Keegs, yes, 7 feet horizontal for every foot of height.
Some say evergreens will protect downwind as far away as 10:1. All the old farm houses I've seen, that had evergreen windscreens, were never as far away as ten times their grown height upwind of the house.
Privet hedge verses evergreens, I'd see which grows faster in your growing zone. And keep in mind that once you get over a certain height, windblown drifting snow does not go over it, like it can with lower screens such as fencing. Likely why so many old timers used evergreens rather than fences.
Paul