You might consider running a continous run ridgevent along the length of the ridge minus any overhang when you roof if it's going to have a pitched gable type roof with a ridge.

Here is a link that might be useful: ridgevent

Good morning, and thanks for your information. Before posting my THS note I had built the roof. The turbine vent was installed yesterday. Afterwards, I'm not so sure the ridge vent wouldn't have been the better idea. I placed the vent closer to the house as I proposed. My immeidate assessment is I think I should have put it in the middle. I have patio doors entering to the porch below the vent. As the vent twirls it might be pulling air from the house that could interfer with it pulling heat from the porch ceiling. But, I'm talking about one day's assessment. Maybe time will tell. Thanks, Gene