It is ok to install all 40 feet of ridge vent as long as it can be balanced with intake ventilation.
Intake versus ridge roof vents.
This option might be the updated system which most newer homes use but if you have an older home then you might need the soffit vents too.
The reason you do not mix them is that the ridge vent can turn the box vents into intake vents.
Most building codes define a balanced ventilation system as one square foot of ventilation for every 300 square feet of attic floor space with half the ventilation represented by intake vents and half by by exhaust vents.
We added the edge vent for proper intake and replaced the roof louvers with continuous shinglevent ii ridge vents said jason vogen ceo of elite.
If you have altering roof heights only the highest ridges should have ridge vents installed on them for the exact reason you mentioned in your comment you do not want the lower ridge vents to unintentionally become intake vents instead of exhaust vents.
Roof ridge vents provide a costly system of ventilation that may not be suitable for the checkbooks of some homeowners.
Exhaust vents like attic fans ridge vents are primarily placed at the very top of the roof or the highest pitch where hot air gathers.
You do not want a box vent acting as in intake vent b c it will suck air in and can also suck in rain or snow with it.
Intake vents such as soffits are placed lower on the roof usually under the eaves.
That means roof ridge vents.
Multiple types of vents can work together to create an equal inflow of cool air and outflow of hot air in your house.
The whole point to a ridge vent is that it takes air from all along the bottom of the roof line and exits it out the top kind of like a toilet.
The intake vent should be at the bottom of the roof whether it is a soffit vent or an edge vent.
Even without soffit vents a ridge vent is much more effective than gable vents paulcp thinks hammer is right.
Roof box vents and continuous ridge vents are separated by a few differences and deciding which one to put on your roof depends on which better fits the type and situational roof you have.
The problem with gables is they short circuit the air flow paulcp writes.
Which ultimately will increase the longevity of the roof and the life of his home.
This can cause a leak.
If the amount of intake ventilation cannot match the entire 40 feet of ridge vent consider reducing the width of the ridge vent slot thereby reducing the vent s nfa per linear foot to accommodate the amount of intake nfa available.
In this back by popular demand article see the difference between roof box vents and continuous ridge vents.
The soffit vents act like the air intake for the home.