I have a 40-50 year old house. Someone put dormers in the center of the house leaving 3 feet of original roof on each end. My problem is that I had ice dams this past winter so I decided to rip down the walls and ceiling, reinsulate the attic and the walls. Now I'm being told that I need ventilation on the lower parts of the roof so it can get better air movement. I went to a friend and he told me about fasia vent and to put them in, but he doesn't know how many or the calculations for finding out how many. My house has no soffits, I have gable vents and it is still hotter than hades during the summer and cold as all get out during the winter. Would you know the formula for finding out how many vent I should put in for the air flow my house needs?: