTO the sun to avoid this problem.