Cutting the slots in the soffit is a good idea.
Roof vents will work without soffit intake.
If you read a piece of paper it does not work.
How long did your last roof last? This is an important question. If your roof lasted the years it was supposed to, then there is enough ventilation for the shingles to last this time to. If you have a moisture problem, then more ventilation will help. Finding the way the moisture is escaping your house into the attic is a better use of your time. Then close off these spots.[/quote]
Yes, ventilation from thermal buoyancy will still allow air to escape from the Exhaust Vent products, but they work considerably better with either a Balance or slightly higher amount on Intake Ventilation added to the equation.
Without the proper Balanced Intake Ventilation, the FHA Guidelines and the Code Requirements and the Manufacturers Specifications require the amount of NFVA to be DOUBLED.