been a roofer for many years. Ventilation is a must through soffits, ridge vents and maybe a couple of turbines. Biggest problems of most home owners is they tend to have all of thier tubines closed up with trash bags thinking they would be saving on thier energy bill, but in the long run thier going to end up with rotten wood or worse a mold infested house. An attic for year round weather, as you may know needs insulation, but ventilation will not hurt your heating or cooling bills as long as your attic has proper insulation first and then your ventilation will not have an effect any condesation or moisture build up above your insulated attic. Air needs to be there circulating. Whether automatic thermostat controlled fans or wind driven turbines.