[Xringer]

If your air intake is close to the peak, it will create a low-pressure area, right under the ridge vent.
Especially if other air sources (vents) aren't close enough to the low-pressure
area to normalize the pressure.

The amount of outdoor air pulled in, will depend on the type of ridge vent.
If it's designed for a lot of flow thru, back-wards flow will happen.

That might not be good during a windy rain storm.
Make sure you have a humidity sensor on your blower control hardware.

My ridge vent is 40 feet long, so the blockage is a small percentage of the total.

I've never had any moisture problems in the attic, during the 35 years,
before we had the ridge vent installed..
So, I could block up a lot more of the vent if I really needed to.

Anyways, you can use sensors and tell if back-wards flow is occurring.
If the sensor near the vent shows 70F air, but 60F air is being pumped down,
there is cold air mixing going on.
After I plugged up the ridge vent close to the intake,
the heat of the air being pumped down, was the same as the peak sensors were showing.