The design of many older houses omits eaves which maximizes the amount of sunlight.
No vent in attic.
Static roof line vents are effective for ventilation but generally aren t recommended due to issues with leaks.
This is called passive ventilation.
Typically you would have a gable vent on each end of the attic.
If you re wondering how studor vents work after the toilet is flushed the water flows down the drain resulting in negative pressure.
The most common way to add ventilation to an attic is by installing air intakes in the soffits and putting an outlet at the gable of the house.
Normal vented air likes to enter the attic lower down near the bottom third of the attic and as it passes through it will exit higher up near the top third of the attic space.
This creates a natural air flow by drawing in the air from outside pushing it up and out through the vent at the top of the house.
This negative pressure causes the vent to open and let in enough air to relieve the pressure.
A combination of air sealing and insulating the attic floor while providing ventilation considerably reduces the potential for condensation as warm moist air is less likely to enter the space and condense on cold surfaces.
Too often mechanical ventilation ducts from bathrooms kitchens or laundry rooms deposit warm moist air into the attic instead of outside the building envelope.
For proper ventilation it isn t enough for air to simply get into your attic.
For an attic without soffit vents you may have the option to use gable vents instead.
Gable vents may circulate air through only a small percentage of your attic.
Problems when roof has no overhang.