|I am looking for a couple of suggestions regarding fast growing conifers here in zone 6 (to be used as a screen between houses).|
|I've got three suggestions for you. There are many other hardy conifers, but for a variety of reasons, I am not suggesting them. (Break easily, slow growing, not too disease resistant, etc.)
The first one is the Balsam fir (Abies balsamea). It is hardy and quite attractive. It is full at the bottom and even has attractive cones you could use for decoration. These can get to be 80 feet tall!
Next would be the Norway spruce (Picea abies). This is quite a rapid grower which tolerates most soils. It does like full sun. These trees become very large as well.
Last, I would suggest an American Arborvitae or White Cedar (Thuja occidentalis). This tree is wonderful in that it tolerates drought (little care), low temperatures and pollution, which can be a problem if you are close to a roadway. This one gets to a height of about 60 feet.
All of these trees are tall enough to be a good screen between houses. They all have decorative cones and a decent shape with branches that go quite close to the ground, creating a good privacy shield.